Principal Deposits of Strategic and Critical Minerals in Nevada (1985)
Comprehensive inventory of Nevada's strategic and critical mineral deposits as of 1985 — tungsten, antimony, mercury, rare earths
Overview
Principal Deposits of Strategic and Critical Minerals in Nevada (1985) is a 1985 critical-minerals report by Various, preserved in the Mountain Man Mining research library. Comprehensive inventory of Nevada's strategic and critical mineral deposits as of 1985 — tungsten, antimony, mercury, rare earths…
This 1985 document, Principal Deposits of Strategic and Critical Minerals in Nevada (1985), is preserved in the Mountain Man Mining Library for research and reference. Original source: archive.org.
at | : . com/|
Id'
A Text-Book
Op
Coal-Mining.
a
Id'
A Text-Book
Op
Coal-Mining.
The New Ycp.K
Public Library
'
A Text-Book
Of
Coal-Mining.
For The Use Of Oollieky Managers
And Others.
By
Herbert W. Hughes.
ASSOCIATE OP THB ROYAL SCHOOL OP MINES; PELLOW OP THE GEOLOGICAL SOCIETY;
Associate Member Op Thb Institution Op Civil Engineers; Certipicated
Colliery Manager ; Past-President Op The British Society
Op Mining Students.
With Very Numerous Illustrations.
London: Charles Griffin & Company, Limited,
Philadelphia : J. B. Lippincott Company.
The New York '
Public Library
Tot, Tiloen Founoations
R 1916 L
t
r r
k
Preface.
In the preparation of tliis volume ray aim has been to supply a text-book of moderate dimensions, giving all the infomifition with which the student and the practical miner should be familiar. In order, however, to economise space, I have bad to omit reference to many appliances which have become obsolete from their antiquity, or by reason of their failure in practice.
Although it is impossible within the limits of the book to furnish exhaustive descriptions on all points, yet the details of general colliery work have been fully described, on the ground that collieries are more often made remunerative by perfection in small matters, than by bold strokes of engineering. All modern collieries are practically identical 80 far as general machinery and arrangements are concerned; nevertheless, it happens, in particular localities, that the adoption of a combination of small improvements any one of which viewed separately may be of apparently little value, turns an unprofitable concern into a paying one.
At the end of each chapter will be found a carefully selected list of Memoirs in which fuller information can bt sought This will, it is hoped, prove a novel and useful
vi PREFACE.
feature in a treatise on coal-mining, for, scattered through the pages of the Transactions of the Mining Institutes, numerous valuable papers exist ; but, owing to the lack of general indexes, they are unfortunately not consulted so much as they deserve to be.
All the figures elucidating the text have been specially drawn for this work, the majority having been reduced from original working drawings.
In conclusion, I have to express my cordial thanks to the many friends who have rendered valuable help in the preparation of the work. Especially, I am indebted to Mr. B. H. Brough, Assoc. E.S.M., F.G.S., Mr. H. G. Graves, Assoc. B.S.M., and Mr. H. F. Bulman, for important suggestions and able assistance while the volume was passing through the press.
Herbert W. Hughes.
Conbygbb Collisbt, Dudlet,
September f 1892.
General Contents.
Chapter I. — Geology.
The Stadj of Geology . Rocks
Classes of Rocks
Aqueous and Metamorphic Rocks
Igneous Rocks.
Stratification .
Laminae
Intrusive Rocks
Induration
Fossilisation
Inclination of Strata . Faults
Reversed Faults
Trough Faults . Conformable and Unconformable
Strata Joints in Rocks .
Cleavage Order of Succession Carboniferous System in Britain
Fossils
Bibliography
Definition of Coal Formation of Coal Classification of Coal
Lignite
Bituminous Coal
Chapter II. — Coal.
lO
lo
Id
Steam Coal
Cannel Coal
Anthracite Commercial Value of Coal Gases Occluded in Coal
Chapter III. — Search for Coal.
Prospecting Boring
Choice of Site .
Various ApjUianccs used Boring
in
I) Clearing Instruments Levers . . . . (/) Spring Poles . Frames . . . . Devices Employed to meet Difficulties of Deep Boring (a) Lighter Rods . (6) Free-Falling Cutters
Obtaining Cores Special Methods of Boring (a) Mather and Piatt's Sys
tem (6) American System . (c) Diamond Boring Accidents in Boring (a) Accidents arising from the Boring Tools themselves (6) Accidents arising out of the Nature of the Ground
Lining 32
Widening Holes . -33
Withdrawal of Casing . 33
Record of Boring -34
VUl
Contents.
Chapter III, — Search for Coal — (contt7iued).
Pa.Ob
Pa.Ob
Coring—
Releasing Gas Proving Faults
Cost of Boring .
SarveyiDg Bore-holes
35
Steam and Rope-ways .
Uses of re-holes .
Bibliography
37
Tapping Water
Chapter
B
REARING Ground.
Contracts
Machines Worked by Electricity 7 1
Hastening Work .
Goolden
Tools Used .
39
Jeffrey.
72
Shovels
Van Depoele
Picks
Cost of Coal-cutting
Dressers .
Stanley's Heading Machine
74
Wedges .
Boring Cross Cuts .
Hammers .
Explosives
75
Gunpowder
75
Percussive Hand-tools
Nitro-glycerine
Scrapers
Dynamite
TampiDg or Ramming
Blasting Gelatine .
77
Hand Machine Drills
: tl
Gelatine-Dynamite .
Transmission of Power
Rackarock
Air
Blasting in Dry and Dusty Minei
Air Compressors .
Water Cartridge
Valves . . . .
Roburite
Dancing of Valves
54
Ardeer Powder
Conduits
Carbonite
Receivers . . . .
Tonite
Motors
55
Ammonite
Electricity . . . .
Firing the Charge
Alternating and Continnoui
Squibs, or Germans
Currents . . . .
Fuses
Terms Used .
Blasting by Electricity
Preventing Sparking .
Tension Fuses
Efficiency . . . .
:
Quantity Fuses
Power Machine Drills .
Comparison
IngersoU Drill . . . . Adelaide DriU .
Frictional Machines
Magneto-Machines .
Brandt's Drill . . . ,
Simultaneous Blasting
Supports
Bickford*s Volley Fuse .
Electric Percussive Drills
Position of Holes
Forms of Bits .
Blown-out Shots
Use of Water in Boring Holes Cost of Machine and Hand
Various Methods to supersede
Blasting Elliot Multiple Wedge .
Drilling . . . . Coal cutting &[ Machinery Machines Worked by Com-
Haswell Mechanical Coal-getter
pressed Air Gillot and Copley Rigg and Meiklejohn .
Burnett's Roller Wedge Hydraulic Wedges .
Lime Cartridges
Baird
Bosseyeuse
Harrison . . . .
Prohibition of Blasting
Ingersoll-Sergeant
Bibliography
.
Contents.
Chapter V. — Sixkixg.
Poation of Shaft ... 92 Form of Shaft 92 Siie of Shaft -93
Operation of Getting Down to ''Stone Head** ... 93 {a) Where the Ground is Modemtely
Hard -93
Method of ProceedingAfterwards 99
Keeping the Shaft vertical . 100
IHnding Debris .101
Covering over Pit-top .102
Guides 102
Lining Shafts 104
Number of Bricks Required 104
Mortar 105
Thickness of Brickwork . .105 Ordinazy Curbs . 106
Water Rings .
Wslling Stages
Supporting Curbs . Ventilation
Lighting Doding with Water . Keeping out Water by Tubbing
Coffering
Iron Tubbing .
Strength of Tubbing
Corrosion
Cost of Tubbing Sinking by Boring
Kind-Chaudron's Method
Lippmann*s Method Sinking through Quicksand
Triger*8 MeUiod
Poetsch's Method . Deepening Pits already Sunk Widening Shafts Cost of Sinking . Bibliography
no
"7
"7
Chapter VI. — Preuminart Operations.
Undeigronnd Roads . Means of Keeping Direction Means of Keeping Gradient Operation of Driving Ventilation bnjTOorting Roof. Tunbering Joints .
Chocks or Cogs . -135
Double Timbering .136
Driving through Loose Ground 136
Iron and Steel Supports . -137
Masonry 140
Arrangement of Inset . -145
Bibliography . . .148
Chapter VII. — Methods of Working.
The Two Main Systems tthaft Pillar and Subsidence Arrangement of Labour Bord and Pillar Working . lAncashire Method liongwall Method Doable Stall Method . Worlung Steep Seams Working Thick Seams— South Staffordshire
Fennsjlvania . . . . Working Seams Ijing near
Together Spontaneous Combustion {a) Oxidation of the Organic Constituents
(c) Friction from Slippings Development . Prevention
Bibliography
Contents.
Chapteb VIII. — Haulage.
Primitive Methods Rails .
Length of Rails
Gauge
Method of Laying Rails
Fish-Plates
Sleepers Wood Iron Steel
Switches Plates Turntables Tubs .
Bodies
Frames
Height
Size.
Wheels and Axles
Drawbars
Pedestals
Lubi ication Haulaee bj Horses
Feeding
Cost of Feeding
Cost and Life of Horses
Cost of Com-cutting Ostlers
Shoeing
Arrangement of Stables
Cost of Horse Haulage Self-acting inclines
Arrangement of Rails
Blocks or Stops
Drums and Pulleys .
Brakes
Rollers
Junctions
and
i7S
Transmission of Power Compressed Air Electricity Different Systems of Haulage Direct Acting Haulage
Size of Ennes Required Main and Tail-rope Haulage Devices for throwing Drums In and Out of Gear .
Methodsof Working Branches 201
Endless Chain.
Attachment of Tubs
Driving Pulleys
Taking up Slack .
Working Branches and Curves
Minimising Breakages Endless Rope Haulage
Jt) C-pulleys . ) Grooved Pulleys ing Up Slack Rope Clutches for Working
Branches . Brakes for Branches Arrangement of Tubs . One or Two Road Systems Rails at Junctions Clips Clips for Under Haulage Clips for Over Haulage Automatic Detachers Threading the Rope Comparison . Locomotives . Electric Locomotives Bibliography
>9S
Chapter IX. — Winding.
Pit Frames 229
Wood 231
Iron 233
Pulleys 233
Skips and Cages 234
Shape and Construction . . 234 Means for Keeping Tubs on
Cages 239
Ropes 236
Wire Ropes 237
Attachment to Cage . 239
Cage Chains 240
Method of Taking off Strain . 241
Guides 243
Rails 243
Wire Ropes Conductors between Cages Guide Shoes Guide Troughs . Engines
Position of Engine-house Drums Brakes Counterbalancing
Tapering Ropes
Flat Ropes
Conical and Spiral Drums
Tail Rope beneath Cages
Meinicke's System Expansion . . .
CONTENTS. Chapter IX. — WmDiso—{oontinued).
BloDcheC Pneumatic System
Koepe Sjstem . Preveatigu of Over-winding
C&takes at Pit Top Changing Tabi .
Fencing the Pit Top Tab -controllers . Signalling . Bibliography-
Chaptee X. — Pdmi
Bucket Pamps Plunger PnmpB
Hollow PloQgerB Stocks or Trees . Joints. Bapportlng Pipes in Shaft Spear Rods . Guiding the Rods Counterbalancing Connections to Itodii .
Quadrants . 8uBpDded LirtB . Cornish Pumping Engine Bull Kngine
Davey Differential Engine . Direct -acting Steam Punipa Worthington Pumps . Pumps for Sinking Arrangement of Supply-plpeg, i Air Veasels,
Condensing Arrangements . (.alculationH as to Size of Pom] Effect of Acid Water . Draining Deep Worlcinga .
Hydraulic Power Moore's Arrangement .
Electricity
I'uLsometer
Blbliograpbj
CS AFTER XI. — VeSTILATIOX.
Walker - . . .
Quantity of Air .
Walker's Shutter .
Gases Uet with in Uinex .
Driving bv Straps and Ropes
Carbonic Acid
3U
CaiboDtc Oxide
Sulphuretted Hydrogen . Light Carburetwd Hydrtn
Effect
Effioienoy of Pans ,
After-damp .
31S
CoaI.dQ9t ... -
Fans
Action ol Moisture .
Laws of FHciioD.
34
Doors
Nataral Ventilation
37
Regalating Doors .
Kumace Ventilation
37
Air Crossings
Loss In Ciroulation .
Measurement of Air Ourrents
Quibol.
Waddle
Barometer and Thermometer .
Schiele
Water Guugea
Cookson
Bibliographv
xu
Contents.
Chaftbb XII. — Lighting.
Naked Lights Safety Lamps
Davy's Invention
Clanny .
Stephenson
Maeseler .
Design of Lamps Modern Lamps .
Hepplewhite-Gray
Bonneted Maeseler
Ashworth's Maeseler
Morgan .
Marsaut .
Defleotor .
Tin-can Davy
Thomeharry
Sight Lamp Conclusions Oil .
Wick . Glasses Looking Lamps .
Magnetic Looks '
Leful Rivets
Ryder's Lock .
Casting Rivets Relighting Lamps Cleaning Lamps . Electric Light Underground
Secondary Batteries
Primary Batteries Delicate Indicators
Pieler Lamp .
Ashworth*s Lamp
Coloured Glass
Liveing*s Indicator Bibliography
Paob
ChAPTEB XIII. — WORKS AT SURFACB.
Boilers
Mechanical Stoking Coal Conveyors .
Coating Steam Pipes Workshops .
Chapter XIY. — PasPABATioir of Coal for Market.
General Considerations Circulation of Tubs Tipplers
Front Tipplers
Back Tipplers .
Side Tipplers .
Duplex Tippler Screens
Movable Bar Screens
Jigfi Screens Revolving Screens Spiral Screens . Greenwell's Screen Varying the Sizes Screens . Plating Combs . Variable Crossbars Belts . Revolving Tables
made by
Loading Shoots . Typical Illustrations .
Pemberton Colliery .
Brinsop Hall Colliery
Hilda Colliery .
Hewlett Pit
Aniche Colliery, France
No. 5 Pit, Basooup .
Cross Creek Collieries, sylvania Coal Washing
Sizing Apparatus
Trough Washers
Robinson's Washer .
Copp Machine
Conclusions Dry Coal Cleaning Briquettes . BibUography
Penn-
Index
Abbreviations.
Thb follovdng abbreviations have been used to denote the publications most frequently quoted in this work.
The Boman numerals designate the volume, and the ordinary figures the page. For. Abs. Foreign Abstracts.
so. WALES INST.
Soc. Ind. Min.
Ches. Inst. .
Fed. Inst. .
Bbit. Soc. Min. Stud.
N. Staff. Inst. .
Inst. O. B. .
Ameb. Inst. M. E.
Man. Geo. Soc. .
Eng. And Min. Joub. . 80. Staff. Inst. .
Bey. Univ. . Min. Inst. Scot. Mid. Inst. .
Ann. Des Mines .
Transactions of the South Wales Institute of Engineers.
Bulletin de la Socite de I'lndastrie Minerale de Saint Etienne.
Transactions of the Chesterfield and Midland Counties Institution of Engineers.
Transactions of the Federated Institution of Mining Engineers.
Journal of the British Society of Mining Students.
Transactions of the North of England Institute of Mining and Mechanical Eneers.
Transactions of the North Staffordshire Institute of Mining and Mechanical Engineers.
Minutes of Proceedings of the Institution of Cinl Engineers.
Transactions of the American Institute of Mining Engineers.
Transactions of the Manchester Geological Society.
The Engineering and Mining Journal, New York.
Transactions of the South Staffordshire and East Worcestershire Institute of Mining Engeers.
Revue Universelle des Mines.
Transactions of the Mining Institute of Scotland.
Transactions of the Midland Institute of Mining, Civil, and Mechanical Engineers.
Annales des Mines.
Text-Book Of Coal-Mining.
Chapter I.
Geology.
/ of Geology mny \te divided into two parts, which trent of inorganic matter, the laws to whii-h such mutter is subject, and the chemical and physical changes through which the crust of the earth has paseil ; the other deals with mid iavestigatee the order, character, and succession of organic life, and the relation which the varioiiH forms bear to each other. As no written records exist, which go back to the remote times when life Snit existed on our globe, the geologist has interpreted the changes which hive taken place by careful observations of phenomena met with; and as histories of extinct races have been built up from the interpretation of hieroglyphics on monuments, so by similar results has the order of succession of geological strata been established from observations of the life forms preserved in a foil fitat in the rocks which constitute the crust of the earth.
Books. — By this term is meant, not only large masses of coherent miittr,as limestone, which build up mountains, but also the soft and loose gravels, or clay, which are found nuEOciated with them.
Claaaea of Rocks. — Rocks are divided into tbi'ee classes — aqueous or stratified, metauiorphic. and igneous or ejected.
Aqueous and Hetamorptaic Books. — These are made up of regular beds, or strata, and are probably all produced from the denudation uf igneous i-ocks, although they appear to differ p-eatly from them. The great agent of disintegration is the atmosphere, and the rain which is precipitated from it.
IgDOOUB Books. — These rocks may be broadly divided into four divisions, according to the quantity of silica they contain, tlrsti they are separated into acid and basic ; a third class is formed
2 Text-Book Of Coal-Mining.
of rocks containing an intermediate amount of Bilica ; while last of there is a small, but important, class called " ultra-basic." the acid type, (nntaining on an average about 74 per cent, silica, belong granite and porphjiy ; white the basic type, containing an average of 50 per cent, silica, is represented by gabbro and basalts. The intermediate class (syenite, diorite, and some obaidians) contain 00 an average 60 per cent, silica {the ultra-basic, 39 per cent, silica) and a hit;h proportion of alkaline earths and oside of iron. viirieties are common in the acid series, rarer in the interraedinte setiea, and still rarer in the basic
Stratifleation. — When the fi'agmenta are large, the stratification, or bedding, is vei-y imperfect, but if the pai-ticlen are small, it ' Ls very perfect.
Lamlnee. — When we have verjclose stratification, and get the thinnest paper-like layers in the planes of deposit of a stratified rock, it is said to be laminated.
IntruaiTB Books. These are sometimes great raoiwes forced up through the surrounding strata in no definite direction, or frequently, intrusive matter is forced along definite planes, forming dj/kea, where the sides are fairly parallel ; a good example of thi& is the great whin-dyke of the fi'orth of England coal-field, which proceeds nearly ninety miles in a straight line. Theee intrusions were originally forced into their present paiition in a molten condition, evidence of which afforded by the way they hav altered the adjoining Htrata, coal seams in many instances being charred and rendered worthless for several yards on either side. It may happen that only the upper side of the stratified rocks below the igneous bed will show signs of baking, fi-om which it is seen tliat the lava-flow was contemporaneous or interbedded with the rocks, while, if both the upper and lower surfaces of the beds ore afiected, the lava-bed was certainly intrusive.
The rocks of the globe present very different appearances to th& gravels and sands which are formed every day on our sea-shores and at the mouth of rivers. All the sti-ratified rocks have been originally deposited in a manner similar to that now going on, but changes have taken plne in them subsequent to formation.
I . Induration. — In the depths of the earth's crust, by the longcontinued pressure of " miles " of strata above a bed composed of finely divided particles, the effect is very great. In this way, muds pass into finely laminated clays, and finally into shales. The effect of induiation is well ehown in the white limestone of Antrim, which was originally formed in the same manner as the English chalk, but, owing to the superposition of at least jooo feet of basalt, has been hardened into a hard splintery rock, showing no trace of chemical action. Induration is, however, greatly aided by chemical action, the particles forming the rock being cemented together by substances deposited from boIu-
tion in water. At great depths the rocks are iindoubteilly saturated with water, and this facilittca the deposition of materials round the rock particles, or, as in the case of limestoueei, Ac., the solution of some of the rock materials themselves, which are afterwards crystnlh'sed out from their solution in the water. Disintegration usually undocii all this work ; the cementing material first fields, is removed, and the particles of the rock are set free again.
I. Segregation. — Again, aegregatiou may be going on, particles of the i-ock separating from the remainder and segregating together, this being especially well seen in limestone cont&iniug silica ; the pailieles of silica are drawn together by tliia action, forming the flints and cherts of the chalk.
FoBsiliaation.— Thi-s is merely a case of segregation round organic matter. In many clay ironstones, the nodules of iron have been formed by the segregation of the mioei'al round fossil remains, and, on breaking open the nodule, the fossil is found in.-iide, generally in a beautiful state of preservation.
laclination of Strata. — Generally speaking, sti'ata were laid down in a horizontal position, this being shown by the lie of pebbles in rocks, and by the position of fossil treea. It is, however, very rare to tind the beds retaining thispositiDn, though the folding may be of the slightest. If a bed is at all inclined, it must reach the surface somewhere, and the space where this happens is said to be the auUrop of the bed. The nature of the outcrop and its width, depend on the thickness of the bed and the degree of inclination ; it cannot be leas than the thickness of the bed, and is wider, the smaller the angle of inclination.
In order to define a bed, two things must Iw known— first, the direction in which the inclined bed reaches the surface, and the inclination of the bed. The angle which beds make with the horiKon is called the dip, and the hne in a horizontal plane, the strike, the latter necessarily being at right angles to the dip. When the surface of the ground is horixontal, the lines of outcrop and strike coincide, but, if the strata are inclined, the outcrop is inclined also ; the strike is always hori.ontAl. Angles of dip are usually measured by an instrument called a clinometer, but, iji doing this, care must bo taken to distinguish between the true and apparent inclination ; the latter can never be greater than the former, Fio. t.
but it may be less to any amount.
When the strata are bent in arches, they are said to have a synclinal fold, when the arch is downwards ; an anticlinal, when the arch is upwards (Fig. i); when the folds are small, they are called trooghs and saddles respectively.
Vaults. — When the preeaure is too great, or is apphed suddenly.
4 Text-Book Op Coal-Mintno.
or if the Toch refiuwie to yield, and then bre&ks, instead of bending; ' K difllocatiou is obtained ; the divided segmente ai* thrown out of level, and do not fit, one side being higher than the other. This is called 8 fault. In raining districta, euch trm is applied loosely to anything which interferes with the Beams that are being worked. Generally Speaking, when contortions of the strata are niuneiflus, faults are few ; and wee versA. The position of every fault is defined by two directions, as in the case of beds : the strike of & fault is spoken of, but, in the place of the word " dip." the term hade is employed, this being, however, the inclination measui'ed from the wrtieal. To determine a fault accurately, it is necessary to know two other things — (i) which side is throw-up, nnd which is throw-down ; (2) the amount of displacement. The former is in the majority of instances easily determined, as faults usually hade or incline towards the down-throw, so that in driving roads under ground, if the fault is first met with in the roof it is a downthrow, while if struck on the floor first, it is an up-throw. Again, rockfl before breaking usually yield to bending a little, and such signs are very useful to the miner, especially where the hade of fault is nearly vertical (Fig. 2).
' No rule can give the amount of displacement, as sometimes, when the hade is small, the throw is large, and at other times, with a similar hade, the displacement is smalt. The throw of faults is always measured vertically, and may be variable at different points, often chiinging fi-om a few feet at one end to hundreds of yards at the other. In addition, there ia often a variation in the throw of the same fault at different levels. When the amount is small, they are called hitches, troubles, or sUps.
Beversed PaultB. — It has been obseiTed above, that ordinaryfaults incline to the down-throw, but in rare instances they incUna towards the upthrow, and are then said to overlap or I'reversed faults (Fig. 3). The most noteworthy of this class in our own coimtry, is the overlap fault of the Somei-set coal-field, which occurs in the Countess WaldegiBve's colliery at Ejidstock ; by it, the seams of coal are doubled for a breadth of about 150 yards, the alteration ia level .imountiog to 44 yards. The dislocated walls of a. fault are often in contact with each other, but frequently, especially when the beds are of varying hardness, ajwices are left between tilled with broken fragments which have been removed from the adjoining rocks. The distance across a fault may therefore vary from a few feet to many
When the rocks are very hard and the fault is a clean-cut one, we get a remarkable polisliing of the sides, known as " slickensides,"
tio. 3.
caused by the eiiormoufi pressure of the rocks od ea'h other during the displitcement of the beds.
Trough Faults.— These are caused by two faults, enoh haWng a down-throw ton-ards the other. A very good example of this is the Dudley Port Trough Fault, of the South Stafibrdshii-e coal-field (Fig. 4). Here two 4-
fault are separated from each other by half a mile — -one a down-throw to the south, and the other a down-throw to the north. Each hades towards the other, sd that they meet at no great depth, and, as the throw is eijunl and opposite at the point of meeting, no dislocation takes place.
Conformable and TTnconformable Strata — Subsidence has taken place in nil times, but when this action waa uniform, bed succeeded bed in regular order, and prmhiced what are called conformable strata (Fig, g). When, however, the beds were tilled up before the succeeding layer was deposited on them, or, as in many
Fig. s- Fig. 6.
instances, the older beds were in addition ilenuded or worn away, the strata are said to be unconformable to each other (Kg, 6).
Joints inBocka. — The bedding of a rock is produced during deposition, but there are other jarallel struutares produced by forces acting ou it subttequent to formation. Une system of divisional planes rimning through most stratified rocks, and which isentii-ely indejiendent of the bedding, is that called jotiite. There are genei-ally two systems of joints at right angles to each other, one better developed than the other, the first being called the master joints, and the other the secondary joints. These joints tend to break up what would otherwise be a continuous mass into rectangular blocks. Sandstones, gi'antics, and rocks which do not easily undergo solution in water have closed joints, while limestones, ibc, which are easily soluble, have open joints. The force which produced those divisional planes must have been very great, for pebbles of quart?, lying in the du'ection of the joint planes are always found split right through. Not oi>)v mentary rocks exhibit jointing, but some igneous ? possess this structure in a marked degree. O
6 Of Coal-Mining.
are very irregular, but many igneous rocks, especially basalts* have developed columnar jointing. The reason for a rock splitting into columnar structure is not hard to discover ; a mass of fused matter, on cooling down, tends to split, and, if of large extent, has no special form to follow, and therefore divides into the easiest forms, either the triangle, square, or hexagon. Three cracks only are required for the latter, so hexagonal columns are generally found.
The divisional planes, called decU by the miner, which run through coal nearly at right angles to each other, and subdivide it into rectangular fragments of varying size, are referable to jointing, but it differs from ordinary jointing, inasmuch as it is carried to small subdivisions.
Cleavage. — Under the influence of great pressure, the particles of which a rock is composed, which usually have a long and short axis, tend to re-arrange themselves along the line of least resistance, thereby imparting to the rock a fissile structure, known to the geologist as cleavage, extending over large areas. Coarsely grained rocks never exhibit cleavage; it is best developed in argillaceous rocks, altered clays, and shales. As a rule, when a rock is cleaved, it loses its power of splitting along the bedding, the latter being completely obliterated by the force which produced the cleavage. Nodules and fossils which are included in cleaved rocks, are altered and distorted in a curious manner.
The order of succession has been divided into four great divisions — (i) archan ; (2) pakeozoic, or primary ; (3) mesozoic, or secondary ; and (4) cainozoic, or tertiary ; to which is sometimes added the quaternary, or recent. These divisions are split up into systems, each system into formations, which usually receive the name of places where they are well developed, and, finally, the formations are subdivided into beds, characterised in many instances by certain fossUs being always associated with them.
The following summary shows the classification at present adopted : —
I Post-pliocene. Pliocene. Miocene. Oligocene. Eocene.
Mesozoio,
Ob
'Cretaceous. Jurassic.
Permian, or dyas.
Cambrian. Aboh.£AN.— Crystalline rocks, schists, &c.
Upper, middle, and lower coal measures. Millstone grit. Carboniferous limestone.
Geology. 7
It iniiat be observed, that these formations i-arely succeed each other in the regular oixJer given ; breaks occur, catieed by metnmorphimn and denudation, or by original non-depoeition owing to local circumfitacces, and only by observations at numerouti places hoA the order of succession been established.
The coal-miner is more iuterestid in the carbouiFemiis formation, that being the one in which beds of coiU occur to the greatest extnt all over the globe. In this countty, with one or two small and rare exceptions, the whole of the coal mined is extracted from beds of the carboniferous strata. The greater part of the coal measures of Europe and the United Slates also belongs to the carboniferous but in the latter country large deposits of coal in the cretitceous formation, while a, large portion of the New South Wales conl belongs to the tnassic.
Carboniferous System in BritBin.This is divided into the fallowing members :— (i) The Coal Measures, consisting of boils of shale and sandstone varying in thickness fi-om loo to t3oo feet, Aud containing numerous heds of coal. The coal measures proper, may be further subdivided into upper, middle, and lower divieioaB, each of which possesses chai-acters moi-e or less peculiai* to it ; no fiharp line of demarcation has, however, been yet satisfactorily estdtblished between them, each passing insensibly into the other. One peculiarity of the upper coal measures is worth noticing — namely, the occurrence in them of thin beds of a fresh-water limestone, cont&iningimmense numbers of Hgmall shell called theiSror- Am dirbmutriua, from which the beds are called spirorbia limestone. (2) The Millstone Grit, consisting of coarse sandstones. This rt'ceived, in the Sooth of England, the name of the " farewell rock," as it contains no coal seams in that paj-t of the country. Thin rule, however, does not apply to every distnct, as, in the North of England and in Scotland, beds of coal and shale are found. (3) The Carbmuj'erotic Lttiuatone contains in Scotland thin beds of coal. This portion of the carboniferous system is built np of thick beds of limestone of marine origin, full of the remains of animal life.
Fossils. — The coal measui-es contain in varied abundance the remains of luxuriant vegetation. As an example, may be cited the occurreace of the plant known to tbe geologist as Ltpidodendron, which attained dimensions of fi'ora 40 to 6a feet high, and severai feet diameter. This plant is allied to the lowly club-moss of the present time, whose height does not excel a few inches. Another example that may be referred to, is the jointed and Hnted stems calleil Calamileg, repi-oriented in our iields and uiarshes by the equisetiita, or hore-taii. Portions of ferns are very abundant, some of which attained enormous dimensions. Remains of the stalks (rachis) of ferns have been met with, measuring in their compressed state 5 feet ar 'Eury describes the frond of a fern
measuring ' classification of these ferns has
8 Text-Book Of Coal-Mining.
always presented difficulties to the botanist, owing to the fragmentary manner in which they are found, but recent researches of Williamson and Kidston in our own country, Grand 'Eury, Schimper, Zeiller, and Stur on the Continent, and Dawson and Lesquereux in America, have greatly extended our knowledge of a most fascinating branch of geology, and one in which the mining student is most directly interested. A knowledge of the flora of the coal measures is essential to any one searching unknown districts for indications as to coal-bearing rocks, and it is not too much to say, that vast sums of money have been thrown away in fruitless attempts to prove coal to exist, where a little knowledge of the fossils of the carboniferous formation would have at once shown the uselessness of any search. The classification of these ferns has until lately been quite arbitrary, form of leaf and arrangement of nerves, being the points usually relied on. Living ferns are referred to their several classes, by the arrangement of their fructifications, which are usually borne in small rounded dots, called sori, on the back of the leaflets. Much knowledge has recently been gained of the fructifications of fossil plants, and hence a more reliable classification is the result.
Bibliography. — The following is a list of the more important memoirs dealing with the subject-matter of this chapter : —
Ttie Coalfields of Cheat Britain, E. Hull, 4th Edition, London, 1881.
N. K. I. : Tke Northern end of the Bristol Coalfield, H. Cossham, x. 07 ; Coal Mining, dbc, N. Wood, J. Taylor, and J. Marley, xii. 149 ; 2 he South Wake Coalfield J T. Forster Brown, xxiii. 197 ; The Larger Divisions of the Carboniferous System in Northumberlafid, G. A. Lebour, xxv. 225 ; The Carboniferous Bocks of Cumberland and North Lancashire, J. D. Kendall, xxxiv. 12$; A Further Attempt for the Correlation of the Coal Seams of the Carboniferous Formation of the North of England, M. Walton Brown, xxxvii. 3.
so. WALKS. INST. : The Southern portion of the Somersetshire Coalfield G. C. Greenweli, i. 147 ; Some of the Geological Problems in the Bristol Coalfield, H. Cossham, xii. S4 ; Tlte Somersetshire Coalfield, J. McMurtrie, xii. 424.
CHES. INST. : Economic Geology of Derbyshire, A. H. Stokes, vi. 60 ; Geology of the South Derbyshire and Rout Leicestershire Coalfields, G. 8. Bragge, xv. 198.
FED. INST. : The Geology of the Southern portion of the Yorkshire Coalfield, R. Russell, i. 123 ; On the Coalfield mjoininp Barnsley, R. Miller, ii. 7 ; A Geological SketcJi of tlie Toim and District of Nottingham, G. Lewis, ii. 22 ; Sketch of the Geology of the Birmingham District, C. Lapwortb, iii. 10 ; A General Description of the South Staffordshire Coalfield Simth of the Bentley Fault, W, F. Clark and H. W. Hughes, iii. 25 ; 17ie Northern Fart of the South Staffordshire Coalfield, A. Sopwitn, iii. 50;
BHIT. 8OC. MIN. STUD. : Forest of Dean Coalfield, H. R. Insole and C. Z. Running, vi. 61 ; A Month'tt Visit to the North Staffordshire Coalfield, A. W. Grazebrook, xiii. 127.
Chapter Ii.
Coal.
Definition of CoaL — The question, " What is coal ? " appears a very simple one to answer, but that such not the case, was proreil by the now historicsllawsuit over theTorbane Hill miuerol in 1S53. liie owners of the Torbane Hill estate had leased all coal contained in it, and in the course of working, the lessees extracted a combustible material containing a huge amount of gas. The lessor claimed that tKis minei'al was not coal, and disputed the right of the leases to work it. A trial resulted, and geologists, chemists, Mid gae engineers gave evidence on both sideH. In summing up, the judge remarked, that "to find uHcientilic definition, after what hae been brought to light within the laat few diiya, ta impossible." For our purpose, coal uiay be deliiied as a solid stratified substance, capable of undergoing combustion in contact with oxygon, not containing sufficient earthy impurities to prevent its being applied as a source of heat in Furnaces and fii-places, and varying' in colour from brown to black.
Formation of Coal. — liowever much geologists may ditTer as to the question whether coal was formed on the spot on which the forests that produced it grew, or whether it resulted from the iiccumulatiou of drift, every one agrees that it results from the decomposition of vegetable matter. The hypotheiits most generally accepted is the former, although it is perfectly clear that in a few isolated instances small areius of coal have Iteen formed by organic matter drifted into lakes. The common-seuae view, that the land became submerged at intervals, and that the uudei-claj-s of coal seaiaa form the beds on which the plants originally grew, is the great argument in favour of the in situ theory, as it is an everyday occurrence to find tiie roots of trees firmly embedded in tDe underclay. Exposed to thf action of the atmosphere, vegetation decays and goes to enrich the soil, but supposing that the organic material fell into water, decay is incomplete, layer would deposited on layer, and under pressure deDoeite of cool aiv formed. In peat bogs, for instance, living the aui'facu,
lower down the forms of plantM while the
bottom portion ii; very com can
lO
Text-Book Of Coal-Mining.
scarcely be distingiiished ; as we go deeper in the mass the quantity of carbon increases. The conversion of woody tissue into coal takes place by the elimination of oxygen, which combines with carbon to form carbonic acid gas, and by the separation of carburetted hydrogen fire damp " of the miner) and water. To illustrate the gradual change in composition in passing from wood to anthracite coal, Dr. Percy gives the following table, the proportion of carbon being estimated at the constant amount of I GO : —
Substance.
Carbon.
Hydrogen.
Oxjgen.
DUpotabUi Hydrogen.
Wood (the mean of several analyses Peat „ „ „ „ Idgnite , 15 varieties . . Ten-yard coal of SonthStaffordshire Steam coal from the Tyne . . . Anthracite coal from Penn., U.S. A.
Note. — Certain bodies existing in Nature are composed of substances that cannot be resolved into any simpler form, these being called dementB by chemists, and designated by symbolic abbreviations. The smallest indivisible parts of these elements are called atoms, and these, by combinion with each other, form the substances occurring in Nature. The number of atoms of each element comprised in any substance, is shown in chemical formulsB, by a number following the symbol of each element. Thus, water contains one atom of oxygen and two of hydrogen, its chemical symbol being H,0.
Classifloation of Coals. — The classification of the various coals occurring in the sedimentary rocks is best done by dividing them into heads according to the relation between the proportions of carbon and oxygen. In this manner, is obtained (i) Lignite, (2) Bituminous Coal, (3) Steam Coal, (4) Cannel, (5) Anthracite.
1. Lignite, — Found in our own country at Bovey Tracey, in Devonshire. Some varieties show distinct woody texture, while others are structureless. They contain a large proportion of water, bum with a disagreeable odour, and are brown in colour. Lignite coal contains about 67 per cent of carbon and 26 per cent, of oxygen. A subdivision of the class is sometimes made, called proton coal, which contains a larger proportion of carbon and less oxygen than the true Lignites. They occur in large quantities on the Continent and in some of our colonies, an analysis of brown coal from New Zealand showing, carbon 72.2, oxygen 22.4, hydrogen 5.4.
2. Bitumiruyua Coal, — The proportion of carbon in this class varies from 75 to 90, and the oxygen from 6 to 19, They bum
Coal. 1 1
with a more or less smoky flame, antl are largely used for household purposes. As the pi-oportion of oxygen decreases, the coal gets blacker and less aonoi-ous, and the fiiabUity increases. The bituminoua class of coals, may be further subdivided into noncaking and caking varieties : the former, when burnt, up into fragmentfi, while the latter soften on the fire and swell up, the particles bind together, and form a pasty mass. This property is an extremely valuable one, and from this class of coal are made great quantities of coke. The small pieces are heated together in a suitable oven to a certain tempeiature, and when the mass is withdrawn and cooled, a. hard glistening mass is obtained, in which all form of the original particles is lotta. It has never been established, to what this property of caking is due, but it is certain that tUtimatc analysis forms no guide. M. Gruner gives the following analyses of two coals :
Carbon .
Hydrogen .
OKjgen.
'. i6
Aah . . .
Water .
S-4
These coals are nearly identical in composition, but while (a) cakes, (b) does not. Chemists can determine the amounts of the various elements present in coal, but are quite unable to say how tbeee elements are combined amongiit themselves, thew intenial combinations being the probable explanation of the different bebaviouis of coals of the same ultimate analysis. For commercial purposes, proximate analysis is all that is reiiuired, this giving us the amount of filed carbon (coke), volatile matters, and the amount of impurities. There appears to be no mle for determining the caking (qualities of a coal, except actual experiment, as this property is possessed by coals differing widely in composition. It appears to be influenced by the method of conducting the experiment; thus, in some cases rapid heating will cakea non-caking coal. The amount of ash present doc not seem to influence the result, as examples are known of a caking coal containing 30 per cent, of ash. On the other hand, many coals lose their power of caking fay long expoeiire to the air.
(3) Steam CoaU. — Thee ore principally worked in the South Wales and North of England coal-fields. As their name denotes, they are mainly used for the production of steam ; their evapcaative power is high and they give off scarcely any smoke in burning, white on account of their etructiir, they bum more readily than anthracite.
(4) Cannd Coal. — The chief deposits of this claws occur in the Lancashire and Scotch 'dii. CaDnel is very rich in hydnigeu, and is tr wtion of gas, as it yields by deeitractive di L. of volatile matten.
I a TBXT-BOOK OF COAL-MINING.
It is verjr hard, decree, and structureleee, and is eometimes used for the manufacture of omamenta. In this division of ooala may be included certain Bhalee, contaioinf; large quantitioB of bituminouB matter, which on distillation yield liquid and solid paraffin. The Boghead cannel, over which the celebrated trial took place, may be coneiderod the representative of this type.
(5) AttthracUe. — The darker and denser varieties of ordinary coal gradually pass into the anthnicitic varietiee, which are characterised by the large amount of carbon they contain. They do not soil the fingers, are very hard, and break with a conchoidal fracture. The formation of anthtncite has probably been effected by the alteration of bituminous coals under heat and pressure. In the South Wales coal-field, the same seam of coal, which is of the ordinary bituminous variety in the eastern district, posse by gradations into steam coal in the middle of the coalfield, while in the western district it is changed into anthracite. Enormous deposits of this class of coat are met with in Pennsylvania, our own store being confined to South Wales. Anthracite contains from 93 to 95 per cent, carbon, 4 to 3 per cent, hydrogen, and 3 per cent, oxygen. It is practically smokelets when burning, and is much used where sunh a property is valuable, as, for instance, in malt-drying and in some metallurgical opemtions. The ooke is brittle and useless for commercial purposes.
The following table* (p. 13) shows the percentage composition of different classes of coal.
Commerolal Taloe of Coals. — The value of coal as fuel depends chiefly on the Calorific Potetr, which is the total heat developed by combustion, expressed either in units of heat or of evaporation, and by the amount of ash and impuntiee present.
In detennining the calorific power of fuels, the same difficulty is met with, as in judging of the caking properties. The composition, and the units of heat developed by the combustion of each component of the coal, being known, the theoretical calorific power can be easily determined, but, as before, we neither know how the various elements are combined together, nor what quantities of heat appear or disappear during the breaking up of the complicated compounds of which coals are composed. Direct experiment is resorted to for the actual calorific power, the operation being performed in an instrument called a calorimeUr. The most convenient of these for practical purposes, is the one designed by Mr. I.ewis Thompson, which consittts of a glass vessel (a. Fig. 7) containing a known quantity of water.
Compiled ttom Dr. Percy's MetaUurffg C'"*'. >c.), London, 1875.
Fia. 7.
llt'JltllHI'll",
;5l?fr5li?sJlpK
5 1 3 f 1 5 1 1 2 1 1 3 1 1 f 1 !
Bovey Trace, Devonshire . Bodonspatak, HuDgarj Auckland, New Zealand
Northumberland . Aberdare, South Wales Mertbjr, South Wales Llwynypia, tSoutb Wales
Aix-la-Chapetle .
Wigan
" Lesmahago," Scotland
'BogbeadP' Edinburgh
South Wales
South Wale, near Swansea
Pennsylvania .
It
J-
"3 Sw
Text-Book Of Coal-Mining.
A weighed invariable quantity of the ooal to be with, is intimately mixed in a mortar with about ten times its weight of a mixture of three parts potassic chlorate and one of potassic nitrate. This mixture is placed in a small copper cylinder b, which in its turn is covered with another copper vessel c, furnished with a tube and stopcock d on the upper side, and pierced with holes e on the lower end. A fuse is placed in the smaller cylinder containing the mixture, this is lighted, the stopcock closed, and the apparatus let down to the bottom of the graduated flask containing the water. When combustion has ceased, the stop-cock is opened and the apparatus is moved gently up and down, care being taken not to raise it out of the water. The temperature is noted at the beginning and end of the experiment, and from a table supplied with each instrument, the calorific power is found. The rise of the temperature, plus lo per cent, of this rise, will give the number of lbs. of water which I lb. of coal will convert into steam from and at F. The importance of calorific power is not at all understood by consumers. One coal may be obtained for a less price than another, but if the lower-priced coal has less calorific power than the other one, the consumer may not be obtaining the best value for his money. Coals rich in oxygen never have such high calorific powers as those containing a smaller amount, as the quantity of hydrogen available for heating purposes in any fuel, is not the total amount of that element present, but only that portion of it (called disposable hydrogen) which is in excess of the quantity required to form water with the oxygen contained in the coal. The amount of disposable hydrogen in any coal can be ascertained, when its composition is known, by dividing the quantity of oxygen present by 8 and subtracting the result obtained from the total quantity of hydrogen present, the remainder being the disposable hydrogen. Calorific powers of a few coals are given in the following table :
Locality.
tret fhim Aab.
Toala, Russia . Manosque, Basses Alpes , France and Germany England .
Basin of Donetz, Russia Le Creusot, France .
Basin of Donetz, Russia .
Lignite
n
Brown coal Caking coal
n
Anthracite
The ash of coals is the substance remaining when total combus- CodLj Us Hiitary and Uses, 1878, p. 250.
Coal. 15
tioa hns been effected. It is composed of the earthy impurities originally present in the coal, and may be easily determined by burning a weighed quantity of coal in a porcelain eniciiile, either over a Buneen gaB-bumer, or in a muffle. It ia important that not only the quantil'j of ash should be deterrainetl, but also its nature. Some ashes tend to fuse together and form " clinker," which ia very objectionable ; more attention is required from the stoker, as he has to be continually stirring up the fire, and even n-hen this is done thoroughly, the di-anght is materially interfered with, and imperfect combustion is likely to take place. Goal may contain such a large proportion of ash as to be practically worthless as a fuel. The amount of iron pyrites present has also a great effect on the nature of ajh, as fusion is assisted and a tendency to form clinker results. Sulphur, too, which is contained in pyritee, is very objectionable in some metallurgical operations.
Oasea occluded in Cool. — The majority of coals contain various gases, which are given off when exposed to the atmosphere. Generally this takes place slowly, and may be observed by the singing noted at the working places in fiery seams of coal, or by the sudden outbursts of gas which are known to the miner by the name of " blowers." Certain coals of a porous structure readily yield up the gases contained in them, while other-s of a denser character, although containing even more gns stored in them, do not discharge it in Buch quantities. In vacuo, and under the influence of a gentle heat, coals readily diharga the gases they contain. Mr. J. W. Thomas* baa made a series of experiments on this subject which throw a great deal of light on the question. He finds that the gases occluded from bituminous coals consist mainly of carbonic acid, and that the quantity yielded is very much smaller than that given oil' by the stam and anthracitic varieties. Steam coals evolve a large quantity of gas, the chief component of which is marsh gas, which in some instances reaches as high as 87 per cent. Anthracites yield by far the largest volume of gas, with a composition closely resembling that from steam coal. The following table (p. 16) shows the quantities of gas evolved from coal at 100" C. (212° F.) in vacuo, and its percentage composition.
Mr. Thomas points out, that these results were obtained in a laboratory, and that it must not be supposed that coals which contain the greatest quantity of gas in their pores are the most dangerous to work, the rate of discharge being controlled, as has been before pointed out, by the structure of the coaL Anthracites, for instance, although holding large quEUitities of marsh gas, are by no means dangerous to work, as only small quantities of gas are dis' charged at the working face owing to the jet-like nature of these coals, such structure being emineutly favouiable to the retention
Ooal, ifine Gaia and I'tnlitalioi
iOp.c
.p. 34S-
Text-Book Of Coal-Mining.
of gas. On the other hand, steam coals, although containing a smaller quantity of gas, readily give it up, owing to their porous nature, and the quantity of gas evolved at the face of the workings in some of these coals is enormous. From these results we are
No. of Sumple.
Nitare of Coal.
Compoaition of GaiM.
Cirbonic Acid.
Oijgen.
Manh Gaa.
I Bituminous
o.c.
Semi-bituminous
a64
4 Steam
87
25a I
able to see where the explosive gases in mines are obtained, and can readily understand that mine-gases and the gases occluded in the coal stand in definite and fixed relationship. Mr. Thomas experimented in this direction, and the results he obtained are summarised in the following table : —
No. of Sample.
1 Composition of tb Oaa.
vvncmer a uiowor or oouuncu by boring into Coal.
I Marsh Carbonic Gaa. i Add.
Oxygn.
Nitrogtn.
Blower
Boring
Blower
—
Boring
—
.t
2a 30
Blower
. i 94.84 o.io : —
Id
The enormous pressure under which these gases are contained in the coal >vill be realised when it is stated that in the 4-ft. seam of the Harris Navigation Colliery, at a depth of 700 yards from the surface, and with a bore-hole put 30 feet into the face of the coal, the pressure was 143 lbs. per square inch ; while a borehole 50 feet deep, in the 4-ft. seam at Merthyr Vale Colliery, at a depth of 450 yards from the surface, registered 280 lbs. per square inch pressure of gas; it may be further added that these pressures
Coal. 17
are by no means the maximum ones that have been obtained in different collieries.*
Blowers " of small dimensions usually follow the face, and as this proceeds, the older ones die out and newer ones take their place. A thin seam of coal overlying the bed worked, is very favourable for supporting this action. By the sinking of the strata, cavities are formed in the measures above the roof, and these are filled with accumulations of gas ; a crack is by some means formed, and an outburst of gas residts. This action is guarded against in some collieries, by a regular system of putting up in the roof, and thereby gradually draining all the gas from the measures. In driving exploring works, large blowers are frequently met with which yield enormous volumes of gas, sometimes for long periods of time, and sometimes for smaller ones. In the former case, the gases are conveyed to the surface through pipes and burnt ; while in the latter the district has to be temporarily abandoned until the outburst has exhausted itself.
On Experiments showing the Pressure of Oas in the ikiUd Coal, Lindsay Wood, N.B.I. XXX. 163.
Chapter Iii.
Search For Coal.
Prospecting. — The preliminary operations in searching for coal in new districts, consist in carefully examining surface indications to determine the nature and position of the beds exposed in the area \mder examination. A knowledge of geology is indispensable for such work. The banks of streams and cuttings should be closely examined, and all outcrops noted and laid down on a rough sketch-map. Rocks and fossils ot Carboniferous age afford the best indication of the probable existence of coal, but it is not absolutely necessary that such should be found at the siuf ace, nor is it certain that, when they are found, coal surely exists beneath.. For instance, in this country, the greater part of the Somerset coal-field is covered with rocks of newer formations (Lias and New Red Sandstone); while in the north of France and Belgium, thick deposits of the Cretaceous formation are passed through beforereaching the Coal Measures. Perhaps the most remarkable instance of the reversal of strata, is afforded at Drocourt, in the Pas de Calais, where, after sinking through the Cretaceous, they passed,, at a depth of 413 feet, into the Devonian; and after sinking in this formation to a depth of 958 feet from the surface, met with very disturbed Coal Measures, and beds of coal, which were worked for a considerable period. The shaft was sunk deeper and deeper,, until, at 1886 feet, a fault was reached. On passing through this,, the ordinary Coal Measures of the district were met with, and are now being worked. The Devonian, and first portion of the Coal Measures met with, had evidently been bent completely over before the Cretaceous was deposited.
Boring. — Even after the examination above referred to, from which the probable existence of minerals may be reasonably inferred, further proofs have to be obtained. If outcrops of actual seams have been found, a great deal can be done by sinking shallow pits or by driving levels. Indications at small depths are, however, seldom conclusive, especially as regards the quality of the coal seams, and the operation of boring is generally resorted to.
Search For Coal. 19
Choice of Site. — For proving coosidei-able areas, sevenU holes may be required, the sites of which are determined by the extent, location, and general features of the land to be developed. The preliminary survey decides these general features, but oonsidera* tioQ haa also to be given to the suitability of the spot for the erection of the diilling appamtus and for carrying on the work.
Various Appliances lued in Boring.— -(o) 2iiu. — For shallow holes in soft ground, the boi'er couiiists of some heavy instrument of the "scoop" kind, the general form being a cylinder, the cutting edge having a slit up its side like a gimlet. In soft, loose ground, pipes furnished with a cutting edge can be driven down by blows of a heai-y wood block, dropped through a considerable height. A eecoiid pipe, of smaller diameter, is lowered inside the drive-pipe, and through it, a strong stream of water is forced. This second pipe follows the cutting-shoe, and stirs up the loose material and washes it to the surface.
This method is largely used in America, up to 300 ft. of gravel being easily got through. The pressure of water is sufficient to force up gravel of about J in, diameter, but if larger pieces than this are encountered, they must be chopped to pieces.
For harder ground, bits of chisel-shape have to be employed. These ore suspended from rods, which are raised up and dropped down, thereby chipping off small quantities of rock. The rods are rotated after every blow, so that the tool drops in a different place each time.
The general form of chisel employed, is that having o. 8. a straight edge (Fig. 8). The angle enclosed by the catting edges is variable, depending on the nature of the rock. For hard rocks, a chisel with an acute edge is too likely to break ; the angle shoidd not exceed 70°. The size of the chisel should be carefully measured before it is lowered into the hole, as, if it is too wide, it will jam, while if too small, the hole will get too narrow. As with all tools, the chisel was formerly made of wrought iron tipped with steel, but is now universally constructed of steel throughout. For very hard rocks, a V-shaped chisel is sometimes employed. Various other shapes have been tried from time to time, but abandoned, owing to tho difficulty of sharpening.
(&) RoJi. — Those may be either of wood or iron, the latter being most common. Their usual size is about 1 in. square, and from a8 ft. to 36 ft. long. Shorter pieces for making up lengths are also used. As the hole gets deeper, tha tliitikncea of rods hoa to be increased. The rods are pro ">d socket
ends. When first used, the t uly
together, but only the first tb' t
worn, more turns are given, 1
u
TETI'lSfXjK OF COAL-3iDirSG.
KA \0t hrMjt tofethcr. or the etmcnmon win thrHwiti to jism. ac/1 ravler o BHeic w in g' imposnble. ff th nxk efit IcfthamfefL when ther begm to fcirr.k#YA off ft&d f reih eivi pMces wMed on.
AfVT mIi blow, the rods aiul cfaMel are turned through a wmaH \ir thik tiller" rFig. 9), which is attached at the snrfiace. To eutr/le thift opentuAi to be easily carried oat. a swivel joint is mtrrnetd Am the of the hole slowly increases the rods AcsimuilydMcend, being allowed to do so bthe use of an instranent called the stirmp" (Fig, 10), whidi consists of a ooQar grkdoAjlj working down a long screw. When the limit of traTel fA thill inAtmment is reached, it is detached, the screw nm back inu> the position shown in the iUostration, and a short length of rod iiMerted between it and the main length attached to the tooL TYtin €ffentum is repeated ontfl soffident distance has been bored.
n
KiG. la
Fig. II.
to allow of the insertion of an ordinary length of rod, the smaller ranking-up pieces being then removed. For unscrewing, an ordinary spanner key is employed.
(0) Guides. — To keep the hole vertical, a guide-block is fixed at the surface. This generally consists of a block of wood (a, Fig. 11) about 9 feet long, through the centre of which passes a hole of the same diameter as the bore-hole. It is fixed truly vertical, and secured by four pieces of wood arranged in the form of a square. Its upper end is furnished with two stops (6,6) turning around pins. A piece is cut out of each shutter, leaving an opening central with the hole, and of a size slightly larger than the rods, so that when the latter are in position the space is filled in. This shutter really fills two purposes, as it prevent anything falling down the bore-hole, and also suspends the during the operation of unscrewing, the hole tlumi .it large enough to allow the rods to pass, bat not a joint
m
When thia
SEARCH FOR COAL. n
In deep holes, other gtiideH ai-e inserted iii the rodn at regular intervals. A common form is that shown by Fig. 12, which readily passes through water. Discs and othetshapes have been abandoned, as even where fig. 11. Kio. 13. water-waye are left through them, they set up eddies in the water tilling the bore-hole, wearing away the sides, and causing them to fall in, if the rock is at all soft.
(d) Cleariitg /nsfrKwiento.— When a. nufiicieut amountof cutting has been done, the debris which has accumulated at the bottom of the hole is removed by the "sludger" (Fig. 13), which con - siste of a tube fiwrn 4 to 6 feet long, having a valve at the bottom, either of the ball or flapdoor type. The removal is usually done with a rope, sometimes a few lengths of roda being added to give weight. When the sludger reached the boltom,it should be picked up and dropped several times, before raising to the surface. For deep and large bore-holes, a superior class of sludger is employed, having, in addition to the valve at the bottom, a piston working in the barrel portii jiiston is drawn up, it sacks-in the slime.
(e) Lei'er. — The most general way of working the rods in percussive boring, is to attach them to the Khorter arm of u lever (Fig. 14), the longer end of
which receives an up-and- Fiq. 14.
down motion ; as previously mentioned, the rods are suspended by a swivel, and are turned by the bore-master after each blow. Where manual labour is employed, two or more smooth crossbars are attjicbed to the longer arm of the lever, so that more men are able to work at it. With cross-pieces 8 feet long, six men can work on each side. For deep holes, manual labouiis iuite out of place, and the long end of the lever is depressed at intervals, either by large teeth on a i-evolving wheel driven by steam, or, preferably, by directly connecting it with the piston-rod of a cylinder.
(/) Sprii PoU. — In our coal districts, the vibratory movement is often given to the rods by the use of the spring bar, which consists of a wooden pole having one eud fixeii to the ground, a fulcrum placed further on, and the rods attached to the other end. '"pblowis struck by depressing the beam, the rods being raised itv of it. The lengths of the parts on each side of aally 1 ; 3 or 5. For shallow holes, the axia may
be fixed, but for deeper ones it must be movable. An elaboration of this method consists in the employment of two spring poles. The first is from 60 to 70 feet long, fastened at one end
(Fig. 15), and at of its length Fig. 15. from the fixed point it rests on
an upright. To the other end, are fixed two cross-bars which the workmen press down on to a second springpole, thus producing a dancing movement. Between the upright and the cross beams is attached a hook, from which the boring tools are hung in the usual manner.
(g) Frames. — In order to enable the rods to be raised perpendicularly, a frame of three shear legs is erected at the surface, to which a pulley is attached at the top, one of the shear legs having steps on it so that this may be easily reached. For shallow holes, a windlass supplies motive power, but in larger holes a steam engine and drum is employed. To save labour in unscrewing the rods, it is advisable that the frame should be made as high as possible, so that a long length of rods may be raised at a time. This is done in the following manner : — The stops (6, Fig. 11) are
opened, and a hook (Figs. 16 and 17), at the Fios. 16 AND 17. end of the rope, is placed beneath a joint in
the rods, these being then detached the end of the lever. The rope is then hoisted up until the limit in height is reached, when the stops are closed beneath the nearest joint, and the rods above that joint unscrewed and removed. This operation is repeated until all are withdrawn. The sludger is then lowered, either by the same rope, or, if the boring is a large one, by a second one passing over another pulley lower down the frame. After clearing out the debris, the rods are replaced by a reversal of these operations. One point must be specially noted : the rods when not in use should never be stood on end, but always suspended.
DoTices employed to meet DifUcidtieB of Deep Boring. — As the depth of holes increases, a large number of difiiculties arise, the greatest one being the weight of the rods themselves. Bods I in. square weigh about i ton for every 200 yards. In deep holes, not only does this great weight injure the screw joints, alter the structure of the iron, and break the tool which receives the blow, but it sets up excessive vibration in the rods, injures the sides of the hole, and accumulates a mass of broken material above the tool, which often leads to rupture when an attempt is made to withdraw it. To overcome these disadvantages sevend methods are employed.
(a) Lighter Rode. — Hollow iron rods were first suggesledi Ham
Search For Coal. 23
weight 01 these for the same strength aa solid ones being in the ratio of I to 1.35. They were, however, found to bo too expensive. Wooden rods were then introduced. They possess certain advantages over iron, as not ouly are they specifically lighter, but, when the bore-hole contains water', as their size is also greater, a larger volume of water is displaced. They also fit the hole tightly, and do not rattle about from side to side like iron ones. When a. rupture occurs with iron rods, the large weight dropping down, causes other breakages and the bending of rods in the hole, often rendering it a most difficult matter to get them out. On the other hand, when a break-down occurs with wooden rods, tfaere is generally only one fracture. The great objection, however, to their employment, is the large diameter of hole requu'od, owing to the necessity of using rods 2 to 3 in. square for shallow depths. For larger and deeper holes, this objection is removed, and such rods have F108. iS, 19, 20. been largely employed in Canada and ixa the Continent.
(6) Frte-faUimj Cirffcr*.— The greatest advance made in percussive boring, waa undoubtedly the introduction of what are known as "free-falling cutters." By their use, vibration and , , shocks in main rods are practically avoided, the only portion of the apparatus that is really let fall being the boring tool itself, and as much of the apparatus as is neceesary to give weight to the blow.
The tool designed by Kind has been , largely employed. It consists of two fangs or pincers (n, o'. Fig. 18), working about centres b, b'. These fangs are enclosed at their upper extremity by a collar c, connected to a circular disc of leather r/, through a rod e; at their lower end they grip, during certain stages of the operation, that part,/, of the rods to which the tool is attached. As shown in the illustration, the I'ods oi'S making their upward stroke, and the pressure of water in the bore-hole depresses the leather disc, pushes the collar c down on the fangs, and causes them to retain their hold of the lower part of the I'ods carrying the tool. When the limit of the up )>broke is reached, a sudden change of motion takes place in the opposite direction, causing the pressure of water on the underside of disc d to lift the collar-, thus opening the fangs. The tool and lower rods fall quickly and deliver their blow, while the
ft-long
length of upper rods follow at a dower speeil. When this has descended to the proper point, a slight upward motion, producing pressure on the upper side of the leather dL'ic, causes it to descend with the rod e and collar c, and so close the fangs.
The above apjwratus retluced in a marked manner the breakages of tools and rods, and consequently the cost of boring. It is, however, inapplicable in dry and narrow boles, is somewhat complicated, and causes the water to form streams, whilst the slime from the hole collects on the dic, and prevents it from acting.
Numerous other complicated appliances have been used from time to time, but pi-actically have all given way to the sliding joint invented by (Eynhausen. As befoi-e, the rods are divided into two lengths, but a sliding joint forms the connection between them. The two lengths a and b (Figs. 19 and 20) are raised together and also fall together, until the lower part b, to which the tool is attached, strikes on the bottom of the hole, when its motion is arrested. The upper part, however, continues its downward movement (the collar sliding over the stationary lower rods), and is gradually brought to rest within the limit of length of the slide by an elastic stop placed beneath the rocking lever at the surface. By this means, the shocks received by the tool and lower rods do not reach the upper part.
Obtaining Cores. — It is of the greatest importance that satisfactory samples of the strata cut through should be obtained. Fig. 21. With the took already described, evwj'thing is chopped to small piece(, and it is necetistiry to examine the contents of the sludger very closely, to determine what material the hole is passing through. In order to obtain more definite resolbt with percussive boring, a tool is put down, consisting of four or five chisels, arranged I'ound a cylinder (Fig, 2t), which cuta away an annular space, leaving a central core. A second tool is then lowered down to the bottom of the hole, and a cutting tooth at the base is pressed inwards by means of a spring. This tool is i-evolved several times, until the greater part of the foundation of the core is cut away, and then by ft sharp jerk the whole is detached, and brought carefully to the surface.
Speoial Uethoda of Boring, — The greatest change which has taken place in percussive boring is that due to suspending the tools by a rope, in place of the rigid bw. Ttf To the Chinese, belongs the credit of first employing this means. Tlie shank of the tool consists of a heavy cylinder of iron attached to a rope of bamboo fibres, the torsion of whf ' is Kulhcient to rotate the tool after each blow. Motion ia eo municated at the surface by means of a spring pole.
(a) Mather and Platt'a si/slem. — In this method," the tool
Welt Boring. Y. Mather, I'rc
Search For Coal.
suspended From a, fltit bempea rope, hut the system diHers from all others iti the measures employed or rotating the tool, and giviDg it the necessary perctisaive action. The rope to which the tool is attached (a. Fig. 21) pusses over a pulley b, over the hole, and thence is p,g 22,
directed by a guide pulley c to the drum of a, winding engine by steam power. This rope can be clumped at an intermediate point by means of the clutch il. The up and down motion is obtained by connecting the pulley b to the piston rod of a small vevtiuil cylinder e. As the rope is clamped on one side at the point d, when the piston moves upwards it curries the tool and rope hanging in the hole, with it, and / allows it to full on the return stroke, As the hole deepens, the rope on i drum is gi-adually let out. A self-acting valve motion, worked by tapjiets moved by the piston rod, is employed, and the length of stroke can be varied by altering the position of the tappets. Before the valves cun be opened, it is necessary that the piston rod should move; a. small quantity of steaia is therefore kept continually blowing on to the underside of the piston, through the small port /. As the exhaust port is situated a little higher up the cylinder, this really serves an additional Fio, 23. purpose, AS it interposes a cushion of steam between the piston and bottom of cylinder, preventing any chance of the latter receiving 11 blow on the return stroke.
The boring head (Fig- 313) consists of an iron bar about 8 feet long, having a cast-iron boss a at the bottom, into which the cutting tools are secured with taper shanks b, so as to be firm in working, but easily taken out for sharpening. Two guides ai-o employed to keep the tool pi-rpendicular ; one, c, being a plain cylinder, the other, d, hating i-ibs of saw-tooth form arranged round its circumference. These ribs have a longpitcb, judas they bearagainst the sides of the borehole, iLBsist in turning the tool. Each alternate plate has the ribs inclined in opposite directions,so that one half are acting to turn the liar in rising, and the other half to turn it in the same direction ii 'ini;. The definite rotation of the tool WBfltediAih 'two cast-iron collars,
hee apart. The top side of the the upper collar, have deep
Text-Book Of Coal-Mining.
ratchet teeth cut on them. Intermediate between these two, and sliding freely on the bar, is,a third collar g, having ratchet teeth cut on both its faces, but those on the upper side are set half a tooth in advance of those on the lower side. A wrought-iron hoop is attached to this third collar, through which the bore-head is attached to the hook and shackle shown in Fig. 22. When the tool is dropped and tlie blow delivered, the teeth of the collar g fall on to those of the bottom collar e, and, through the teeth not being opposite each other, receive half a twist backwards; on commencing to lift again, immediately g engages with a further twist backwards of half a tooth takes place, so that the flat rope is actually twisted through the space of one tooth. As soon as the lift takes place, it untwists itself, and so rotates the tool.
The sludger is furnished with a clack at the bottom, and inside is fitted a bucket having an indiarubber valve on the top side.
The boring head can be lowered at a speed of 500 feet per minute, and raised at the rate of 300 feet per minute. The percussive action gives 24 blows per minute, and if this rate be continued in New Bed Sandstone or similar strata, about 6 inches will be drilled in 10 minutes, when it becomes necessary to send down the sludger, which is effected at the same speed as the tool, but it only remains down about 2 minutes.
(fi) American System, — The development of the oil industry in the United States required rapid boring, and considerable improvements under this head have been effected. The whole operation has been elaborately described by Mr. J. F. Carll.* The success of the operation seems to be due more to the perfection of small details than to any startling novelty. The first thing done is to erect ear legs and fix the wooden conductor box previously described, this being set truly perpendicular, and carried down a few inches into the bed rock to fasten it securely. Should the bed rock lie at a considerable depth beneath the surface, the wooden conductor is replaced by a wrought-iron stand pipe, which is carried down by the method already alluded to. The engine furnishing power is regulated and controlled from the boring stage. The tools are attached to a rope, and an instrument called a temper screw " (a, Fig. 24) connects the rope to the lever through the " stirrup " b. The lever receives an oscillating movement from a connecting rod and crank, turned by the band wheel. The length of stroke can be varied by adjusting a collar-pin in any one of several holes placed in the crank at different distances from the centre of its shaft. Sepai'ate
♦ Second Geo. Survey of Pennsylvania, Report I'.
Fig. 24.
Search For Coal. 27
dmnu are provided both for windiDg out the drilling rope and the dodger, these being driren hj gearing thrown in and out by olDtdiM. Tba eSective catting blow of the tools ia given by the weight tit the chisel, the Auger stem, and the lower link of the "jars." The JMiB is K modification of (Evnhausen's slide, arranged in such a manner that the anger stem and bit are given a decided jar on the up ttroix, so that the bit is loosened, in CAse it has a tendency to wedge fast in the bole. As the tools rise and fall with the rocldng lever, they are const;tntly rotated by baud, by a short lever inserted in the rings of the temper , and the hole deepens and the screw of the stirrup reaches its limit, the clamps (e) of the temper screw are slacked, and a short length of rope payed ouL
The withdrawing of toola is carried out by first taking up all the slack rope, then loog the clamps, throwing the connecting rod out of gear with the baud wheel, and lifting up the lever out of the way. The tools are then run up, but are stopped when the bit reaches the level of boring-floor, where it is loosened by large wrenches. The tools are then lift up clear of the hole, and the rope disconnected from the steam engine, the hit being removed and replaced by a sharp one. While tliis has being going on, the sand pump, or sludger, has been run up and down once or twice by the friction gear, &c., already described.
The first 60 feet cannot be drilled in the ordinary way just described, this being done by the method called " spudding." The auger stem and bit are attached hy the rope socket to a short pieceof cable (15a to 160 feet long), the other end being passed over the pulley at the top of the frame, round another wheel, and then a few turns taken rouud one of the drum shafts. The engine is eturted, and one of the drillers takes his stand near the drum, with the loose end of the cable in his bands. A slight pull on this, tightens the loose coils on the drum shaft, which is rapidly revolving ; the tools are raised, the rope is immediately slackened, and the tools drop in the hole ; another slight pull is given, and so on, until sulficient depth is attained to enable the drillers to replace this motion by that of the rocking lever.
This method has been introduced into England, and was used in September t886 for boring for salt in the neighbourhood of Middlesbrough. Mr. J. DagUsh* stated that it proved exceedingly satisfactory, the progress having been remarkably rapid. An average rate of progress of 63 feet per day was attained, with a maximum of 5 feet per hour.
(c) Diamond Boriiuj. — This method differs from the others in the fact, thut the tool receives a lipid rotary motion instead of a percussive one. It consists in placing a series of miaU. diamonds
'uUmial AdJnti. K.E.I. EST
Text-Book Of Coal-Mtntng.
ftTound the lower edge of an annular tube (Figs. 25 and z6) called the "crown." This part is composed of soft w-rought iron, in ] which the diamonds are bedded, the edges of the holes being knocked down to keep the stones in position. The t
Figs. 25
variety of black diamond (bort) is employed, as the cost of the rare gems would be too great. The ci-own is provided with a series of vertical gi'ooves (u <i. Fig. 26) round its circumference, to allow water to pass from the centre outwards, and it is made slightly larger in diameter tlian the main boring-piece, so Fic. 27, that the latter can revolve finely in the hole. The main boring-piece consists of a wrought-iron cylinder (Fig. 27) in twp pieces, the upper one being open at the top. In the centre of this cylinder is placed a horizontal disc of metal, a, which divides it into two portions, and also serves as a connection to which wrought-iron pipes, b, are screwed. These pipes are carried to the surface, and are connected by mitre geai'ing to a. steam engine, thie giving the rotary motion to the tool. A stream of water under pressure is brought down the centre of these pipes, passes into the lower chamber c, on to the bottom of the hole, and escapes by the side of the crown through the waterways already referred to. So long as the water is eirculatjng, the debris is canied away upwards, but as soon ss the pressure is taken off, the slime would fall between the sides of the bore-hole and cylinder and jam it. This is the object of making the top piece open. All the falh'ng debris settles in the space dd' (Fig 37), ai-ound the water delivery pipes,
A cylindrical core is produced, which is removed in the following manner : A circular split band of iron, with vertical ribs, is placed inside the lower portion of the boring tool immediately above the ci-own (Fig, 25), the surface on which it slides being an inverted cone. In boring, the core readily passes upwards, as it can slip through the split ring, but when the boring tool is raised, the core drags with it the ring, and gradually forces it on to the smaller
to tea Jwinnriw. At loa-
*TM- w.;arc:r t-:iii iJiN£
ltd op VK-n 'JM ifi J -uiA fju m. -.f Tiss-cTiT- ; iVs
the 1
a-so;-
3°
Text-Book Op Coal-Mining.
water, which ie hieompresBihU, and entirely/ prevents tht dropp\
of the roda. When a cavity is Ktruck, the hydmiilic feed continues j
downwards as regularly as in drilling through hard rock.
An important detail uf this hydraulic drill is the friction, bearing [kk. Fig. 38) ; one set of balls suatnins the weight of the rods as they hang in the di-ill chuck, the other set suataiu the upward thrust of the rods in drilling. Thin device reduces to a minimum the amount of work lost in friction, leaving the whole , power of the engines to be devoted to drilling.
The great advantage and superiority of the diamond boring Bystem, is the perfect coi'ea obtained from rocks of moderate hardness, which enable an accurate section of the rocks passed through to be easily constructed. In ordinary soft measures (such as coal), owing to the rotary and vibratory action of the , bore tube breiiing off the core, which falls to the bottom of the hole and becomes ground into mud, the indications aflbrded by ' this method in such ground are scarcely better than the slime and dfibria removed by sludgers in ordinary boring. The breakage of the core has lately been obviated to a considerable extent by the boring of lander holes, the larger amount of core inside the crown being better able to stand shocks the smaller ones of the earlier borings.
A further improvement, by means of which the amount of core ' extracted has been considerably increased when baling through I coal and soft rocks, is described by Mr. James Barrow,* the I boring tool being so constructed that a core of the strata can drawn up intact. This is aawmplished by the use of an internal I stationary core tube, rivetted to the socket of the ordinary boring tube, an annular space being provided between these two parts for the passage of water. The crown on the boring tube is stepped, to facihtate the cutting of the core, and as the boring tube revolves, the crown penetrates through the strata, and the core enters the inner or stationary tube, which when the Iwre rods are I raised is lifted with them and extracted. When in operation, a. I constant stream of water is passed down the annular space between the exterior of the core tube and the interior of the boring tube.
This modified tube was employed at Vitlefranche (Allier) in 1876, and M. Bauret states that the success has been complete, as the greater poition of the cores wei'e exti-acted in an unbroken condition. Not only did they obtain a complete section of the rocks passed through, but tbey reduced the breakage and giinding of cores at the bottom of the hole, which so materially increases the power required for turning the tool and augments the amount of debris to be removed.
The modified crown was put to work on ijth Oct, 1876, when
Seabch For Coal.
the boring hod reacted 1684.7 from tbe surface, and by the 5th of January iSj;, 745.6 feet bad been bored, m&king tbe total depth from the surface, 2430.3 feet. The length of core extracted was 734.18 feet, or 97.1 per cent while with the original form of crown, only 39.9 per cent, had been obtaiattd. During the months of Oct. and Nov. 1S76, 462.3 feet was bored (from 1609.7 to 3073.0 feet) at au avera rate of 1 1.S87 feet per working day, operatious being suspended port of thiit time, while negotiations were being entered into for proceeding deepeiwith the borehole.
For very soft ground the diamond drill is quite useless, and if a hole i3 proceeding ou that system, and such groand is encountered, tbe crown is removed, and percussive boring tools employed.
Aooidents in BoriDg. — If it were not for accidents, boring would be a comparatively easy and rapid operation. It is in this division that the skill and knowledge of the bore-master is put to the teat. Tbe accidents themselves, and the tools employed during such accidents, nre so numerous and complicated, that a full dntcription would be quite out of place here, and indeed impoeaible to give within the limits of the book.
(a) AecideitU arising from the Doriitg Toolt tKemtetveg. — Tbe constant vibration and ocks to which tbe rods are subjected tends to rapid deterioration of the iron, and frequent breakagee follow. Often the workmen do not screw tbe rods properly together, or negligently allow them to drop down into the bottom of the hole during the progress of unscrewing. To lift up the broken part of the rods, a tool called tbe "crow's foot " (Fig. 29) is employed ; it is slipped down the Fios. 19 hole, and twisted round until tbe hooked part catches a>'D 30.
If, however, the fracture bad taken place some distance above a joint, when the rods were raised the top part would catch the side of the hore-bole, as tbe crow's foot itself only gripe at a joint. In such cases, an instrument called ft " bell " is let down. In one form, this is a bell-shaped tool (Fig. 30), with a screw cut on its inside. It is dropped down on to the broken rod, and cuts a screw thread on it. All screwing tools for removing broken rods are cut with their threads right-handed, so (ts not to disconnect tbe joints of either the rods to wluch they are attached, or those that are broken in tbe hole.
If & piece breaks off the chisel, or any small tool or other hard obstruction drops in the bore-bole, an attempt is made to extract it with an implement resembling a double corkscrew, called a
Text-Book Of Coal-Mining.
(Fig 31). This is generally successful, but if all attempts to dislodge the obstruction fail, then the only alternative is to chop it to pieces. Mr. Mather, in the paper already referred to, states that it had been found necessary to remove both the heavy boring head and sludger employed in his system of boring by such means. Powerful magnets have also been used with success.
In case of a fracture in the rods (tubes) of the diamond system, an ordinary screw tap is let down and a thread cut inside the broken pipe ; in large bore-holes, where the diameter of the holo is large compared with that of the tube, a crooked piece of iron (a, Fig. 32) is placed at the lower extremity of the tap, this guiding that piece into the tube in case it should be leaning against the side of the hole.
Fig. 31,
Fig. 32.
&
(b) AeciderUs arisiiig out of the Nature of the Oround. — Unless the 8ti*ata passed through is of considerable hardness, the constant jarring of the rods, and washing action of the water, soon causes the sides to crumble and fall in over the tool. A very soft bed at any point is a source of considerable danger. In order to prevent serious accidents, it becomes necessary to line or case the sides of the bore-hole.
Lining. — This is done by forcing down wrought-iron tubes in lengths of from 10 to 12 feet, the connections between each length being made '' flush " ; that is to say, there are not any projecting points. The lower tube is provided with a steel cutting edge (a, tig. 33).
For small holes, the tubes are driven down by dropping a heavy block on them, about 20 to 30 blows a minute being given. A superior method to this is to use two small jacks, which exert pressure equally and gradually, and avoid shocks and risks of bending.
For larger and deeper holes, hydraulic pressed are employed
Search For Coal.
having a stroke aiiflicietit to fife down one length of ttibo at a time. A strong fnimiug is built over tlie bole, iind beneath this the preRses are secured. Both the hydraulic vams and tubes are carefully guided in a truly vertioaJ direction.
HeauB of Wideniiig Holes. — When a hole is cased, and boi-iug has to proceed further, it is obvious the diameter of the hole must be reduced, o& the toot has now to pass through the tubes. In order to prevent this, before inserting the first length, the hole is slightly enlarged by a tool called a " reamer," which is very similar to the " hell," except that it is provided with a cutting edge round its circumference. In diamond boring, the reamer consists of a guide the size of the drilled hole, and a face above it, in which diamonds are set, and which cuts away the sides of the hole above the guide.
After the sides have been caed, and boring it fre- (juently happens that additional casing is required at some point loner down ; then either narrow tubes must be sunk thi-ougb the fii'st set, to I'each the dangerous part, or the old casing is removed by one of the methods described below, and the hole rebored large enough to take in the original size of tubes. As a rule, the latter method is not adopted, except when the bore-hole has become bo narrow by repeated linings that the first method cannot be employed.
A special tool, introduced by the Diamond Boring Co., is described by Mr. James Barrow.* It consists of an undercutting or expanding crown, a simple arrangement set with diamonds, which is lowered down through the lining tubes,and expanded Fiq, directly it gets beneath them. In revolving, it cuts away 34. and enlarges the sides of the boro'hole, after each la, or 30 feet had been bored in advance with the ordinary crown. After this, the lining t>'bes are lowered to the bottom, and boring resumed in the ordinary way. With I suoh a tool, and the use of hydraulic presses, 800 lineal feet of wrought-iron lining tubes, weighing about 50 tons, I have forced down a boi'e-bole in one continuous j length.
Withdrawal of Casing. — Eitherwhen the hole is finiiihed and abandoned, or when inserting tubes of gi'eater diameter, the luiing has to be removed. Where the friction is not I great, Kind's plug (Fig. 34) can be used. Tliis consists of I an oval ball of wood slightly less in diameter than the inside of the tube. It is lowered down on the rods, and a f hands uls of sand or gravel thrown on the top. This cau it to bit, when the tubes can be lifted out.
Should the friction be too great to allow the casing to Ite removed in one length, it is cut through by the tool shown in
So, Valea lust. xL 318.
Text-Book Of
Fig. 35 and 36.
ft
S6
Fig. 35. This is provided with a sharp catting point a, pressed against the side of the tubes by a strong spring 6. On reaching the point where the severance is to be made, the tod is revolved
round and round until the lining is out through, when the upper portion can either be removed by Kind's plug, or by a similar class of tool (Fig. 36) having two spring clips a which are pressed inside the shank 6 so long as lowering is taking place, but which spring out and catch beneath the lining, immediately the place cut through is reached. These clips cannot be forced aside in the upward passage, and so the casing is withdrawn.
Beoord of Boring. — Exact records should be kept of the work done each day, the strata bored through, and its thickness. Each sludger full of material should be carefully examined, and samples taken and kept for reference. These are best kept in small wooden boxes and labelled. The label should note : place, date, depth, sort of material, and any remarks necessary. Memory should never be relied upon. Neglect of these precautions hasresulted iu the loss of considerable sums of money, owing to misinformation, at a subsequent date.
Cost of Boring. — This depends in a great measure on thedepth to which the hole is carried. A common form of tender is,. that the price per foot increases at a certain figure for every stated increase in the depth. As a result, one foot at the bottom of a hole may be more expensive than several feet at the top. In view of this fact, when commencing a boring, a shaft is generally sunk down some distance, and the bore-hole started from the bottonu. The low rate is then counted from the shaft bottom, not from the surface, so that, by sinking the pit, a length equal to its depth is cut off from the bottom of the bore-hole, which would be at the highest rate. It is stated that the bore-hole at Sperenberg, 4170 feet deep, made with rigid rods and percussive action, cost 41a. per foot ; while an average of a series of 37 rope-borings, with depths varying from 80-1300 feet, cost 41 8, d. per foot. Mr. T. J. Bewick f states that the first hole at Middlesbrough, bored by Mather and Piatt's system, was 1200 feet deep, and cost about 68. Sd. per foot. It is nearly impossible to compare the several systems, as the conditions may be quite different in each instance. In ordinary strata, the Diamond Drilling Company will contract to put down a hole, commencing at the surface with a diameter of 9 in. at a price of 1 59. per foot for the first 500 feet, and from 500-1000 feet, 255. per foot, 20. per foot for looo-
N.E.I. Xxx. 88.
t Ibid.
Search For Coal.
feet; the compnuy providing all labour and tackle (except liaitig tiibw, should such be required), fuel, carriage, and fai-ea ; but tlie employer baa to provide, gnitia, on the site of the boring, about lo to 12 gallons of water per miuuto for engine and other purposes. This price would not vary much even if the hole was of smaller diameter.
Mr. H. M. CboQce states that the average cost of drilling a weU, by the American rope system, in the oil country in 1878 (including the cost of the plant) for a 1500-feet hole, was 403, or a little over 6a. per foot. As prices were at their lowest ebb then, this estimate should be increased about zo % to make it available for comparison with other methods in i8Sz ; but as the plant would have some value when the operations were concluded, he states that the net cost of a 1500-feet prospecting hole (in 1&81) would be 380, or about 5*. per foot. At the same time, he points out that the cost of drilling holes by this method in the anthracite regions will be very much greater than that shown by the above figui-es, because the rocks are much harder, and are inclined at considerable angles from the horizontal. Mr. R. A. 8. Redniayne t states that the bore-hole put down by this system at Middlesbrough for salt cost 8s. per foot, the depth reached being 13 lo feet, ami the diameter 8 in,
anrreying Bore-holes. — The great difficulty in boring ia to keep the holes truly vertical, and, in spite of all effoi-ts to the contrary, crooked bores are common, espednlly where the beds are inclined. No rules can be given ; the only thing lo be done is to exercise the greatest care. Unfortunately, bore-holee, by all the methods, aro liable to deviate from the perpendicular, the diamond drill, which was assumed to always bore a perfectly straight hole, being no better than any of the other systems. However, if an accurate survey be made, a crooked hole gives just as valuable information as a straight one.
In the method devised by Mi'. E. F. Macgeorge.J clear glass phials, filled with a hot solution of gelatine, and each containing m suspension a magnetic needle ftiitt a very dehcate plumb-bob, are lowered into the bore-hole, and allowed to i-emain there until the gelatine sets, when they are withdrawn, and by means of a special instrument the angles of the and the plumb-bob are noted. Another suggestion § is to lower into the bore-hole glass cylinders containing hydroHuoric acid, which etehes a line oa the glass. Both these methods are reviewed by Mr. B. M. Brough,|| who gives a full description of the instruments employed and the way of using them.
rt JlC., p. 39.
3G
Text-Book Of Coal-Mining.
The usea of Bore-holeB in Uines are many and valuable. Every eoUiery ought to be provided ivitb a set of tools, and men instructed in their use.
Tapping Water. — A provision of the Coal Mines Regulation Act, 1S87, is to the effect that all roaiis approaching old workings, where there ore likely to be dangerous accnmnlations of water, should be preceded with bore-holes. One bore-hole is usually kept Btraight ahead for a distance of about 5 or 6 yards, and flank-holes, at an angle of 45' with the centre line of road, are put out for a similar distance on each side. The general practice with the leading hole is to bore in a certain distance, and then remove part of the face, a further length being then bored before any more ground is removed. In this way, the distance from the face to the back of bore-hole is never lees than 5 yards. Where water is expected, plugs should be kept in readineeK to drive in immediately it is releoEed; or, if the pressure is likely to be great, it ia best to bore through a length of pipes fitted J with a tap. I
(6) Releasing Gna. — In collieries liable to sudden outbursts of I fire-damp, bore-boles are systematically put out of the working 1 places into the layers of strata in which the gas accumulate, in order to drain it out gradually. At Whamcliffe Silkstone, and other collieries where this procedure is adopted, it has met with succeed.
(fi) Ptomng FaulU. — Bore-holefl are of the gpeateat assist&nca in determining the amount of throw of faults, and have saved considerable sums of money, whirh would otherwise have been spent in unprofitable exploratory work. With their aid one can determine the gradient required to drive the roads that will intersect the dislocated seam. Especially is this the case where the hade of the fault is vertical or ill-defined, as they actually prove in such instances, whether it is an upthrow or downthrow.
Owing to the confined space in roadways, the cost of boring is rather high, as much time is wasted in screwing and unscrewing rods. From a number of cases carried out under the author's direction, the cost per foot averaged 4. for distances bored of about 30 feet, with diameter of hole 3 inches, the rate of wages paid to men being ja. 6d. per day of eight hours. The cost of boring uphill seems less expensive than downhill, if the weight of boring tackle 1 is counterbalanced, as the disadvantage of clearing out the h ' and unscrewing of rods for such purpose is removed.
{d) Stenvt ami Rope-wai/e.The anthracite i-egion of Penn* sylvania supplies numerous instances of the employment of boi holes for stm and rope-ways passing from the surface to t interior of the mine." At Shenandoah City slope, an 8-in, 1 bored by the method employed in the oil regions, and lined v
" School of Mines Qaarterlj, New York, ii. 189.
SEARCH FOll COAL.
5-10. casing, through which a rope travels, the space between the casing and the rock being filled in with cement. The engines and boilei-s are on the surface. Another hole, 6 in. diameter, was then bored, and two lines of z-in. gas-pipe laid in it, the interstices between being filled in with cement. One pipe is used for a speaking-tube and the other for a bell-wire to the engineer at the machinery on the surface. At East Fniaklin Colliery there are two bore-holes, each S in. diameter, isaed and cemented, 763 feet deep. These holes lire 7 feet apart, and are used to hoist from a double-track underground slope. At Lincoln Colliery, an 8-in. hole is used to convey steam to an underground pump through a 4i-in. steam-pipe. As this hole wns remarkably dry, it was not cased. At the Clear Spring Colliery, West PittBOn, a 6-in. hole was drilled 270 feet, and a line of 4j-in. steam-pipes inserted. This hole was not cased, and, owing to the flow of about in. stream of water down it, condensation was so great that the pressure was lowered from 120 lbs. at surface to 40 lbs. at bottom of hole. Afterwards, the space between the rock and the steam-pipe was cemented, anda4-in. steam-pipe placed inside the4j'in. pipe, with the result, that the steam pressure at the bottom of the hole was the same as on the surface.
These holes have also been successfully used in dealing with mine fires, for providing water supplies, and for other purpose? connected with mining.
— The following is a list of the more important memoirs dealing with the subject matter of this chapter :
OBES. ISST. : Boring and Boring Madtina, A. H. Stokes, lii. I92.
AUEn. INBT. U.E. : Improvtmenit in £>iainoiid DrilU, W. V. Blake, i. 39S ; The Diamond DrSl for Detp Boriug, coBiparrd mlh other tgittnu of Boring, O. J. Heimich, U. ?4i, and Supmentary Paptr, lU. 183.
S. X. I. : DeMfrlpHon of an Initnimenl for aKerlainini/ Ihe Inelinationfrom Iht JWpendiatlar of Bore-kolet, C. Z. Bunning and J. K. Guthrie, xxiz. 61 : On Diamond lUxk Boring, T. J. Bewick, xn. 93.
800. IND. mv. : A'otiet tur ta appareiU de Sondage employit par ia Sodtti Anonyau de Commeutru PourchambauU, M. I/ecacheax, (2* 8£rie) II. 337 ; Kott lur Vmitiuage cnlo'/c daru qiulqiiti Undagei da Oard, M. Sarnui, (2* Seiie) ix. 453 ; Sondaget dtt Bouha ri de NeBvilU exieiMt il Vaid de la couronne a diamanti, M. Bniire, (I* Sirie) xiv. 5
BO. WALBS ISST. : On the ifarJiiaery tucd in Boring Arlttian WelU, and ill ajiplicalion to Mininp/nirponu, W. Mather, W, 51 ; parlicutarM of Boring ipith tht Ihaniond DriU, A. Baaaett, ii. 130; and Hon, Huxbam, ix. aai ; Large and Dtip ilort-Aobi the Diamond DriU. James Barrow, xi. 315, And xU. 4'
&IID. IKBT. : On lit Diamond toA, iii. 354; A
Rittory of Drep Boring f ihe Continent,
J. C. JelTeraon, r. 105, u
Chapter Iv.
Breaking Ground.
CJontracts. — The greatest proportion of the miner's work, eonsistB ' in removing and breaking up different varieties of rock, and to do this various special tools are employed. Usually the tlifierent qualities of ground are let by contract to men, and it is here that experience is of the greseet use, as only from that is it possible to judge of the value. Hardness, in a mining sense, is different from the same term looked at from a mineralogical standpoint. Ground that is hard and brittle, will often bore better than a softer variety which ia tough, because in the former instance, the blows break off small pieces, while in the latter, the chisel has to cut its way. Another point, is the question whether the ground will " shoot" well, that is to nay, whether it contains a number of faces, or joints, which easily break away from the surrounding mans under the action of explosives, or, at any rate, allow the material to be BO shaken that it is easily removed by wedging. At one of the collieries under the author's chai-ge, numerous intrusions of ha- 'saltic rock are met with, and he has adopted a system for judging the value of roading, which is worthy of mention. A sample of every intrusion is kept and labelled, with the price per yai'd paid for dtiviiig through it, and in addition, a microscopical section is cut from the specimen. When other inti'usioua are met with, a piece is broken from each of them, and a section cut and carefully compared with other pieces and sections of which the price is known. From this comparison, the price to be to the workmen is found.
Methods of Hastening Work. — The commonest plan of hastening work, and one that gives good results, is to pay the jnen a bonus for every ejttra yard they drive over a cei-tain stipulated amount. So far as working is concerned, perhaps, the cheapest way is to only work one shift, for, ns a rule, the night shift leave work behind for the day men to do. If different shift of men are employed, the best way is to measure up the amount each shift does, and pay them on it, as by this means each set of men know that they will receive the money for all the work they J
Breaking Ground,
do, and consequently work Imrder. Where rapidity is the main object, Gix'hour shifts are adopted, with one workman always remaining to, and starting from, the middle of a shift. This one does all odd work, fetching tools, Jkc. ; the regular workmen are then able to keep constantly at the face.
TOOLS USED. — Shovels are principally used for removing broken debris, and always have pointed noses, to enable them to get post the larger pieces of loose stuff. The length of handle varies; commonly it is about 30 in., this being set at an angle of from 140° to 160° with the surface of plate, which varies from S to 16 in. across. In some districts, baskets are used for loading in prcfei'once to shovels, the coal being raked into them. They are largely employed in the South Staffordshire coal-field, and are made of wicker-work for the working places, and of iron forgave-i'oads, the reason of this being, that the former are practically noisetesB. With them, a man certainly loads more stuff than with a shovel, especially where the ground is uneven, as in such cases the shovel catches on projections. Their application is limited to thick seams.
PiokB.- — These vary much in shape for different uses and different qualities of ground. For holing purposes, where the blow is struck in a horizontal direction, the weight is small, generally about 3 lbs., with a head 15 in. long, and a helve from 34 to 33 in. The head will be dightly curved for holing along a straight long-wall face, as the miner naturally swings his pick in a curve, and the blow is then delivered in the direction the instrument is moved. If, however, the miner it under-cutting in a narrow road, and working in the comers against the " fast," the curved head cannot be employed, as the curved portion would catch against the side before the point entered. For cutting coal or breaking rock, the shape of the shank, or stem, is usually square in section, tapered to a point ; white for dressing rocks when sinking, a chisel-shaped edge is employed. For coal work, the shank tapers uniformly from the eye to the point; but for stone work, the point tapers suddenly, like the sharpening of a pencil. The head part is fitted into a wooden stem, called the helve, upon which the greater strain of the work is thrown ; so, to prevent rupture of the wood the eye should be made as broad and long as possible, and the two side cheeks carried down the helve a good distance. On the other hand, for under-cutting, where the tool works in a narrow slit, the eye must be made as slim as possible; if not, the pick-head cannot be tui-ned suUiciently to enable the point to catch the aides of the cut. Helves ai* gen eially made of good straight-grained ash, nicely rounded to fit the hands of the miner.
American hickory helves are becoming largely employed, the only objection raised agatnat them being that they are ratlier too springy, and jar the hands in delivering a blow. This objection, probably, arises more from prejudice than anything else.
Texj-Book Of Coal-Mining.
A pick worthy of mention is that known as the Jtlvelaiiie, employed by the French and Belgian miners for holing in thin clined Beams. It is made of flat steel, about in. thick, and the helve is fi'om 3 ft. fi in. to 4 ft. long {Fig. 37), so that the miner does not have to get his arms under the face. A very narrow Bitt is made, and waste is reduced to a minimum.
In the day, a workman spoils the points of several picks, which he has to bring to the surface to get sharpened. The labour of doing this is considerable, and numerous de'ices have been brought out with a view of lightening it. The oldest consists in employing loose points, held in position by a screw, but the idea is a failure, owing to the difficulty of keeping them tight and firm,
Fig. 37.
3S,
which ia only possible when they ui-e new. A better plan is that of the Hardy Pick Co., which consists in making the head loose, and either employing a tapering helve, getting slightly broader towards the top, and thi-eading the head over the end of the handle, and allowing it to slide down into its proper position (Fig. 38), or by recessing the head of the pick, and fitting it into a rectangular iron collar at the top of the helve, and securing it in position by means of a sliding wedge (Fig. 39}. Originally a, double wedge was employed, with a view of making a more secure joint, and allowing for wear ; but experience has shown that no necessity existe for this, and the single wedge pattern is most in favour. ,
The tendency at the present day is to construct picks entirely of stel, instead of wrought iron with steel points. Without repeating this remark again, it may be taken as true with regard j to every other class of mining tools. The texture of steel is such, t that it transmits a blow better than softer iion, and as it is
Breaking Ground. 4"
stronger, the weight of the tool less ; consequently the joint receives the impact better. Then again, the wearing (.'ttiiacity of Bteel tools is very much greater, repairs lire consequently less.
Bressers. — For breaking up all large pierea of coal and rook, a tool shown in Fig, 40 is used. The direction of the blow being downwards, it is inade very much heavier than an ordinary-pick. One side of the head forms a curved pick, and the other a hammer. The helve is not straight, like that of a pifk, but curved, and ufi it in largely used for wrenching purposes, two strengthening side stripe, a a, pass from the eye up the helve.
Wedges. — These ai'e most useful tools for bi'eaking up hard i-ocks, and getting down pieces shaken by shots. Their shapes are few, but hoi'der rocks require smaller wedges than softer ground, as in the tatter case a small tool would only push its way into the rock, and be buried in it. The general shape is shown in Fig. 41. The striking end is made small, so that the blow is delivered in the centre. For soft, cloddy vaiieties of ground, the penetrating end is made somewhat of a chisel shape, as this tends to split it very well ; but with harder vaj-ietiea of rock, small dumpy wedges are adopted, gradually tapering towards the ejrtremity, and suddenly sliarpened to a point.
Hammera. — Tlie cumraouform (Fig. of an eyeand two Btems, tapered down to form the striking faces, which are slightly convex, and liave 'heir edges rotmded or chamfered off, BO thai t&a fcaiwiislani aS the object struck when the blow V to the hand of the man holdbetween hammers and sledges
Text-Book Of Coal-Mining.
is, the latter are heaviei', ivnd the blow is delivered with both hands. For wedge-driving, long, tapering heads are adopted, so that they may follow the wedge right into the mineral ; while for drilling, shorter heads are used, as in them the material is well concentrated, and the blow takes greater effect.
Drills. — For the present, it is proposed to treat only of those drills worked by hand. These may be dirided into percussive and rotary borers. The former are either worked by the miner grasping the tool, and giving it a reciprocating action, or one end of the tool is struck with a hammer. The latter may be subdivided into two classes, one of which wears the mineral away (diamond), while the other crushes the rocks, and reduces them to small fragments, this being done either by a. screw working through n nut, or by hydraulic pressure (Brandt's).
Compaidng percussive borers with rotary ones, the useful effect of the force expended is decidedly in favour of the latter. la hand toots of the former class, about hn,lf the time is expended in bringing back the hammer into place to deliver a fresh blow, and, in addition, a considerable amount of power is wasted in tha inertia and rigidity of the tools. Ill-dii'ected blows ore also a source of loss. Even with machine drills, the same objections bold good, but here the advantage is the obtaining of deep holes. In harder rocks, percussive action is necessary, but ill softer materiids, easily disintegrated, the debris tends to choke the hole, jam the drill, and cushion the blow. As the generality of coal-measure rocks can be penetrated by rotary drills, it seems preferable to use that class.
Ferouasive Hand-tools. — For soft rock, the tool employed is called a " jumper," the hole made being a large one. It condsts of a bar of iron, from 5 to 6 ft. long, having a broad curved bit at one end. This bar is grasped by the miner in both hands, and a reciprocating motion given to it, and at the same time it is slightly turned between each blow, so that the cutting edge strikes in a fresh place each time.
This method is only applicable in soft varieties of rock, and is soon i-eplaced by the system in which the tool is Rtruck a blow with a hammer. Here two divisions of labour, called single and double hand sets, may be noticed. In the former, a man holds the drill in one hand and delivers blows with the other; in the latter, one man holds and turns the drill, while the striking is done by another man, and sometimes, in very hsj ground, by two men. In single-hand tools, small drillsare employed, and the power expended is more effectively applied than in double-hand sete using laiier tools, as in the latter case one man is solely employed turning drill. The bits too, in small drills, stand better than large ones, which is probably accounted for by the more uniform temper. Th blows delivered with the small diills are more rapid and light, this being advantageous in a hard siliceous rock, as there '
BREAKING GEOrND.
dency to break it off iti small pieces, requiring the expenditure of less power, and there is also lea liability to injure the took. The drills of both classes are composed of a stem (generally of octagonal section), a striking fac, and a bit. The end which receives the blow, made smaller in diameter than the stm, so that the blow strikes dead in the centre. The remarks previously made about constructing' picks of steel apply more especially here. Steel being so much stronger than iron, the etem can be materially decreased, and the mass through which the blow has to be delivered is correspondingly reduced, with tho result, that the power expended is more effectively employed.
Tlie edge of the chisel is always curved to a certain extent, more so for softer rocks than for harder ones. The edges also are less acute for the latter class. In boring a hole of any depth, the first tool used is shorter than the following ones, and the breadth of the bit of each succeeding drill is less than the one before, so that the tool can cleaiitself and follow freely in the hole. The great thing in hand-drilling is to properly turn the drill, so that the hole is round ; otherwise it is iuipossible to bore deep holes, and the cailridges employed for blasting do not fit properly, leaving spaces in which the gas expands when the shote are fired, and the useful effect is lessened. In the Cleveland iron mines, triangular holes are bored and loose powder employed, it being claimed that such form is specially tidrantageous in the deposits of that district ; but machine drills, boring round holes, are making great headway there.
There is a special art in sharpening and tempering tools. The blacksmith must be experienced in the different qualities of ground. The only objection raised against steel tools is, that the pconts sometimes break off with the first blow or two after being put to work. The fault in such cases does not so much lie with the Btel as with the smith, as the explanation of the sudden fracture is that, in hardening and tempering the point, the tool is plunged into cold water whilst a portion of it is yet at a red heat, the consequence being that the steel is made as brittle as glass. In sharpening, in no case should the tool be heated to more than a blood colour, and no further up the etm than is absolutely neces- Baiy, and it should then be hammered lightly and quickly until quite black. After being sharpened, it is perhaps best to allow the tool to cool down before it is tampered ; but such is not absolutely necessary, so long as it ts not made red-hot too far from the
In hardening, the tool should not *urther jp than
I in. from the point, and it is tJi- ' watier for
about J in., leaving in. stiU of the
tool will then be filed, fo that t 4al is
to the atmosphere, w' top
{Mu-t gradually passes towRrai s
TEXT-BOOK OF COAL-MimNC!.
y appear on its surfiice, these miiicattD' tbe temperature the metal hae att-tuned nnd the degree of harduesa stilt remaining iu the Bteel ; when the desired colour appears, the article is plunged into water, completely cooled, and retains the temper, as it is called. The colours appearing on the steel during the tempering process vary from a faint yellow, through brown and purple, to a full blue colom-, the [oi-mer giving the very hardest temper, while iu the latter the metal is bo far >rtened as to permit of a little bending in small articles befoi'e nny fracture takes place. The experience of the smith is the only guide as to which hardness the tool should be tempel'ed. It must be harder than the mineral to be attacked, but should also soft and tough enough not to be brittle. There ia no advantage in having a very hard, brittle tool to cut soft rock.
Scrapers. — In percussive boring, the debris produced at the bottom of the hole is cleaned out from time to time by the use of a tool called a scraper, which generally consists of u rod of copper, with a circular disc at right angles to it at one end, and a semicircular groove, like a cheese-scoop, at the other (Fig 43). Unless
E2£?=
the disc end is considerably less in diameter than the hole, the powdered mineral is pushed right to the back, and prevents the bit getting at the rock when it is re-inserted. To dilute the sludge, and prevent the tool from sticking and getting hot, water is in downhill holes ; a little ring of straw, or a piece of leather with a hole in it, through whicli the tool passes, is put over the hole to prevent the sludge spurting out. .
Tamping or Bamming. — When a hole has reached ita required depth, the blasting charge is inserted and rammed ; that ' is to say, some material is placed over it to prevent the escape of the gases through the front of the hole, and so online them at the back of it, their only escape being to blow out the roclc. In preparing the hole, it is cai-efully out for the last time, and if water has been used during boring, it is dried by connecting to the scraper a small wisp of hay, or rag, which forms a sort of plug, and sucks up moisture ; or, if the hole is very wet, the claying or " bulling" iron is employed. This consists of a stem of wood (a, Fig. 44) and an iron head (b) through which a hole (c) 1 passes. A lump of clay is inserted into the bottom of the boreal
Breaking Ground.
hole, and the atwmp of the clivyiog iron driven in, forcing the clay into the interstices of the rock, and acttinlly forming a Uiiing round the hole. The bulling iron is lifted out by passing a cross- hM-through the hole c. The charge and tamping are then put in, the latter in email quantities at a time, each quantity being auMeesJTely rammed with the tamping-rod, which consiets of a bar having at one end ii flat face, while the other terminates in & cone having a groove cut in it (Fig. 45), to allow the means for hghting the shot to lie against the side of the bor-hole. This may be either a needle, or pricker where straws arc used, or fuse, or wires if electricity is the agent. The farther the tamping is from the charge, the harder it is stemmed. In .strong rocks blowB are given to the end of the rammer by a hammer.
Hand Uaohine Drilla.— The general type of these consists of a screwed spindle working through a. nut, with a socket for the boring tool at one end, having a square on it for the i-hatchet-handle which communicates yQ
power.
The siete of a screw-spindle a, working through the nut collar b. The boi-ing-bit is of the ordiniiry auger form, with a V jioint. The screw is revolved and pressed gradually against the rock hy tiuuing the ratchet -handle c. small pieeeK are broken ofT, and the hole is bored. When the advance lias reached the length of the drill, it is worked back into its sheath again, and a lunger one insertetl. Witli an ordinary nut arrangement, as many revolutions have to be mile with the screw to replace it in its sheath, aa took place during boring. To prevent this wawtp of time, a split-nut, having lugs on each half tapped with right-and left-hand threads, is adopted by the Hardy Pick Co. These lugs are connected by a screw, cut with a n'ghthand thread at one end and a left-hand thread at the other, and can therefore either be brought in contact with, or disengaged from, the main propelling screw. Consequently the drill and screw can be withdrawn without being wound back.
With this type of drill, a tree or prop has to be set near the face, to support one end of the machine. To prevent loss of time, many machines are suppli' -hose length is adjustable
, aa it is formed of UDon eadi other,
and be clamped t™™**""" made by an
ordinary length
In the ElUot worm-
Text-Book Of Coal-Mining.
wheel in the teeth of which, a square-threaded feed-crew
I. pitch, takes its bearing. Thia wheel is canied in a ring, having a hinged joint at one side, and a screw clamp b on the other, BO that more or less friction can be set up between tha V and the worm-wheel. The feed is thus automatic, and the extent is regulated by the tightness, or otherwise, with which ths ring is screwed up. If the resL'tance is exceeaire, the wheel slips round to a cei-tain extent, and reduces ths full advance of the drill, which may vary from J in. per revolution to nothing.
If the clamping screw 6 is slacked, the drill can at once be withdrawn without being wound back.
When boring near the sides or roof, the crank-handle cannot bo completely rotated, but has to be worked backwards and forwards,
and a ratchet employed, thus all the time devoted to one half the motion is lost. To remove thi disadvantage, the ciank-handlfl is not connected dii'setly to the screw, but thi'ough the intervention of bevel gearing, iiornSt's* machine is so fitted, and in addition, the nut in which the feed screw works ia seated in a sprinff box, so that with an iiici-ease in pressure, when working in hart strata, the feed is equal to the pitch of the screw, less the amotint of compression of the springs. "When these are fully compressed, the nut slips out of its beatings, and revolves with the screw, the feed being then governed solely by the spring pressure, untU the resistance decreases, and the nut again occupies its seat.
In thick seams, ordinary stands cannot be employed. In tin anthracite mines of America they are replaced by a clunptnff device, showu in Fig. 48, attached to the Howell t drill, one a j
BREAKING GEOtrND.
Fig a. 49 and 50.
the best kiiownin that coa.l-fiel<[. To fix the machine, u hole, 3 or 4 in. diam., is first cut into the face, and the olamping-bar a, which is supplied with a number of spikes, is firmly wedged in it. The illustmtiou to a great extent explains this. The auger bit ie rotated by bevel wheels, geared down from i : 3 to 6. A point worthy of attention, is that two or three holes can be bored from one position, owing to the sector ami 6 allowing movement either to the right or left.
The merits of a drill depend upon its weight, the facility with which it may be set and used in different positions, and the wearing capacity of the machine itself. The rate of boring depends entirely on the form of the cutting tool and the quality aF the steel, because, unless the latter is suitable metal, it is no use making it of a suitable form, as that form is soon lost by rapid wear. A great deal also depends upon the men. Unless a certain amount of skill is shown in setting the machine, and properly clamping it in position, as much time is occupied in drilliiig holes in ordinary varieties of rock as if they wei put in by hand.
The most suitable shape of the points of the twisted augers for drilling ordinary rook-binds and coal, is showti in Figs. 49 and 50. This form penetrates with greater speed and less labour than any other pattern, and ifi easy to reptiir. The piece cui out of the centre, sfaould be a little more than one-third of the width of the point, and of a broad V shape, in order to keep the two outside portions as strong as possible. Tliese should be kept as thick and stiff as the section of the steel will admit. Tbe cutting point should be carefully kept sharp, with a good clearance left at the back. As a rule, the greater the opening in the middle, the more rapid is the penetration, especially in coal, shale, and soft sandstone ; but the size of the V opening is governed by the hardness and strength of the rock to be bored. When great pressure is necessary', the opening at the top of the V should be narrow.
The best results are obtained in tampering, by heating one inch of the points to a blood-red, and then plunging tbem into coaltar, as the cutting edge ia made extremely hard, the pointJt gradually becoming softer as the thickness of steel increefies. Drills eo treated, can be rearpeued once or twice on a grindstone, until it becomes necessary to put them in the fire again to enlarge the points.
example is given : — At a collier* Hd
was driv for 61 yards, en> dl.
J
The secdoa of the road was 6 ft. wide at the bottom, 5 ft. 1 the top, 5 ft. high, and it was driven at a down gradient of in, to the yiuTi. Time occupied, 5 weeks; rate of progress, 11 yards ] per week. The cost was: labour, 47 los. ; powder and fase, 1 I iSg. gd, ; total, Bh. gd. The total cost per yard run j was 19.488s, etjual to 6.386*. per cubic yard; and the coat of J explosives per yard run was 3.9148. The hardnesa of the ] measures varied considerably. A small portion could be worked ' with the pick, but other parts consisted of a hiud, gritty sandstone, nearly too haril for the drill. Very little timbering was required, so this did not interfere much. Ventilating pipes and rails had to be laid. The road might be considered a very fair sample of a cross-cut in the Coal Measures. Similar work in another part of the pit, without the aid of a drill, cost jQi a lineal yard.
TBAirSlf ISSION OF POWEB. — In considering the que tion of transmitting [lower to the machines used in breakin ground, choice is limited to compressed air and electricity ; th other means of steam and wire ropes are inapplicable. Steam is, to a certain extent, out of place in a mine, although, under certain exceptional conditions, it is employed, and gives good i-esulta ; but ' its use in confined spaces, where either coiLl-cutting is in progress or rock-drills are being worked, is ijuite out of the question.
Compresaed Air. — Air may be considered a perfect gas, and obeys the laws relating to such a body. These are :
(i) That if the temperature be kept constant, the volume varies inveraely as the pressure ; if for example, the pressure ia doubled, the volume will be reduced to onehalf.
(2) If the volimie be kept constant, pressure varies diredly
as the temperature. Thus double tempeTature gives double pressure.
(3) If the pressure remains constant, the volume varies directly
as the temperature. Thus if the temperature is doubled
the volume is doubled. If the above laws are clearly understood, it will be at once seen that great losses must occur in compresang air. When the volume in the cylinder is reduced by the piston, u considerable rise in temperatui-e takes place, which can only be produced by an expenditure of power, heat being simply work in another form. If the compressed air were used immediately at the point where it was generated, no toss would take place. This, however, is never done ; the heat produced by compression is lost in the transmission-pipes, and all the power which it is lost also.
The increase of temperature during compression, expands the air in the cylinder and increases its ]>ressure, so tliat the piston is met both by the natural resistance of the air to compression, and tiy the increased resistance due to expansion by heat. Another loss thi-ougU this heating is that, at the moment of discharge tha
Breaking Ground.
air bears the pressure it should do, but as it cools the pressure fiilk. It has been noted that, in an ordinary compressor, the air was compretised to four utmospheres after the piston hnd travelled |tha instead of Jth.i of its stroke (see first law above), the com' pressed air occnpjing ths instead of Jth of the space in the cylinder.
A third loss is due to the fact that the sides of the cylinder become heated, and the air on entry is expanded, so that when the piston commeucea its stroke, the air contained in the cylinder is actually below atmospheric pressure. A smaller mass or weight of air is in the cylinder, but the increase of pressui-e duo to the temperature makeB the pressure norraitl.
From these considerations it follows that, to secure good results, there should be (i) thorough cooling during compression, and (j) the air on introduction should have as low an initial temperature aa possible.
Air CompreBBors. — Two systems are in use by which the heat produced during compi'essioQ is absorbed. In one, water is not admitted into the cylinder, while it is in the other. The former are called " dry " and the latter " wet " compressors.
In dry compressors, air is cooled during compression by the use of a water-jacket on the compression cylinder, but at the best the action of this is very imperfect, as the area of surface exposed to the cooling action is small, compared with the volume of air compressed, so that only a small portion of the confined air can come into contact with the inner surface of the cylinder. In addition, air parte with its heat to a metal cylinder very slowly, and, with a compresiur working at moderate speed, there is not time between the inlet and discltarge
to effect sufficient ductioQ in the temperature.
Wet compressors may be subdivided into two classes — those where the air is compressed by a piston of water, (li) where a fine spray of water is injected into the cylinder during compression.
The former type, the design of which is due to Sommeiller, is illustrated in Fig. 51, and consists of a piston a, moving horizontally iu a cast-iron cylinder kept full of water. From theextremities of this cylinder spring two vertical cyliii''' their upper eutla by covers bolted on. Th" through rectiugulur openings c c, in
cylinder, the Buction-valve being of leather, while diechiu place through a conical bnuis valve d, situated in the top. The reciprocating movement of the pL'tton causes the water to rise on one side and fall on the other. A partial vacuum is formed above the falling water, which causes the ad simon-valve to open and the unoccupied spaces to be Hlled with air ; while on the retain, (itrolce the watr i& driven back, and the air with it, untU coEapresHion in the cylinder is equal to the pressure in the receiver, &nd then the dehveiy-valve opens.
These compressors have been largely employed on the Contiaeal the idea being that, if the air during compression with water, all heat would be absorbed. Such, however, is not the case. The air is only exposed to water on one side ; a thin film of this noon gets hot, and, water being a bad conductor of beet, little cooling during compression takes place. As, however, a certeia quantity of water ii carried over into the delivery-pipes at each stroke, the air is cooled before it gets to the receiver ; but to be of any economical good, cooling should take place during compress , sion. Indeed, it haa been found that, to get good results, spray injection has to be introduceil near to the outlet-valve.
Oompressors of this clsis resemble pumps, and must work at' slow velocities. As a large body of water baa to be set in' motion and stopped at each stroke, considerable friction is caused, and the machine subjected to severe shocks. It must, therefore . be made very uti-ong, and to produce the same quantity of air as a. high-speed compresiior, must be considerably larger, and taker more power to drive.
The actual position of affairs seems, therefore, to be that, by the assistance of & water piston and spray injection, a certain economy in compression is gained, while this advantage is neutralised by the extra power required to drive the machine. In addition, there is the difference between first cost and cost of maintenance in the two systems. It is impossible either to purchase large engines, or to keep them working, at the same cost as smaller otiee.
The second division of wet compressors is that in which water is injected directly into the cylinder. This answers well in keeping down the temperature, provided that the water is in the form of fine spray, that it meets the piston during compression, and that it is in thorough contact with the air. A further economy results from the fact, that the power required to compress moist air is less than that required for dry air. The injected water also fills clearance spaces, and prevents loss From this cause. The absence of these in a compressor cylinder is a point of high No spaces should exist between the piston and the cylinder at the termination of the stroke, because such spaces with air at high pressure, and, on the retreat of the piston, air expands and fills the cylinder, no free air entering unUl pressure is reduced to that of the atmosphere.
rise OD 1 above
BREAKING GROUND. gi
It is, however, believed that the cooling results obtained by the use of a spray of water ore deceptive, as they take place principally after the air is completely compressed.
The objection to the injection system is the wear of the cylinder and piston, caused by the fact that water is not only a had lubricant itself, but its presence in the cylinder prevents oil, or grease, getting to the working parts, as it floats on the top of the water. The situation is bad when clean fresh water is used, but much worse when, as is often the cae, it ia necessary to employ acid water or water coutaiuing grit or sediment. Another objection is, that the compressed air produced contains a considerable auiouot of moisture, and that when used the exhaust ports of the motrire become clogged up by the formation of ice. By a proper arrangement of I'eservoii-s, nr draining tanks, moat of the moisture in the air am be removed before it is used in the motors.
The difficulty in getting rid of the heat produced by compression has hitherto pi-evented the use of even moderately high pressures, but the nieana adopted at the Paris installation have overcome this. The air is compressed in two or more stages, and thoroughly cooled between them. Tiiis intermediate cooling is easily and thoroughly effected, the air being taken through tubular vessels which present any amount of cooling atirface that may be required.
The genera] type of modei-n air compressors, consists of a pair of engines having the air cylinder arranged, tandem fashion, bebiad the steam cylinder. With a single engine and air cylinder arranged in a straight line, it is impossible to construct an economical machine, because the greatest work in the air cylinder has to done at the end of the stroke. At the beginning of the stroke, when the steam ha: full pressure, the air cylinder contains air at atmospheric pressure, and ofiers no resistance, but at the end of the stroke, when the pressure in the steam cylinder would be low (if expansion were used), the resistance in the air cylinder is at its maximum. All sorts of arrangements have been designed to equalise the power and resistance, but have given way to the straight line paiitype, with cranks set at right angles. Espansive woriung can then be used, as one steam cylinder is always exerting its maximum power at tho moment when the air cylinder of the other engine ia finisliing its stroke.
This explains the seeming pai'adox, how steam, say at 50 lbs., can compress air to 70 lbs., where both cylinders have the same <liametr and stroke. Whenitisremenibered, that at the commencement of the stroke the pressure in the aii' cylinder is nothing, that fur three-fourths of the stroke it is considerably below jolbe., and that only at the moment of discharge does it reach Htka *iu. nigtigQ jg self-evident.
TEXTBOOK OF COAImXIXG.
Varioiu Valves on Air CompreMon :
Walker' $ IWret. — The inlet valve is oonnectad bja link (a. Fig. 5 2), and pictou with a ocmtroUing spindle c, these redptorating with the movement of the valve. When the piston retieatSy auction opens the valve, which is prevented frcmi going too far bj the spring J, which becomes compressed. Immediately the piston starts to return, the valve is closed by the spring, and pr evented from being violently 'lashed on to its seat by the coUar fj which moves with the spindle, coming into contact with the ind-rabber buffer kf carried on a fijced abutment /, suspended by two bars m, attached to the cylinder cover n. Messrs. Walker's experience has shown that it is abjo desirable to buffer the valve on its
Figs. 52 asd
in-stroke, this being done by a second india-rubber washer striking against another fixed abutment i. It will be noticed from the drawing, that the tension of the spring, and the position of tho Ht()|>8, can be varied, if desired, by a nut and lock-nut amiiigenient, e and/.
The outlet valve (Fig. 53) is balanced by making a portion of the spindle passing through the stufSng-box hollow, the outer end passing into a small cylinder a, into which air is admitted at thesame pressuie as in the receiver. The valve is prevented from too lupidly by the spring 6, and is buffered on its in* stroke and out-stroke by stops, c, c', arranged to engage the i blocks, e, e' (carried by a fixed ci'oss-bar/), just prior to tiU'inination of tho valve's trjivel.
Tho india-rubber blocks are annular in form, but nf a T-shape in cross section, the faces of the annulns I
Breaking Gkound.
oat to leave ft projecting flange at the inner and outer peripliery. With thia sliftpe, it has been found that the life of the bloclcB is cotuuderabl]!' increased.
Sturgeon's Viilre. — The feiitui-e ot Sturgeon's Air Compressor consists of a. stuffing-box inlet valve, which is opened by tha piston-rod at the commencement of its sti-oke, this doing away with pj ,,
the necessity of forming a vacuum, in order to cause the valve to open. A complete cylinder, full of air at atmoepheiic pressui'e, is taken in at each stroke, and immediately the piston starts to return, the valve shuts. In Fig. 54, i ia the inlet
valve attached to the stulHng-box / " - " " - " ' "
of the piston-rod. By means of J futon
the nuts, a, a, sufficient grip caa
be obtained to ensure the valve
opening on the forward and bacJc-
ward ttrokea of the piston. The
stops, 6, b, screwed to the valve,
limit its travel in one direction,
while its flange portion performs
the sanie ofl&ce in the other. The
piston is recessed to fit over the valve at the termination of
each stroke, and reduce clearance to a
valves, o, o, are usually eight in number and
separately for repairs, or remo\-ed by unscrewing. A spiral spring
c in mch oae, serves to bring it back sharply on to its seat. The
ction of the air both from the inlet and de-
TEXT-BOOK OF COAl-MINING.
hii/ertoU- Sergeant Voire.' — This consists of two auaiil&r (a, Fig. 55), placed in a hollow piston of a, double-KCting air-<7linder, free air being admitted through n hollow tail-rod attached to the piston. The valves do not require the aid of springs or other connections, bnt are opened and closed at the proper moment by their own inertia. The arrows show the direction of the intake and deliverer ; the outlet vaJveii are shown at b. To reduce clear* ance, small recesses, c, are turned in the cylinder coverR, into which the inlet valve fits at the termination of the stroke. As there are no inlet valves in the cylinder covers, water-jackets, d, d, are provided at each end, as well as around the eidee. Fig. s6. e,e. The air passes into the receiver through/.
A perspective view of the valve is shown in Fig. 56.
Means to prevent " Daocing" of ValveB. — In the ordinary foi-m of valves to which a spring is connected, \-ibratory motion is set up, because the air tries to pull the valve open and the spring to shut it, and first one and then the other pre-
The dancing of the valve in Widkei's Air Compreesor is reduced by causing a certain amount of friction to be set up between the spindle {c, Fig. 52) and one or more of its To accomplish this, where the spindle passes through the cross-bar {p, Fig. ja), the bearing is split longitudinally, so that the boi'e of the bush I can be slightly contracted by means of a I screwed spindle (a, Fig. 57), having a handwheel h, and lock-nut c, connected to the top 1 half of the step. To proride a greater fric- I tionnl surface, the spindle is made of large j diameter where it passes through the bearing, and is surrounded by a carbonite washer, which acts as a lubricant and prevents heating. Only a small amount of friction is applied, go as not to J interfere with the free working of the valve to any apprciable extent. This device gets over the difficulty of " dancing at ordinary speeds, but increases the power required to open 1 valve.
A very simple but elTective device is in use at Lens Colli (France). The inlet valves are of the ordinary poppet tyj closing being effected by a spring, a, Fig. 58 ; when opened, h ever, the pull of tluK spring is taken olf in the following ma Each end of the cylinder is provided with two inlet valve spindles of which, b, pass outside the cylinder cover. OppoatBR valves is fixed a small shaft c, which performs one revolt**"
Fio. 57.
Breakittg Ghounb.
each revolution of the engine, and on this shaft, opposite each valve, ia keyed a cam d. At the corainencement of the stroke, the face of each cam engages with the spindle of the inlet valve, puahcH it wide open, and keeps it there. The small revolving abaft turns this cam, and its shape is so arranged that when the piston starta to make its retnm stroke, the cam is past the spindle, and the spring brings the valve back into its seat.
Conduits. — Air is conveyed from the producing machine to the motors through pipes, and a loss of work takes place from friction, governed b; the following laws : varies directly as the length of the pipe, (2) inversely as the diameter of the pipe, and (3) directly as the square of the velocity. The loss from the first law cannot be done away with, as it is impossible to alter the distance between the compressor and the motor. By uiiing pipes of large diameters, the loss fi'om the two latter laws can be kept within
V limits, but the expense of doing bo is considerable. The experiments at Paris* show that when the velocity in the pipes exceeds 50 feet a second, the loss in pressure becomes serious even in the distance oF one mile. The loss, however, for two miles is not double that of one mile. The size of the mains can best be reduced by adopting high initial air pi-assures. Friction in mains may be reduced to a conderable estent by employing glafis-Uned pipes, an invention lately introduced.
BeceiTSrs.' — From the compressors the air is discharged into a receiver, fitted with a safety-valve and pre.ssure-gauge, placed near by, which not only serves the purpose of a reservoir, but correct* the irregular delivery from the compression cylinders. Bceivera also rid the air of moisture, and should be bo arranged that the air passes in and out on the same side. Drain-cocks are provided at the bottom, to get rid of the water. If the motors are any oonaiderable distance away, small subsidiary receivers should be placed near to them in the workings,
— lu these, the greatest loss takes place through leak- ' h an ordinary engine the condensed moisture
;.E. cv. 191.
Text-Book Of Coal-Misixg.
on the udes of the cy lioders acts like paokiiig, and helps to keep the pistol tight; but compressed air is dry and hot, and leakage becomes serious. The most economical results are obtained by heating the air before it passes into the motor, whicli serves the double purpose of not only heating the air, but helps to pack the piston It, however, introduces this disadvantage, that the exhaust ports are likely to choke up with ice, through the moisture freezing ; but this can be prevented, to a cerbiin extent, by having ]arge ports, and by allowing the exhaust to take place directly into the atmosphere, and not through pipes.
EIiEGTBIOITT.It would be quite foreign, in such a work as this, to enter into an elaborate description of what electricity is, how it is produced, and the different systems and methods of using it ; but as the mining engineer of the future will require to know a considerable amount about it, some brief description here will not be out of place. Every one is familiar with a magnet — its power of attracting bodiesand knows that each end is called a pole. This magnetic influence is exerted in certain lines, radiating from the poles, which were called " lines of force " by Faraday, who discovered that if a closed loop of wire were passed through them, a current of electricity was set up in the wire. This is the principle of the dj-namo, which consists of a number of coils of wire revolving rapidly in a magnetic field. The electro-motive force depends on the rapidity of revolution, strength of magnet, and the sigh at which the coilB of wire pass through the miigaetic £eld, wtuch should be as near right angles as possible. Tlie ciurent, however, set up by such action does not flow in one direction, but consists of a series of roversida in opposite directions.
Alternating and Continuous Currents, — At this point in reached the division line separating the two systems of electricity. In one, the current is transmitted through conductors, and used as it is generated in the machine, that is to say, in a series of starts and stops or complete revei'sals, such being called the alternating current ; in the other, by introducing into the dynamo a device called the commutator, the current pi-oduced in the armature is, HO to say, straightened out, 0ows in one direction, and there is then obtained what is called the continuous current.
The latter is the system most generally applied, especially for the transmission of power, because up to the present, with probably one exception, an efficient alternating current motor has not been discovered. Once staited, they work very well, but the great difficulty is to get them to move against a load. There is little doubt that this will be overcome, and then a very line field will bei| open for such system, especially in mines, as an alternating moto is moi'e compact than a direct -current one, possesses no a mutator, or brushes, sparking oidy results by severing action, i the extreme simplicity of the winding and geueiul construct makes it very unlikely to get out of repau'.
n
Jm
Breaking Gkound.
S7
The great aclvnutage of tfae alternatiiig system is the ease with which currents of high tDsion can be converted into ctuTente of lower tension, but of a larger quantity. This is a point of conliiderabte importance, because in mines it is often ueceesary, in order to obtain the fullest benefits from any system of transmitting power, that small machines can worked at isolated points where required. Now, small motors developing a few horBopower are exceedingly difficult and costly to make to worse with currents of high electro motive force. As pointed out further on, for any extended application of power, the coet of conductors can only tie cut down by transmitting the current at higli potential in the mains. To transform this into a lower pressure, ia wasteful with the continuous current, and expensive machines have to be employed to do it. With the alternating system, however, the problem is a simple one. It is well known, that if two wires be placed side by side, not in mechanical contact, and a current passed through one wire, a current is developed in the second wire at the moment of starting or stopping the current in the primary wire. It therefore becomes necessary, if a jiermanent flow is be produced in the second wire, that the current in the primary wire must consist of a series of starts and stops, which is actually what takes place in the alternating current system. If the two coils of wire are of the same length and diameter, the current in So. 2 will be the same in No. i, but if the relative length and di&meter of the wires io the two coils are varied, and thesecondary coil consists, comparatively speaking, of a few coils of a larger diameter wire, while the primary coil is a large number of coils of a smaller diameter wire, the current generated in the former will be feebler in its intensity, but larger in its quantity.
TenuB ITsed. — The only difficulty in undrstandinf; the question of the electrical tranRmis-sion of power consists in not knowing the menning of the various terms used. The whole question of electrical distribution has been popularly illusti-ated by its analogy to hydraulics. Supposing a pump is circiUntiug water through a circuit of pipes, every engineer understands the meaning of such terms as pressure, gallons per minute, friction, ibc, wbeu applied to such a current of watr. If dynamo be for pump, wire for pipes, and electricity for water, the conception of the elementary phenomena of electrical transmission by a continuous current becomes clear. In dealing with water, the pressure in lbs. per Bi|. in., the number of gallons to be delivered, and the friction of the pipes, has to be known ; in electricity the pressure is spoken of as Electro Af olive Force (usually written E.M.F.),and is measured by volts, the quantity is called amperes, and the friction is called resistauce,tuid measured byoAfiM. Toobtoin the measure of electrical energy, the pressure (%-olts) is multiplied by the quantity (ampfires), [ volt-amperes, called One watt one volt watts are equal to one boree-power.
S8 Text-Book Of Coal-Minikg.
As in hydraulics, the longer the pipes and the smaUer tlieir iliameter, the great will be the lose in tramanisGion ; bo with electridtj, the longer the wire, and the smaller its diameter, the greater will be the resistance and the loss. On the contrary, if the wire is short and its diameter lare, no appreciable loss should (theoretically) result. The resistances of a long length of wire may be so great, that all the current may be wasted in overcoming them, and none reach the points where it is required to do work. In such a caee, increase the size of the wire aud lessen its resistance. Copper is the metal generally used for electrical conductors, and it is a costly one. The resistances in a long length of wirs may be so great that, to overcome them, a wire of so large a diameter would have to be used, that its cost would be outside the bounds of possibility. One other alternative is open : increase ths E.M.F. Electticia&s have from the first recognised the pressing necessity of a current whose voltage is as high as postdbl since the coat of copper for line wire varieH in the inverse ratio cf the square of the voltage employed. Thus, supposing 2000 lbs. of cupper are requu-ed to transudt a giveti quantity of power ft certain distance under an E.M.F. of 50 volts, 125 lbs. only will be necessary if the E.M.F. is increased to 200 volts. For the voltage having been increased four times, the cost of line wire will be reduced Kixteen times. Currents can be produced in practice, whose E.M.F, is 10,000 volts, and if a current of such high tension be used, the cost of conductors could be reduced to a minimum. This, however, is the point with which the minings engineer is directly concerned. Currents of high tension are dangerous ; if the circuit became broken, the current would leap the break, and produce a spark which would ignite gaa in a fiery mine; while if the current were by any accidental means passed through the human body, death would result. The collietT' manager is, therefore, placed in a difficult position — he wishes to use high-tension currents for the sake of econopiy, and low-tension ones for safety. The general opinion seems to be, that 500 to 700 volts must be considered the maximum E.M.F. for use in
Means to Prevent " Sparking." — The chief danger is feared 1 from the production of sparks, either at the brushes, or by the severance of the cable. To remove the probability of gas being,] ignited by the former, Messrs. Atkinson* enclose the a brushes, and commutator in a casing, which bears c ring fixed to the pole pieces, aud also on a turned plate or risiE which acts as a brush-holder, and which may be rocked If' brush-holder, so that the position may be to the [ where sparking Is nil. The safety arrived at by tliia metb depends on the principle of excluding gas.
Inst. C.E. c
Breaking Gkound.
FlQ. 59,
1
Messrs Davis and Stokes have recently patented an airangement,* whei'e the brushes are placed infide the commutator, and hIso enclosed in a casing ; sparks take place inside the commutator, and cannot get through to explode the atmosphei-e outside.
To prevent the breaking of the cable by falls of roof or sides, and consequent sparking, the general method is to allow plenty of " ilack" between the points of support, so that if a weight falls, the slack is drawn up, and the cable accommodates iteelf. To still further reduce the probability of severance, the cables at Plymouth Colliery t are protected by a double alieath of No. 8 8tel wire on the outside of the insulation, the first stranding being of thirty-eight wires, and the second, thirty -sis wires, laid in reverse directions. As a result, the cable is capable of resisting heavy falls, its tensile strength being aliout 30 tons.
Mr. L. B. Atkinson has recently introduced a safety cable,I constructed on the , following piinciples : — In Fig- 59i ". are the two poles of the dynamo, and b, h' those of the motor, or lamps. Tbeee are each connected by two wires, a main conductor, "c f
c, c", and a subsidiary condticlor
, d, tf, which, as they are of the same length, carry current in proportion to their area. Cut-outa e' and//*), proportional to tne carrying capacity, are arranged in each main, and in each Bubeidiary conductor. If the main conductor gets broken, and tbe subsidiary conductor d does not, no spark is produced, as tbe circuit is still closed, but the whole current now passes thixjugb the secondary wire, and at once melts its cut-out. A weight suspended by tbe fuse then drops on to a switch, and the whole circuit is instantly disconnected. In it practical form, the cable consjista of a close wound spiral of tinned copper wii'©, braided over, but not heavily insulated. Over this is laid a properly insulated stranded conductor of the required area. It the cable be torn down, or broken in any way by tension, this inner conductor extends to an indefinite extent, for as it geta drawn out, the diameter of tbe spiral decreases, and it becomes quite loose in it tube.
Effloieiicy. — Tbe absolute elhciency of the ordinarymeans of producing the electric current by a steam-driven dynamo is small, as the electricalcnergy developed is only 6.4 % of the energy existing in the coal burnt umJc'r the boiler, and little advance is to be hope for, so long as steam furnishes the motive power, as modeini dynamos and BWton have Already high efiiciendes in themselves. Looking at the
6o
Text-Book Of Coal-Mixisg.
ease with which electricity is convertol into heat, it that tlie solution of the cheap geDeration of electricity will come about from the reverse operation. The direct conversion of heat into electricity has been possible since 1823, but the low efficiency of the process (only 0.35 % of the hent in the burnt) prevent its commercial application. Experiments ore, howerer, being carried ou, and the last results announce an efficiency of ne&riy 5 % , with hopes of a still greater increase. It is not too much to say that the discovery of a successful process with high eHicieiu, will revolt I tionise the generation and transmission of power.
A new departure, giving great promise, was tried in 1891 at the Frankfort Exhibition. A dynamo too miles away produced three alternating currents of different phases at a tension of 50 volts, which were transformed into three currents of 17,000 volts, andconveyedalong three wires J in.diam, to Frankfort, where they were re-transformed into 60 volts, and used for the production of power and lighting in the Exhibition . The motors were of stronger construction than usual, thick bars and plates being used (suited to the work of a miner), instead of the line wire and delicate insulation which so often gives trouble,
FOWEB MACnrNE DBIIiLS.— These machines impart to the tool a reciprocating motion. Tlieyconsist of a cylinder and piston, to the rod of which is attached a . The requirements of a good machine ai-e, that it should be of simple and strong construction, occupy little space, be easily handled, and, above all, the wearing parts should not only be easy of access, but easily replaced when broken. Am all the work of the drill Ls done during the forward stroke, while in tlie retui'U only the weight of the tool and friction of the machine have to be overcome, the piston is reduced in area on one side. In order to bore a round hole, the tool is partly rotated after each Kti'oke, and as the hole deepens, means are provided for moving the machine forward, so tluit each blow is delivered with full force. Numerous attempts have been made to perform the feed automatically, but although success has attendeil these efforts, the machines become much more complicated. With an automatic feed, the advance is regular, white often, owing to the varying nature of the ground, it is required to be anything but I'egulai" — sometimes faster, sometimes slower. Then, again, men have to kept to look after drills while they are working, and may just as well employ themselves in feeding forward the tool to the best advantage, as to stand by and do nothing. In the old type of machine drills, the piston was made' to admit and cut off the admission of air into the cylinder, by striking tappets attached to a valve, and altiiough these jiarts were made rs light as possible, yet for every stroke of the drill two blows were struck, with the result that the jMirts were mpidhr worn away, numerous breakages occurred, and the expenfle maintenance became very great. In modern power driilB,tlif|'
BREAK CSG GROUND. 6i
of tappets has been abandoned, and what are known as steam (air) moved vaJvBS are ndoptd ; their eoiistructiou Ls therefore more mple, as the machtQe only consists of two moving pai-ts. In some types, a further simpiificatioa has been canied out ; by means of suitable ports and openings in the cylinder, the piston is made to admit and cut off steam by its own mo-ement. They then consist of only one moving part, and that the piston itelf.
It would be ({uit impossible to give a description here of even tbe majority of machines that exist, so well known representatives of the tno main tj-peshave Iteen selected foriliustrating the way in which they work.
The IngQTSoU Hock-drill.— The cylinder A (Fig. 60) has admission ports, F, P', And exhaust )>oi-t E, and also two open passages, F, F', connected with the exhaust port through the small passages, D, D", so that if there were nothing in the cylinder to close
D, D', each end of the valve would be open to the exhaust. The piston B has, however, a movement from X to Y, and is provided within annular space or chamber SS', whose iengtJi is such that it can never be open to both the passages at D, D' at the same time. The valve C is spool-shaped and travels on the guide-pin T, In the bottom of the steam chest are two passages erosging each other, which connect E with D', and R' with D. In the illustration the drill is ready to deliver a blow. Air is admitted at O, and fills the spaces N, N' and R'. As R' is connected with D, which is closed by the pUton, no outlet is possible. R is connected to D", and is open to the atmosphei'e thi-ough the annular space S and passage F'. No motion of the valve therefore takes place unljl the piston moves. Air passes from N through P" to the bock of the piston at M, and drives it forward ; the exhaust passage SS' approaches D, and when the distance DD' is traversed, is open to it. At the same instant, D' is shut off by the buck end of die piston, D is suddenly opened to the atmosphere, and the chamber H' being connected with it, is exhausted. The air around the valve rushes towards this opening, carrying the valve with it. Thus the valve is reversed, the machine exhausts, and the motion of the piston also I'reversed.
The Adelaide Rock-drill. — This contiiins oaly one moring , the piston, iu thiii respect reeembliiig the Darliogtoa drill invented in 1873, but posEHitig on advantage over that type, &B the air is used espanaively and the consumption reduced. It will be seen from Fig. 61, that the one moring part (the piston C) works in a cylinder having ports and passages no arranged that the air oi' steam is automatically cat off and admitted by the piston itself. Air is admitted through an atatuiar port A, by which means the pressure is equalised on all sides of the piston rod, and unequal wear avoided. The exhaust takes place through port B. The piston rod is hollow, and small ports through the piston head allow Free communication between the back end of the cylinder and the interior of the piston rod ; the front end of the piston is of smaller area than the back end. As illustrated, the piston is just completing it forwai'd stroke.
The piston peiiorms the action of a valve in the following manner : as soon as it reaches B, free communication is opened with the atmosphere, and exhaust takes plaoe, not only here, but also through B', which has by this time passed outside the cylinder cover. The inlet aperture A, being always in free connection with the air receiver, the pressure acts on the small area at the front of the piston, and drives it biikward, until such time as this part also is brought in connection with the exhaust ; at the same moment as this takes place, B' comes opposite A, compressed air enters through the hollow rod C, passes into the back end of the piston, and drives the drill rapidly forward against the rock. Admission takes place during half the stroke, the air working expansively for the second jiart.
The object of discharging a portion of the exhaust at the gland, or working end, is of great practical importance, as by this aimple device all the fine dust wliich falls on the machine when diilling uphill holes is blown away from the piston-i-od, and the wear and tear of the rod and gland from this cause is entirely avoided.
The means employed to rotate the tool are the adopted iu aU modern drills. A spiral or rifled bar D, three grooves, is lifted at its head with a ratchet wheel E,
Breaking Gr0T7Nd.
6j
d into the cover of the cylinder. Two detent*;, also fixed in the cylinder cover, are forced by sniall springs to engage with the teeth E. The grooves in the spiral bar accurately fit into corresponding projections on the recess in the piston-rod, and hence, through the action of the detents, the pLiiton turns the bar during the out-stroke, but in the in-stroke the bar turns the piston, and the tool nssumea a new position for the delivery of the next blow,
Brandt's Drill. — This machine is of an entirely diflerent character to any othen?. It consists of a hollow steei drill, fastened to a head-piece, which is again fastened to a cylinder, and rotated by means of worm-gearing from two water-power engines, driven by hydranlic pressure. The stone is neither powdered, as with percussive borers, or worn away, as with diamond drills, but is broken in the path of tool into small pieces, and a core formed in the centre. The water under pressure not only rotates the drill and presses it against the face of the ixxsk, but keeps the hole clean and free from debris. By opening a valve, water is conveyed to the front of the revolving piston, so that the drill can be drawn out of the hole when required. The drill itself is of conical shape, with the base turned towards the rock. It is furnished with four cutting edges, two arranged in the outer circumference of the aonulus, one set directly to the front, and the other outwards, while the other two edges are arranged on the inner circumference, directly ahead of the other towards the inside, thereby reducing the core.
At Shamrock Colliery, Westphalia,* this drill has been employed several years driving a drift 5000 ft. long, the water being obtained from behind tubbing, and conveyed in pipee in. diam. Two drills were worked, and a ventilator driven by a turbine. Three seta of holes, zjin. diam. and from 4 ft. to ft. long, were drilled and fired in each 34 hours, each set occupying about 2 hours. Each drilling machine used about 1 cub. ft. of water per minute. With hand-drilling in sandy shale and sandstone, the average speed was 1 7 in. per day, at a cost of i8. 6d. per ft. With the machine in similar strata, the average speed was 6j ft. per day, at a coat of 299. 6d. per ft. An elaborate series of experiments have been carried out at Beihilfe Mine, near Freiberg,t on the power, effect, cost, and wages earned, by driving with Brandt's, compressed air, and hand-drills ; the three systems being simultaneously employed in three levels, with sis men in three eight-hour shifts per day. Taking the diameter of the hand-drilled holes as unity, the ratio of thesizes of the holes with the compressed air, and Brandt's drills, were I'espectively 8.05, and the power necessary to drive them as I : 3.26 : 8.04. The useful effect of the compressed-air drills
For. Abs. N. E, I. j
+ Ibid. zxii. 45.
Text-Book Of Coal-Minisg.
was 2$%, while the hydraulic onw only had a duty of 8.5%. The speed of dri\-iDg by hajid was .0774 feet per man per shift; by cumpi-essed air drills, .413 feet per man per shift; while Brandt's drill advanced .472 feet per man per shift.
This machine can only be used in situations where water is easily got rid of. As a rule, mining engineers have quite enough difficulty in dealing with water alridy existing in minefl without introducing any more.
SapportB.- — The wupporta upon which a drill was carried were originally either a rigid framework of clumsy coniitruciion, introduced with difficulty into narrow and uneven rock excavations, or a heavy marriage moving on rails, the latter, although carrying
several machines, I'requiring that the i-oad should be clear of dl before the drills could be set to work. The modern form consists of. vertical column {a. Fig. 62} resting 00 a base, in which lengtiiBiting screws are provided. By this means the necessary breadth base is obtained to give stability to the column, and to permit ' mounting on it of a swinging arm li, upon which the drill is attached. Iliis arrangement allows the drill to be used upon all siilea of the column, for drilling holes inclined in any direction. Bars are passed through the holes, c, c, in the top of the lengthening screws, and prevent them from becoming loosened ' vibration. With a stretcher bar, drilling immediately after blasting, as the drill and column separately carried over the debris. With such a support, machine is adjustable in all directions. It may be slnitedl ways on the arm, raised and lowered on the column, and, iff
Lised upon all !ny direction. f the length- 1
Breaking Ground,
tightening the clamp d, the arm and machine may be bodily swung round the column.
Instead of attaching the drill to the clamp through a centrebolt, the Rand Drill Co. have designed an arrangement (Fig. 63) in which the foot of the shell carrying the drill is made of a cone Khape, and grasped by a hooked bolt b, which is distinct from the bolts binding the clamp to the arm. If a similar clamp ia attached to a tripod, the drill am be changed from one support to the other with little labour, and without disconnecting the feedscrew and removing the machine from its guides, which has to be done with the old arrangement.
Where the length of the stretcher-bar exceeds 8 ft., an amount of objectionable vibration is set up, and, in high places, drills have to he mounted upon tripods. These consist of a light, strong frame, generally made of steel, consisting of three cylindrioa! telescopic legs, which can bo lengthened or shortened to accommodate ' uneven ground. These legs are fastened into sockets in the top, and are kept in position by having weight hung upon them when the tripod is in place. The socket-joints are bo designed, that the legs cau be moved backwards or forwards, or one or moi-e may be thrown up into the air out of the way, and indeed adjusted into any position whatever, so that the tripod may be adapted to the most uneven surface.
Electria Ferouaaive Drills, — Numerous attempts have been made to construct a percussive electrical drill, but until recently with little success. The difiiciUty has been largely overcome by employing the principle of the solenoid. A solenoid consists of insulated copper wire coiled in the form of a spiral, but is only complete when a portion of the wire passes in the direction of the axis in the interior of the spiral. If a current bo posed through a solenoid, it has the same power of attraction as a magnet.
In the Marvin drill,* two solenoids are placed against each other, end to end, and a plunger plays freely from the centre of these solenoids. The whole is placed in a boiler tube casing, having a spiral spring in the back part. The plunger is composed of a oentital portion made of wrought iron, and a forward and backward portion made of aluminium bronze, all rigidly connected together. The generator furnishing the current is of the simplest kind, so that the polarity of the wires is reversed at each half revolution of the armature, with the result, that through the action of this current on the solenoids, a reciprocating action of the plunger is obtained, as first one and then the other solenoid attracts it, and pulls it in opposite directions. About 60a blows luiiiute is found to be the be-st speed. The object of the spiral , sprint; store up the energy of the back stroke, and return it 'he lorwaid stroke, helping the magnetic impulse, and greatly igth of the blow,
id Min. Joar., May 23, iSgi, li. 609,
Textbook 0? Coal-Mining.
In a trial made in the hard granite of Qutncy Quarries,* a hola ili in. diam, was drilled at an average) rate of 3J in. per minute, with an expenditure of less than 4 H.P. delivered to the generator. The chief features, however, were the extreme ease with which the power coiitd be transmitted from the generating station, and the great simplicity of the drill itself. For the purpose of <!exhibiting the ease with which the drill could be taken to pieces, and defective parts replaced by others, it was several times opened and entirely taken apcirt, the time required for this being less than three-quarters of an hour.
The Engineering and Mining Journal t states that the results obtained from the machines in practice are unsatisfactory, as not only are they of faulty construction, a defect probably easily corrected, but they present a more serious trouble — viz., the heatiii of the solenoids and piston. The heating of the eolenoids seems to be due to the rapid reversing of the electric current through their coils. This not only means loss of efficiency, but the beating; is often eo intense as to make the drill objectionable in a smAU heading. An important installation of these machines was mode at Lake City, Colorado, in 1891, but after experimentH through September and Oetobei' they were withdrawn owing to the objectionable heating. The inventors are now endeavouring to overcome the defects thus shown, with every probability of ultimate
Forms of Bit. — Like ordinary hand tools, the first form of Wt far machine drills was that of a chisel. In order, however, to obtain more striking surface, two chisel edges crossing each other at right angle were tried. This did the work bettet', but as the hol got deep, ready escape of the debris was prevented, as the tool nearly filled the hole. To remove this difficulty, the two chiseU were made to cross each other on a slope, forming a tool like the letter X, which ia the shape now generally adopted. Bits like the letter Z have been ti'ied with most satisfactory resulte, so far as the efficiency of the boring is concerned, but the difficulty of sharpening them prevents their' general application. For making and dressing the drill bits, a set of tools called " swages " are employed. These uj'e like moulds, shaped to the form of the bits require
Uao of Water in Boring Holes. — Experience has proved that by using water in the holes the speed of drilling is considerably increased, and such is always done in drilling down-hill holes. With up-hill holes, water cannot be employed with ordinary I means. Messrs. Dubois and Francois exhibited at the Paris Exhibititxi a device which has over-come the difficulty. Water is in— I jected right on to the cutting edge of the drill, instead of simply I into the mouth of the hole. A small copper pipe is fixed in fti
Breaking Ground. 67
groove extending throughout the length of the drilling bit, and is connected by a small flexible tube to a tank fitted to the back of the piaton-rod, but prevented by suitable menna from rotating with it. With each stroke of the piston, water is thrown right on to the place where the cutting edge Rtrikea, the bottom of the bole ia always kept clear, and tlie full eSect of the blow from the drill is obtained ; the deeper the hole, the greater the efiect.
Cost of Machine and Hand Drilling. — For two years at Ramsbeck lead mi oca,* careful eompariaous have been made between the cost of driving levels by hand and by machines. The strata consbt of hard soliiata and greywncke. With hand boring, the average speed of driving double tramway roads waa found to be g ft. 10 in. per month, while with machines it was 35 ft. The saving, taking economy and speed into account, was 304 per cent.
£n6 u
Interest on capital and amortizement was taken at 13 [ler cent. Repairs to drills amounted to 10.49 to"' working cost.
Experiments have been conducted at the Rammelsberg Mine in the Hartz.t where six types of machine drills have been tried for several years. It appears there was a saving equal to 3*. 3.89. per ton of ore won in favour of machine as comiiared with hand drilling, including all costs, during the year t8So-8i. The saving in favour of machine drilling for the years 1877, '78 and '79, was 10.391/., i. .07, and la. 5.2, per ton resitectively, which shows a progressive inci-ea.se, probably due to improvements in the machines and training of the men.
The following figures relating to the Vosberg Tunnel, U.S..4..,t show the dillerence in the speed of ms.chine drilling compared with hand :
W-
Hand drmiDR . .
6o.3i
mi
OOAZ. CUTTIIfO BY MiCH INERT— Under suitable conditions, coal can be holed much cliwiper by machinery than by
hand, except, probably, when wages are low. The great advantage, however, is that less Email coal ia produced, as with the pick a man, to under-cut a certain distance, has to remove enough height at the face to get his amis in. To a certain extent, machinea cannot well be used in old rained, the work requiring to be specially laid out for them. With a good roof requiruig little timber, they are used with a considerable amount of euccees, but in a tender coal, the roof is crushed down upon them, or supports have to be set near the face. These get in the way of a machine, which cannot movB . round them like a collier. The different types employed may J divided into (a) the circular-saw class, (6) the Imnd-saw (' (e) the percussive, and {d) the bar type.
Haohines -worked by Compressed Aii.GUloU and CopUi/a is a representative of the circular-saw type. The cutter wheel is a malleable-iron disc, 4 ft. diom., furnished on its outer periphery with a series of chisels, these being of two kinds, single
Kic. 64.
l And double, placed alternately. Power is supplied by a „ ., liaving cylinders 9 in. diam. by 10 in. stroke, geared down about. 5 to I. The machine is drawn forward by a wire rope, which is attached to tbe hook (n, Fig. 64), then passed round a pulley at the end of the face, and finally brought to, and coiled on, the drum h, by the action of a ratchet'wheel and pawl, which can be so regulated that either one or more teeth are taken at a time, thereby allowing the machine to be fed slower, if tbe under-cutting is hard. Tliis machine cuts from back to front, and brings its d6bris out, if the cut is above the floor.
Rigg and MeOdohn'a machine also cuts like a circular saw, but with this advantage : it holes into the face on the underside of the sleepers ; or, in other words, flush with the bottom of the coal. It can be employed in the thinnest seams, as its height is only 16 in. It is provided with four adjusbible screws, one 00 each comer, by means of which the cutters can be made to work at any angle, and the azle-boses are also adjustable to allow the machine to progrees at any angle, irrespective of the level of the rails. It revolv* "
L however, from front to back, and carries the debris into the O
ir ir
BREAKING GROUND. 6g
requiring the EerviceB of an assistant to clean it out. The cut can be made alternately in opposite directions.
Baird'a machine represents the band-saw type. The cutters are of various shapes, and are mounted on an endless chain, canied by a jib which projects beneath the coal, from 3 ft. up to 5 ft. as i-eqiiired. Motion is given by an 8 in. cylinder by la in, stroke engine, through gearing, to a cylindrical shaft in the centre of the machine. On the bottom of this shaft in a cam, or spi'ocket wheel, which drives the chain carrying the cutter teeth. As this chain has to be carried over the top of the rails, the machine cannot undercut in the bottom of the seam unless the floor ia taken up. The difficulty is got over to a certain extent by canting the machine when at work.
Marriatm's machine, which is largely employed in the United Stutee, consistB of a percussion drill which chip away the coal. A broad pick bit ia secured to the end of the piaton-rod of a small cylinder mounted on wheels. The cutting tool is chisel-ahaped, with a triangular slit in its face.
To perform the under- Fia. 65.
cut, two boards, 6 ft, by close to the face and slightly inclined towards it. The machine, mounted on 14 inch wheels, IS run on these boards, air turned on, and the face attacked at the angle
shown in Fig. 65. The machine is balanced on tlie wheels, and the operator, lying behind it, sprags the wheels with his feet, keeps the machine up to its work, and by means of the handles swings it about and regulates the direction of the blow.
Machines of a similar type have often been designed, but the violent shock agjunat the rear bead of the cylinder, when the pbton made its backward movement, not only made it impossible to keep them to their work, but broke them to pieces. Indiarubber cushions are not siilbcient remedy for this evil. Here the difliculty is surmounted by interposing between the piston and cylinder head, an air-cushion of adjustable pressure, and in addition tJie valves are so arranged that the rebound of the pick actually aids in moving them. Prof. Wbeeler states that it takes about 6 minuteii to shift the boards, min. to change the bit, and 16 min. to cut 4 ft. wide by 4 ft. deep. To disconnect, load up the outfit OQ a truck and remove to the next place, unload and start to work again, takes about 20 min- The cutting capodtyip to be between 60 and 70 lineal ft. per lo-hours shiT'
School of Mines Qnarterlj, New Ti
preeeure of So Iba., the average for six lOAchineK fora month bem 63.8 ft. A Harrison machine weighs only 700 lbs, and costs aboti jC20. The cost per day for power, repairs, interest, and depre ciation, is put at 3d. per ton.
The IngeraollSunjeant machine is similar in general appearau to the Hajrison, but is furnished with an air-moved vaJvt their drills. It is claimed to be simpler in conruction, to 1 more under control, to deliver a harder blow, and to be c economical in air than the Harrinon.
The Legg coal-cutter is a representative of the bar type,and difFeil from all others not only in the way power is transmitted to the cutb
bar, but in the direction in which the cut is made. The machine consists of a bed frame, occupying a space about 3 feet wide by 7 ft. 6 in. long, composed of two steel channel bars, the top plates on each forming racks, with the teeth downwards, into wbiui the feed wheels of the sliding frame engage. On the rear end of the latter is mounted a pair of 5 in. Iiy in. engines, from which power is transmitted through straight gear and worm wheels to the rack, which feeds the hiding frame forward. The cutter-bar is mounted on the front end of this sliding frame, and contains the bits, a, a (Fig. 66), made of tool steel, held in place by set screws. and so set in a spiral along the horizontal bar as to make a c tinuous semi-cylindrical cut in one revolution. Tho cutter-b ' revolved by an endless curved link steel chain b, and i
Brkaking Ground. 71
revolved, is advanced into the coal, the bed plate being cl*ipad firmly bj two braces fitted with iengthBning iicrews, one of which is bIiowd at c. Small link belts, d, U'liind the cutter-bar, push back the chippings prmluced during holing, by aid of the sliort projection, e, e, and keep the undercut free.
The essential difference between this and other machines, is the diniotion in which the cut is made. Here it is pai-allel to the faoe, while in all others it is at right angles. This machine really does its work in the same direction as a miner. When the cut has reached the required depth, usually about 5 ft., the bar is thrown out of gear and withdrawn, the machine moved sideways along the face over the length of the cutter-bar, and another cut made. This gets over two disadvantages : (a) the inability of most coalcutters to work in stalls which are set with timber at short intervals, since so long as the props are wide enough for this machine to be got between (about 3 ft. 6 in.), it can easily be placed in positioQ, even if they are close to the face ; (b) the irregular holing generally produced when the floor of the seam is undulating. Rotary wheel machines must cut a straight groove ; this machine can follow any variation in the floor which takes place within the length of the cutter-bar.
The rapidity of the cutting is claimed as a further advantage of the machine. It is, however, expensive in first cost, and la repairs. The present cutter-bar is, however, an improvement on those formerly used. InNtMd of being weakened at the sprocket by being squared to admit the straight link driving chain formerly used, it is now increased in diameter at this point, made round, and a curved link-chain used, thus not only strengthening the bar, but greatly increasing the levei'age of the chain, which lessens the power required, and reduces the friction and wear on the chain. The feed con readily be thrown off and on by means ot a lever.
MttohinoB Driven by ELootricity. — Although machines under-cut coul cheater thoii manual labour, under suitable conditions, the (lilhculty of driving them by compressed air or wire ropes, nullifies the advantages to a certain extent, even where favourable conditions esist. The cost of installing eompreesed air is not only considerable, but its tnmsmxssion to the face presents serious difficulties in coal mines ; not only are the pipes expensive, but the cost of labour in laying them is targe. If the pipes are carried along the side of the road on supports, any fall of roof or sides will break them ; while if they are buried beneath tbe floor, leaks cannot be detected. These latter considerations are not so important in tbe main roads as they are in those approaching the face which are constantly being altered in dimension, and in which repairs are frequent.
Electricity appears to be particularly applif* of coal -cutting. In the facility with whio'
Text-Book Op Coal-Mtning.
about, this medium stands uniivalleil, and the cost of up-keep is less than with other systems. The only objection seema be the danger that may result from parking at the motors in situations where explosive atmospheres exit. lu the author's opinion this danger appears to have been exaggerated. Tn the first plaoe, the great majority of mines do not contain explosive atmospheres, and in the event of a sudden outburst of gas, the motor might be immediately stopped. Sparking at known points, or by short circuiting, appears to be preventible, as it depends on the design of the machine, on the intelligence of the workmen opei-ating it, and last, but not least, on the common-sense of the pui-chaser. In the desire to secure economy in outlay, less money is oftea spent on safeguards than should be the case.
The Goolden' cutter consists of a loug bar, taper or paralleJ, having a series of steel tools arranged on it. This bar is rotated at the rate of about 500 revolutions per minute, the electric motor running at about 700 revolutions. The cutter-bar is drilled with a series of holes, each of which is placed in a direction nearly, but not quite, at 90° to the next adjacent one, with the result that the cutters form a left-handed spiral, which serves to equalise the cutting action, and also a right-handetl spiral, which acts as a sort of corkstrew, and di'aws the debris out of the cut. After trying various forms for the cutters, a V- shape has been adopted, with the edge nearest the machine sloping across the cut ; so that when the tool hiw entered uljout I or J in, a wedging nctioQ commenceB, and the ridge of coal left between succeeding cutters is split off.
This machine is practically the only one which has been at work in England. Messi-s. Atkinson state that oa an average 20 to 30 sq. yds. per hour may be cut in fairly hard coal, all stoppage&t being included, while as a maximum performance, 55 yds. were holed an average depth of 3 ft. 8 in. in 75 minutes at NosteU Colliery.
The Jeffrey machine, which is most in favour in America, cousieta practically of the Legg machine, already describeil, with the ordinary engines replaced by an electi'ic motor. The current required is from 30 to 50 amperes at a pressure of 320 volts; the arm,ture is calculated to run at 1000 rev. per min., while the cutter-bar makes 200 revolutions. The momentum of the armature is such, that obstructions met with by the cutter-bar are not perceptible, so that the machine is caused to run steadily. Mr. H. C. Spauldingt states that 23 of these machines have been applied, and that the amount of work done by each averaged from 600 to 900 ft, of under-cut in lo hour-s.
Van-Depode.X — A machine of the pei'cussive type has recently been placed on the market in America. With a stroke of from
Behaking Geoond.
J
n,
e
a
I'.
ji
n
s
B
£
¥
lis.
®
®
1
h
k
Text-Book Of Coal-Mining.
5 to in,, obtained by the action of a solenoid, it delivers from 3C0 to 350 blows per min., and weighs a little over 700 lbs.
Coat of Goal-outtiiig.Mr. R. W. Clark gives the actual figures for a day's work, taken at haphazard, as 6f lineal yds. of under-cutliog per hour, as the average performance of four machines during three shifts. He states that the holing was exceedingly hard, and that this may be taken as a fair performance, as, almost always, little delays will occur. The working place should not be too long, as if there is any delay in filling the coals out, the machine will be stopped od its own journey. The chief point on which success depends, is the removal of the machine from one place to another. This must be made as expeditious and as simple aa possible. A great deal depends on the i-eadiness of the men. Three men have moved the machine about zooo yds. up some very low roads, taking aUjut 1 5 hours in unfixing, i-moving, and fixing
FiQ. 67.
up again. The deputies should be men of quick ohservatioD and ready resource, and able to estimate how much work there ia to be done in every shift in every face, and to arrange for the regular working of the machines. In 1888, was paid lineal yd. cut, this including removal of machine and laying pipes in the roods leading to the face. ' J
Mr, Geo. Blake Walker gives a comparison, repi-oduced on p. 73, 1 of the relative cost of coal-getting-by hand and by machine. t 4
It will be noticed that the greatest saving results from the duction in the amount of small mAde by machines.
Stanley's Heading Machine. — None of the machines yet de scribed, except the Legg, can be applied for driving narrow roads. The Stanley Header (Fig. 67), has been designed for such purpose, and consists of a cutter-bar driven, through gearing, by a pair of vertical engines. The cutter-bar is composed of a massive iron casting, placed parallel to the face of coal, and carrying c
Brit. Soc. Min. Stad. i. 124.
+ Fed. Inst. i.
Breaking Ground.
extremity n bar of ii-on, 2 ft. lonp, to ihe ends of which the cattrknives are attached. Tliis tool ie revolved, and cuts out an annultvr excavation, leaving in the centre a core of coal, which is removed by hail d- wedging.
The machine may be considered a practical success. It has now been working several years, and has given Batisfaction in every case. The actual aimed of cutting is from z to 3 in. per min. The wedging down of the core, and placing machine in position for tt fresh cut, takes on an average about an hour. The chief saving results from the proportion of large cool, and the rapidity of the work. The actual cost of driving is said to be less than by
Boring Croaa Cuts. — Machine drills, for boring air-holes.* to serve as connections between winning head-wayH, are largely employed in the Saarbrucken coal-field. They are of the rotary type, having jagged teeth cutting-in the ciivumference of the drill. Four men can drill from 34 to 46 ft., 1 2 in. diam. hole, in an 8-hours shift. With the Muuscheid and the Hussmann machines, two men m-e required, who will Iwre a ho!e so in, diam. at the rate of 1.09 yds. jer hour; with holes 11 J in. diam., the cost of boriogiegivenat is. 4M. per yard. Theonlinary luzesarefor holes 14, 16, 18, and 30 inches diam., the first cost of a machine being about ;35.
EXPLOSIVES. — Qunpowder.— This is the explosive commonly used in mines, and althougli numerous: attempts have been made to replace it with other substances, it still remains unrivalled for the special operation of getting down coal. Normal gunpowder consists of a mechanical mixture of 75 per cent, saltpeti-e, properly refined, 15 per cent, charcoal, preferably made from alder or willow wood, and 10 per cent, of sulphur. With a view, however, of producing something cheap, not only have the proportions of charcoal and sulphur been increased and saltpetre decreased, but instead of putting in pure articles, impure ones hare been employed, with the result, that in common gunpowder, the purcher pays for quantities of useless material that do no work.
In the manufacture, the ingredients are first pulvensed separately, and then mixed together and ground under heavy rollers for from to 10 hours. Even if suitable proportions and materials aiv employed, grinding must be carried on for some time, or the mechanical of the ingredients is incomplete and combustion imperfect. High-grade sporting powders are milled for 10 hours, uut so much with a view to increase their strength as to prevent or decrease " fouling," and as it is just as essential that no smoke, or aa little possible, should be given off when the charge is fired underground, blasting powdeni '
for a sinuiar length of time. The beet resn'
For. AbB. N.E.I. xxj
Text-Book Of Coal-Mining.
in Germany by the use of rye straw for charcoal, carbonised browDiieBS, with sulphur reduced from to per cent, to 3 per The problem is to get rid of the sulphur altogether.
The so-called smokeless powders may be defined as compounds, and generally consist of gun-cotton and picric sometimes alone, sometimes in combination, mixed with retarding agents to prevent detonation. The absence of smoke is a great advantage, but safety in storing and reliability in keeping quality is greater. The slow-burning character of gunpowder nuJies it an admirable rending compound. It gives out ite energy in a constant heaving force, anil brings down coal in large lumps. No other explosives do so ; their energy is locally developed, smashing up such a soft substance as coal, and entailing a loss to colliers and colliery owners. So far as cost is concerned, gunpowder comparesfavourably, in all oi-dinaiyoperations, with any other explosive. So long as powder will blow the bottom of the holes out, nothing in gained by using more powerful explosives ; but in strong rocks, the employment of powder means shallow holes and slow progress. Where everything is sacrificed to speed, the holes are bored deep, and Buflicient explosive used to break up the rock into sm fragments, and so hapten its subsequent removal. Gunpowder possesses an advantage which is not shared by any other explosive : it can be used either with or without detonatore, and be made to do more work at will,
iritro-Glyflerme. — This substance ia formed by the action ol a mixture of nitric and sulphuric acids on glycerine. It ia a bright, oily, colourless and odourless fluid, has a faint Hweet taste, and is poisonous, causing headache and colic. It is such an unstable compound, that its use has been forbidden bylaw in this country and in several continental ones ; but, mixed with other substances, it forms the base of the majority of modern high explosives.
Dynamite is a plastic substance of red dish -brown colour, consisting of nitro-glycerine absorbed in porous kieselguhr, which is earth consbting of the shells of diatoms (nearly pure sihca), found in Hanover and other localities. Many other absorbent materials have been tried, but kieselguhr has given the best results. This choice has been further justified by the absence, after explosion, of the noxious f umesof carbonic oxide, which render charcoal, although equally absorbent, so hurtful to the health of the miner. Ordinary dynamite contains 75 parts of nitro-glycerine and 25 parta of kieselguhr. In the open air, hi. gtnall quantities, it bums freely, quietly, and without explosion. One advantage of the dynamite class of explosives is that they are plastic, and therefore, when tamped, flt accurately into the hole. Metal rods, or rammerS( should never be employed to tamp the charge. A wooden rod should be used, and the cartridges gently, though firmly, squeezed into place.
etardinc '
Breaking Ground.
Blasting Gelatine is said to be the most power-ful of known explosives, and is a tough, slightly elastic, semt-tmnsparent substance, resembling ordinary gelatine. It contains 93 per cent, of nitro -glycerine, together with 7 per cent, of nitro-cotton, and on explosion resolves itself into carbonic acid, watr, and nitrogen, there being just enough oxygen to combine with the nitrogen and hydrogen. It ia stated to be 50 per cent, stronger than dynamite, nud more insensible to Khocks than that substance.
GelBtine-Dyniunite. — Tliis is a compound better known to miners and contractors, being more used for blasting in rock which is required to be removed in as large pieces as possible, as its action is a heaving and rending, rather than a disruptive one. In appearance it is more opaque than blasting gelatine, and consists of 80 per cent, of that explosive, with nitrate of potash and wood-pulp added in proportion.
Gelignite is similar in composition. It consists of 65 per cent, of blasting gelatine and 35 percent, of theabsorbing powder.
In cold weather, all nitro-glycerine compounds freeze, even at a tempeisture of 46° F., and are very dangerous to use when in such a state. The cartridges may, however, be softened, without danger, in warm-water warming-pans. They must not be put in the warm water to do so, but first in a water-tight vessel, and then that vessel placed in warm water.
Backarock. — This explosive is largely employed in America. It is composed of So per cent, of potassium chlorate and ao per cent, of nitro-benzol. The former of these ingredients is solid, and the latter liquid, and both are non-explosive during their manufacture, stoi-age, and transport. Little danger attends the use of this explosive as explosion can only take place after mixture, this generally done immediately liefore charging.
BLASTIITG IN DRY AHD DUSTY MIITES.— The passing of the Mines Regulation Act, 1887, materially modified the use of explosives underground, ae General Rule 1 1 states that " in places likely to contain either accumulations of gas or coal-dust, a shot shall not be fired unless the explosive ia so used with water or other contrivance as to prevent it inflaming gas, or is of such a nature that it cannot infiame giis." The one fault of gunpowder is that it gives off a certain ajnoimt of flame on explosion, and its use is, therefore, not allowable under the circumiitances just stated. To meet the altered conditions, and yet to continue tbe use of explosives, numerous methods have been proposed.
Water Cartridge. — A cartridge of gelignite (usually of such a size that only one is necessary) is held in a skeleton cose (a. Figs. 68-70) having a number* d tb'" ™"tBl diaphingms 6, which keep the cartridge in the centr 'it's. 63 and 70) containing
the water. A del ha last cartridge,
and a fuse, or elect outside of the
bore-hole. The sp e case is filled
Text-Book Of Coal-Mining
Fios. 68, 69, AKD 70.
with water, and the autr end firmly tied round thi ing fuse or wires d. A guide wii-e e, is also placed in thebag to keep the charge iii the centre long ways. The objections to this apparatus are (i) the large number of parts and delicate handling they require; (2) the water acts as a sort of cushion between the explosive and the sides of the hole and so lessens the effect ; (3) the large-sized hole which has to be bored ; (4) and a liability of rupturing the ca£e and letting out the
To overcome these disadvantages, which reduce elficieucy and convenience, several new explosives have been developed.
Boburite. — This belongs to the hydrocarbon class of explosives, and consists of two compounds (which are harmless and inert separately) mixed and ground up togetlier in a mill, the resulting product having a sandy granular appearance, resembling common yellow sugar. The two substances are nitro-benzol and ammonium-nitrate, the latter being the ojty gen-yielding body. During the procesa of mixture these two substaDces are subjected to a process of chlorinisation, with the result that the compound produced, upon being detonated in the usual manner, evolves gases which quench any flame produced by the explosion. The practical efiect is somewliat similar to that produced by the water cartridge, with the distinction, that the quenching element being chemically combined with the explosive, there is a smaller risk of failure. Hoburite cannot be exploded by blows of a hammer, as it reqidrea a very powerful detonator, and when ignited bums slowly. It is very safe, as far as regai'ds storing, and has more of a heaving action than the nitro-glycerine class. It does not freeze when exposed to cold, but is fleeted by damp and loses power, although its strength can be restoi-ed by drying ; the cartridges are, however, placed in a pedal waterpi-oot covering, which, to a certain extent, removes this disadvantage. Statements have been made from time to time that the fumes produced on explosion have an injurious effect on the health of the workmen, but in every instance where these have been investigated (in Lancashire am! the North of England) no ground has been found for such complaints." 8ome cases of illness have been traced to its use, but these have generally been found to bo due to the neglect of the proper precautionft in its use which are published by the manufactureiB. Workmen Fed. iDBt. il. 36S.
Breaking Grocxd.
having onte, or skin knocked off thar hands, sfaoold be earrfol when handling the cartridges, and shoold wash their haodsbrfoce eating food, or there is a danger of aome of tfae safasUnce getting into their mouth.
Ardoer Powder. — Uailer this trUe Ueesra. StAti baTe recently introduced an explosive practically iiJMitiea] in cooipoeitiaD with " Orisoutite," which has given sucli good results, and hAs met with much favour on the Continent.* The bese of the compound is dynamite mixed with 45 per cent, of common sulpbue of mngneeia (Epsom Salts), introduced for the object of reducing tbe temperature of explosion.
Carbonite is another explosive of late introduction. It is said to be composed of uitro-glycerine, sulphur, and nitro-benzol.
Tonita.— Tonite, whi consists of 52.5 per cent, of gun-cotton and 47.5 per cent, of barium nitrate, by itself fires gas in the same manner as ordinary gunpowder, but, if tamped with Trench's Compound, flame produced by the explosion is quenched.
Anunonito. — An explosive of recent introduction is that known as Ammonite or Favier's explosive, which belongs to the hydrocarbon class, being composed of ammonium nitrate and nitrooaphtbalene. It can only be exploded by a verystrong detonator, is not affected by beat or cold, but readily by moisture; for this reason each cartridge is enclosed in a tinfoil case hermetically sealed, which has to be cut into just before use to insert the detonator.
There are numerous other new explosives each claimed by the makers to possess advantages over the otiiers. All are stated to be flameleis, but nono are absolutely so. Everything seems to depend on the tompiog. Mr. Walton Brown t states that the experiments of the French Commission showed that the retardation of ignition characteristic of fire-damp mixtures, tbe almost instantaneous mixture of the gases resulting from the explosive with tbe surrounding atmosphere, and tbe quick cooling conse<|uent thereon, combine to make explosives, whose temperature of detonation is less than 4000° F,, incapable of igniting explosive fire-damp mixtures under normal conditions of use ; that is to say, if properly stemmed. Tlie degree of safety becomes greater as the temperature of detonation falls below the above value. With any of the dual mixture explosives, the greatest care in manufacture IB necessary, as it ia essential that perfection be ensured in the mixture. The safety of ignition in explosive atmospheres also depends upon the almost instautnneous mixture of the gasee resuttiiii' from iletouiition with a sufficient volume of surrounding air, il .iihahle that it mny be dangerous to fire a shot 1! I'ice, and with a weight of explosive too
fim " ' " " '889-
8o
Textbook Of Coalmining.
great For tbe voluine of the stirrounding air, as compared with the ! Tolume of the gnses pi'oduced by the detonatioD.
Firing the Charge. — Explosions niny be divided into two claaeeB — (a) whci-e combiiKtion proceeds slowly tlirough the mass of the compound, and (6) where instant ignition takes place, called detonation. The power in (a) ia applied slowly, with rending eSect ; while in (6) the gases are instantly generated, their force ! is loealised, and a shattering effect results. To produce the latter action detonators have to be used, these consisting of a small quantity of a powerful explosive, fulminate of mercury, enclosed in a copper capsule.
Three modes of firing charges are in use — ( i ) squibs or Oermans, (i) fuses, (3) electricity. The first can only be employed with gunpowder, but the second and third with any explosive.
(1) Squibs, or Germans. — These consist either of n straw or paper spill filled with fine powder. When " Germans" are employed, a copper rod, about y' in. diameter, called a " needle," has to be inserted in the hole during tamping. Thiii needle reaches from the outside to the cartridges, and is turned from time to time to 1 prevent it getting jammed, and finally withdrawn, leaving t open pnRsage through the tamjiing to the powder. The squib ia ' then inserted in this hole, and a slow match applied to the outside '
(2) Fuses, — Frequent mi-sGres with straw squibs, and prematui'e explosions, together with the production of a shower of sparks, led to the introduction by Bickford, in i83i,of safety fuses, the prindle of which is to enclose a thin string of gunpowder in a sheftth of some material or combination of matenals, with a view of protecting the core from rough usage and moisture. Many different qualities ore made to meet the varying conditions of employment — viz., the time stored before use, influence of climate, temperature of mine, and presence or absence of moisture.
For ordinary work the thread of powder is protected with rope yam, coated with dilfereat vamiahea, or, if moisture ia present, a further lining of tape and varnish is given. For blasting under water, gutta-percha coverings are employed, but such fuses cannot be stored long, owing to the rapid oxidation of the gutta-percha. To prevent this, an esteiior coating of tape and composition varnish ia apphed, which not only delays oxidation, but retains the effidency for a long time. Metallic fusee, in which the core is covered with lead pipe, have been introduced, but are not much employed, owing to their weight, brittleness, and liability to damage by torsion.
Ordinary fuses are sold in coUs 24 ft. long, and burn at the rate of 2 ft. per minute. Misfiree occur, generally through deterioration and the use of inferior qualities. The atore-room should be d the powder will be affected, and the fuse should not be ii
BREAKIN'G GROTWD. Si
with any oily or greasy ai'ticle. All gritty and sharp substoucea shoultl be avoided in ramming, as the fuse is often cut through, anil a misfire follows.
Under the Mines Regulation Act, powder can only be tuken into a mine in cartridges. These geneiully consist of a reel, or bobbin, of compressed powder, having a, hole, conical at one end, passing through the centre. In firing with n fuse, it in first cut to obtain a fresh surface, and threaded through the bobbin. One end of the fuse is doubled hack into the conical hole at the bottom of the cartridge, and pulled tight, the subsequent bobbins being threaded over the front. In doubling the
fuse back to bind it in the cart- Fibs. 71 akd 72.
ridge, care should be tnjcen that the string of powder rests dii-ectly againfit the cartridge (fig. 71), and not against the return portion of the fuse (Fig. 72). Numerous misfires may be traced to the neglect of this simple precaution.
With detonating explosives, a piece of safety fuse is cut clean, and Inserted into a detonator until it reaches the fulminate. The upper part of the cap is then squeezed with a pair of nippers, with a view not only of securing the fuse in position, but also of developing the power of the fulminate.
For use under water, care should be taken to make the upper end of the detonator water-tight, where it joins the fuse. With nitro-glycerine explosives, a cartridge is opened at one end, the detonator pushed in (leaving about one-third of the copper tube autdde the cartridge) and securely tied in position. The detonator should not be pushed too far into the cartridge, or the fuse may set fire to it before the spark can explode the detonator. Holes are charged by putting in one or more cartridges, and squeezing each with a wooden I'ammer, a cartridge with detonator and fuse is then inserted, bal must not be aquMsed. Loose sand, or water, is alt that is required for tamping, but the power of the explosive ts increased by tamping. A good plan is to insert on the top of the priming cartridge and detonator a ball of soft clay and press it home, then put further tamping on this.
In firing shots in mines, where naked lights are not allowed, a small cop[)er wire is commonly employed, one end of which is made red-hoc by putting it into the flame of a safety lamp, while tha other b inserted into the fuse. The wire generally passed through a small hole in the glass of the lamp. To get rid of the difficulty of passing wires into huups, and prevent the emission of sparks when the fuse is fir Bickford have designed an
phial, holding sul a small quantity of
-f-'hlomte of pota fuse is inserted into
8s TEXT-BOOK OF COAL-MISING.
Uh ofMO end of the tube, and the gia phial brokea by going tbe tabe witb a pair of pioders {Fig. 73). The sulphuric acts on the mixtiire, lights the end of the fuse, and all sparks produced are kept within the ttibe. 7J- At the Aubin Colliery ta the
department of Avevrou, Prance, a modicatioD of the device for lighting pipes, cigarettes, Ac., by the beat generated by the compression of uir, has been in use for aome time. It consists of a metal cyUnder, in which a well-fitting
Et43n moves, the rod of this cariTing a cross-piece so that a firm d in given for the hand. One end of the fuse is passed through a amnll hole in an india-rubber ring into the cylinder. A quick uid strong thrust is given to the piston, the air in the cylinder ootnpreesed and heated, and the core of the fuse ignited. It ia aid that, with a little practice, ignition always takes place at the first thruKt, and as the sp:u'ke from the burning of the tiret inch of flue ore thrown out inside the cylinder, they are thereby cat off from the surrounding atmosphere.
Blasting by Electricity. — The practice of igniting shote hy
the aid of the electric current has been gaining ground for a coandemblo
number of years ; with it, no question cau arise aa to
whether shots have missed fire or not. Ignition with ordinary fus
aometiiiies bnge for & coneid?rabl time, even up to twenty -four
I bouTB; sporka from the fuse are got rid of by numerous devices,
f bat aa no Bporkji ore produced by electricity, it must be better.
' Then again, there is no chance of premature explosion. Every
one can be in a place of safety before the shots are fired ; indeed
in some coUierieiii where blasting might produce an explosion, all
the shots are fired from the surface when the pit is free from
men.
Two systems are in use ; in one, electricity of high tension and mall quantity is employed, while in the other, the electricity is ot low tension and of hirge quantity. The former are called " -enaion," or " machine," fuss, and the bitter, " quantity," or " buttery," fuses.
Tenion Futet. — These consist of two copper wires, with the ends separated from each other by a small intei-val, in which is placed ft priming composition, and the whole inserted into a detonator. The current, in leajnng across the interruption, meet* with gint resistance from the low conductivity of the material passed through heat is generated, and the priming and iletonator fired. The priming composition generally employed is known as " Abel's," and consists of a mixture of 10 parts of sub-phosphide of copper, 45 parts of Bub-Kulphide of copper, and 15 ports of chlorate of potash, well rubbed together in a mortal*, with sufficient slcohoL bo moisten the mass, and afterwards carefully dried.
Beeaking Ground. S3
QiiatUiti/ Fuses. — Here the two copper wirea are joined together by a very thin, short length of pliitiniim wire, and surrounded by a 8ultance inflammable at a low temperature. The current posing down the copper wires meets with great reaistajice in passing across the small Bection platinum wire, and generates sufficient heat to fire the priming. As the circuit is nnintemipted, quantity only is required to heat the wire to redness, and therefore an ordinary battery may be used.
Comparium. — The advantages of high tension lie chiefly in the convenient form and ready action of the machines employed to excite electricity. These are of small dimensions, light weight, simple in construction, and do not readily get out of order. In addition the means of discharging the machine may be removed until the required moment. For this reason, such system is useful in mines where the operations are carried out by men of no acientifio knowledge. A great advantage, however, i.'i the fact that a large number of shots can be fired simultaneously with more certainty than with a battery, and that line resistance has a. small efiect on the current, so that cables of small diameter can be used.
The disadvantages are, that the fuses are more or less affected by moisture and heat, and that the wires carrying the current have to be well insulated. Low tension fuses are more trustworthy than high. Certainty of action is always possible, as each fuse can be tested before use by passing a weak current through it, and the insulation of the line wires need not be very perfect. For ordinary mining work, low tension is not so convenient as high tension. In tbe first place, only a limited number of shots con ba fired simultaneously, unless a large battery power is available. Batteries soon get very cumbersome, and, furthermore, always require a considerable amount of attention. Low tension fuses can, however, be fired from an electric light or power circuit while high tension ones cannot, and as dynamos are becoming at collieries the natural result is that low tension fuses a and more applied.
For firing tension fuses, two types of machines a (a) those in which the current is generated by friction, (6) I magneto type.
Frietumal Maekinea. — The machine most in favour is that of Bernhardt, which, from its simplicity, compactness, and portability, jiosses-ses many advantages. Electricity is generated by the friction of two revolving discs of ebonite against two smaU cushions covered with cat-skin, and is received by two cones, and trtuiamitted by a metallic conductor into the interior of a Jjeyden jar, from wtuch it discharged by pressing a button. The appHi&tua ia, bWavw, very delicate; both glass and ebonite iwakdMlM Uiat. nine can rarely be depended upon Unless the places in which V and warm, the machine will
fumiiiti no current, as the electricity is conducted away by the condensed moistui'e ae faeb as it is generated.
Magneto-Afachittes. — These consist of an electromagnet, between whose poles an orniature, wound to a, very liigh resistance, is caused to rapidly revolve by means of crank motion and gearing. An electric current, of high potential, is generated, and at the moment of masimum intensity is sent out to tbe outside circuit in which are the fuses, the explosion of these being instantly accomplished.
Simiiltaneoiis Blasting. — The advantages of firing a number of Rliots simultaneously, especially in shafts or headings, are selfevident, particularly where machine drills are employed. In tbe first place, as soon aa the machines have been removed and the holes charged, the rock should be shot down as quickly as passible. Then all the shots going off at once assist each other, their force is applied collectively, and the whole of the rock is brought clean away, while if tired separately, each individual blast has to tear out the mass of rock allotted to it, the reeult being that in the former case less explosive is required, and in addition a minimum amount of time is taken up in the operation. Another advantage of simultaneous firing, is that all the smoke produced by the explosion is generated at one time, and the men only have to wait for this to dear away, while if shots are tired independently, they have to wait aftr each blast.
For firing a large number of abota at Fioa, 74. 75 AND 76. once electricity is particularly useful, tbe reduced quantity of explosive used balancing the cost of the electric fuse, the saving in time, ali-eady referred to, remaining as an advantage. Another point of importance is the question of miieed shots. When firing with fuse, one can never be sure whether the shot baa really missed or only hung tire, and unless explosion takes plaoo the working has to be fenced off for a considerable time, thus entaihiig a loss; but with electricity, nothing of the sort occurs; After the current has been passed through the wires the place can be approached at once without danger.
For tiring by electricity two "in'n syatema
of connecting the wires to tbe machine
In the first, the fuses are
nected i
the first I
series — that i
s connected to C
tbe second hole, and the 'eof the third bole, and sc
will be one wire of the last brie
Breakesg Grocxd.
wire of the first hole left These are now joined by 9 of conducting wires, to the machine a considerable distance away in a place of safety (Fig, 74).
The second Eystni is known as the parallel one. In this, one wire of each shot is connected to one caUe, and the other wire to the second (Fig. 75),
Modifications of both these systems are possible, as the boles may be connected in multiple series (Hg. 76).
The disadvantage of the series system, is that the power of the machine has to be equal to that required to fire each fnse, multiplied by the number of fuses, and thut unless the fuses have all the same rest&nce, or vary only within narrow limits, only the most resistant will be fired.
Bickfard's VolUij Ftite, — To render the operation more simple than with electricity, Meijsrs. Bickford have designed a method in which ordinary and special fuses are employed for simultaneous blasting. A length of safety fuse is connected to one side of an explosive disc in a tin tube. The reijuired number of Special fuses are snuy tied together, thr ends cut clean and level, imd inserted into the tin tube, touching the other side of the explore disc. The mouth of the tube is protected by a waterproof substance, such as piteh. To fire, the length of the safety fuae is lighted, this ignites the explosiTe disc, which starts all the special fuse burning at the same time. The particular point, however, consists of the special fuse, which is manufactured to hum at the rate of 9000 ft. per minute, the speed of ordinary fuse being only 2 ft. per minute. To enable operators to adapt the instantaneous fuse to any available length, to suit their particular requirements, the inventors supply on demand the ignitors with fuse looped as in Fig. 77, so that if the whole length of fuse so looped ie, say 10 ft., the miner can cut it into gle lengths of 3 ft. and 7 ft., or any proportion of 10 ft. (tiUcing care not to detach it from the ignitor). This does not affect the simolCatieonffieM of the explosion, as, owing to the tapidiqof burning, small difiei-ences in the lengths of the special fuse are not of any moment.
Positioii of Holes. — The situation and inclination of boles in rock drifts, depends on the nature of the rock, and on the system of drilling employed. With ham! drilling and single blasts, everything depends on the skill of the miner, who cai-efully esaniinea J -— fni the position, direction, and depth of the have to be fulfilled being, that the rock 4e on one sde, and tliat neitlier too
Fig, 77-
S6 Text-Book Of Coal-Mining.
much, nor too little, rock shoulJ be attempted to be diBlodged. the former case, if there is too much resistance the hole will act like a cannon, aod the tamping wll be forced out, producing what is known as a "blown-out shot," while in the latter case the explosives will be wasted.
With machine drills and simultaneous blasting, there is not so much necessity to consider the lines of least resistance, although such is generally done. Many different arrangements can be employed. The foUowing may be considered a typical example.* A wedge, or core, is first blasted out of the centre of the heading, this being known as a centre-cut, the sides being blasted out afterwards. A centre-cut needs about eight holes, divided into two sets, four each, arranged in nearly vertical lines, at equal distances
Figs. 78 akd 79.
from the centre line of the heading Each hole of one set of the centre-cut is drilled in a direction intended to meet the corresponding one of tl e other set at the centre line of the heading, so as to form a edge. These are dnlled fully ten feet deep. Whero the character of the material only requires one set of holes in sides, these are usually three in number, and drilled from seven to nine feet deep. The inclination of the holes in the different sets are shown in Figs. 78-81. The holes inclining upwards, are drilled dry. those horizontal, or inclined downwards, wet. Sometimes second side rounds are requiretl ; these will consist of two holes each.
Blown-out Shots. — The combustion of powder produces large quantities of gaseous products, which, in the case of blown-out shots, are driven violently into the ixxidways and at the point of discharge act tike a piston, (hiving back the air flowing past tlie
Tif ru4beTg TuRtiei, Leo V. Rosenberg, p. 34.
YAXttnm
BXjASnSOt.— 2mH Htfafc bw m.
oratig these, can be ren.jiJT i*t- ;V.: cUinieid being that only a small -jiied the weight of the wliote appuKtns, wedge, is vety small, while tb ex owing to the fiict that the impu' other means of applying wed
Haswell Heohanical Cool-getter.* — In thiK mnhine, the rending action is accomplish&d by a wedge between two feather, the wedge being drawn out by a combinatiou of a screw nnd lever. The bursting action takes plare towards the back of the hole, and uot at the face where least required.
Burnett's Boiler Wedge. — The amount of fiiction between the Bides of the wedge and feathers, in ordinary systems, is very great. To overcome this difBculty, Mr. Burnett t has designed a roller wedge, in which rolling is substituted for .'sliding friction. It consists of two external plugs, or feathers, with an Internal wedge running on roller lieai-ings. This wedge is drawn out by the action of a screw and nut, driven by a ratchet and pawl arrangement.
Hydraulio Wedges. — To increase the jxiwer of these machines hydraulic preesiii'e hns been called into requisition, A man's strengtli acting on n lever working the piston of a small hydraulic pump, is capable of producing an enormous pressure, wliich can be applied to driving in wedges. Instead of applying the hydraulic apparatus directly to the wedge, which compels the openitor to stand close to the face, in some designs the pressure pump is fixed a considerable distance away, and the water b conveyed to the wedge through a pipe.
Lime Cartridges. — Messrs. Smith and Moore have designed a process for bringing down coal by utilising the expansion of quicklime, when water is appUed to it. Ordinary mountain limestone is oalcinedand ground to a fine powder, and com pi-seed by hydraulic
1 lower into a cartridge, having a groove running along its full ongth. The cartridge is about 5 in. long and aj in. diam., and when taken from the press is wrapped in a sheet of paper, and placed in an air-tight bos to keep away damp. Coal is holed and shot-hole drilleil, in the ordinaty way, and cartridges placed in them. Aji iron tube J in. diam., haring a small external channel on the upper side, and provided with perforations, is inserted along the full length of the hole. Several cartridges are placed in each hole, the grooves formed in them during the process of manufacture lying against the tube just referred to, and the mouth of the hole is tamped in the usual way. A small forcepump is connected by suitable means, to the end of the tube projecting from the hole, and water forced in. The hand pump is then detached and carried away to another hole. The watr acting on the time greatly expands its bulk, and the coal is forced down.
This system has been employed and given good results at Shipley Colliery for a considerable time, but has not met with much favour elsewhei'e. It can only be used for certain classes of coal, and great cai'e has to be exei-cised to keep the cartridges dry,
N. E. I, xixiii. 37. t Min. lost. Boot. viii. 2.
Breaking Ground. 89
They readily absorb moisture fixnn the atmosphere, and cconpletely Lwe their efiiciencj.
BOBseyeiue. — For a considerable length of time aa apparatus has been in use at the Marihaye Colliery, Belgium, wbicli of a rock drill of the Dubois' Francis type, boring a series of boles, grouped in a certain pattern, in the face of the work. The drilling tool is removed and replaced by a hammer head,ii number of plug and feather wedges are then put lu the holes, and driven in by the battering rajn,till the rock is broken down and split up. No explosives are used, and trials over a period of uauy years show that the employment of the machine bits not increased the oost of working.
Frohibitlon of Blasting. — From time to time, snggeetions are made that blasting should be prohibited in mines. Undoubtedly, there are seams of coal which can be economically worked by wedges, but such are few and far between. With a seam that is thin, hard, and blocky, and adheres tenaciously to the roof, wedging ie of no use, the coal breaks short, and wedge after wodge is inserted with little effect. On the other hand, where the coal is soft, the wedge on expanding Mmply widens the sides of the bore-hole. As in too many cases the direct causes of explosions can only be conjectured, every cause to which explosions have been traced shares a prejudice which evidently does not rightly belong to them all. Although the occurrence of some explosions can. be directly traced to blasting, it must not be assumed that all are due to this cause, or that if it won stopped entirely, they would cease. When a large explosion takes place, the loss of life is so serious that public attention is directed to it, and the other accidenta which happen in mines are apt to be lost sight of. Statistics, however, show that the death-rate is higher from several other causes than from explosions ; for instance, falls of roofs and sides. Now, with blasting, the men are away from the working face, but with wedging they must be there, and ai-e liable to be injured by falls which take place, especially in thick seams. Wedges are claimed to produce more roimil coal than when shots are used, but such is not necessarily the case. If the chai'ge employed is property proportioned, it cau be made to do what is required ; all that has to be done to produce the coal in a large round state, is to vary the amount of explosive.
To show the increase in cost due to prohibition of blasting, Mr. W.Y. Craig* arranged for the best miners at Podmore Uall Colliery to be employed to work at day wages on two places for one month with, and one month without, powder. In a 13 yd. drift, working one month without powder, the wages paid were j£i6 OS. lod., quantity produced 233 tons, 11 cwt., 3 qrs., cost per ton i. 4</; same worked with powder, wages;!; gs. d., including
N. StafC. Inst, iv, 53.
TEXT-BOOK OF COAIMfSING.
St. for powder and fuee, ctal produced 327 Uids, 16 cwt., cost per ton I*. To this bas to be added, the inrreaeed coet per ton of tbe fixed ch&rges, such as superintendence, timber, und road maintnJUice due to the diminution in (juantitj-. In each shift, 10,64 tons were got without powder, I4'z6 tone with powder, the difference being 3.1 tons per shift, so that the quantity was 14 j per cent-less than when worked with blasting. Tbe total increase of cost, minutely and carefully calculated, waa it. sld. per ton by working without powder.
The accidents due to firing can be best prevented by careful supervLsioD of the work, by placing the operations under the control of a well-regulated sUxS with a steady and attentive person at the head, by careful examination of the working face before firing, and, atiove all, by good ventilation. Finally, tbe loss of hfe may be entirely removed by tiring all the Shots simultaneously from the surface, when all the workmen are out of the pit, this being the procedure at some of tbe South Wales Collieries.
Bibliography.— The following is a list of the more important memoirs dealing with the subject-matter of this chapter: —
as. ISST. SCOT. : A'oUi oa (imlCaalag Ilaehiiteiy. Q. B. BegR, 1. a6o ; Tit Harri-> Coal-GtniiM Mockint, v. 5S Mid 77 : BumettU IiUnt BoBrr ilinimi/ Walfft and IfnUiiu/ JVanCiu, a Bumelt, Tiif. 30.
ISO. & MIS. JOUB. : EdiitM Eltetrie /fcmwKut thrill, U. 400 ; Elrdric IWrvMioB li. 6o9i lij, 49, ud lii.720; Comprencd Air ForwMUr, W. L. Saimden, lii. 48.
BSn. SOC. MIS. BTUD. Coal Gtttimg Coimrttted Lime Proani, 3. H. W. LaTerick, vil. 34 ; \ BylrauKe Eotk-Boriag JUachine, C. Z. BoonitiK, vili. 6 1 A'uIm mh Bobriu, G. B. Walker, z. 109 ; Caal OttHtig J/orAiWry al Liggett Ciery. R W. Clarke, x. 134 ; CWficratin Jtrttitlt rJ-f-tintti /ran DrUUng JfocAi'im worhing Irontlone in i lerrtamJ, W. Walter, Jun„ x. 130; 'Hit lugeraoU-Sergtant Digger W. Bziv. 115.
mar. CS. t A'Mm im C o mi pmi rd Air, J. , Ixzix. 31 1 ; Xotei im Eltelrie iltelWf CAi'aa, C W. Kinder, Ixxx. iSS; The TVoKiinu.ion 0/
lUttlrie Miainf Mafiireru, L. 6. and C. W. Atkinson, civ. 89 ; TAe MMwiiPB m( IMitriSitliim BrmtT from Cetilral Statumt by "r. W. C. UowlD, CT. iSo.
O. VAL18. IXBT. : Brmiii't Sjltlem tf Mining by menu of Boriag Sfaekinerv, il))MH>,w< Klertriait Blmtivg. Siml. Dnvi, vijf. 13S : lAtrge avd AiaB BortMn m emplotnJ in JUiutiitg Operaliimt, Ueary Lewis, jj. aO; O wi r w tW Atr .uoehiatr. A. J. Stevens, xi. 363; Note* un Cemnurd Air, W. H. JIiu*ey. lii. 344.
too, HtV. ! .VhIm mr rajiiiticalton da Btt/gent TuOaniqueM on cretuemtHt Jf mitt tl det galrrit* cm ri*T, A. Pernolel (2* Wrie). i. 381, ii. 5, Dd Ul. 595 ; de frrforaliim mienqae A VEipaiititm de IWit. 1S7S, Ch. ItaJFson (P Biiiv), viii. 873 ; L'air etmprinii mix mif dt Blmuf. F. Uatbet (j* 8ric). it 65 ; AppareiU de perfora- tM> 4 Jd MM, llH. DiuoLre et MaiUanl (3> &6rlej, ii. 305.
V B L ' ti .iffSrmtitm iff Jlaekinen icorkid ty CuHiprtted Air at tht CMitriH ff Start Lcngtiitmii: J. Daglish, ixi. 199; Dtmgen of
J
Breaking Ground. 91
iarJu produetd from iVioteri and SCeiitiaeri iisfil for BUat'mg Arpou, H, Lawrence, xziiii. 3 (see also CoUierv Guardlim, Ixi. 207, Jbn. 1891) ; Tie 3fJianical CoalGetUT, W. F. Hall, xzzili. 37 ; TraniminKum of Poaier bij Steam. Messre. Liddell & Merivale, XXXV. I 9, and zzzvL 13 ; Bi/ilem of tVarking Iroitatone at Luiapiey AIiM urtlh Hgdraulie DrilU, A. U'steavenson, ixxvi. 67; BanUt'i Sand-Boring Alaehint, E, L. Dumas, xxsvU. 1 17.
FSO. DJBT. : Tke DUtHhUioa of Electrical Energy over Extended Areai in lina, A. T. Snell, i. 141 ; Coat-Oeltiig ly'Jlaeliiwry, G. B. Walker, i- 113 ; Experiraenl* irilk EjyiloiiBei vied in Sliae*, U. WaltOD Brown, H. 49; ExjirriTaenti irilA Carboaile, M. WbIwo Brown and W. Voggio, ii. Ss ; An Ineettigation at to wliether the Fume* produced by the vie of Bobvrilt and Tonite in Coal Mlnet are injurioue to health, with Appendiies, li. 36S ; Tht Loie Teiuion ilem of Shot FaiTtg, T. M. Winstanlej-Wallis, ii. 553.
AMKE. IHST. M.B. : A new Boek Drill without CutMon, A. C. Rand, xU!. Z49 ; Eleclrie PoiMr TrantmiMton in Mining Operation!, H. C. Spaulding, xii.=S8.
CHBB. msr. : On Compreaiing Air, J. Sturgeon, vili. 290 ; Stanley'i Coal Seadiag Maehint, Jt. Stanley, xvi. 193.
MID. TH8T. : Simuitaitetnu Btanliug in Sinktng Piu, C. WoUccr, vi. 196 and 361 ; ffj/dro-carbon Eeplotinei, O. B. Walker, zi. lot and 138.
B. STAIT. IVBT. : Prohibition of Blaattng in <hoU3tineii ; iti Effect on the Cott of Production, W. Y. Cnir. iv- 53 ; Tlie Compreiied Air Power Buitem, 3. Stuieon, ix. 45 ; SteeJuiniaii Coat-Oelter, E. Mould, ix.
aKV. train. : Note tur NloMliiement de machine H tomprimer Voir aa chm-bonnaga du Ltmant-du-FUnu, H. Uativa (2* &eri), L 69;
BipOTl lur let experience* failtii mi LeiiOnt'dt-FUnii tar la peifaralioa viieanique, U. Uativa (2° Srie), iii. 651 ; Note eur la perforation isteanitme aux minet lie Jliinubeek (iFeetpkalie, C. Haber (3* Srie), 111. 557 ; Note* tur dei erpiricncct failed mr let noureaux rxplatifi ei notamauHl lur la gritoulite en pr/tense det poiasiiret de charbon et du f/ax, B. Braive (3* Serie), iv. 24S and v. 67 ; Note mr let Tioumiax exjilailft hydro-carbonii, J. Ilenrott (3° Serie), V. 87; Exprienert falle* le II Heptembrt 1S90, an ckarbonnage de Marchieane mr diver' erpUuift en pritenee du gritoa et de la poattiire de charbon, E. LannovAiz (3' Serie), litJ. 193 ; TVaiwioMiioa du travail i, dittance par Voir aitiiprimi,G. Hanarte (3° Serie),XTi. 113.
ABU. DBS UINBB : Note mr Cemi dx I air eomprimd pour le pereemenl da long tunndt, D. ColladoD (S* Srle). xii. 469 ; Happort tur Vitude det guettiont relaiivet it Pemploi det en pretence du gritou (S* S£ri), xiv. 197 ; Emait pratiaue faitet queiuet exploilaliont det minet ivr divert explofifn indiquit par la commitiion det luhtlanet tajlm'ft, M. Mallard Srio), xvi. 15 ; Nate relative rt det tttait Jintet dux nti'nci de Liiinn tar let ejplotivet de turiti, A. Simon (8* ae), ivUi. 580.
CoKtd Air Production, W. L. Baundere, New York, 1891.
1,'Air Comprimi, A. Pernolet, Paris, 1S76.
Maekine Mining in the St. LoniM Coal Eeyion, H. A. 'Wfacelcr, Sobool of Mines Qiiarterlv, New York, vol. ii. p. 399,
Blading: A Hamlbook for the (/o/£iiyi*Br, O, Guttmann, London, 189a,
Chapter V. Sinking.
Position of Shaft. — The commercial success of collieries depends
ill a great measure on the positiou of the shafts, and before deciding on their fdtuation, every point should be given careful consideiwlion. In proved districts where the inclination of the seams is known, the shaft is generally placed in the deepest point, especially where quantities of water are expected, as both water and coal gravitate to the shaft and render haulage easy. Dealing with water in dip-workings is most expensive. It is advisable to place the main shaft somewhere about the centre of the royalty so that equal areas can be worked on all sides of it. Surface considerations may, however, overweigh the majority of the underground poiuta. The disposal of the produce must be canied on easily and cheaply ; proximity to towns or placea where a household trade can be carried on is important, Communication with railwaj's or waterviaya should be studied. A supply of water for Imitera, &c., is requisite, many colheriea labouring under great cost and disadvantages thi-ough being unable to obtain this. In unexplored districts, it is well not to make the first shaft a principal one, but to sink it down to the seams, and after pro\-ing their inclination, &c., to decide on the positiou of the main winding-shaft, from data so obtained.
Form of Shaft. — At the present time, so far as European practice is concerned (except in Scotland), the general custom of colliery districts is to make shafts circular. Various other shapes have been tried — square, elliptical, and polygonal — but have been abandoned iu the majority of cases. In order to economise space, many of the earlier shafts were made rectangular, and are still often so sunk in Scotland, and in the United States, but it has been found that round shafts are easier and cheaper to sink, moi'e capable of resisting the pressure of " heavy " sti-ata, absolutely necessary in running ground (the pressure being equalised), and more suitable for the application of metal tubbing, The waste of space and other disadvantages due to circular form are less considerable than bad been supposed ; indeed, by careful arrangements the space wasted may become almost noljiing. The ventilation of large coat-mines could not be well carried out with rectangular shafte, as the
Sinking.
running of the cages would ioterfei'e too much with the p
of the nir; indeed the spKkce unoccupied by the cage) is a positive
advantage in Dumberlces iDstncea.
Where stone, bricks, or iron are cheap, the circukr form is preferred, but where wood is abundant and krgely employed for securing the sides, and other material absent, the rectangular shape is adopted.
Size of Sluift. — This depends entirelyoii the size of tub employed and on the output re(|uired. After deciding on what daily quantity is to be extracted, and the weight that each tub shall contain, the number of tubs to be drawn each day and each hour can be obtained. Knowing the depth of the shaft, the speed at which winding is to take place, and the time occupied iu changing the tabs on the cage, and allowing margin for interruptions, the number of tubs to be raised at each lift is easily found. Then after deciding how many decks or platforms thei* are to be in the cage, the number of tubs on each deck is established. As the tubs have to be of a certain size to hold the quantity they have to contain, the number on each deck detei'mines the 8i7.e of the cage. If the shaft is only to have one cage working in it, its diameter must be such as will allow a rectangle of the size of the cage to pass through freely, allowing a margin for clone'ance of from three to six inches at the comei-s. If two cages are to be employed, two rectangles should be plotted on paper, with a cleamnce space between of from nine to fifteen inches, and a circle inBcribed round them, allowing a similar space aa before for clearance at corners. The dinmetr of this circle gives the size of the shaft.
Where pumpa are required and have to be placed in the winding shaft, the room they take up must also be allowed for. The better plan is, however, to keep everything except winding appliances out of the main shaft.
OPEBATIOH" OP GETTINa DOWK TO THE "STONE- HEAJ)."— The first openition in sinking, is to get down to solid regular strata, technically called the "stone-head." In the majority of instances, some drift or loose deposits have to bo passed through before firm ground is reached, and a foundation obtained for the masonry, or other means which are to be employed for permanently securing the sides of the excavation. Often this preliminary operation is very troublesome and expensive, depending entirely on the nature of the strata.
(a) WliBTO the ground is moderately hard it is usual to first dig down a few feet and then place at the bottom of the excavation a circular frame of timber called a "crib" or "curb." This
consiata of an annulus divided into a number of segments having Jcnnta (Figs. 84 and S5); with narrow curbs, the segments are
Kioa. 84 AND 85.
Text Book Of Coal-Mining.
usually connected together by one bolt, but in broader ones, two will be employed. At the surface, a Bquaro frame ia formed by four pieces of timber intersecting each other, held by notches where they cross, and with the ends projecting to some distance beyond. This ia often held down by pegs which give it a grip on the ground. Timber laggings will now be driven behind the curbs, at necessary points where the nature of the ground requires them for support, and the two frames are then connected by nailing on strips of stronger planks (called "stringing deals") at intervaJs round the shaft on the inside ; in addition, short vertical struts called punch props are placed between the curbs to keep them in "' "" Then the ground is removed for a further distance down, a third frame put in, lagged behind, and hung by a further set of planks from the second curb (Fig. 86, /, 2, J, are the curbs, a a the laggings, b b the stringing deals).
Instead of timber laggings, the space between the curbs is often filled in with a dry walling of bricks called " back casing," the curbs being hung from each other by stringing deals as before.
If the ground is soft and does not afibrd sufficient support for the curb at the bottom of the excavation, the whole structure is hung by chains or iron bolts from strong baulks of timber placed transversely across the shaft at the surface. These tio-bolt< are added to, and lengthened, as additional curbs are fixed below until the firm ground ia reached.
Instead of employing wooden curbs for timbering through loose ground, the practice is becoming general of using iron " binding " rings. Four of these go round the circumference of the shaft outside brickwork, and are made of flat strip iron about 3 in. by in. They are connected together by bolts, each segment overlapping at the joints. When placed in potation laggings are driven down between them and the sides of the esciivation. By arranging a number of bolt-holes in each segment (Figs. 87 and 88) they can be made to overlap each other more or less as desired,
I Q g I H. if necessary.
The permanent lining is then put in by one of the methods described further on, care being taken that all the temporary timbering is removed.
{b) "Where the ground ia loose, difierent methods to the foregoing have to be employed. Sinking through quicksands and
Figs. S7
Sintcing.
heavily watered beds, is one of the moat costly operations connected with mining, and calls forth all the skill and experience of engineers. The means used for reaching the " stoae-heidi" where qiiickinds are present, depend in a great mea-suro on the thicknesB that has to be passed through.
(i) — At one time the general method adopted wad by what is known as " piling," which eonaiats of driving vertically downwards, all around the circumference of the shaft, wooden planks with their edges touching each other, and supporting them internally with curbs. The planks or piles used ai'e generally from ten to fifteen feet long, siz inches broad, and three inches thick, having their lower end tapered ofl' to a cutting edge, and their upper one etrengtheneil with a wrought-ii'on hoop, so that they are not split by the blows of the wooden driving maul. In fOTming the cutting edge, all the taper ia given on the inside, the outer side not being touched, as if it wtis cut to a V form the piles could not well be driven down vertically, as the tendency would be for them to incline towards the centre of the shaft. In bard ground, the cutting ends of the planks are whod with iron to enable them to penetrate more easily.
The width of the supporting curbs depends on the size of the excavation. They are, however, generally made about six inches broad, and placed at closer vertical distances in large shafts than in smaller ones.
When the bottom of the first length of piles has been reached, and a curb placed round as a support, a second set are driven down iTiside the lower' supporting curb, so that the diameter of the shaft is reduced in that length by twice the thickness of the ladings and twice the breadth of the curb, or, if 6 in. curbs and 3 in. piles are used, by iS inches. As this reduction takes place with each course of piles, the shaft has to be commenced at the surface with a diameter sufficiently large to allow it. It therefore becomes necessary that the thickness of the quicksand to be passed through should be approximately known, such being usually found by boring. If piles 15 feet long are used, a fresh course will have to be put in about every twelve feet, therefore if the quicksand is (So ft. thick, live reductions will take place, altogether amounting to 5 ft. If a 15 ft. shaft is being sunk with brickwork lining 1$ in. thick, the diameter at the bottom of <]uicksand must be at least 18 ft., and at the surface the excavation will require to be 18 -1-74= 25! ft. diameter.
Commencing at the sui'face, the ground ia excavated as far as it will stand, and the curb carefully laid down, with its centre ooinciding with the centre of the shaft ; the lining of piles is then driven down as far as possible, and the ground tfn out on the inside till a sufficient distance has been sunk to require the support of another curb, which is accoivlingly placed in position. The pilea will then be driven down a further distance, more ground
$6
Textbook Op Coal-Mining.
Figs. 89 and
excavated, and so on until the bottom of the &ttit set of piles is nearly reached. A supporting curb (a. Figs. 89 and 90) will then be fixed against, the piles and a Kecond one b, 18 in. lees in diameter, will be placed inside it, leaving an angular space of 3 in. between tbe two. A second set of laggings, c, will now be driven down in the space left between the two eurbe, and the same cycle of operations gone through as before. This process is repeated until the solid ground is reached. I Tbe method just described is the one 3 generally adopted in the North of England, and where the ground is very loose and of a watery ilescription. SometinieB, however, instead of driving down the piles vertically they are inclined outwards {a. Fig. 91), and then as the ground is excavated towards their lower end, the pressure gradually drives them forward. When the ground has been got out for a short distance in the bottom, supporting curbs b are fixed in the same manner as before. As the piles in this ioetance do not touch each other at their fH
lower ends, straw, or similar h ."
material, ia pushed between f" 1
the joints, to prevent the
sand from flowing into the '
shaft. '
When the ground is very loose, or watery, the difficulty of using the latter class of piling is surmounted by the so-called method M " quartering," in which only a portion of the circumference is attacked at a time. Commencing from the Tipper curb, ground is taken out for a depth of 3 ft. in the centre of shaft, piles 4 ft. long are driven down for a length of about S ft. round the circumference of the shaft, and when each has gone in its full length, the top end is knocked back under the curb. Tbe ground ia got out for a length of 3 ft, in fi-ont of the piles, a segment of a curb laid on the bottom perpendicularly under the upper one, and the space between filled in with dry brickwork ; when this is completed the two curbs are connected by nailing on stringing deals, and a further series of piles driven down at the end of those already in position. Sufficient ground is then excavated in front of the piles, until room is obtained for another segment of the curb, this joining up to the first one laid. The space between this and the upper curb is then filled in with dry brickwork as before, more piles
Fig, 9:.
SINKING. .j7
driven down, the ground escaviited, a thii'd segment laid, aad process repented, segment after segment being "quartered" in, until the whole circumfei-enee is firmly secured for the length under consideration. A lower length is then attacked in a similaimonner, and then another, and su on until solid 'ound is reached, (i) Drum. — The method of pile-tbiving is an exceedingly expensive one, and is often superaled by one of the so-called "drum" methods. In this sj-stem, a drum either of wood or iron of a diameter sufficiently large to allow the permanent walling being inserted infiiJe it, is sunk through the sand.
Wood. — A curb (Fig. 92), 14 or 18 in, broad by 6 in thick, is first laid truly level on the top of the bed to be sunk through, and a tier of Via. gz.
masonry built on it to a height of about 3 ft., /'' '
when a second curb will be laid, and pon- ' ' nected to the first by iron tie-bolts passing through the brickwoi'k. In order' to pi-event the dislocation of the moaonry, and to reduce friction during descent, a close lining of planks is nailed around the outer circumference, these being planed at the edges where they meet, to ensure a water-tight joint. A further length of masonry is then built on the second curb, a third one laid and con- 1
nected with bolts, and laggings placed round the outer circum' ference, as before. In Fig. 92, a and h are curtis, a wroughtiron connecting bolt, and d the lagging planks. Where the ground in of looi description, the weight causes this drum to sink, but if the beds are moi'e coherent, the bottom curb is pravided with a cutting edge, either by bevelling off the inside, or by attacliing an iron shoe. Opinions difier as to the advisability of employing cutters at all, it being contended that they are merely a source of weakness, as when any exceptionally hai-d substances are met, the tendency is to turn the cutter outwards, and often rupture the drum. The ground In the centre of the shaft is then slowly I'emoved, and the cylinder sinks. A man stands on the drum with a straight edge and level, and gives directions as to where matenal is to be excavated if one side " hangs " behind, but cai'e is taken not to remove any ground near the curb for feaithe drum should suddenly sink, and " cunt " over.
When the drum has sunk, say a distance of 3 ft., more brickwork and another curb will be added at the top, and connected to the others by bolts as before. This ia every time the drum sinks the cei-tain specified distance, until, in the course of time, the solid ground is reached.
The great difficulty encountered in sinking by this operation is in keeping the drum truly vertical. Constant supervision and care must be exercised to prevent " canting." As a matter of fact,
Text-Book Of Coal-Minixg.
tbe dnuu never goes down regularly, but doeB bo by Gt and etai-ts, J fiometimea f aUing throtigh live or six inches nt n time. With endi such movement, croBS-stairs are placed on the curbs, and a spiiifi I level applied, to Bee it the apparutiis is honzontal. If it is not, either a bdulII quantity of ground is tjiken away fi-om beneath the highest paH, or additional weights are added to the drum nn that side.
(6) Itv7i Drums.-'The objection to wood drums is, that they require nearly as hirge an excavation as if piling was employed, for often, after getting down some distance, the whole structure sticks, and cannot be moved. A second one has then to be sunk telescope fashion inside the first. To get over this, wrought or cast iron drums are used, as although they sometimes have to he telescoped one within the other, comparatively little space is lost. With cast iron ones, the circle Ik composed of a certain number of segments, varying from 4 to g feet long by 2 feet deep, strengthened by vertical and horizontal ribs, similar to Fig. 1 15 ! As these strengthening ribs .ire on the inside, the outside surface is smooth, and meets with little resistance in passing I through the ground. The joints between the different segmentB ai-e made with sheet leatl and bolts, and a cutting edge is attached to the bottom segment. The procedure is very similar to that with brick drums. They are usually weight, and to make this more easy to carry out, the ribs arc made broader. If sufficient weight cannot be applied by placing material on these ribs, two sets of timber buntons are placed across at right angle.-* to each other, and a platform laid on them, upon which any amount of debris can be placed, a passage being left through the centre for the workmen to reach the bottom of the cylinder.
On tbe other hand, it often happens in very watery ground, that the drum has a tendency to sink too fast, and, unfortunately, not to do this equally, but to get lower on one side than the other, and AS this is a point which it is particularly desii-ahle to prevent, the tubbing is hung at four points by a chain and lowering-screw arrangement from strong transverse beams at the surface. Where such means are employed, the tubbing is easily kept perpendicular, as, even if the sand is watery on one side, or boulder-stones cause an obstruction, it is only necessary not to let out 0. screw on the side which requires checking. Instead of cast-iron drums, which are liable to break, owing to the imequal strain to which they are subjected, wrought iron ones are sometime employed.
Comparing the two systems, there is little doubt that, where the thickness of ground to be passed through is large, the iron drum possesses certain advantage.s, as by its use a smaller excavation is necessary ; its sides do not oSer such a resistance in passing through the strata, and the time of sinking in less, owing to the ready way in which the various parts are put together and added
Sinking.
; but iiufortunfttely it often breaks, whicii occasioaa months of
I delay, and iucreasea tbe coat of Kinking. This is the only adv&n-
I ta possessed by wooden drums ; instances are to be found where
' Buch hiive been puslied into an oval form, and yet hav" not
collapsed.
When the sinking hae reached the stone-head, no matter what system hns been used, the procedure nfterwtirds is always of a similar clara<'ter. The ground is carefully prepai-ed for the seating of a curb upon which the permanent lining is brought np to the surface by one of the methods to be described further on, all temporary timbering being removed a£ the work comes upwards. As a matter of fiict, the lining is Usually can-ied a Bnort distance above the surface of the surrounding giKiund j secure some " tip " for the debris which is excavated fi-om tl
king.
METHOD OP PBOCEEDIHG AFTEBWAHDS.— Ott reaching the solid ground, excavation proceeds witli the tools described in the previous chapter, those employed depending entirely on the nature of the strata which have to be passed through. Several difSculties are encountered where machine drills are employed. Owing to the uneven nature of the bottom, the ordinni'y tripod stand is used with dillictilty, taking from 5 to lo minutes to fix, and then the legs move during drilling if the ground is soft. As no roof exists, the vertical stretcher Imr has to be replaced by a horizontal one. This is not eaiiy to fix, and takes so mucli time to adjust, that often, instead of moving the bar and drilling boles in tbe most favoiirablu position for they are put down in auch places as suit the drill, and not so
k ffactive. Considerable time
U also lost in raising drills Fic- 9J'
f and bars out of the way when blasting takes place. To obviate these disadvantages a boring frame is employed consisting of 4 main stretcher bars a a (Fig.93), hinged to a central support, b, and suspended by a ofaain, c, and capstan
t Tope. Each of these bars
I fa provided with a lengthen-
r ing screw and claw, so that
I the whole structure can be
J readily clamped iu position,
i gxed against the side of the shaft, it is equally easily withdrawn,
To keep the structure from lifting by the impact of the drills
1 vhn boring, four secondary arms, li (2, are arranged near the
:hifl
loQ TEXT-BOOK OK COAL-MINING.
top of the fmnie, these being Btruttd against tlie Mdes at a slight inclination upwards. If the drilJR nre ntiunted on swinging arms (see Fig. 62) they can be placed at any angle and clnmped in any poeition, aoid the holes put in anywhere.
Where drills are adopted, the general procedure is to first bore all the holes required, hoist up the frame and drills with an engine, lire the holett lumultaneously, and then load up the debris until the bottom is cleiir, when the drills are again lowered and fixed, and drilling recommenced. Jn hard ground, probably only one set of holes will bored and blasted and the rock removed in 24 hours. Another practice gaining ground, is to lower the walling stage to about S or 10 feet from the bottom, wedge it there and form an artificial roof, and then nine ordinary vertical stretcher bars.
Another method proposed, and indeerl, tried in two instances, is to stai-t at the surface and bore a series of boles 200 or 300 feet deep with the aid of diamond drill, and fill them up with sand. Blasting then commences by removing 4 or 5 feet of Hand from the holes, and firing them in gj-oups, this process being repeated until the bottom of the holes is reached, when the drill are again introduced, and a further distance bored. Tlio Pottsville shaft, U.S.A., was sunt in this manner,* 35 holes being bored ij in, in diameter about 3 ft. 3 in. apart in one dii-ection, and 4 ft. in the other. Tlie central group of holes wnw always fired first, and the outside rows afterwards. The process was expeditious, but the financial result does not appear to be satisfactory. At Harris Navigation Colliery, the same method was tried for about 70 yards but abandoned.
With the object of providing support for the curb caiTying the upper length of lining, when sinking recommences, the excavation is eiirried down for about 3 to 5 ft., I'l'; I" likeable with the inaitU of the curb (t
Fig 94), then shorn back until the dian eter in large enough to tnke in the permanent lining, and afterwnrdB carried (downward.s tliis size, until the strata require more support than temporary timbering affords. A seating will then be for a curb li. leaving a space e in thebottom of the shaft for the collection of water, il'c, and the walling built on it up to the curb above, the ground a being removed for this purpose, not all at once, but in sec-tious.
EeeplDg the Shaft 'Vertical. — This lb done by the iiid of ii centre line which IS either a of special manufacture alxiut 3 in. in diameter,
' A Aei VctlalofS J n Shaft: K. H. Coxe. Amer. Icsl. M. E, i, a6i.
SINKINO. loi
or prefeifilily u, copper wire, long enough to reach from the surface
the bottom of tbe 't when completed. One end of this
line La coiled on a small drum situiited near
thetopof tbepit,andtheotherendisledby kig. 95.
pulleys to the exact centre of the lihalt. As ,- .
rule, the central point is a hole bored
through a baulk of timber placed ocro&s the
shaft, but the best plan is to pi-ovide a
masonry. 'When in use this is kept in its
proper position by the stop b, but if not, it Is
folded upwards into the position town by doited lines at e.
After the line has been paed through the centre hole, a link ix
attached, from which a weight can be hung, this dipping into a
buclcet of water at the bottom, so that the line is steadied. As
8oon as the proof han been made the weight is removed, and the
cord wound up again on the drum.
For determining whether riufficientgj'ound Km. 96.
is removed, the master-sinker is provided with a "centre" staff, which is a wooden rod about tj in. square, and equal in length to theoutwidernrfiiia of brickwork. This Ls moved round the central point as excavation continues.
For setting out the curbs exactly Iwueath each other a series of cords (d. Fig. 94) are hung all i-ound the circmu Terence of the shaft at intervals of about 3 ft. These are attached to the inside of the upper curb, and serve, not only to set the curb below, but alsoasaguidefor the nuiount of excavation. Every third cm-b will be cheeked by the main centre line, the intermediate ones being set nut by the side lines.
Winding Debris. The material excavated is brought to the surface in wi-ought'
iron barrels called kibbles, hoppits, or bowks, the general shape being shown in Fig. <j6. At the top is a bow of wrought-iron swung to the body by two eye-pieces riveted to the Ndee of the kibble. Attachment is made to the winding 97-rope through a spring hook (Fig. 97). With such con- sU-uctton time is lost at the surface, as the full bowk TS' has to be taken from the roj* anil replaced by an empty ll one. For this reason the tipping kibble is prefeiTed. Its lioily is similarto the one ah-eiuly figured, but the wroughtcjj™ iron bow is not attached at the top but at a point below 'jy the centre of gravity, so that when fidl, the tendency is for the kibble to turn over and empty itself. To prevent this
Text- Book Of Coal-Mining.
Fig. 98.
happening during hoisting, a short veilicjil pin (a, Fig. 98) is
riveted to the inside of the bucket, and an ordinary chain link,
sliding on one of the arms of the bow, passed over it. On reaching the surface this safety link is lifted off the pin, when the hoppit immediately turns over and empties itself. With such a system the kibble is only removed from the rope at the bottom of the shaft, one disconnecting being saved.
Covering over Pit Top. — This was originally done by means of a travelling platform, which could be wheeled over the shaft when the kibble reached the surface, and removed again when descent had to be made. The labour here is considerable, and time is lost. To get over these drawbacks two hinged doors, with their weight counter-balanced, are adopted. These when open, form a fence protecting the pit top on two sides ; the other two are guarded with a permanent fence. When these are
down, they entirely close the opening, and two rails on the upper
side of each door form a continuation of the tramway going to
the dirt heap.
Even, however, with these a little time is lost as each door has
to be lifted separately ; so, to remove this complaint, Mr. Wm.
Gralloway has designed an arrangement of levers and counter-
FiG. 99.
balances (Fig. 99), by means of which both are opened at the same time. Two hinges, a a, are bolted to each door, and keyed on cross shafts, h 6, to which, by means of a handle, c, and connecting links, a movement of rotation can be given, and as the hinges are fixed to the cross shafts, the doors lift when the latter turn. The weight of the doors is counterbalanced by four blocks of metal, so that they will stand at any position in which they are placed.
Guides. — The introduction of guides in sinking pits is desirable to prevent the oscillation of the kibble, which gets especially
Sinking.
Iwge in "leep tindertaldDgs, (considerable time being lost in Bteadying it before winding commences. Two methods are adopted, in the first 11 single guide rope is passed down the centre of the fihaft, while in the other two ropes ui-e used. In each system these guides, which are of flexible wire, are coiled on a drum worked by a capstan engine at the surface, and can be lengthened as the Kinking proceeds, and also form the means by which the walling stage is i-aimed during briekmg operations. In the former, however (see description, p. 124), the walling stage is removed diudng sinking, and the kibble is guided to the bottom of the shaft ; while in the latter, one end of each guide is always attached to the walling stage which remains in the shaft during sinking, and the kibble is only guided to the point where the walling stage is suspended. Each system bas its advantages, as with one central rope the kibble is guided all the way, and if a heavy weight be hirag at its lower end, the centre hne of shaft is obtained with- Fio. loo.
out any fui-tber trouble, while in the tworope system walling can proceed while sinking is going on below, thus saving considerable time, an advantage not possessed by the other method.
The system of employing two guides was patented by Mr. Wm. Galloway in 1875. In it, two wire ropes (a a. Fig. 100) are connected at their lower end to the walling stage, and pass over two pidleys on the headgear to drums worked by a steam crab, each drum being able to he moved independently, to provide for any casual irregularity in the length of guides. An iron frame, consisting of two legs joined together by a cross-bar, called the " rider," clasps the two guides loosely at four points, h h, thus preventing any chance of cross-binding. The winding rope passes through a jk.. ,0,.
hole in the centre of the rider. The capping connecting the winding rope and chain going to the kibble, is provided with a butter,c, consisting of alternate layers of india-rubber and sheet iron, which are of larger diameter than the hole in the I'ider cro.'is-bnr, and therefore cannot pass through it. When the kibble arrives at th*) surface the liolonoed doors e closed, a tipping waggon (one
the aketcli explaining itself) run beneath, and the kibble emptied into it. The waggon then removed, the doors opened, and the bucket and rider lowered away, until the walling stAge is reacheil, when the arms oF the rider are caught by two bnSers on tlie bridle cbaina. The kibble and winding rope continue theirdescent, passing through the square opening in the stage until the bottom of the shaft is reached. In ascending, the winding rope slides through the central ojiening ui the rider cro8B-bRr, until the biifier on the capping comes in contact with it. The rider is then lifted to the %\iriac6.
In sinking the Harris Navigation shafts, the time occupied in . winding, changing, il-c, before adopting guides, wa 4 min. 49 sec. from a depth of 475 yds., whei-eas after the guides were put in, the time fell bo 3 min. 26 sec. from a. depth of 530 yds."
LINUTG- SHAFTS. — In describing the operation of getting down to the stone-head, both timber and iron were alluded to as being employed for securing the sides of the excavation, only , He a temporary means. As sooD as tlm point is reached, some other method of a more permanent character is adopted. Several substances are employed for permanent hniug under ordinary orcumstances, such as wood, stone, or brickwork, but except in canea where the two former are plentiful and cheap, they are rai-ely used. Bricks are plentiful in most colliery districts, and in the great majority of instances are adopted. Sometimes they are moulded to the idiape of the shaft, and when such is done the labour of laying them is reduced, and the joints are well made, but in large shafts, whei'e the curvature is great, ordinary y in. bricks are generally employed as they are much cheaper.
Briokfl.— For all mining purposes, the bricks used should be good hard unit ones, and Ei-eefrom cracks and ftoiies. The clay of which they are composed, should be rich in alumina, and thoroughly ground in a pug-mill ; they should also emit a ruining sound when struck. The surfiice should not be too smooth, a probable result of over-burning, or the mortar does not readDy adhere to them. When made by machines in which wires tire used for cutting the blocks of clay into the required shape, the edges are left rough and this instead of being a disadvantage really asnista the brick in laying hold of the mortar.
Number of Bt'k required. — The easiest way to find out how many bricks are required for walling, is to calculate the cubic content8 of masonry for each yard in depth, and then multiply by the total depth.
If D the outside diam. of brickwork in ft. and d the inside diam., (D" - d>) x .7854 will give the area in aq. ft. of the annular ring : this multiplied by 3 (number of ft. in yd.)and divided by 27 (cnb. feet in cub. yard) gives the number of cub. yards of masonry
' Inst, t
E. Ulv. 26.
Sinking.
'05
for encli yard of depth, or simpler still, divide at onco by - 9. Oi-dinary bricks are 9 X4J x 3 inches, so that a cub. yd. of masonrywould contain 4x8x12 384, if mcirtar was absent. As this occupies a certain space it is usual to consider in practice that 1000 bricks will build 3 cubic yartlfi.
U mortar. - The mortar used is generally composed of lime and sand, and should be of a slightly hydraulic character. The ingredients whatever they may be, are usually mixed in a mortar mill, which not only considerably reduces the labour of production, but also the cost, lut with it all rough parts lu'e ground up, and no refuse is left, as there would otherwise he if ordinary luind-made mortar was employed. As a substitute for sand, cHnkev-ashes from underneath boilers are largely employed with most satisfactory results, as they give ordinary lime somewhat of an hydraulic character, and the mortar sets very much quicker and harder, than when sand is used. It is, however, very necessary that these ashes should be free from the finer or smaller parts. As they are a waste product at collieries, considerable economy results from their use. Where the strata are wet, and t he brickwork has to resist the passage of moisture, cement is often used, either b}' itself, or mixed and ground up with lime. Where cement is adopted, it should be used an quickly as it is made, if not, it partially seta, and has to be broken up, and maile over again. Thus, not only is time lost, but tlie cement sets neither so well nor so quickly on the second operation, and the strength is materially
Whatever quality of mortar is employed, too much must not be used, as it is not so good for resisting pressure or the passage of water as a brick. The proper thing to do is to lay a beil of mortar, and not place the brick in its proper position, but drop it down a few inches away, and then rub it towards the place at which it is to be fixed. When the bricks are of a close-grained character they absorb moisture so quickly from the mortar, that the mixture dries before it is proiwrly set, so, to prevent this, it is usual before laying such bricks to sonk tliem in water.
Thickness of Brickwork. — The thickneB.s of walling depends entirely on the diameter of the shaft and the nature of the strata. If it is coherent rock a single is used, more as a preventive of weathering action than as an actual support. In looser ground, brickwork from 14 to 22 in. thick is put in. Opinions ditt'er as to whether brickwork in shafts should be made solid, that is to say, whether it should be carried up to the limits of the excavation, or whether it should be finished off at a certain distance, and some looser substance interposed between it and the hitrata. The author's experience is decidedly' in favour of the latter. Where the brickwork is made to abut gainst the rocks, and heaving takes place, it is either bulged or taken, but if, on the other hand, some soft packing substance
roC
TEXT-BOOK OF OOAL-MINIKt!.
is interposed between tlie s-ides of the rock and the bitckuork ' in the shaft, the first result of pressure is to compresR und tighten this loose material. If any heaving takes piace at one point, all the pressure is not thrown on the brickwork opposite to it, but, owing to the soft compressible stuff being intei'posed between, is distihuted over a larger extent of surface. At the same time, it should be pointed oiit that no spaces or cavities should be left between the brickwork and the sides of the shaft, but every opening carefully filled in with loose, fios material. Coke dust or well-burnt small ashes are excellent for such use, and often the small dust from stone-breaking machines, I where such can be obtained, ia employed. Sand is too heai-y for I shaft work. I
Ordinary Curbs. — The brickwork is put in in sectionfi, each I length being supported on ciirbs. Wooden curbs ai-e generally employed, similar to those ali-eudy described, but as they decay J somewhat readily, cast iron ones are often substituted. A curb 1 of this materiul employed in a shaft ig ft. diam. is shown in
Vui. I02- Fig. 101.
Fig. loi. It is join, broad by 4 in, wide by J in. thick. Ten segments form the circle, and each one is strengthened by two ribs. Two holes ore left in the transverse riba at each end, through which bolts ara passed to connect the segments together.
Water Bings, — If the strata are at all wet, more or less moisture always percolates thivsugh the masonry, and is collected in what are called " water rings " or " garland curbs," from whence it ia conducted down the shaft in tube. The ordinary construction of water ring consdats of an iron curb oast with a hollow groove. These are bedded as usual, but the brickwork for a short distance above, is shorn back (Fig. 103), so that the water readily passes into the groove.
A superior construction for larger quantities of water is illustrated in Figs. 104 and 105. For a few courses the brickwork is made solid, and an ordinary curb a fixed iu position. All the joints in the curb and between it and the brickwork are made with tarred flannel, and the space behind the curb is well rammed with puddled clay. Two courses of brickwork b are laid, but are set back from the rest of the work as figured. A shrouding, e,
Sinking.
'ide, is nailed all round the trout vertical joints being maJe with iries of bricks d are then placed, a b and c, but
t'lGS. 104 AND 105.
jii-ovidod witli 11 ledju'e ou the his of tlie curb, the homontal and tarred Haunel as liefore. A s( bridging over the spice lietweei these are not continuous nil rourid the , blank spaces being left alternately ; the result is, that II Keriea of jiigeon-holes are formed, e, Fig. 105, the object of which is both to allow water to rendijy piss into the apace/. Fig. 104, and to aflbrd meana for removing the sediment which collects in the course of time. After two rows of these bridge bricks have been put on, a light curb g is &xed, and on it the ordinary brickwork of the shaft is built.
Walling Stagea.When commenced, the operation of walling is cairied on as rapidly as possible. It was formerly performed on ordinary scaAblds supported by cross-baullts of timber, which rested on the brickwork already put in, holes being left at intervals for tlie insertion of byatta. This necessitated the labour of raising the scaflbld each time the work got too high for the masons to reach. Such procedure is entirely superseded by employing a cii'cular stage a little less in diameter than the finished size of sliaft, which is bodily lifted up by a crah.engine on the surface. In its ordinary form it conaist of three parts, a central one, and two kigs. 106 Avn 107. side pieces working on hinges, connection being made to the ropes by two sets of thi'ee bridle chains. The greiit advantage derived by this latter method is speeil, as instead of having to lift the scaffold, it is only necessary' to signal to the engine on the surface to have it drawn up. Aa soon as it arrives at the proper point it is steadied, either by pushing a seines of ftmall radial bolts into holes left out in the brickwork, or by driving down two wedges into the annular space between the stage and the niaeoury.
In large shafls the walling stage is a vei elaborate and substantial structure, and is 1 constructed tliat sinking can be earned underneath while bricking proceeds at a higher level. Mr. Wm. Galloway, in the No. I pit at Llanbradach, has adopted a form, shown in Figs. 106 and 107, which eonsists of a wooilen floor on an angle-iron frame, fixed and part movable, and an upright tulw connected I
loS
TEXTltOOK OF COAL-MINING.
this iron frame. Tlie lower frame eoiieists of fotiijiiec angle-iron, d' d'', crossing each other at right angles, a circular liand of angle-iron in three segments, and a straight piece of Hngle iron joined to the short endn of d' and to the ends of the circular frame as illustrated. The object of the latter piece is to enable the hinged door, h, to be placed in the pturt i forming the smaller segment of the circle. Vhen the stage j ia taken past the pipe buntons the door in raised up. Four upright pieces of angle iron connect the upper frame and the lower one, and four plates of sheet-ii'on, attached to the fotumirightR, form the fence around the eentrnl opening in the stage. 'Hie roof is lo ft. 6 in. above the stage proper. It is formed similar to the floor, but is of iitthei' smaller diameter, and is iveied with sheet-iron. An iron Indder, m, p;'ovidea a means of 1 riccess from one stage to the other. The whole structure weighs J iibout five tonic, and is suspended from the guide ropes, n n, which are 5 ft. 6 in. apart from centre to centre. In the No, i sltaft the details have been altered somewhat, two openings being provided, as two kibbles are employed for winding purposes. In this instance, suspension is made by two ropes, which serve the purjiose of four guides, by the following attachment : The end of J iocfi suspension rope is iittached to a strong screw in the pit-bead pulley, and |>a8ses downwards to the walling stage, then round ft .-imall pulley Jixed on it, proceeds a short distance across thestage, round another pulley similar to the first, then veiticiilly up the
shaft, and 1
motliei' pulley c
slowly raised, and another
the pit-hnul fi'ame, finally going to the drum of th t-apstnn engine.
A model of a similar appliance WBJ4 exhibited by the Koche la Moliere Company at the Paris Exhibitiot consisted of iin iron i-ing from 25 to 39 in. deep Fig. loS) of the exact diameter of the finished shaft, suspended from bridle chains. A similar ring was hung about 10 ft. below, and the two connected together by a series of iron rods. These two rings support two scafiblds, on the upper one of which the men stand to do the bricking. The hmckfi, &c., are placed round in contart with the upper ring, the platform
loy
In thitt the time iiiiiiiilly spent in measuring tlie diameteiand ikscertaiiiing the verticality of the shaft is saveO, the top ring being kept a few c'oiirseH above the brickwork to give a guide to the masons, the object of the two rings evidently being to keep the soaSblil in a vertical line. Where the spates lietween the masonry and the sides of the aloft are to be filled in with cement, dic deeper rings are employed, so that more of their height might be left below as a support until the cement seta.
Supporting Curbs. — It often happens that when the sinking is passing through rotten ground, lengths of walling are required to be put in to secui-e the sides, hut suitable places cannot be found on which to seat the curbs. In such cases the difficulty ia got over by one of two methods, either by putting in what are called " square fntmea," or by supporting the cui'b on a series of iron plugs driven in all round the cii'cumference of the shaft.
A square frame, with its sides equai to the diameter of the shaft, is placed at the point where the walHng is to commence. and as the corners of this fi'ame project a considerable distance beyond the circumference of the pit (Fig. 109), sufficient support is
Fjos. 109.
alibi'ded to the curb. In large aliafts the amount of ground to be excavated for a square, having its sides equal to the diameter of tlie pit, would be so gi'eat that the cost would be a serious mattei-, so to remove the difficulty, and yet obtain some support, the square is replaced by an octagon (Fig. 1 lo).
The better method is to boi'e a series of holes, a in. dium. and 3 to 4 ft, apart, around the circumference of the pit, to a depth of 3 to 4 ft., depending on the strength of the ground. These must be on a truly horizontal plane, and wrought-iron or steel plugs are firmly driven into them, leaving a projecting portion upon which the curb is bedded (Fig 1 1 1 ).
Tentilation. — This is usually done by laying u line of sheetiron pipes from 15 to 2o in. diam. down the side of the shaft, and connecting them with a. small blowing fan at the surface. These pipes are held in position by dog-hooks driven firmly into the mafwnry.
Lighting.— In districts liable to sudden outbursts of gas, the same precautions have to be in sinking osin ordinary working, and iiafety lamps are employed, but these give a very imper-
TEXT-BOOK OF COAL-MtNIXO.
feet light in ii direction, where the kcr wants it most J partifulurly. 01" later years the electric light hits been employed, J
g to the clear light given, A cluster of incandescent i genemlly employed, this G wound on a. ili-um at the 8 of raising or lowering the i-emove tbem out of danger
with satisfactory results, as, i the men do iv gi'eat deal more work, liunps, protected by a {.'lass globe, i being suspended from a. cable, which it surface, and which gives a i-eady n lamps, either to give more lignt, oi when shots ai-e being fired.
Dealing with W&ter.The presence of a small amount of water largely increases the cost of sinking. A small .[uantity i got lid of by baling with a bucket into a tipping barrel, similar to I the tipping kibble, and then winding it to the surface. This if very slow and costly procedure, and where the (|uantity is at all large, one of the different classes of pumps will have to be employed. These are described in the chapter on pumping.
To save the time and cost of biding, Kius. [i AND iij. Mr, Galloway has designed a pneumatic water tank, which consists of a cylindrical barrel, 4 ft. 2 in. diam. u,nd H ft. high, closed at the top in which there isadoor (a, Fig. Ill) bolted to the cover, this giving access to the interior when necessary; the bottom, c rf, is 5 in. above the base of the cylinder, and has a central opening 18 in.diJim.for the valve seat which is turned in a lathe. The valve 6 consists of a block of cast iron, (Fig. 1 13), having its lower face turned true, and over which a sheet of leather is tightly capped. A circular plate of iron, 16 in. diam., is )>bolted to this valve, by bolts having countersunk heads, as shown in Fig. 1 13. .A spindle, A, working through two guides, having a turned ball in its lower end, is held loosely in a socket in the valve, as shown, by which means the vertical movement of the valve is secui-ed, while the ball-and'Socket joint enables it to readily accommodate itaelf to the ae;it in any position in which it may be turned. At k is one half of an instantaneous coupling, supplic<:l by the Vacuum Brake Co., constituting the outer end of the pipe /, which passes through the aide of the cylindei', and rises to within i in, of the top of the barrel. A glass gauge, in, shows the height of watr in the tank, this being protected from chance blows by strong ribs of angle iron.
Vacuum is created by air pumps at the surface, and is equiva-
SINKING. Ill
lent to 20-22 in. of niei-cury; 3 in, pipes ai-e canieJ down the pit itiid conDected to 30 ft. of flexible bose, liaviug a stop-cock uiid a corresponding half of An instaDtaueaiis coupling. The barrel is in 30 seconds. It was [Kisttible with this aniiDgement to stink in Pennant sandstone, with 5000 galls, per hour, at the mte of 5-5 1 yds. per week, or with 7000 galls, rather under 4 yds., the rock being very hard and compact. The highest rate of progress in the same ground with only 500 galls, per hour hod previously been 6J yds."
KEEPIWG OtTT WATER BY TUBBING.— Ordinary masonry in of little u.se for stopping back water, if the measures contain large quantities, and it is desired that thbi should not liave to be ooutinually dealt with. As a i-ide, it happens that water-bearing beds are usually succeeded by others of an impervious nature, so that if tliei-e can be introduced at such point some water-tight material, the water la prevented from coming into the [Mt. Such lining is called tubbing. The material employed may be either wood, cast-iron, or masonry ; the former, however, is tteldom employed at the present time. Its up-keep is great, it is scarcely ever water-tight, and its only recommendation. is cheapness in first cost, where wood is plentiful.
Coffering. — Wliere the pressure is not excessive, a special setting of ninsonry, technically called " cotlering," is largely employed. It is cheaper than cast-iron, and where properly put iu is very successful. The foUowiugis a description oF what is pixibably the largest application of this method, the shaft being 20 ft. diom. iu the clear, the coffering extending about 55 yds. (from a depth of 105 yds. to 50 yds, below the surface).
After passing through the water-bearing beds, the sliaft was sunk 20 yds. below the point where the laat feeder was met, and & cast-iron curb put in, and supported on iron plugs. Upon this, about 26 yds. of 14 in. brickwork was biult, and then the walling was carried up solid for 12 ft., untU the waterlearing strata were met with. The object of doiug this was to provide some substantial support for the coffering, and to prevent any risk of the masonry settling and cracking. It was decided to put in the coffering 2 ft, 3 in. thick. Some means have to be adopted tc caiTy off the water running from the rocks, and to prevent it parsing over the brickwork and washing the mortal' joints away. To do this, what are called " plug boxes " wei-e bedded on the solid work. Six of these were placed at equal intervals around the cii'cumference, and were formed of wood, 1 2 in. square by 2 ft. 9 in, long, having a bote 3 in. diam. bored along their longer axis to within z in. of the baek (n, Fig. 1 14), and then a vertical hole, li, bored from the top to meet the horizontal one. In this latter, vertical wooden pipes hiiving horizontal openings were carried up behind the brickwork,
So. Wnles lnr.1. xii. lig.
ami allowed the wateito pass away thi-ougli the openings in plug-boxes. Theholee in tbe water troughs were favored at vertical ' intervals of 3 in. As the brickwork and puddle reached each hole it was plugged up and the watereonveyed away through the next higher one. The solid walling Via. 114. was then brought up level with
the top of tbe plug-boxes and the coffering commenced.
This consisted of five rings of brickwork, tbe special feature of this system being that the joints are broken both vertically and horizontally. Header courses are not employed, stretchers only being used. To commence with, the first ring, c, is of ordiiiary hrick ' 3 in. thiok, the second ring, li, for 1 theVft course is laid with bricks [J in. thick, tbe thiii! and fifth rings, e and g, are similar to the first one, while the fourth ring, y, for thefirat course is also made with li in. bricks; afterwards, ordiuai-y briclu, 3 in. thick, are used in all tbe rings, so that the horizontal joints of the second and fourth courses throughout the work are the thickness of half a brick below tlie others. The method of laying the bricks is the usual one for the first, third, and fifth courses, and when these are in position, the spaces between are filled with thin liquid cement, and the second and fourth rows are laid by dropping the bricks into the mixture reposing in the gullet, these being what are called " floating courses."
After getting up about 12 or 18 in. the space between the back of the brickwork and the strata is lilled in with good loamy soil, which should be free from pebbles and should be well and cnrefuDy rammed, no spaces being left. Instead of eoil, well puddled clay is sometimes used, but experience is more in favour of the former. With clay, no matter how carefully the work ia done, there is a tendency for " faces " to be formed between successive layers and lum]>s, through which water find!* its way. The mortar used for laying tbe first, thii'd, and fifth rings was a mixture of lime, cement, and ashes well ground in a mortar mill ; foi' the intermediate lings, pure Portland cement was employed.
Iron Tubbing. — Where the pressure of the water is great, and long lengths have to be put in, masonry tubbing is not applicable ; indeed every form has given way to that in which cast-iron is employed. At one time rings going completely round the circumference of tbe abaft were employed, hut the difliculty of getting them into position, and their liability to break, together
Sinking. 113
with the iinpOMsibility of repairing them, caused an early aliandonmentof this t'oiin, and the use of segments ha iiowlieconiegenei'al.
At first the flanges were placed towards the centre of the pit, and the attachment of one to the other whs made by means of bolts, but in conse(|Uence of the lowering of the ground, and the eflect of side pressure, it was found that bolts were not to be trusted, and that frequent ruptured tools place. In England this method has given way to the system in which the flanges are placed away from the centre of the pit, it being found that the pressure of the sides and the wedging whicii is adopted, is suffident to retain the segments in position, and to keep the joints watertight. Theauthorwassurprised to find ou a visit (in JS91) to the Continent, that the old system of placing the flanges towards the inside of the shaft was still in use there. The engineers at the difierent collieries vtaited contended that no reliance could be placed on wooden wedging, as it is always decaying, and that although some little difiiculty is encountered through movements of the ground, these are counterbalanced by the more pei'fect watertightnees of the tubbing. In tLLs method the fianges, both horizontal and vertical, are planed in a lathe, and two V grooves cut in them. A layer of sheet-lead is tlien interposed, and the two segments screwed tightly together by means of turned bolts, the pressure forcing the lead into the V grooves already alluded to.
The method of putting m the work is the same whatever eyetm is adopted. After getting through the water-beai-ing strata, and reaching some impervious beds, a bed in first formed on which the wedging curb can be placed. This is dressed truly level with the aid of hammer and chisels, blasting being strictly forbidden, so as to obviate any possibility of fracturing the i-ock. This is the keystone of the whole operation, and requires the greatest care. Formerly wedging curbs were constructed of oak, but this has beeu abandoned in favour of cast iron. They are built up of segments which, in the case of upcast shafts and furnace ventilation, ai'e sometimes of smaller diameter than the tubbing plates, the projecting portion being afterwards used as a foundation on which a lining of brickwork can be built. For an important undertaking they would be about 18 in. wide by 6 in. dep, and are cast hollow to lessen the weight. The segments of the curb are set in position on the bed prepared, and half-inch sheeting of soft deal placed in the joint* in such a manner, in this and other cases, that the end of the gi-ain of the wood is presented to the inner port of the shaft where wedging lakes place. The important operation of wedging the curb is then commenced. All around the circumference, in the space between it and the sides of the shaft, is placed well-dried timber, free from knots, with the grain upwards. As many well-dried, finely-tapered, pitch-pine wedges as possible ai'e then driven in, care being taken that this operation proceeds all round the shaft at the same time in order
ti4
Text Book Of Coalmining.
to distribute the pressure, and prevent any chance of the Begtnen being displaced ; propa are also set from the sides over each joint to keep the curb from lifting. When no more timber wedges can be got in, steel chiselK are employed, and, in the spaces tliey make, further wood is inserted. A second wedging curb is usually placed above the first, and Kometimes a third one. The top one rf J these always has a rebate oi' ledge placed on it, against which segments of the curb abut.
Tubbing platen (Fig. 115) are cast in segments of such a length I that the circumference is divided into parts, their height J
£t evct'tloTt-
o£ -BtfoJk
r J
11
r J
1
varying from 18 to 36 in., according to the pressure to be resist*. Flanges, croea-iibs, and brackets are cast on the back to give strength, and a hole is provided in the middle of each to allow water to pass through while the operation of laying the plate ia proceeding. The top and one of the side flanges are proWded on the outage with a projecting ledge, which keeps the joint sheeting and adjoining segments in position.
When the wedging in finished, the first layer of tubbing plates will be laid on the curb, sheeting being placed between both horizontal and vertical joints, and a wedge tightly driven down between the back of the plates and the aides of the strata as a preventive against any of the segments moving. A second lajrer of segments is then laid on the first in a similar manner, and the process repeated until the top of the water-bearing sti'ata is reitcheil, the vertical joints being broken in each course, a.s in
Sinking. Ii
buil.ling miLKonry (Figs. :i6 and 117). The apaoea between tl plates and the Kides of the exiiavation are filled in with soil ( concrete packing, A wedging curb will lie placed on tlie top tJ it ia found that the water rises above the level of the Inst line plates. All the horiEontal and
Flca 116 AND I
vertical joints are then fidly wedged, as long as the grain of the wood between the joints can be opened with a chisel, commencing at the bottom and prooeediug upwards, attacking each ring in orJei-, and plugging up the hole through the centre of each /
segment at the same time. If this operation is carefully perform it will he found that the length tubbed will be quite
In m&ny in-stances much time and money is saved by not wiuting until the bottom of the water-bearing beds is reached,
but putting in wedging curbs at intermediate places and building tubbing up from one to the other, auccesaive feeder of water met with being thus kept out of the shaft. Of course, for the success of this operation, it is necessary that the nature of tlie beds met with is such as &IToi-ds foundation for the curbs, but although each wedging curb mny not be water-tight during the time of tdnkiiig, yet when the pressure of the lower length of tubbing is brought up against it such leakage may be altogether or nearly stopped, and, although each foundation may be bad by itself, yet when they are brought to beer in support of ooch other, the water may be stopped back. In the Seaham wiiining* ten successive lengths of turning were thus put in, and, although the total quantity of water which the engineers had to contend with at different periods of the opemtion was 6140 galls., yet never more than 540 galla. per minuta was actually in the pit bottom, this being the maxtmum amount, the average quantity lieing 136 galls. The total amount of water tubbed b.ick ivas 4880 galls, per minut, which woidd have been the (juantity required to have been raised or pumped to the surface, if intermediate wedging curbs hod not been inserted. After reaching an excellent foundation in the coal measures, three main wedging curbs were put in as the base of the ii-on tubbing, and the sinking through the coal measures commenced without a Jrop of water in the bottom.
Text- Hook Of Coaj.-Mixixg.
Messrs. J.J. Atkinson and W, Coiilson* were the first to point out the curious accidents which happen to tubbing fixed between an up{)er and lower wedging curb through the confinement of water and fjas. It has never yet satisfactoiily explained, how air and gas confined behind tubbing can have a greater pressure than that due to the hydrostatic head, but it is a fact that such is so, and unless some escape is provided, no matter how tliick the tubbing is, the inevitable result will be that it becomes ciucked or displaced from its seating. To prevent siich occur-ences, either the water behind each lift is connected with the water behind the other lifts, by means of small pipes, and thus, in effect, rendering the whole of the tubbing open-topped through the medium of the uppermost lift, or a pipe is cjinied up from behind the tubbing to the height necessar}' to Imlance the pressure of water. As thi takes up a large quantity of a shoi-t length is sometimes inserted through the tubbing near the top of the lift, and only extended a small distance up the shaft, but a loaded valve is pi*©- vided at the top, where all the pressure of the water is. This
valve discharges the air and pi'events the pressure getting higher than is due to the water alone.
The more general pi'actice is to place a valve rt. Fig. 1 1 8, in the wedging curb, and to carry- a length of pipes b the tubbing to the next wedging curb. After the tubbing has been wedged and plugged, the water rises and drives out all the air. When water has been running through the pipe for some hour*s the valve a is closed.
Strength of Tubbing. — The thickness of castiron tubbing vaiies directly with the pi'essure it has to support and the diameter of the shaft. As the pressure also varies as the depth, if the diameter and the depth are both doubled, the thickness of the tubbing will have to be increased four times. Mr. J. J. Atkinson f gives a complete reasoning for the following foi-mula, from which the thickness at any depth can be found :
Fig. ii8.
i
'I'-i
whei-e t equals thickness in inches, d equals the diam. in ft., p equals the pressure in tons per sq. inch due to depth, m equals the working load or resistance to crushing of the material employed. Remembering that a cub. ft. of water weighs 62.5 lbs., a cub. in. will weigh 0.434 lbs., so that for every foot of depth a pressure of 0.434 lbs. per sq. in. is exerted. To obtain, therefore, tlie
♦ N. E. I. xi. 9.
t J bid, ix. 175.
SINKIXfi. r.7
preBHUi-e per sfj. inch due to any hend of water, the ilepth fi'oin the surface in feet it) multiplied by 0.434. The i-resistance of castiron to crushing (average of various qualities) is about 90,000 Ibe. per sq. in., but to be on the safe side, th of this amount 15,000 lbs.) is taken as the working load, luid should be sub- -etituted a.s the value of m in the formula given above. To the thickness so found, inch should be added to allow for coiToeiun of metal and wear and tear.
In shafts of large diameters the thickness of the upper segments should never be less than J inch, or they are liable to be fractured by blows. In the above formula notice is not taken of the sti-ength imparted by flanges and ribs, which will give additional secmity. Tbeoi-etically ench segment ehould be different in thickness to the others, but as this would involve eonsiderjible expense in casting, the thickness in varied about every 8 or
Corrosion. — Certain eubstjincee contained in solution in water have a very injurious effect on iron, saline matters and chlorides being especially destructive. No satisfactory means have yet been devised for stopping such action, the best preventive, prolmbly, being a coating of a hard varnish applied before the tubbing is eetited. The front of the segments in upcast pits, where fumaoe ventilation is employed, in alto attacked by the gases generated by the combustion of the conl. Sulphurous acid is produced, and mixing with water forms sulphuric acid, which rapidly eute away the iron to such an extent that in a few years its nature is completely destroyed, and it gets so soft that it can be cut with knife. The best and genemlly used preservative is a lining of fire-brick, a seating for it being mode by fixing one of the wedging curbs so that it projects from 3 to 6 ineheM into the shaft. The great objection to this procedure is, that by covering up the face of the tubbing, the detection of leaks ia made diflicnlt, but of thf two evils tbelerwer is chosen.
Coat of Tubbing.— Mr. G. C. Oi-eenwell" gives the followinji; eitateraent of the actual cost of putting in metal tubbing in a sliaft 14 ft. (; in. diameter:
Cati of uKilgina curb : —
Dressing and preparing bed for turb, and laying vime £ a, J,
ready for wedging 34 9 o
Wedges (5435 useil) and sheeting (material aiiii raunufacture
ija
Wedging curb 1 10 segments. vach 7 cwt. i ijr, 17
74 cwi. I llis., & 6 9 per cwi,] . . 24 ly 7
i'74 "6 S
ii8 TEXT-BOOK OF COAL-MINING.
Co8l jyer yard of tubbing : —
lo segments to circle, each 18" high x H" thick, weighing £ >i. d. 4 cwt. I qr. 12 lbs. 85 cwt. 2 qra 24 lbs., % 6/9 per cwt 28 18 6
Painting tubbing, sheeting wedges* (4428 used) and
liking with soil, marl, etc 416
Putting in and wedge tubbing:
Putting in o 10 9
Wedging (twice in going up and once in going
£ZA 12 6 These wedges were 44" long by 14" on face by 4" thick.
Shireoaks shafts have more tubbing in them than any others in England — viz., 1 70 yds., put in, in eleven lengths, and weighing about 600 tons in each shaft. The internal diameter is 1 2 ft., and the pressure at the bottom is about 196 lbs. per sq. inch. Mr. John Jones, the present underviewer, who put in the tubbing, states that the cost per yard of the lower and stronger part, which has a thickness of if inch in the body, was as follows :-—
Fixing and wedging
£
2 u
SINKING BY BOBING.— Eind-Chaudron Method.— Looking at the ease with which bore-holes are put down through water-bearing rocks, the idea occurred to engineers, that supposing the tools and implements employed were made large enough, it might be possible to bore shafts. Little difficulty was encountered with the actual boring operations, but, for a long time it was found impossible, to successfully dam back the feeders of water, as no means were at hand to put in a water-tight lining. Cylinders of tubbing were lowered into the pit, but it was found impossible to make a joint at the bottom impervious to water. After many failures, the difficulty was surmounted by Mr. Chaudron by the introduction at the base of the tubbing of what is known as the moss-box, and he, in conjunction with the celebrated bore-master Kind, devised a scheme by means of which numerous pits have been successfully sunk through beds containing a very large amount of water.
The boring tools are similar to those ordinarily employed, modified to suit the changed conditions. First of all a smaller shaft, 4 to 5 ft. diameter is bored, which is kept 50 or 60 ft. ahead, and then the main shaft is taken out to the size required. The
SINKING. iKj
cutter for tiie smaller shaft consists of an iron framework (Kig. 1 1 9) in the base of which are fised, in pockets, a number of stel cutting tPtli a, which can be easily replaceil if anything goes wrong. This tool is fitted with two guides, b and e, which are olao furnished with cutting teeth. When the shaft has been bored >iul£ciently deep with this tool, a larger one (Fig. ijo) is inserted, this differing from the first, not only in its size, but in the fat't the teeth in it are set on an inclined plane, and that the central part is furnished with a. loop or guide a, wliich fits into the smaller hole already bored. Owing to the shape of the teetli the stratti is cut in the form of an inverted cone, and nil the debris
pi-oduced, falls down the inclined 8lo|>6 into the smiilleishaft, in whicli. at the bottom, ia placed an onlinary kibble, which collects the material and renders the use of a sludger unnecessary.
These tools are moved up and down by an oscillating lever at the surface, just the same as in an ordinnty boring apparatus. A winding engine, drums, and ropes are provided for the rapid removal (during changing) and lowering of the tools. Sinldtig thuK proceeds until the solid is reached, where the seating for the base of tubbing is found.
While the shafi is still full of water, a water-tight joint is mode by the moss-bos. This consists of two rings of tubHng (n and h. Fig. lai), which can slide over each other, and eneh
lo TEXT- BOOK OF COALMINING.
of which has a bottoui flange turned oiitw&i'dH and an upper fluoge turned inwards. These two are strung together by iron. tie-rods c, and the space between them completely filled with moie, so that when the upper one sUdeB down, this mofiti is cooipresRed. Other segments are connected above these two rings, all of which have the flangeti pointing inwards. The tubbing consists of cylindrical rings, ulxjut 4 ft. 6 in. high, cast in nn entire pieee. There are no vertieul joints. A strengthening rib is cast inside each ring, and the top and bottom flanges are turned in a lathe, and bolt-holes bored in them. Before being used, each ring is tested by hydraulic pressure, in a specially constructed box, with from two to Ave times the pressure it has to support. These rings are put together at the surface with Jth of an inch of sheet lead between the joints, and the whole structure lowered bit by bit, by screws and strong ijon rods.
The chief point upon which successful lowering depends, is the means adopted to balance the enormous weight of the lung length of tubbing. Near the bottom a diaphragm (rf. Fig. izi) is fastened to the flange of one of the segments, and in the centre of this ia a tube. When lowering is being caiTied on, the weight of the tubbing foi-ces the water up the ceuti-ul aperture ; the amount displaced by the diaphragm and the resistance it meets with during its passage through the water ai-e so great, that a large portion of the weight of the tubbing is supported; indeed, in some instanceN, it is more than couuterbalanced, und where such happens, water is introduced at the top of the diaphragm, to be pumped out again if necessary. ITiia regulation is operated so successfully, that in one case where the entire weight of the tubbing was Soo tons, it was so counterbalanced that not more than 40 tons was ever on the lowering roils at one time.
IiippmEinn'B Method.— To the foregoing method several objections may be taken. It has beeu found that nearly as much time is taken to enlarge the small shaft as to bore it, and attempts were therefore made to carry out the whole opera- Kio. iiz. tion at the same time. With a straight chisel ' turned round a centre, blows are struck more Dsely neaithe centre of the shaft than at the rcumference, and considei-able labour is wasted. Messrs. Lippmann have got over this difficulty by making a drilling tool in the shape of a double Y (Fig. Ill), in which two teeth are placed in that portion cutting ivund the oircuDifereoce of the .(Imft, and only one towards the middle; more blows are thus given at the periphery than at the centre. Another impi-ovement is that the engine is not connected directly to the boi'ing lever, but motion is comm animated by means of an endless chain and eccentric, which prevents all shock. The debris is extnicted by au h-on box,
Sinking. 121
divideO into three compuittnents, each which hiis nine holes, closed by valves oieuing outwanlH. This box is lowered to the
Kit bottom, and alternately raised and (h-opped for about 15 minute, etng at the time gradually turned round. The sludger has iHuiilly to be filled twice before recommencing to bore. For seciiriDg the sides, aimiUr tubbing to that of the Kind-Chaudifln method Is nd opted.
SINKIITG THHOTTGH QUICKSANDS. — Triger'a Method.— In this system, sheet iron cylindei-e, divided into three aictight compartments, ai-e sunk into the gi-oinid, and compressed nir forced into the lower one. Tlie worltmen are thus placed in a aort of diving-bell, and if the pressui-e of air ia gi'eater than that of the water in tlie sand, the latter is forced back, and preventeii from entering the lower compartment. The rubbish excavated in removed in a small kibble. Trap-door allow communication from one chamber to the other, the joints of these ieiii); mule carefully air-tight. The doors of the second tind third chambers are never allowed to be opened at the same time, so that little loss of compressed air takes place. Sinking proceeds nntU solid ground is reitcbed. Tlie depth which can be attained by this method is limited, for as the pressure of water outside the oylittder increases with the [lepth, a higher pressure of air has to be usoi! in the lower compirtment to atop the influx of water, and a point is soon reached above which the men ntnnot work. At Ais-la-Chapelle, 121 ft. of [{uicksand wn. passed thiuugh by this method, the greatest prcsisure of the air I'mployed lieing 2.8 atmospheres.
Foetflch'a Method- The moat recent improvement for sinking through water-bearing strata, k that introduced by Mr. Foetch, which consists in freezing the running grounil, iind tiitnsforming it into a solid mass of ice, through which sinking proceeds by ordinary methods, ju.t as if the ground was of a tenacious and solid character. A well-known principle is that, when any liquid is rapidly converted into vapour, it absorbs a considerable ijuantity of heat, and that the absorption is more rapid the more volatile the liquid. In the machine employed for producing the freezing mixture, liquid ammonia is placed in connection with the receiver of an air-pump, and rapid exhaustion set up. The ammonia at once commences to boil, and the vapour produced is absorbed by suitable means, with the result that a still more rapid evaporation is produced, which communicates intense cold the mixture employed for the freezing operation. The liquid used for this purpose is a solution of chloride of calcium, adopted because it does not freeze until the temperatui reachai — 34" 0.
The actual pi-ocedure is as follows : — A series of bore-boles are sunk through the water-bearing strata until the solid measures are reached, and are hned with tubes Fig. 123) )\s they go down. After penetrating through the quicksand, the lower ends of these tubes are made water-tight by means of lead stoppers b,
Text-Book Of Coal-Mining.
aod several layers of cemeiit c are poured into tbe
greatest care ia exercised in getting the joints of tiie outside pipe
water-tight, as if they are not, the solution of chloride of caJciuui
escapes uito the ground, and renders freezing very
difficult. Into the centre of each of these larger pipes
'3' ft smallei' one il, of about one-third the diameter is
J , introduced, having its lower end open. These latter
, pipes are provided with stop-cocks, and joined to a
central distributing pijie, suspended above the top rif
the shaft. The freezing mixture, prepared as above,
is then forced by a pump down the small tube, and on
reaching tlie bottom circulates in the annular since
between the two pipes, risee to the surface of the
ground, and is collected in another series of pipes e,
from whence it is again returned to the frying
machine, and used over again. By this means the
ground between each pipe within the shaft itself, and
also the gi-ound outside the limit of the shaft, is frozen
hard enough to give solidity. The most intense cold
11 is at the bottom of the pipes, and as a result small
j p't cones of fiwzen ground, with their bases downward,
are first formed, the dimensions of which increase
progressively.
The method of sinking after the gi'ound is frozen, is to excavate
a upRCT with tbe aid of pick and wedges, bltistliig being expreeely
forbidden, and then to secure tlie sides by means of ordinary curbs,
and laggings. Second and further lengths will be sunk, and
timbered, in a similar manner, until the quicksand is passed through
and solid ground i-eached, when a wedging curb will be put in, and
c-ast-ii-oii tubbing brought upwards.
At EmUia Pit, Germany,* the apparatus was charged with 950 quarts of solution of ammonia, the daily consumption of which was atxmt 3 . Freezing occupied 53 daj-s, when sinking was commenced and done without any difficulty, at the rate of about 3 ft. per day. Sinkers were paid 558. per running yard. The circulating tubes were removed very easily, the solution of chloride of calcium cooled. Total cost of plant was 3000 ; expense of erection, 960. Total coat for shaft, completed and walled, allowing per cent, of first cost (if plant, for depreciation niid expenses of ei'ection and removal, was about i6 per runuing foot.
Deepening Piti already Sunk. — The common way of doing this, without stopping the pits drawing coal, is with the aid of a tail-rope fastened below the cageR, If any depth is to be carried out, the rope employeil will be made in two lengths with a view of saving time. Tht> pi'eparatiun is rather a simple one. First of
for, Ab*. N. E. 1. !
SINKING. Hi
all, lueaiiB ai-e provided a,t the inset level, for i-receiving the dObt-is out of the Rinloiig kibbles. Then no' on.linAry rope in provided with a capping ut each end, and the upper one passed through the bottom of the cne, nnd made hy driving an iron pin througli the eye of the cajipiug, and usually further secured hy glands to the of the cage. The kibble is attncbed to the other end of the tail-rope, and when the cage is by the winding engine at the surface, the kibble iii lifted also. The method of procedure ta to till M. kibble at the bottom where sinking is going on, lift it to the inset, empty the contents into tubs standing there, and then lower down again. Sufficient tubs are provided to contain all the dirt pi-orluced in the night-time, and the tail-rope is then taken off tile cage (an operation done in five minutes), the cage lowered to the inset level, and the debris wound to the surface.
The aliove system can only bo applied when the pit is not winding coal. In many senses this difticutty is Hurmounteil by commencing at the iuset level, a short distance away from the shaft, and sinking an inclined pit until its aKi-s meets that of the drawing shaft, when it is continued vertically downwards. At St. Adolphe Pit, Haine St. Pierre Colliery.* with such proeedm-e, the shaft was deepened from 984 to 1246 ft. without stopping winding. The debris was drawn by an engine ut the surface, a rope from this passing down
Fig. 134-
the side of the winding pit, und then deflected by pulleys along the line of the incline, finally passing into the vertical position required forsinking, by being conducted over a pulley supported on a cirriage, the rope piiKsing through aholein IZ4). When the kibble is at the bottom of the sinking, the carriage is at it lowest point, and the rope hangs vertically in the pit, but as the kibble is lifted the can-iage is pushed up the incline, the kibble hanging in a vertical direction until the inset level is reached, when it in removed, and an
empty one put on. On the return journey the carriage follow*, the bubble as it is lowered, until it comes to the end of the guide. Tlie rope then descends vertically downwards. A spring is place just above the capping on the rope to pi-event any shock when the kibble strikes the csirriage,
For, Ab-. N. E. I. xxxvii. 5S,
Text-Book Of Coal-Mining.
K1G8. 125 And 126.
Fig. 127.
At Alexandra Pit, Wigan, a shaft 19 ft. diam. wa.s deepened from 260 to 772 yds. in two years by the following method, coal being wound all the time. One cage was taken out, and a balance weight, to a cage and four empty tubs, put in its place, this working down the side of the pit on two guides, the winding rope being diverted from its ordinary position by means of a pulley on the head -gear (Figs. 125 and 126). Three scaffolds were put in at the Pemberton 4 ft. inset, to prevent anything falling on the sinkers, and a hole left through for the passage of the
kibble. A platform on wheels was provided on a level 6 ft. higher than that employed for caging the coal, which could be run over the hole left in the scaffolding. A small winding engine at the surface drew the sinking debris from the bottom of the shaft up to the level of this platform, which was pushed over the shaft, the kibble removed, and the dirt tipped into ordinary tubs standing at the level of the inset. These were then placed on the cage, and drawn to the surface. A capstan rope, worked by a special engine at the surface, passed down the centre of the shaft and formed a guide for the sinking kibble, duringsuch timesas bricking was not being proceeded with. When this rope wab not in use it was kept in position at the bottom of the pit by a heavy circular elongated block of iron. Fig. 127 gives an enlarged view of the guide employed ; a Ls the capping of the winding rope, to which is attached the detaching hook b. Below this comes the guide c, and weight d, the latter being of cast iron with a hole bored out to receive the vertical bar e, which fits into d loosely, so as to be readily withdrawn for examination. Above the weight a horizontal bar c projects, clasping the bar e above the weight, and projecting to the capstan rope on wliich it runs freely with plenty of play." Below the weight comes the kibble and bridlechains. The capstan rope g is placed absolutely central in the pit. When about to fire shots the men were signalled away first,
I I
wms ruad a few TTiris at &s en- -:€ iL-r wav of the de'ori*.
The brickiiig scadTxd va ni&tie of ti=i%r. Az.-i -i-spirndei frotii bridle dudnsw and oocsaateii of iL;£- fLr:.. & orr-tre -zzxand two side pieces working on r.:nge>- I-irin briekiiijr operadoo winding rope was izawa: ckat. il-r weiLr on ir.e capstan rope taken odl an*i the L&cter connrcteii to *L-r bnilehiEJi of the Bcafibid, which, when loc in -ise. wi> in the shift from cross baulks pbooi there ckitti'.!.
For short distance!-. *LAfts arv: 5.:ii-rtin:r srirj: upwipl*. A dividing bratdoe z'iucii ijcr>? -Jie . and the deJjriallowed toaocomilateoTer :n-r-nilf :t* tLir forming of natural platform on wniin z'zjr n-rn scn-i to work. For the purpose of TentiIat:on. wien '-.ci-e-, .r tr-.-bL*. ire Viilt in the debris.
Widening Shaita. — Tni- i "-Ty.- kwiri ind cf*!tlT of*r*- tion, if winkling ia to w earrirri '.n it t r aiie time. In -'jch caseB. it is osxial to ZrJi i 5rrK> :f Tif_-- --r bun t/:.ni. flow ea/:h other, in such a tiisdtLon tLit tL-? oasr :::i.''.is tLtn.. At Liifhttime these ban ton* are ccrfTrii OTer Trit li links. and £<siffoidfcxmed. on which tb& m-e- w:ri:_ i- : :.ii:e .it the grind.
If the shaft n-'.-t rttriiryi ::r xli.-:i: g p::r>>!e. tr.e oednre is to nil it Tp tbe -rrfixr "s-tr-nori-<jr/hTef.r materiaL which is reiriTei i-iin i- t.-.e o!i .;: jr.<] -ide ;fi-e taken oat to tL rvzLmi -izie. Tni- -iT*?- all 'jiryir and tiiiif? of changing In a ie*rp -nift. jr.n:on- o!:.iy of it Ien;?tri would be died i if at a ti:::.e.
Cost of Sinking. — rrjtZ ietrn L- on the r.arine Ad indination of tirr <r4ta-ini r?-T.ir:ci.il.v ,:- tr.e '-*Af-t;ty of -*;iUrr. If the beds are nignlj itxineiitne rjet ;freavrr. the rock>* do not Wow well. TLe i--*! i- t/> ofxair. .der- f/r sinking and willing-ti-sr "i'-ie ieptr.. : V/ disk w.'tr* '-)c;rtiiin quantity of wat?r. If tni- .AJ-t.ty 1-e.freed'r'i- either a.io'afi/5en are given or iLe contra-:-: r-.k-n. r? 'r,:.tra/.-- a'.-t ver' well, if the nature of tie zro'-ini L- w.l .. -t:: : no 'ii:flc"j>.:e* art: enoountereii. br:t 4.- ik .—i.e. -a.'v jirvnof K&naJJ capttaL So Ivng. tn-erefo. is tie;.' :.--4 icing Us',u*iy. nfry' thing prooeei* -zi/frz.'.j. t:-e If r-.frei of ;iriZi,y. hL with safety. Bnt :: "r ..-i: .. v. a , the ot/Tjtractor's mean* ar* -o".!. e:i--4 ..-Vii: : i.t;.'. -/;. re ;fefjefaIJy bound bv agri:-er.t. yet -.r.:. *i?v.':,.'--: r--.e Vy :;jvi/:. Jrj -r-iew of thL, the ST-tLL ',t -Arr ',r- .v.e:. it A-iVir- 1-
i;6
TEXT-BOOK OP COAL MIXINf!.
was 11.12 billings per cub. yd., nhicli sum includeii tht; liiboiii' o! putting in the walling 9 inches thick and backing the same with soil, all wage above and below ground (exempt winding; engiueinaii and stoker), blncksmithiug, powder, il:c. ; value <if materials used tor lining not included. Colliers' wages nt thio dute were 10 per cent, above minimum of eliding scale. The mnouiit of wnter wns small, nnd oould Ive dealt with by baliug. An allowance of 25s, was made for eat-h water ling put in.
Al Siuidwell Collien', the coutnwt price foi' sinking and walling the No. 3 shaft. 1 5 ft. diain. in the clear, was I ;a. 6d. {)er running yard, equal to 6.82 shillings per cub. yard of ex- OHvation- The above pric rose at the same percentage as colliers' , which at that time were 3*. per day, the minimum of the sliding finale. The contractor found all labour in pit, banksmen, tools, blasting agents, lights, ix., fixed all ecaflbUk, ventiliitiog pipes, iL'c, and deposited the spoil at such places as rajuired, op to 40 yunis from pit top The company found engine power, enginviiicn, tiiikiiig Kibblg, lining material, and sharpened all Uxils. Ko altownnce was to made for water until the (Quantity excited such ns coul be raised by tipping barrels. The total sum [wid under thi.s head for the entire sinking, amounted to j('(i yc/. F' each water ring put in j£i was paid, and for siiUHiv curb 1 5*. The average rate of sinking and wnUinif (niii'liin continually fmui Monday morning to Saturday utekt) vfHs S.04 yiia. per week.
Alwrs. Koi'tt.'r- Brown ti Adams give detailed statements of ihk> aiM of sinking and wutling two shafts each 17 ft. diam., at Havm Navigmtiou Colliery,* including all labour, coitl at boilers, Muitli work. twplcwTes, story, ic. Fi-om their paper the following fiiw !Uv extractwil : —
Aiws per yd. tor dnkiiis 50 yds. id 1"'c near bottom of abaft. Wiilxiui Pn-DL Willi iMnin.
*ith pumps.
jai7
"S 1-9
i
Sinking. I
per Til.p in depth ol 50 yds., ot iS innli woliing with t iron curbs in taoh diBtoaae.
o 17 10.7
Labour (Binker, masoDB, smiths, enginemtn, &c.) Slores (candles, oil and greaMi. sinkers' units, Material (bricks, lime, and coal)
Equal to £1 j-. tal. j-er cub. yd, of a
Where SzJ per cent, of the stnitsi paused through was hard I'ock, Hod iji per oent. sliale, the nvernge depth sunk and walled por week, exclusive of stoppages, was, in u length of 69 yda., 2.19 yds. ; while, where 38 J per cent, wan hru-d rock, and 6: J shale, llie speed averaged 4.08 yds. per week over 11 length of 421 yds. Towards the bottom, the ground only contained 6 per cent, of hard rock, and the speed of linking and walling reached 6,77 yds. per week.
The following table shows the comparative cost of n of sinking through water bearing strata : —
Sink log.
Hmi . . .
ao 17
Saint Waast .
J21
Saint-Barbe .
Saint-Marie .
Archibald. .
1 Koeniga
Quickshnd
I ICanniDK sand and 1
ir bearing chalk j" mdihaak . . .
Chalk, marl, and sand .
Claj, maris, and aand
ATiite mariB
Quicluand
. Ac
Detailed statements of the cost of sinking Heveral shafts by the Kind-Cliandron process will be found in the Collieiy Guardian of Jan. 23, 1880, p. 139.
Bibliography.— The following is a list of the more importimt memoir-a dealing with tlie subject matter of lliis chapter: —
CE. : Dt'p Winninif of Coal in Hoiilk 11',, T. F G.F. AdamB, Mv. aj ; Tht Siniing o/lico S><,i/it , WhUbum Coai Compann, Jolin Daglisli, lixi. 178 iVti ntar Dortmimd, H. romaoij, xc. 330.
For Abs. N.E.I. ixiv. ii.
rler-Brown and Marilat,farlhe JiiH/cini/ of
128 Text-Book Op Coal-Minincj.
AHBB. INST. M.B. : A Xcio Method of Sinliiig Sha/ti, E. H. Coxe, J. 361 ; Shaft Sinking at Ooderich, Ontario, J. H. Harden, v. 506.
FBD. IN8T. : Kotes on the Hinhing at Lent Callitriet by the Ritttch tHj/ittm, ! N. K. Griffith, ii. 441- '
MAS. GEO. 90C.: Boring Shafti in Walphalia.A, Demmler, xiv. 374; Sinkinj/ f aiih a Tail Hopt. G. WUd, iviji, 380.
BRIT. Boc. MIK. BTCTD. : Zkldilt of Sinking Ujiaardt, H. Jcpson, i. 134; Sinkittg at AUimarke JUain CaUieTy,A. MlrSn, J. 1S6 and 232 ; SiiAtng through Qiiiekiandi, JUarU, and (travel Bedg, B. Cloogb, xiT. io6.
GO. WALK§. INST. : On tie Tubbing of Shafts, E. Hedlo;, iv. t04 ; Periomd Eitrimeet in Tubbing SmfU. Geo. WUkinson, x. 191 : Ercarating belle Water Leeel bg meant of Cotimretted Air, Wm. Galloway, s. ajz ; Ah Acanmt of the Sinking ana Ttibbiiin of a Pumping Shaft at Jtaditoek Collitriet, J . McMnrtrie, xi. 66 ; PoettcA't Fret:in Sytttmt Sinking through Qiacktundt, R. de Soldeohof, xr. 143 and 349; Siviivg Ajiplianrxt at IMtabradadi, Wm. Gallowaj, zri. 107 and
NIK. IKST. SCOT. : Xolet oit the Sinking of ShafU and the wag they artfittfd vpfoT Winding and Pumping, Bobt. Belth, riii. 234.
S, K. t. : On Mnrton Winning, Ed. Fotter, v. 43 ; On Sinking through lA Haijnenian LiintntoNx at Seaton and Smutm Ifiitni'iHf, N. Wood, V. 1 17 j On the Strength of TiMing in Shaft) and Ike jireiiaure it hat lo rttitt, J. J. Atk&Bon, in. 175 ; On the yroptr Preeavtioai to be adopted in order to prevent the IKtaeement of in Shoftt, J. J. Atkinson, and Wm. Conlson, Sen., zi. 9 ; On the Sinking of Shaft' by Boring under ratt at praiiited bg Mettri, Kind it CAaaartHi, WariDgton W. Smyth, 187 ; On the Differing of Shafti to keiv ' Jaek Griffith, xxTi. 3; Sinking Set Med with a ntie Windbore Prolectar and Sttclion Stgulalor, H. Rictiardson, xxx. 49; /bi( 0/ mttK)! at the SkeUoa Birk and Lvnijaii-n Mlnti, A. L. BteavenBon, xxxi. lOJ ; A tkronol/igieat Bevieic oj a nunAer of Shaft Boring* (in For. Abs.) ixzit 76.
ISD. MIN, ! Notice tur un nouveau mode d'approfotidiiieineat dua ptiiU d'rxtraetion, U. Delcommune {2° Sfrie], vii. S19; Proeidt Pbtltdi pour tea Irawnx t faire dant let terraimi aquiftret par la eangiUxtioa, A, lAvj (2* Bfirie), Jdii. 583 ; Eniphi de etrket enfer et de platraax en c£ln pour oivetement du puitt Kord-Oueit de la Cie det Mintt de Montieux A St. Etienne, M. Male (z* Serie), xlv. 555.
HIS. ifBT. : On iron and Stone Tidibing, T. W. Embletou, vii. 165 : Artifiat Foandationt and Metliod of Sinking through Quiektnnil, W. E. Garforth, x!. 407.
CJl ES. IKBT. : Sinking at Clifton CoHierg, J. Brown, viii. 345.
S. BTiFlf. INST, : Sinking through Quiehandal PodmoreBall OoUierg, W. R. WilBon. vii. 113.
BBV. UKiv. ; Noliee tur qutlqyet/ailt rdatift ouxjimfoget de puitt a nivenv plein ISj/lUme lAppmana], Ed. Baotier et H. Uativa (z* Mrie), v. 96 ; Note tur la riparation dv cuvelagt dn puila No. 3, Ste Barbe, A. Sohier (a* Wrie), viL 538 ; Note la reparation de detucureloget en boit rl mr rinHaSatioB (Tun ehdtiit 6 molettea fn frr <iu rharboanaget du Viemof), A. IdeDt (2' Srie), xii. 352.
ANN. DES MINBa : ilanoire vr la tnethode de rongdation de M, Ibetteh pour le fonfagt da puitt de mintt et lerraint aqnifiret, V. Lebreton
S' BMe), viii, iit ; Xottiurdetexperieneeidecoaglaliondetttrrmnt, . Alby (8- Srie), xi. 56.
The Frfoang Ih-ooem at applied at Iron Mountain, Michigan, in Sinking a Shaft through Qvicktand, D. E. Morgan, School of Mines Qaaiterly, New York, vol xi. p. 237-
Chapter Vi.
Pkeliminary Operations.
Underground Boads.Having i-iu;hed the seam fi'oui which mineral is Ui exti-acted, the first o]>emotion cotudatH iu driving n serifs of passages called levels or roiids. Their direction is governed by the relative position of tho shafts and area to be won, by tho system of working adopted, and by the inclination of the seam. Tlieir size is governed by the iliinensions of the tuba employed and by the proposed system of haulage, as, if a double line of rails has to be iised, the dimensions of the roads will necessarily be larger tbiko where only a single line is iu opei'a- tion. The direction is also influenced by the question of haulage, for if mechanical means are not employed, the gradieuta of the roads will have to be such a horse can readily draw material along them, and as the dip of the mine and the poeition of the shafts are fixed points, the roads in this ca*e will have to btdrawn in Buch direction that the necessary gradient is given.
Another point is the question of dealing with water. Wherever jxHssible, the gi-adients should be euch that all water gravitates towards the shaft. Perhaps, in all seams of and regular inclinations, the best plan is to drive the main road practically along the strike of the seam, only deviating from line to such an extnt as will give a slight fall towanb the shaft, Whei-e seams have undulating gradients, roads carried along the titrike necessarily vary in direction with each change in the dip. For any system of mechanical haulage, the imut results are obtained where the roads are ilriven straight, bo that when the dip varies we usually find that the Etraigbtne< of roads is more looked to than any ikctual question as to whether they are following the strike of the seam or not, aa it only requires a little more engine to haul along the material.
Heans of Keeping Direction. — Having decided upon the poiiition of the rails, they are kept iu the proper direction by very simple means. At the conunencement two or three point are determined, and marked on the roof, with the aid of a compa.ss or theodolite, and plumb-bobs suspended from them in such a
Text-Book Of Coal-Mining.
position that the straight line made by these three ihnll be in the direction in which the level is to be driven. Three points are much to be prefer-ed to two, bs in casB any movement voices place in any of them, it in usually found out, such not being the case where only two are adopted ; as an additional precaution, it ia better that there lineK (thould not be attached to timber frames or settings, or the pressure of the ground is liable to move them out of position. To detei'miiie whether the road is proceeding in the proper direction, an observer stations himself behind the plumbbob farthest from the face, and lights are held against the othet two linoR. Anotber workman is stationed at the face with a light, which about until its position coincides with the line given by the three fixed suspended plomb-bobs.
In some instiinces the |)ointn are fixed in the axis or centre tine of tbe excavation, while in others they ai-e placed nearer to one Hide of the road, of course preserving the same line of direction. In the latter' case, the point obtained on the working face will not Ite the middle of tbe road, but somewhere about a foot from the de. This latter nrningement is preferable, because if the road does get slightly out of FiGB. 128 AND 129. line when the determining
points U'0 lized in the middle, the straight line given by these points will piss down the roitd (Fig. 12S), but if such points are only one foot from the side it would impossible to get the line through (Fig. 139).
Means of Keeping Gradient. — For haulage planes uniform gradients are iirefeiuble, as the cost of cutting through amnl! m-egularities of the floor or roof, and indeed, dislocations abused by faults, is soon repaid by the ease and smoothness with which the plane is afterwards worked. In the case of large faults, mollifications of the gradients have to be introiluced, but even in such cases it is usual to make the inclination approach as near to the regular one as poBsible. The instruments employed for keeping the gradient uniform ai'e also of a simple character. Often an ordinary T-bob (a wooden fi'nme shaped like an inverted T) and plumb-line are used, tbe vertical piece being placed c ' ' "
KtQ. 130.
I such an inclinathat it corresponds with that to be given the floor. This is rather I clumsy instrument. A more convenient form is that of a straight 1 the upper side of which 11 liivel,~6,
Preliminary Operation'S.
'Ji
IB in a small secondary ti-angular block of wool c, tlie angle thin ktter piece miikefl with the former being eucli that, when the bottom side of the straight edge is parallel with the line of inclination of the road, the level is truly horizontaL
Operation of Driving. Having determined the direction and gradient, the work is, a rule, carried out in the following nuinner : — The finit consists in holing or iniderctitting the seam ; that is to nny, either the lower part of the coal in cut away with a pick, or, if a soft layer exists beneath the seam, undercutting is performed in it with the object of reducing waste, Ijecause holing the coal makes nothing hut " small," which is comparatirely woi-thless. The width of the undercutting is equal to the width of the road, but its depth depends entirely on the nature of the seam. Strong reijiure deeper holing than tender ones. In performing imdercutting, the miner lies on his side, and naturally removes mure height at the face than at the back, because at the former place liis arms and the helve of the pick have to be inserted, while at the immediate back only a space equal to the width of the tool is necessary. If the undercutting is deep, part of the man's body ia also inti-mluced, and conseiiueDtly more of the coal has to be cut away. For this reason, except where the nature of the coal absolutely requii-es it, holing should not proceed any further under than iv man can conveniently reach without inserting his body. The coal undergone is got down by cutting a veitioil groove along one side, and then baking down the remainder either by blasting or by wedging.
In some collieries gas exists in the coal under such pressures that it assists the workman in hewing the coal, and roads can best be driven by attacking the whole height of the seam at one time. If holing were resorted to, it would drain the gas, and render the operation of getting down the coal above, a more difficult and expensive one.
Ventilation. — Except under exceptional circumstAoces, one road is never driven alone, two
patnliel oneji and fc. Fig. Kio. m.
131) being carried forwai-d at the sametime, these being
connected at intervals by Uxw-J"**
other roads, called "thurl- n " —M-'--" 'n a,
the object of which is to pi-ovide a way for air to pass to the face and ventilate it. When the second hurling is driven, the fii-st one is blocked up by building a wall in it. Such obstruction is called a " stopping," its object being to force the air further inbye, and prevent it going back to Ul ' w ventilated the
workings. It is obrioaa, ant of air will
natm-ally pass through load goes
on further, the face w uean.'<
a::
vre adopted for carrjixi ir lx> it. Thiis ii dooe by one of twv jnethodb : either bj carrying btticiug. or br irocu cara or 'oodeii pipes called air iroujbs or trout;.''
Hratticiug k gMsvJJy £xid by putting props along the line of roading, but imtowl of using ordinary short lids to such props, a loDg trip of wood about 3 in. broad employed, and finnlj secured agalnrt the roof In-driving the beneath it. The brattioe cloth is attached to tbeiie htiht by nails, and temporarily di\*ides the roadway into two, ai> shown dotted lines in Fig. 131. The pure air passes up one side and down the other, as indicated by the arrows.
This system is largely employed, and is unsnrjassed where the roof is regular, as the laths rest evenly against it, and form an air-tight joint. With irregular roofs bratticing is impracticable, and air troughs have to be used. These consist of sheetiron pipes, with a socket and spigot end A temporary stopping is built across the roa/l, immediately before the last hurling, and one of these pipes put through it. Am the heading proceeds, other pipes are added* The air passes through them, and back again along the road.
Supporting Boot — In every mine the roof has to be supported, this usually being done by timber, owing to the facility with which it can be introduced into the workings, and replaced from time to time when necessary. The roof in t$ted by knocking on it with a pick, or other instrument, when, if insecure, a hollow sound is given out. It is not alwayvt possible to be sure by this test, as the occurrence of a of small faults, or slips, makes the roof disjointed, and less tenacious than if none were present. Slips are unaccompanied by dislocation, and are very dif&cult to detect, even by careful Where a seam is known to contain them, minute examination must be i-sorted to, as a place might safe on inH{)ection, and immediately afterwards come in.
It does not appear tliat the depth of the mine has any effect on the strength of the roof. The order of working successive seams has an influence on the roof of the contiguous beds, owing to the release of gas ; hut from observations made by Mr. A. R. Sawyer* in North Ktaffordshire, no definite results can })e fore-shadowed.
Two systems are in use for the optmtion of setting timber ; in one it is performed by the workmen theuiHelves, while in the other a special set of men are for the Both systems have advantages. In the former, the miner immediately detects any change in the find can at once set the required support, without running any risk while waiting for a deputy to come ; m the latter, deputies are continually going round (oftener than in the other system), and as they have up to this
AtruUntM in Minen {Faih of Hwt/and tSitUti), p. 34
Preliminary Operations.
>Sx
kind of wurk, are very skilful. lu Yorkshire, certain Kpeciut men "u round to set timber, and pi-epaie the working places for the men, leaving a eutlicient quantity of limber cut into proper lengths, the workmen having iiutriictioiu, in case the ixiof becomes dangerous, to set any extra timber necessary, or to leave the place and seud for the deputy. In Lancashire, most of the collier set their own timber in the face (not in the roads), and the props are drawn by officials The colliers are subjected to the orders of the offidak, who, if sufficient timber is not set, order more to be put up.
The general experience seems to be that if a warkmau has to look after his own safety, and set his timber, he generally does it better than if it wa entrusted to a deputy ; while, on the other hand, an opinion is held that the miner, not being paid for setting timber, is upt to be negbgent, to consider it time lost, and only put up props where absolutely necessary
Timbering. — Oi all the varieties of wood fir and pine furnish the greatest proportion of that used in mining Urth may be
Yk" 131 Ijj Asd Ij4
cousidt'i'ed tin? miners timber ar excellence. It can be obtained in good straight lengths, makes little waste in cutting, resists great pressure, and bends to n considerable amount before bretiking, and its life is a long one, whether the place be wet or dry. For props, Norway lir is largely employed, and for such purposes is perhaps as good as larch, as it resists great pressure if such is applied along its length in the direction of the fibres, and is very straight, easily cut and fashioned; but it breaks rather easily when the pressure is applied transversely, and is therefore not trustworthy for bars. Oak for positions of reliability is universally employed, but is not used so much in roadways and workings, ou account of its cost, and the fact that, excepting in large pieces, it grows very crooked, and is nut easily shaped.
The simplest form of support employed is that known as the pi-op, or tree, which consisttt of a piece of timber fixed in a vertical position between the roof and the loop (A, Fig, 132). These lire employed mainly in the working places, and almost invariably at the top of them is placed a small head-piece, for spreading the surface over which resistance takes place. This is called a " lid," and is generally a piece of wood 13 to 18 in. long and j 4 in. (hick, often made by splitting a piece of round timber through
J4
TEXT-BOOK OF COAL-Ml'IXG.
th#f Diildle. In the working place, two or three rows of these IfTffj** Are employed, those of two consecutive rows altemftting with earth other.
Hrriall nngle props, called sprags," are used for sectmDg the coal during the procem of holing (a, Rg. 132). An elaboration of thiK, employed where the coal liable to break away from the face, w the fipecial timbering to which the name of cocker sprags " is ajifdiel, which oonflists of a longitudinal piece (a. Fig. 133) strutted against the face, and kept in position by the small sprag, b, going to the floor, and a second one, c, binding it from the roof. In other instances, a similar result is obtained by driving in a horizontal strut between the nearest row of props and the face
Where the roof is filled with faces which cross and recroes each other, dividing it into a series of blocks, vertical props are not sufficient support, as they only keep up that part over or near the
dT JrT
Figs. 135, 136 and 137.
lid. In such cases, transverse pieces of timber, called ''bars" or ''struts," are employed. If the sides are firm, these bars may be supported on them by cutting a recess (a, Fig. 135) on one side of the rood, and a groove, 6, on the other, then inserting one end of the bar into a, and driving it tightly into the position shown. If one side of the road and the roof require support, often one bar and one prop are employed (Fig. 136). For the purpose of distributing the pressure, and increasing the surface of resistance, the timber is lined with boards, or laggings, placed longitudinally. If the roof only, re(|uire8 support, laggings will he laid across from ont transverse bar to the other ; but if the sides are also bad, laggings will be placed all round the setting.
For main roads and other positions, where the nature of the ground HMjuires it, entire sets of timber ai-e employed, these consisting of two upright props, and one bar on the top of them (Fig. 137), with laggings around. The chief jwintto be observed here is that no hollow slices should be left between the laggings and the roof. If any exist, they roust he filled up; if not, should the break away, it descends on the with a blow lile that of a hammer, and often displaces it from )>o6ition.
Prkliminauv Operations.
'35
Joints. — Tlie several pieces conetituting a set am held togellier liy ditl'ereDt forms of notching," each of which reeiste presuuro coming from a certain direction. Where it is entirely from the roof, the common practice in to simply flatten the bar eligbtly at the point where it resbi ou the tree, and the weight siii tightens the pieces together. With a, view of obtaining a larger bearing on the propii, they are sometimes hollowed out at the top end
JQ AND 14a
(Fig. 13!), the bar resting in the space so formed, ft is, however, very difficult to shape this groove, so that an equHble bearing is obtained, aiid if thi.'f ia not done, the prop siioti . To resiitt aide press* us well as preacui-e from above, the joint shown in Fig, 139 Is largely employed. It is of the greatest importance that this should be nicely made, and that the end of the proji lihould tit evenly against the shaped portion of the bar. The great mistake is to shape the piece as shown Jn Fig. 140. If thin be done the bar soon splita along the dotted line a.
Where the side pressure is great, the power of i-egih-tanoe is
much increased by placing a secoud horisontul piec'e Fig. 141) between the two vertical props.
ChockB," or " Cogs."— For resisting heavy pivssure, either in the working places or alon the main niads, chocks, or cogs, are largely employed. These consist of pieces of timln-r laid horizoutally, tlie alternate layer-a of which cross each other at right angles (Fig. 14a). They may be composed eitheiof broken timber from " — Trkings, or refuse mal*nal, such as old railway sleepers,
, 01' wiecknge.i. If applied in the face, these chocks ai-e
56
TEXT-BOOK OF COAL-MrNWG.
bitilt OD a, email heap of loose material, which allows them to be eiuiily removed. If i-equired to stand for any length of time, the space in the interior is filled in with loose dut, Tlieir size is an exceedingly variable one ; perhaps the largest are employed in South Staffordshire, where they run from 9 to 11 ft. square, and 10 ft. high. They are capable of resisting enormous weights, as the more pressure applied the moi* they resist.
Double Timbering. — On the Continent, a system of double timbering is used to r'esist heavy preesui'e. The weakest part of a bar being its centre, it ia strengthened there by a longitudinal piece {a, Fig. 143) kept in position by two struts, i, i, which rest ou two other horizontal piece of timber, c, a, these latter being finally fixed by two short sprags, d, d, resting on the floor. In such manner not only is the top bar strengthened, but the two Hide props as well.
Bo much of the useful space is taken out by the two angle struts (h, b, Fig. 143), that this style of timbering could not be
Fias. 143 AMD 144.
employed if the road were a wide one containing a double way. The various parts are therefore arranged in a somewhat different mannei Two longitudinal timbers are placed, beneath the bar, m such position that the distance between the is divided into equal spaces. A transverse strut (6, Fig. 144) is put between the two pieces a, a, aud the hitter are kept in position by a series of cross-struts, ic, c, d, as befoi'e, as will bo readily seen from the 6ket<?h.
In fixing this interior fi-ame, all the longitudinal pieces are first placed in positiou, and held there by a wire lashing, until the uprights and cross-struts are firmly wedged in their proper positions.
Driviiig through Loose G round. In driving through watery aud loose ground, special timbering has to be adopted, and put in with o. view of removing as little material as possible. The general name of " spilling " is applied to such operations. First of all, the frames (a and b. Fig. 145) will be fixed in position, and A probably a sole piece, e, will be added, as well as the two uprights and the cap ; then laggings or planks, c, e, are driven forward bddnF h, these being inclined slightly outwards, at an angle of about 1$
the pressure of the sides gi-aduiilly bringing them close up iigainst the Bete. Other laggings are di-ivon forwarfl, inclined as shown at d, and a small quantity of ground excvatd in front of b, until i-oom is obtained for another set, shown in position at /. When this has been inserted, laggings will be driven, inclined outwards as before, for a similar length, and the process repeated until the ground is passed through.
If the material ia very loose, thesa laggings will have to be driven near together, and the joints between them made as close as possible, and occasionally, in some cases, the gi-ound at the ba<:k of the road will have to be supported by planks, strutted against the first set.
The objection to this system is, that in spite of every care, a quantity of material oozes through the joints in very loose ground, leaving large empty spaces behind. To prevent this, the system ou the Continent is to fill the face and the floor with a series of conical wedges, driving these forward, and so making progress. The sides and the roof are supported by laggings and sets, the foritiAidtivn in, iu the same miuuier as in spilling.
Iron and Steel Supports. — So far as props are concerned, no great success has yet been obtAioed, although in some instances tbey are largely used. The first cost of either iron or steel is always so much larger i'o- 146 an o 147-tiuin that of wood, that if metal props urt: employed it is absolutely essential lluit none should be lost. If they are, the economy resulting frum the decreased breakage in more than eounterbalanced.
Cust-iifln props have been tried, but have not met with much favour. They are nouicwbat eoy broken, very heavy, and consequently dear.
Oi-dinary steel girdei-s of the H form, il" used as pi-ops, present a sharp and uneven surface to the roof, or floor, or to timber lid. Hi'th's lUTiingement i-moves this difliculty. A piece is cut out ol' the web at each end (Pig. 146), and a Hat top and bottom fomicil, by turning over the top and bottom lliin}.'i's luttil th*v meet (Fig. 147)- In addition, I itinched in the web about a
into which a hook may be ii
ted fur the
Text-Book Of Coalmining.
The greatest application of steel girders in English mines is to replace tbe timhei' bars used on ordiDarj sets, ivtaining, however, the two vertical wooden pi'opa. It is obvious that, as the lower flaoge of the girder 18 sBinoth, and cannot be notched like a timber bar, if there is any side pressure, means have to be adopted to keep the props in their correct position, wid prevent them from being pushed inwards. Tliis h; done in a very simple mannei'. About 4 to 6 in. from each end nn ordinary chair is fixed on by the blactsmitb, this consisting of a short piece of bar iron about i in. by J in., crossing the FiGB. 148 AND 149. bottom flange, and, tiirned round at
41' each end, gripping the upper side.
The enlarged sketch (Pig. 148) is a transverse section on line a 6, Fig. 149. Any common scrap iron can be ub1 foi-this purpose. The chairs are placed in position before the bai-goes down the pit, and the labour cost for each girder for such addition is d. Tbe author has had considerable experience of the utility of these steel supports. For bars up to 7 ft. long a section measuring 5 in. by 4 in. by in., weighing 66 lbs. per yd., is employed, these costing g.aSs. They replaced oak bars, measuring 6i in. quarter-girth, costing 2.66s. The price of steel was, therefore, 3,49 times that of wood. As an expL'tiniest, lengths of reading were timbered alternately with wood and steel (bars only, timber being used as props), but before any definite I'esults could he observed, the distriirt tired, was dammed ofi' and abandoned. After a lapse of nine months the roads were reopened, and it was then found that the steel bars had scarcely suflered at all, only a few being displaced through their timber supports breaiting. Owing to the fallen I'oof at places where timber bars had been set, over ;ioo in wages was spent in repairs, which would have been unnecessary had steel bat's been employed throughout, and, in addition, the first cost of the timber was entirely lost. On a main haulage I'Oad, iz ft. girders, of a section 6 in. by 4), in. by J in., weighing 78 lbs. to the yd., and costing 20.95s. each, have been employed, replacing timber bars 9 in. quarter girth, costing g. each. The first cost of steel was here 2,33 times that of wood. The date of firing each girder was noted, and numerous instances could be given of then-lasting out from three to four sets of timber before removal. Two especially may be instanced ; they were fixed at a junction, where the pressure was very heavy, and actually stood for 13 weeks Iwfore removal, while the longest time an oiik bar lasted in the same place was a fortnight; many failed in a week, and i quite useless putting in Noi'way timber, as it broke in
two days.
If the steel bars v
) worthless on removal, the actual cost in
Preliminary Opbeations.
the ulmve instances would be less than timber, but all that hits to be done ie to take them out and straighten theta, and thea they are practically new. Their advantngeH are not ko apparent where timber lasts a long while, but with heavy pressures, and in return air-ways, they are far superior. They must be set very carefully, with an level beai-ing, both on props and to roof; if not, they turn over and pisent their weakest side to the pressure. When they take a jieimanent bending set, the best thingto do is to either turn them over, or, if the bending is large, remove and strwghten. With these precautions, the author has never had one break yet.
On the Continent, complete frames of steel are largely used. In some cases they are composed of two views, the top portion bent into the shape of an achr, and connected at the summit by fish-plates and bolts, the lower end resting on an iron shoe fitted to a wooden baulk, timber lags being driven behind the frames against the sides of the excavation. Elliptical shaped sets are Bo employed, but the common form
is composed of two pieces of circular Fios. 150 and 151. shape Q, Instead, however, of making the joints with fish-plates, the frames are oonnected together by a sliding iron collar, which ta secured in its place by driving between it and the frame two pieces oE wood like rail keys. Figs. 150 and 151 show the application of such a joint at Firminy, where old pit rails are used.
At Lens timber lags have been done away with, and small strips of channel steel, about 2 in. by f in., u.sed in tlieiiplace
. Another advantage of steel is that it doeh not occupy so much space either as timber or masonry, and either a greater effective area of roadway for the ftame amount of excavation is secured, or the cost of driving the road is reduced, because lesi excavation is required tn pet the seine effective
For jiermanent sitna-
I ii where girders are
, 1 "' uiill'*, considerable economy
' V ' 1 e-uits. The worst feature
-'''' almut an arch is the 'iaiga
amount of space which is lost through the semicirculur form at
the top. Taking an ordinary roadway (Fig, ottupied by
TEXT-BOOK OF COAIMDriNG.
work will 1
two tubs, au aith has to be bo made that the curve of its upper portion allowN the tubs to pass through without catching, and aa a result, a high apace exists in the centre, which not only coats a lot of money to escalate, but serves no useful purpose. If a girder, a b, he placed on tho top of the walls, the excavation of the area, a li c, which contains 4.38 cub. yds., becomes uuuecessar}', and, in addition, the cost of the brick- " ' saved. In the illustration under notice this will ,08 cub. yds. per lineal yd., which will cost for labour, material, and mortal* quite 29.32. Agiunat this has to be put the price of the girder, amounting to zo.ijgs. One of these will be required for each lineal yard. The girder and side walls, therefore, effect a saving in first cost of 8.37a. per yd. run in mateiiul, to which haa to be added the reduced cost of the excavation, in this case at least 14.98s.
Side walls and girders are not so capable of resiiiting side pi-eaeure nn an arch, but this difficulty can be overcome by turning small brickwork arches in between each girder (Fig. 153) in the same way as is done with iireproof floors of buildings. There is a certain amount of spring iu steel girders, and, when weight comes on to these small arches, there is a i-isk that the girdei's will bulge in the middle, and allow the arch to flatten. To prevent this happening,
tie-iwis (a, Fig. 153) are placed across from girder tu girder.
Masonry. — For all permanent situations, securing the sides with masonry still finds gi-eatest favour. It is, perhaps, more expensive to put in for reasons already statedvia., the greater excavation i-equired, both for the masoiiiy itself, and to obtain the same effective area, but when requii-ed to stand for many years it aiiinotbe surpassed. It is, however, necessary to make the lining continuous all round the road. The pmctice of building arches without an invert is not to be recommended ; if au arch is worth putting in at all, it should be put in well, and, iu addition, some soft packing material, such as sand, must be introduced between the lining and the strata. No vacant places should be left behind the brickwork, and all timbei' used for the temporary support of the excavation, while the work is being put in, should be removed. The introduction of a soft material between the brickwork and the strata not only distributes the pressure over a considerable area of brickwork and prevents local weight, but, as it gi-adually gets compressed, acts as a resisting medium itself. This packing should not be too much noi' again too little; ticm 6 to ij in. gives the best results. To show how irapoi-tant it is, the result of ail experiment, made by the author in 1888, may be cited. Two successive lengths of 7 ft. ni-ch were built, one iS in. thick, packed with a foot of .-iand, and the other, not less than 18 in,.
n
Prelimtkarv Operations. 141
bwt maiie sold. The latter wna cruBhed to pieces and had to be taken out in a year : the former is still id ajid does not show a cruck.
The sliapeK of ai-ches are many. The circular form ia the strongest, liut requires so much excavation that it is seldom employed. An ellipse is perhaps the nest strongest, but this again requires a large space. The form generally adopted ia a combination of the two. The side walla and top usually form pai-t of one curve, struck with a radius equal to half the width of the road, while the invert, or bottom, is a of another circle having a larger radius. This ties the whole structure together, and prevents either the bottom lifting up or the sides heaving in. Two forms adopted by the author for n single double way are
KiGS. 154 ASD 153,
shown in Figs. 154 and 155. They do not contain imy straight lines. In the 1 2 ft. arch, all the portion above the invert is part of A circle to radius 6 ft., while the 7 ft. arch contains portions of four circles — i.e., the two side wills and invert to radius 7 ft., and the semi-circular upjier part to radius 3 ft. 6 in.
These arches are put in in lengths, which vary with the iiatui'e of ground ; 6 to 9 ft., with a bad roof, up to 5 to ; yds., with a
The firet procedure in putting in arches is to remove the gi-oimd ; to do so, two methods are in vogue. In one — the general English custom — a small road is driven right at the top of the arch, and the ground excavated on each side and downward;;, while in the other, the first road is driven at the base of the aivh and the ground removed upwai'ds.
In timbering the ground, the peculiar point is that all the miLin pieces are set parallel with the axis of the road, and not tmutvwsdy, the reason forsnch departure from the usual practice being, that as the masonry is brought upwards all the timlter has to
I4Z
Text-Book Of Coal-Mining.
I'emoved, and this could not be done, especi&lly in the upper portion, where the two walls are approaching each other, unless it lay in the same line as the brickwork. Another point is, that if ti'ees have to be set, as they frequently have, in the middle of the excavation, the sfnaUer end should be placed downwai'ds, the reason of thLs being that when the masonry in the invert in built round them, other prop are set on the brickwork to the point they are holding up, and then those going through tbe masonry are drawn ont, and if the larger end were downwards it would be
FiGE. 156, :;7, 15S and J59.
impossible to do so. The method of timbering will be understood by examining Figs. 156-9, which illustrate the position of afiaira at two stages of the operations. Supposing in Figs, 156 and 157 tbe top head has been dnven, and an amount of ground, shown by the dotted hnes, has to be excavated, the tirb-t procedure is to set two long bars, a a, one end of which rests on tbe arch already put in, g, and the other on a timber set, /, placed in the head. These two will probably be connected by a strut, h. The ground wiU then be excavated, first on the sides, and other longitudinal bars, e c, put in, connected to the other two by struts, d d, and behind these, lags will be placed if the ground requires it. At this stage Figs. 156 and 157 represent the position of affairs, the two longi-
J
Prelimisaky Operations.
"43
tudiual pieces, c c, beings supported by small temporary props, e e, set uu the floor.
As the excavation proceeds downwards, the props e e are removed, as soon OS splice is obtained for other longitudinal pieces. This process will he repeated until a complete lining, consisting of lougiludinal bars and crosstruts between them, exists oil round the excavation. In heavy ground the lonjitudiual pieces are often connected by transi-erse bars (a a. Fig. 158) and in addition vertical props, b h, are et between, until at the completion the work presents the appearance shown in Figs. ijS and 159.
The masonry is now commenced. First of all a lining of sand is spread in the bottom, and shaped to the curve of brickwork, of course at the pixiper gradient, A wooilen frame or " template," made of the exact sha[>e of the finished inside dimensions of the invert and side wills, is fixed at Mich a height above this sand as will allow the thickness of the brickwork which is gung
Figs. 160 akd 161.
to be used to be placed between it and the sand. The first ring of maaonpy is generally laid dry. Operations commence at the centre line, placing the longer length of tfa(> brick parallel with it, and adding successive rows on each side until a point (6, Fig. (60) is reached. This distance is such that the ends of each ring when joined form a sti'aight line, pointing towards the centre of the circle, of which the ijivert is part (6 a. Fig. 160). The succeeding rings are put on by spreading a good bed of mortar over the one first laid, dropping the bricks down a few inches away from the position they will eventually occupy, jind then slipping them along until they get into their proper places, liy doing this, not only is the excess of mortar in the bottom putted away, but a quautityis gathered up into theend and side joints, and, in addition, clone contact between the mortar and brick is made. This procedure is repeated with each layer until all the invert is put in.
The building of the side wall now commences. The point a li (Fig. 6i) is the weakest in the aieh, so, as a compensation, the brick-
Textbook Of Coal-Mining.
work 16 increased in strength there (see also Figs. 154 and i55)< With the e:inception of the smalt portion of masonry cross-shaded on the left-hand side of Fig. 1 6 1 , all the brickwork in arches is laid iu stretcher courses, but for this small piece English bond is used, and the bricks in each course are alternately at right angles to those of the invert, and, as they are laid horizontally, have be cut into the shape shown enlarged at A. When the point a c (Fig. 161) is reached, the bricks are laid longitudinally agfun, but to obtain the proper curve, citZiiwt or arch bricks are employed for the iirst courae. Each ring is kept perfectly sepai-ate from the others, that is to say, they are not bonded together.
When the side walls have reached their proper height, the centres will be set, laggings put on, one by one, and the brickwork gradually brought round until the two sides nearly meet. To close up the top properly, the mason should be oiitxide the ari'h, but OH this is impossible in mines, the difficulty is got over illustrated in Figf. i6z and 163. When the space between the two sides diminishes to about 3 ft., or such width as a man can conveniently work in, two grooved laggings, a a, are put on. Up to this time, the masons have laid the courses parallel with the direction of the arch, they now put the remainder in tmnaveraely, but stil! keep the longer asis of the bricks in the same direction. Oonimencing near the length already in, the man lays a strip of iron (b, ¥ig. i6z and No. i. Fig. 163) in the groove of the laggings. He then makes up the small portion, supporting it on No. i iron, retires backwards, puts on another iron No. 2, and keys in the part between No, 1 and No, z, goes back again, puts on No. 3, and repeats the process, until the length under consideration in secured.
Instead of using timlter centres, which block up the upper portion of the rood, the author has invariably employed iron ones, which possess the great advantage not only of being light and eiiaily fixed, but also of leaving the centre of the road free. In some instances, they have been made from old inilway rails, dropped into a wrought-ironehoe, or inothei'sof angle iron, at the base of which a return plate about 6 in. stj. is placed (e, Fig. 162) and secured to the angle iron by a small gusset stay, d. The laggings employed are usually about 3 in. thick, and it must he remembered that twice the thickness of these bos to be deducted from the diameter
Preliminahy Operations.
of the (ircli to liiiJ the size of renters veqiiii'ed, therefore, with a 12 ft. , the centre ahould measure 11 ft. 6 in. With iron uenti'CH tlie author has put in over 100 yds. of t a ft. arching in the main road of a colUeiy, and ne\'er stopped drawing throu'h it a single day.
Arrangement of Icset. — In the great majority of awes, the empty tubK, after Ueing removed from the cage, have to be brought back by the wide of the pit
sh&f t, and for sucli ri
lianging-on phice is made
wider than the diameter
the abaft, iodeeil, it is usual
to proviile a passage on both
sides. The shaft brickwork
and the arching are best
rnnectd by " belong " out
the former, at* shown in Fig.
strongest construction, and,
in addition, room is provided
for bearers, to which either'
guide pulleys for haulage
ropes or main supports for
water or steam pipes can be
attached. A sump frame, a f>,
will be provided to receive
and keep the cage steady j
while changing is going on,
and if two or more decks are
used, another frame of croaabearer
, e d, will oe put in.
On the latter the cage rests
during changing, and as it
drops there with considerable
force, Mr. Emerson Bainbridge has employed spill springs at
Nunnery CoUiery, Sheffield, which are simply let into the bearers
aX springs txi each cage, each 9 in. long by Fin. 165
5J in. dinm., mile with coils of in.
stel. All jar and shock is avoided.
The arrangement of the tramways at the pit bottom should always be such that from the point where the full tubs are
remo%'ed from the haulage ropeB, to that where the empty ones are again attached, the motion should be due to gravity alone. To a certain eiitent, where engine power is available, it is, 00m- pnmtively speaking, an easy task to haul the tubs to such a height aliove the hanging-on place that a regular fall is obtained towards
TEXT HOOK OP COAL-MINma.
the shaft for the full tul, ttud a fall iii an opposite direction for the empty one. The landings are technically called " kip," and it is advisable tltat tbey should be as long as possible, so as to get standing room for a largt quiintity of tubs ; winding may then go on, up to a certjiin limit, e'en while the haulage machinery is standing.
The question of caging the several decks simultaneously is ti-eated of iu Chup. IX., and all that will bo doue here is to describe the operation of getting the tubs (waggons) to the appanituB used for this purpose. The beet plan is to arrange the shaft at one extremity of the main haulage road, and haul the tubs by mechanical means to the point a (Figs. 166 and 167) ; the full road is then laid at a slight inclination (about in. to the yd.) towai-ds the shaft, the tube gravitate there, and are placed on the cage by an onsetter. The empty ones gravitate away from the shaft down the slope, b c, having a grade of in. to the yd. to give the required speed, along a ight Bat, c (/, and then up the incline, d e. The tubs will not
proceed far up d e, but do so for some distance, owing to the momentum they have gained coming down b e, and travel just far enough to clear the points at d. As the slope is against the tubs, their direction of motion is changed, and on their return down e d, they are switched ofi* into a road to the left, having a down-hill grade, pass by the side of the shaft to the point g, where they are again attached to the haulage rope, and proceed into the workings. From the time the tubs leave the rope at a to the time they are again attached at g, no labour is necessary, the movement being quite automatic.
Mr. M. H. Douglas* has described, in an excellent paper, sevei-al systems of laying out shaft kips, all of which are worthy of study. One, however, needs special mention, where, owing to the inclination of the caging takes place at two decks simultaneously, without the use of any balance arrangement (Fig. 168). There are two shafts, about 40 ft. apart, each sunk to the same seam, and two engine planes, each hated up with a double line of i-ails. The coals hauled out of the No. 1 engine plane ai-e drawn above the switches, 9, and lowered down into the road, x x, as required, and ai-e hung on exclusively at the high level, the road Brit. Soc. Min. Stud. i. 443.
Preliminary Operations. 147
x being used for So. i, and x' for No. 3 pit. In aiiiinging the roads for the removal of the empties, advantage wnB bike of the natural dip of the fieam, the i-oad 1/ being used excluHvely for
No. I, and.v' for No. 3 pit. The same method ia pursued \vitli the coal hauled out of the No. 2 engine plane, with the exception that these tubs are used entirely at the low levels, the gradient
being formed by driving sUine drift for tbo
The high atid low levels difi'er in height exaotlvS explains itself, if it is remembered that engine plane feed the top decks uf boti'
148 Text-Book Of Coal Mixinci.
No. 3 engine plane fed the bottom decks. Tbe only objection i to such a system is, that equal quantities of mikteria] must drawn by each engine plane.
The inset lit No. 5 pit, Bascoup, Belgium, allbrd.s a fine example of the automatic and continuous niovementn of the tubs in one direL-tioti. The landing is laid with a double line of tuk, and planes through the centre of the shaft, painllel with tbe longer axii of tbe cage (Figs. i69and 170). From eiicb end of it branch ofT twn Hide roads, each laid with a single line of rails; one set proceeds towards the north, and the other towards the soutli. The two roads to the north, and the two roads to the south, rise from the shaft, and each pair unite at ;i point about too yds. above tbe level of the pit Ixittom, where the motive pulleys of the haulage are fixed. Roads branch ofl' level to tbe east, and further junctions ai-e arranged, as shown in plan (Fig. 1 70), each biiving eegiamte wheels on vertical shafts. Two endless chains exist in the roads driven to the lise, one on each, and these pass round the motive pulleys. The full tubs descend towards the shaft in one I'oiid, and the empty tube return from it in the other. The same chain passes upon pulleys on the upright shaft, a a', and also round the I'eturn pulleys, b b', c c', situated at the two osti-emitiea of the itiet, and pisses through the sliafUi without interfering with the igea, or even with the movement of the tubs in the hanging-on place, ns tbe tubs gravitate from i to c, The application is remarkably simple and efficient, a noteworthy point being that the direction of motion of the tubs is never changed, except nt the working ftic. The plan explains this; the pit bottom occupies tbe lowest point, the dotted lines represent the chains, and the aiTowa the direction of motion.
Bibliography. — The following is a list of the more important memoirs, dealing with the subject matter of this chapter: —
UtN. IMST. SCOT. : Beport of DepoUHlon fhi the Slelluxl of Seeuring Jioof aid Sidet, iii. 51 ; Propping at UlraHoa nwl Robt. Hartln. xil s8-
V. B. I. : The MM of Iron SupitorU in the main Toadu of minr instead q/"
Matonry or Titnbtrinff, G. Meyer and W. J. Bird, xnvii. 135 ; "-
llie Iiitroilttetion of Stetl Svpporig for the maiTatnanee ofi
Iht miiia of , A. L. 8toaven9on, xxxvii. zzi . BKIT, 80C. Ml. STUD.: "Km" or Ltrndingi at Hhoftf, M. M. Douglas,
i. 443 ; Timberiiiff in Minrt, H. St. J. Durnford, iii. 207, and W. B.
Gresley, iii. 229 ; Praervalion of Timber, ii. 76. 800. IKD. MtN. : Applicalioa defer on louttnement da piiteria li laliaHiOirt
du Crtiaol, M. de BianiaC (i* SBrie), iii, 563 : Souvomx it/tltmai da H. Dabaron (z* Srie), ix.S73 ; BUndage tUt gerit* rn de RoehebeUt, M. Oerrard {2' Svrie), xv. 391 ; Sff
dirnnapptparationi mr la dare da (Comptcs Rendns Hensoels),
1890, p. M3. CHBB. i8T. : Mine Timbcriag, J. C!ark Jefferson, vii. 170; A'Aaft
Timhrring, J. Clark Jefferson, vliL 209. HID. TS8T-: Thr ,..e of JloUrd tSlctl Oirdemfor 'I.' Hoof!,. J/in
n
Chapter Vii. Methods Of Working.
The Two Main Systems. Broadly speaking, there ai-e two Bystius of milling coal, called " bord and pillai-," and "longwall." Outside tbe Noiili of England and Scotland the formei' is but little practised in this country, while the latter, which originally took its riae in the Midlands, is of very extended application. Endless modifications of each system ai-e employed, and the two gradually merge into each other, until it becotnes impassible to say to which system some methods belong. The tendency of the present day is to employ longwall more and more, and this method is slowly but surely supersedinj: every other one. There are, however, some seams which it would bo imposible to work longwali, that is to say, at any reasonable cost.
Shaft Pillar and Subsidence. — It is necessary that a certain area of coiil around tbe shafts should not be worked, but should remain to alVord support, and to pi-eveul any risk of wliat is known as " creeji." It is impossible to give any general rule by which the .size of shaft pillars for given depths may be detemiineil. Everything depends on the nature of the beds overlying the seam, the inclination of the strata, the nature of the Hoor and roof, and tbe question of stowing the excavation.
It is liard to prevent creep in seams having n .-soft door, especiuUy if water is present. The pressui'e on the pillars of ooal forces uji the soft underclay in the roads between the pillars. When once this action cti to keep the i-oads ogieii ; Perhaps the only iint!. efficient and close [uiikL Mr. J. A. Longilen'' , oolliery, 520 yds. deep, by 800 yds. \u-/. tliL> rjiii eei-iously th.n -i-,-..t If-j.i be lost. Tbe pii W.llon. finally with l.iv.'v. >.r k
mences it is most ditliciilt to stop, c
vciTlliiiif; .seems to be on the move.
. iiiiLi in KiiigwftU work is
,'illais is not suHicient, as
pillar was 360 yds. grind
li.'iiijr lliii, .iiui vi't creep came on so
wi'iw cutiKtiiiii'ii ill. It the shaft would
' times,
'5°
Text-Book Of Coal-Mintng.
The working of beds of coal alvays lowers the overlying strata, giving rise to what is known ae " subsidence.'' A certain height is taken out, and, although the eseavation may be filled with material, such packing, even at the best, is loire compared with the solid coal originally existing. The gob is compressed, and the overlying strata and the surface sink down. If the area of subsidence was limited to the strata immediately above the area worked, the problem of determining its direction, if not its amount, would be easy, but even in level measures the dintittbance extends beyond the limit of the excavation.
With inclined seams the fi-acture of the beds uerer takes place in a vertical dii-ection, but always in a plane approaching the perpendicular to the inclination of the strata. M. Callon* advocated the theory known as the " Normal," that subeidenco takes place at right angles to the planes of stratification, and estenils, without sensible diminution in amount, right up to the surface, whatever may be the depth of the beds. M, Dumont,t after an exhaustive examination of the district around Liege, expressed a similar opinion, but the Colliery Owners' Assoeiationt afterwai-ds drew up a reply, advocating that " the law of the Noi-mal " does not hold good where the strata ai-e highly inclined. The whole subject was reviewed by M. Fayol,§ who, in addition conducted numerous espeiiments. He points out that the theory-of the Normal is based on the eiToneous supposition that lieds break at light aogles to the plajies nf stratilicatioii, at the perimeter of the excavation ; biit, from actual experiment, he found that the plane of fracture is a more or le.ss inclined one. After describing numerous experiments made oneluborate models, and instances of the result of mining operations, M. Fayol|' states that in stratified deposits the zone of subsidence is generally limited by a sort of dome, which has for its base the area of the
If the beds are horizontal, the dome is arranged symmetrically round its axis, which ia vertical. Each of the beds included in the dome links in the foi'm of a basin ; the extent of the movement diminishes in proportion as it is further from the centre of excavation. If the beds are inclined, the dome is no longer Ej-mmetrical, and its axis is inclined.
t affaitaiKnU du sotproduiU par Cfxploiiaiiim lioiiiUire, Lii, 1S71.
t affaitenicnU ilu toi altrilnii/t rexjJoiliilinii lumiUcre, Lipge, 1875.
S Koie mir la monvenienli de terrain jn-uivpifs pur r r-jjiloitalioji lit* riihu, 800. lad. Hid., 2' Si;rie, xiv. 805.
II This paper is the most important one whicli bas been published on the effect of coal-worfcing on the anrface, and throws oonsiderable light on what ia perhaps the most iatricatc problem in mining, sad about which few facta are knowa. A carefal extract from it, aod also of U. Dumont'B J moojoir, by Mr. H. K. Bubnao, ia given in Jour. Brit. Soc. Min. Stud., I
Methods Of Working. 151
In proportion as the Beams become more ineliued, the axin of the dome is inclined also, and tends towards the hoiizontal ; at the same time the height of the zone of sulwidenue towards zero. The axis of the zone of subsidence la quite iudepondent iif the vertical, and of the normal to the .. Vertical, notnial, axis of figure of dome, and line of masimuni Hubsideuce, all coincide when the beds are horizontal ; they are distinct wbeu the beds axe inclined.
When the zoue of Bubeidence croHseu several gi-outx oF lieds at varying inclinations, the axis of the dome ia deflected in passing fi-om one group to another, and approaches to the noi-mtU of the group in which it is. Thus, for example, in beds disiJoseU in the shape of a fan, commencing with the hoi'izontal, the axis of the lone of liiibeidence, stftrting from the vei'ticol, aiTives by desires lit the horizontal. The direction of the axis of the Bone of subsidence must not bo confaseil with thiit of the limits of this sone {i.e., the ciroumEcribing lines of the dome). Sometimes the axis approaches in a. remnrkable mtinner the perpendicular to the strata, and it is this perhaps which gnve rise to the theory of the
From the above considerations it followK that, when the seams ai-e iuclineil, shaft pillars require to be much larger on the rise side than on the deep, The occur'rence of faults must be carefully noted, ad, where they cross the area aU'ectel the lines of fracture aitj dellectt!d am) proceed along them; sometimes they extend, and at others dimiaiah, the area of surface affected.
Whei* the regular beds are covered with a layer of soft, loose, sandy material, the area of subsidence may be unlimited, es]>ecially if the deposit contains water.
Mr. Longden* recommends for level seams the leaving of one yard in bi'earth for each yard in depth, that is, a. shiift 100 yds. deep, should have a. pillar 100 yds. radius or zoo yds, diameter. ThiM seems a large amount, but the en-or, if any, is on the safe
Arrangement of Labour. — Before describing the methods of mining, some reference should be made to the two Kystffls under which the labour is earned out. In one, the miner not only gets the coal, bill, carries out odd work, such as packing, repairs to roadwayH, &c., while in the other, a skilled class of colliers ore employed simply as hen'ers at the face, all dead work being performed by sepai'ate staffs of men. In the latter system, the labour is subdivided, each class of men carrying out special duties.
If the hewus are employed solely at the face, a larger tonnage in hence leae extent of workings ia required, xyjjjjjJlBgwdlMrtipiCHpltt'Mgt of maintaining smaller
Text-Book Of Coal-Mining.
time to breuk up the conl, the i-oof ia always " green " (or fi'eeli), and there is couBeijuently less liability to accident.* Except under special circumatannes, coaI ia invorialily mined cheapest where the face travels fastest ; the exception is, a ieam having a very strong roof and floor, aa here it is possible to move too faat.
The ilivigion of labour iloes not actually produce more coal witli fewer men, for other colliers have to be employed to perfoi-m the work the hewers originally did. The old out-jmt is, however, produced from a smaller extent of workings ; and, on an avenge, about one-balf of colliery cost accounts are capable of reduction in proportion as the output is increased, and the area from which it is produced is reduced. So far as maintaining roads in concerned, the chief point is to see that the gob is carefully [>acked, and that all props are removed, so that the roof can settle, and not break down.
The alive observations do not apply so strongly except in such places where, from the nature of the roof, and the seam itself, the amount of repairs is large, and keeps the miner away from the actual coal-getting for a considerable part of his time. Timber dmwing is, certainly, best performed by a separate staff of men, who should, preferably, be set the work by contract.
Bord &Dd Pillar Worklng.t— After driving out the main I'oads the tirst operation is to divide the coal into a cerieB of rectangular blocks (Fig. 171), by means of drivages, calletl " boi-ds " and " waJls," the line of the latter being genemlly sjioken of as headways course." The bords are driven from 4 to 5 yds. wide, and always in a direction at right angles to the cleat of the coal, or, as it is geneiully termed, " on the face." Headways course is at right angles to these, or, in other words, parallel with the cleat, and as this runs approximately north and south in the North at England coiil-field, headway. oourse is generally taken to 11 north and south, and Iwrdwnys east and west. As a rule, walls are driven about 2 yd.*, wide, but sometimes both boi-ds iind walls HI'S driven 5 yds. wide, and the roof allowed to fall.
The first procedure is to drive out the main ronda. At large collieries there are usually four proceeding at once, two intakes and two i-etums. Before these roads have gone far, bords and walls can be commenced on either side of them, leaving, bov uDident coal on both sides to prevent any risk of ci'eep. At one time, the Pinal's which were cut off by the bords and walls wei made only just large enough to keep the roof up, and were left. This has quite abandoned, and the pillars arc now made very large, quite a common size two, and often thi-ee, chains square. In addition, as soon as these pillars have been formed, their removal is commenceil, while the driving of bords still pro-
[MiBt and stall." and in Scotland i
(peJs oaly n short distHni* awin-. In this manneithe poi-centago of large cwil hns Wii i,„,t,Ti:.My a„.i tiniiillars lire
wM HIHHi
Czuj
TEXT-HOOK OF COALJUINIXfi.
Another practice, which wof introduced by the celelimted viewer Buddie, about the befiicmiig of the century, is the method of dividing the colliery up into what ai* Iedowd as " panels," or "districta" (Fig. 171), thew coiieixting of tin area of from 30 to 40 acres, aun'ounded on all sides by a rib of coal, called a " barrier," these hcirrien; being holed through at jiDints where ronils are necessary. Tliia system of panels is piirticidarly advantageous with a tender roof snd soft floor ; only a small area of the seam is opened iit once, the roof does not weight so badly, nor require so much tinilter, nnd more round coal is produced. In addition, the risk of creep is, to a certain extent, prevented, or it may be conlined to the panel in which it arises. The rLsk of explosion is ileci'earned, as each district has itti own current of air, and should anything happen m one, there is little prolmbility of it extending to the others.
The preliminary' work nf driving the bords iind walls is called " working in the whole," the removal of the Pinal's, which follows
afterwards, "working in the broken," In the latter a proper line of operations, usually a diagonal one, should bo adhered to, aa if portions of a pillar lag behind, or become surrounded by broken workings, the coal is very much crushed, luid quantities are very often lost.
The removal of the jiillais is carried out by a series of drivages, technically called " Jenkins " and " skirtings " ; the former is a place driven in a pillar in 0, bordways direction, while the latter is a similar place driven headways way, although, ac n ride, any place driven alongside the fallen roof is called a skirting. At Eppletoa Colliery the pillars, which are 44 yds. by 33 yds., are worked by driving a fast skiiling out of the waggon-waj% the length of four pillars, as shown in Fig. 172, leaving 6 ft. of coal agiiinst the fallen roof ui the headways. A jenkin is then carried up the pillar alongside the old bords, and then lifts or " juds " an? driven right acroHs, these being 5 yds. wide. As soon as one of these reaches the fallen roof on the wet siikof the pillar, a iecond is com-
Methods Of Working.
'Ss
menceil out of the jenkiii. pillars nre attacked at the same time, the life in each Ijing back m step fashion, as shown The roof is kept up in the JmU by a bene-of iho(.ks or foi-med of timber ij in. long bv 4 in square, peed 4! ft ajtart, and, raiy, 6 ft. from the coal side The space between the loose side ami the chocks is secni-ed oi-dinary props anil laggings, these, except three rows at the fate being drawn every night and the roof allowed to fall behind
At the same colliery, with large pillars b6 yds square, the proces-s of i-emovnl is can-ied out bv dnmip u jenkin up the
Fic
middle, .siilittiiig the pillar into tnu Jmlviand then taking 5 yd life right and left. This is the system I'recommended by Mr U C Greenwell. If the pillarM have in the fiitit inatanct been made large enough, he saya the whole of the wings on each ide may bo brought back simultaneouBly, chocks being iised in double i-ows for the rtiipport of the roof, the back row, or that neit to the gob, being shifted between the front row and the coal aa the face ttdvauces.* The system of working, and the method of i-moving the pillars, have been described by Messrs. R. A. S. Hedmayue and H. F. Bulniau in two excellent papers, t'j which the sttideiit in I'ef erred for further particulars.t
nine Eniilurfring, p. 200.
t Brit. Soc. Hln. Stud, ix, 101 and 174.
S6
Text-Book Of Coal-Mining.
The objectioDM to tliu bonl and pillar systeni are the difficulty (if ventilating the workiiigH, the amount of coal which lost (a thin piece lias always to left on the sides of the bords and walls wliicli ai'e fallen), the smaller percentage* of round coal produced, and the large charge for narrow work ; not only ai'e the bords and winning headways in the whole paid for, but the skirtings and Jenkins in the broken are also subjected to a yardage rate.
Iiancaahire Method. — In the Lancashire coalfield, with steeji Reams dipping i in 3 to 6, a system is employed resembling both bord and piUar and longwall. A pair of roads are generally driven from the shaft direct to the deep, and out of these, levels, 30 yds. , are driven to the boundary (Fig. 1 73), Each pair of levels are somewhere about 200 yds. apart, and the coal is left Bolid between. On reaching the boundary, two nets of levels are connected by a road, and the coal between is diviiied up into pillai-s by a, neries of driviiges ci'oSBing each other at right angles. All the pillars are not cut off before commencing to rem<)ve the coal, but lire gi-adualiy formed, leatUng the face as ahown by the illustration.
The pillars ai-e removed by lifts taken uphill. These lifts vary 12 to I g yds. wide, and 174. 8i taken forward like a loDg-
wall face. A Hue of rails is can-ied by the side of the Rolid coal, and a pack-wall built on the otlier aide (Fig. 174). Two raws of chocks, about 2 yds. apart, are always kept ptirallel with the face, nod ut the same time a third row, ft ft. furtheilck, is living withdrawn, trees or prnpa being set all round them while such is being
doc
in
instances the cut ofi* much jved by
pillars
larger, and s lifts ui> liefore. but here several proceed at the eame time, one leading the other, the face having a, stepped appearance similar to Fig. 179.
IiOngwall Method. — In this system the coal is extracted in a long face, which is gradually moved forwards. The space behind the working is filled in with packing, and what ai'e called "stall i-oads " are luade into the face at intervals. These stall i-oadg are cut off at regular distances by levels, generally branching obliquely out of the main i-oads ; by such means the length of gob reading to maintain in i-eiiaii' is kept within reasonable limits,
Methods Of Working. 157
anil, ill iiddition, the distance which the coal Iiah to hauled iw reduced. Tliis is the ideal longK'all, und its carrTiDg out in practice is well represented hy Fiic. 175, which is a reduction of a portion of the working plan of h colliery. Tlie workiiif; roada
are ho d f JI 1 ues nl le those n 1 abandoned 1 are 'epresented by dotted
The roof at the rear of the workmen, where the Cj down, is generally kept up hy a donble rowflfjl row alternating with those in the other "" goaf pack. When the sprags ore t shot down or falU on iLs own account, a line of rails being laid along the ft
iS8 TEXT-BOOK OF COAL-MINIXG.
np utd tAid with esch advance. The detaik between two itJiII roads ai ehown in Fig. 1 7C1.
Perbape a more vivid impresioD is giren by the two pbotcraphs (trontispiece) taken in the mine by Mr. A, Sopwith, who has kindly allowed their reprodDction here. The upper one shows the miner holing the fuce, with a cocker prag on his right hand. The other is a view up the face, which is holed and ready to be got down, the miner in the foreground being engaged in drilling 11 shot-hole. The line of rails and cogging are clearly shown.
The weight naturally cornea on along the line of face, and when this is continuous, as in Fig. 175, it is sometimes very ejtpenave to maintain. In such cases, the tells are often arranged to lead each other a short distance (fig. 1 79). If the mine is level, the stall ronds wUl be brought into the middle of each wall, but with inclined am?, they will be carried nearer the deep side, as thi facilitatesthe removal of the cool. When the stalls are so aiT&neil the weights localised, and prevented fi'om spreading all along the face. Several disadvantages are, however, introduced : superviuon is rendered difficult, undercutting is not so convenient, one catting side is introduced, and machines cannot be employed. In addition, the pressure on the sharp corners is great and breaks Dp the coal there, producing a large quantity of smaU,
Ab h rule, the seam itself does not suppl)' sufficient matei'ial to fill up the whole width across the face, and in such cage,the pocks are built leaving what are called '' tastes " between. In seams liable to gob tii-es, the packs are best set dm ughtboard style — i.e., first a wnite and then a pack, each waste being sucees.-ively cloeel by having a pack built in front of it. wastes then being formed opposite the back row of packs. In this way, although the gob is not stowed solid, yet a continuous stopping of pack material built across the face.
The stowing material is obtained, not only from the stall roads, but also from the main roads. As the gob gets oompreseed, the roof sinks down, and the roads become too low to allow the passage of men and horses. Recourse has to be made to wliat is known as " which consists in shooting down the roof stone until sufficient height is obtained. Fart of this is always built on each side of the roads, while the remainder is carried into the face, and used there.
The direction of the face is determined by several conditions. In some districts, divisional planes or "cleat," exist in the coal; they usually cross each other at right angles, but one set is always much better developed than the other. If the face is parallel to the cleat, the coal is said to be " on the end," if it is perpendicular to the cleat it is called " on the face," while if another direction is followed, and the face advances obliquely at an angle of 45*, it is awd to be " half on."
Tlie main object of working coal is to produce the grestflst 1
Methods Of Working.
'59
quantity of largo cual m the best condition, and this ijiuiatity Jind condition are materially influenced by the dii'ection of the face respecting the clear. In a longwall face, owing to the compression of the gob, there is always a considerable amuiint of weight on the coal at the face ; such pressure, indeed, in many instances, gets down the coal without the aid of explosives.
If the coal is worked " on the end," the lines of fnicture piiduced by the above-mentioned force coincide with the lines of cleat, and consequently coal readily breaks. If the coal is a good strong hard variety, the labour of getting it is reduced, and the quantity of large coal is satisfactory ; but if, on the other hand, it ifi Hoft, a large amount of small coal is produced. lu such cases, it is far better that the coal should be got perpendicular to the cleat, or "on the face."
The direction of the face is, however, influenced by another point, namely, that of the inclination of the seam, which, in many caseit, determines the dii'ection irrespective of other considerations. In longwall workings, where the inclination is modemte, the direction of the face is generally at right angles to the dip, as all the weight is then thrown back on to the gob, the packs are easily and readily made, and the cool descends from the working places by the influence of gravity. Where the inclination is ateep, the face will be carried half on, that is to say, at an angle of 45 " with the inclination.
The length of the stalk, or the distance between two voaAs, is governed by a variety of circumstances :
( 1 ) If the coal is to produce its best yield and be worked economically, it is advisable that the face should move forward regularly every day, but if such is to be done, the distance between two stall roads: must not be too long. In the Midlands, from 30 to 50 yds. has, by general consent, been found to give the beat results.
(i) On the other hand, the distance lietween the stall roads must not too short. The more these roads are multiplied the higher is the expense of maintenance, because a greater length has to be kept open, and a further charge for the larger ijuantity of ripping required is also incurred.
(3) The ooal has to be got out of the face into the roads, and unless the height in the stalls Is such as will allow tubs to he bi'ougfat in and loiuled there, it is advisable that the stall roads should be as near together as possible.
(4) The stall roads must not be too far apart, as it is only ptwsible to have two tuLs in the stall at the same lime — i.e., one from each wi'V r. ... .mt-put it is, therefore, necessai'y to either muliij' p their length.
(5) The In L-. ilIso influenced in a very marked manner by 1' i i.LilrieM, as to whether the men work singly ' 'I four or Jive men take a stnU.and om . wli.-i-e about as before
i6o TEXT-BOOK OF COAL-MINING.
stated. In the North of liDglAiid every inat is for himself, which necessitates the I'onds being close together, with a multiplicity of working faces : iiuleed, a coniiiion arrangeuient is that shown in Fig. 177, which can soai-eely be called true longwall at all.* Headways are turned out of the main roads at inteniils of 30 yd.s., and after they hnvi' driren t o yds., lifts 8 yds. wide are tivken right and left, and carried 1 5 yds. up, or half the distauce between the headways. A line of mill in laid next the coal side, and a row of chocks on the other side. After the first lifts ai-e driven up a few yards, the winning ]tlnees are widened imt to 6 yds., anil
driven loiw:,nl 1 hi., width, s eath side, li')i\'ing 11 6 ft. mud
By general consent it is ni piece of coal, except the one time it was pretty citn of the main roads, which repairs, and no doubt did i they got deeper it was found that such pillai-s offered little protection, unless they were made inordinately large, and that better results were obtained by taking out the coal altcther.
The method of workiug that has been considered- -viz., working away from homo, and canying the roads through the gob, is the
oiug built o.,
now* admitted that in loDgH'all every haft pillars, should be taken out. At
to leave pillars of coal on each side e supposed to reduce the cost of
hen the mines were shallow.
it. S..y. Mill,
METHOOe OF WOIIKING. 161
one followed in the gi-eat majority of cases ; but another melhocl, called " working faomewanlti," is rtirely employed, altliougli it in often I'eoommeuded as a. cure for all evil reciting to explosion. In it iiMuls are driven out to the boundary, the coal first workeil there, and gradually brought back towards tlie shaft, leaving all the gob, water, gas, ic, behind. It is necesaaiy to say that, with anything like a large royalty, such a plan would involve the outlay of an enormous sum of money, as all the jardnge in narrow work would have to be paid for practically before any coal was won. The output of the colliery would be u low one for many yews, and the interest on capital outlay would more than compensate for any saving I'resulting from the Hmaller employment of timber and repairs. In small isolated case, under special conditions (such as iiu exceptionally bad roof), the method of working homewards is applied with much piu'ces*.
Double Stall Method.— In the South Wales .oal field a svslem
liirgeiy for miuiug sti-aiu imd i.s that kruiwji as the double stall. In the ordinary system of opening, the two nmiu roads will be set away, and out of these side-headings in pairs will be ojiened out to the rise, Ijiking out the coal between. Prom these cT'oss-heads double stallB are ilriven (Fig, 1 78).
Two headings are commenced off the roads, and, after piticeeding fixsm 8 to 10 yds,, are joined, and continued on as a double stall, usually some lo yds. wide, having a road along each Hide, and a rib of coal from is to 15 yds. between each pair of stalls. Tlie stall fi'om one cro&s- heading meets with the opposite one from the other cross heading, and as soon ns tliiit happens the two men, who were working at thi" , separate, one going to the right and the other to the left li 1 '. ' :ec- Imtk lialf the
width of the rib. The other I iy (bt? adjoining;
stallfi, and confiequently the gruii 'I
It is a xysteiu which is beiu' : Wales district, but at the w and stall, in Bome inataooBB, ituM
TEXT-BOOK OF COAIMISTSi:.
Worianc Btep 8enu.Steep stam& dt be worked to Um deep; wlik alknrs kB etoninf of mUa aad remJte m a MiTb of pit work. ImUng ifaafU mnil craw-cnttii iBeMBiw ia vcTj expensive and ibmII srk is wn; bat tf a mam pMnciadrirenitnifAi down, it can be extended at aiiTtne wik additional engine power. It ha been by aetoal capmeneB tbat fim 8 to to per ceot. more coal is frodncBd by workiiig to the deep tban working to tlie liae, whidi w jmtMUj' aeraunted for bj tbe tmet tlaU tbe wieiglit is tltrown off tlw bee in working to the deep. It, bowecer, pomanes dieadraotagea if water be present, and an additional one tn that the gndient ia aJwaya agauut tbe kd. In nee workings p m ri t y
ib
tii-iiigD the coal down to the levels, where it can be rallecteil into Het and hauled aloo the main engine plane, but additional labour ia neceesary in self-acting planes.
In Kome parts of the BrJEtol coal6e!(l,* there the measures are I Hteep, the area Ih Buh-divided into a series of panels, and everything worked to the deep. Each bank has a tparate engine and engineman. The system is costly, but under certain conditions and no water, is safe and produces coal in good condition.
Perhaps the best way is to win the cofU by an engine plane driven i4traigbt to the deep, and as this is in of the workings, all the water is collected there and pumped to the shaft. LevelK, right and left, are branched off at intervals at about icxi ydH. and the coal worked to the rise (V'tg. 1 79). Self-acting -So. Wales Inst. lii. 363.
Methods Of Working.
inclined bi-ing tUe coal to the level, which is then taken to the pliwe and to the pit biattom.
On the Continent, whei-e the seama are not only highly inclined but very much distorted fuid broken np, the general practice ia to flink a vei-ticai shaft, and drive ci'oss puts at i-egitlai' distAiicea
njiai't. At tlje points of intersecting the seams, levels are tsikeii right and left. These are driven along the strike of the bed, and HS the inclination is anything but a regular one, are iihually verjr crooked.
In thti thin, very highly inclined Beams, the coal liotween the
i levels in removed by the method known ah " grains
a series of steps, and ailvunces in the direction shown a. There is one workman to each step, and ' vertical face of coal liefore him, liavini; head. Shoots through the gob oonvev The method of timbering will be und
Text-Book Of Coal Mini
The s7Btm of working U in every i-espect idiiticnl witli that known to the metal miner as overhand sloping.
In the more moOeratly inclined eenms, isay up to 40 , tb method cftlleil "tiiilles montaiitcs," is employed (Fig. 181). It ia , u system of pure longwall. A number of stepped faces, about 20 wide, ai-o ciirried up ahout 4 or 5 yds. in advance of each other. Each stall is served by a road kept through the gob, but these are cut off every 55 to 65 yds. by 11 horieontal cross-level.
The more moderately inclined tteitms are worked by the Bj-stem called "tallies chassantts" (Fig. 1S2). A road is carried up from one lei'el to the other, and branch roads put off right and left, about every 15 to 20 yds., measured along the inclination of the seam, taking out the foal for a distance of from 50 to 100 Vik. on ench side of the main incUne, the face, its before, presenting
a series of steps ; at intervals, diagonal roads are put up through the gob, cutting off the lei-el roods as illustrated.
The extm cost of working steep seam.-; L; tonsidetsbly larger than moilenitely inclined ones, [irobably much as one half more, in some instances frequently third.
Working Thick Seuna!— South Staflbrdshire. — Xo matter what c'stem of working Ls adqited, the invariable rule in the Ten- Yard seam is to drive out to the boundary and bring back the work, leaving the gob behind. Two main gate-roads proceed akmg the strike of the eam, serving as haidage roads, and the diataoce between them varies from 35 to 45 yds., being alv-ays sndi, that in the operataoD of getting coal, these preUminary drirage will form a portion of the chambers, and, as it is called, "come in to work." Where a lat area is to be won, roads are branched oat right and left of the main roads, and coal gotten ac the extremity of these, even before the former have proceeded much past tfaeai, the only precaution to be adopted being, that the coal so worked should be a sufficient distance from tbe shaft not to affect it by any subsidence. While this portion is bein worked oat. the main
MKTIIODM OF WORKING. tf's
roads pixicwd on their course, and braucli roads we Again aent out at suitable distsmceN, and when ther i-each the boundary, either of the lease oi' of tlie diati'ict, work U opened iiw before,
The methodn of working commonly employed may be divided into {a) square work, and (i) lungwall, the whole thickness being removed at once, 'fi-ue longwall is, however, unknown in the thick seam. It might preferably be defined as boi-d and pillar, the large blocks lieing pillars. If ko, the syat-em of working is the Mtme as the one pursued under the sine title in the Northei'n coalfield ; the removal of the pillars being similar with modifications occa.-iioned by the greater thickness. The coal is sometimes worked in two divisions by a modified longwall system, but although thix possesses some advantages, yet the numerous practical drawbacks, such as the increased quantity of small coal produced, the inferior mineral obtained when working the lower slice, &nd the frequency of gob fii'es, have re8ultd in its general abandonment, except in a few isolated special cases.
(a) Sqwiit IVm'k. — In this system the coal is worked out in a series of rectangular chambers, separated from each other by riba of coal, internal support for the roof being afi'orded by a aeries of square pillars of solid coal. The old method of o[>ening a aide of work was to drive a serie of lo yds. wide, leaving lo yds. of coal between each, and then a second set of lo yd. stalls at right angles to the dnit, the i-esult being that pillars id yds. sqiuu'e Wei's formed. Thin ciptnition would be curried out in the bottom coal, the top coal got by the method described a tittle further on. Pmcticully, however, opening a side of wwk in tJlis way is a thing of the past. To dn it with any succeMs requires an exceedingly strong roof, even then coal is uot got out so clear as it should be. At tlie same time, it is adviMiible to drive the stalls, in the first instiuice, at leiist 5 yds. wide, and so save the cost of narrow work.
With an average roof a convenient size for the ojienings is 10 yiils. wide, and for the piUai-s H . square, and in such case the ordinary gate-roada opening out a district will be driven, leaving a piece of coal 53 ydi'. wide between them. On reaching the boundary of the district the two gate-roads will be connected by a croBs-drivage Fig. 183). This will be widened out by " side-Ian ing," which consists in treating theside of the i-oad asa longwall face, and holing it out to a deptli of 10 yds., as shown at b. While this is being done n second crass-drivage, c, about 5 yils. wide, will be cairici] liplwfn tiie Iwi. j;iite-n.ida, cutting off block of coal 8 yds. \Mi' h laneil ofi' to 10 yds. vi 1 block of coal remaini' 8 yds. square are am ii> wide, and on the foiitll> -il'. thi has been iwrrierl in tlm Jowgi r n
'ijieniiigs 10 ydH. 5 yds, wide. All
66
Text-Book Of Coal-Mining.
In tlie liack opening the top coal will now be got down in ectioD8, slice aftor slice being vertically. Tlie whole distance across this opening is not attacked at once, only ii certain portion of its length being worked at a tuue. The top coal is got down by cutting veiiical grooves up through the overlying measure of coal, leaving between each length of six feet what are called " Bpiirns." Thee spuruB ore narrow webs of coiJ, holed through in the upper part, When the layer that is lieing attuckevl htm been cut through in this maimer on both sidefi, the Burns ai-e reduced by the Hid of a pick, and are then finally jobbed " (knocked) out with a " pricker," which is a instrument very similar to a boat-hook. A pum is always left nt the face, and when this is removed the whole mass falls, and ih then in a position to be taken away by the loaders.
Willie tliis ifl going on a third cross-cut will be driven between
. r83, 184 AMI 1S5.
S
the two uiiun gate-i-oads at a distance of 13 yds. ftiam the lust one (u, Fig, 184}. The opening c (Fig. 183) is then widened out to 10 yds., as shown at b (Fig. 184), the main road side-laned off as before, c c, and a middle hurling, d, 10 yds. wide, driven across, forming two more pillars 8 yds. square. While this is being done in the bottom coal, the top coal has been got down aixjund the two pillars shown in Fig. 183. A fourth cross-drivage is made between the two gate-i'oads at a distance of 13 yds. from the last one, and the pillars there cut off, as ah-eady explained, so that at this stage of the operation the side of work considered will have the appearance shown in Fig, 185— viz., 6 pillars each 8 yds. Bquai'e, surrounded by a series of openings 1 o yds. wide. The top coul by this time will be removed all over the side of work, except on the tluve sides of the laat two pillars, and will gradually be got down there until nothing remains. Fire-dams will then be put in at the points, a a, and a new ide of work started, cutting off & Hb of coal 8 yds. wide.
iMTigipail ill One Dh-iaioii. — Gate-roads are liivt dri 7 j ft. wide, leaving 40 yds. of coal between. The ciiiss-holings are
Methods Of Wokking.
Flos. :86, 1S7 AND
=1E
Tr
Hf
45 in clear, so that the commencement of each [lintrict is
U) liub-diviile it into pillars 40 yds. by 45 yds,, such dimenMon
liltowing of all the roads coming into work. Upon reaching thi>
boundary of the district, the removal of the cool is commenced bv
186) to ti this being carried an all
acroHS the fac. While such is being
done a narrow stall, b, 4 yds. wide, in
driven parallel with it, cutting off a rib
of coal 7 1 ft. in the cleai*, and then this
rib is split into pillars 7 yds. square, by
a series of croes-diivages, e e c, each 4
yds. wide. The block of coal between
two roads in thereby divided into four
[Hilars and tbi-ee openings. This work
is carriiMi out in the lower 6 ft. of conl,
and while it is being done, the top ciniI
in the 8 yds. back opening is got down
by cutting through and dropping down
the successive luyera.
The removal of the pillai-s b copied ont as illustrated in Kg. 187, Cogs of MUd atone, a a, are built in the stalls next to the and the central stall widened from 4 to 8 ydB., a slice being taken off the pillai-aouBHch side. The top coal is got down in the opening so ftimied iti the usual maimer. The cogs are then removed, and placefl in the [Kttiitioa shown by the X. The remainder of the pillars ai'e then got out, together with it portion of the two pillars on the side of die original gate-roads. Fig. i38 now shows the position of atfoirs. The two pillars remaining in tliis block, together witli the two half pillars of the adjoining blocks, are removed in 11 similar manner, cogs lietng built at e for this purpose.
During the whole of the above operations, half the coal produced goes down one gate-ixiad, and half down the other, as shown by the arrows, the tubs being taken straight into the face. While this hafi been going on, another row of 7 pillars and 4 yd. openings have been cut off in the bottom coal, and the pillars removed in a similar manner. This operation is reiieated, until such time na fire breaks out. A rib is then cut off, duul put in, aud workings again opened on the other side of it.
Foe the success of thLs system it is neoesury that the coal should have a soft roof, and one that comes doa ([uistly without much weight. In some parts of tl roof, which will bear a large a however,in the words of thecd nothing can stop it. SuobRif
hurd
'I'lie iidvantages claimed axe : The greater first yield and total cleiU'ance of coal.
The disBdvimtagea are : The large ti.mouut of slack pi-oduced (this being due to the 'luautity of gimpowder employed), and the smaller total yiM per sere. A greater quftiitity is obtained per acre tlian by the Urst cleai-auce in the sijtiare-work xyxtem, but, lifter the lapse of some cousiderable time, the ribs and pillars left in this latter metliod of workiug ore cleared out. In many cases, the reiDuaDtfl of the thick coal are worked a thii'il time, thut obtaining a further yield. The total produce of winning the broken is about one-third of the quantity obtained by the first working, of which one-third will be conl, and two-third slock. The expense of winning the broken mine is somewhat greater than that of getting the solid coal.
In every system of thick coal mining, dip work is advantageous, jis the falling roof-stone ifllls away from the workmen.
Fennsylvonia. — The system of working the Mammoth Bed, which KometimeB attains a thickness of 60 ft., as described by Messrs. H. M. Chance' and Franklin Plattt is similar to the double staU method of South Wales. Either from the bottom of the shaft or out of a slope, if no shaft is sunk, a main road, called II "gangway," ie brunohed out following the strike of the seam. A parallel road some few (10) yards away, called a heading, is driven for the purpose of ventilation. When the coal is quite flat, the Btallri, or, as they are called, " breasts," are opened at right angles to the gangway. Where the dip is too steep to allow a I wiiggon to be used in the breast, if so driven, it is opened at an , angle to the gangway, thus decreasing the inclination.
Two plans of opening such breasts are in common use. In one, the breast ia openetl at the gangway to its full width of from 8 to 12 yds. ; in the other, an opening just wide enough for the wiiggon is driven from 8 to 10 yds., and the breast then opened to its full width. The inclination of the bed usuaUy limits the length of the breast to 300, 400 or 500 ft., and coal lying at a greater distance from the gangway is mined from a second series breast, opened from a second gangway driven above the first sei
The distance to which the gangway is driven on each side of the slope, or, in other words, the lineal distance worked from & single opening, is limited by the cost of keeping the gangways open and the cost of haulage. If the coal is hard, and the roof good, it ia often cheaper to mine coal lying two or three miles from the slope than to open a new one, but when the cottl is soft, and the roof had, it may be cheaper to open a new slope than to attempt to keep one mile or less gangway open.
Second Geo. Siir¥e\' of Pennsylvania. Report A.C Caiil Mining. i Ibiil. Heport A 2.' (Xiil WaKlt. Tbe chapter on Mining is by Mr. J P, Wettierill, and is an expansion of a paper oriinallv contribiilei' "
Methods Of Working.
Tbe breiiijts ure not worked thi-oiigh into the gangway above, but are driven up to within 5, 10, or ig yds. of it; the (lUlarthus loft is called a " chain pillar." When the breasts are worked out, the pillarK are robbed by taking; off from watch fts thick a slice as pusaible.
In very steep breoste it is impossible for a miner to keep up to the working face, sk he has nothing to stand upon, and it ia therefore necessary either to leave the loose coal in the breast or to erect fiome artificial support. A common of opeaJag out work in such cases is illustrated in Fig. 189. The breasts are opened by ilriving in two shoots for a distance of 8 to 10 yds., connecting them by a cross drivage, and then ciir- I'ying the working foi'wai'd its full width. Four strong props, a, are set just alive the pillar so cut off, and against these, two log butteries are built, in each of which in left an opening, say 4 ft. sijufire, that will permit large lumpH to pass through freely. Koail.s ore kept up each of the breatit by the use of inclined props, called "juggle's,"whicli are into the Hoor and sides, and have 2 in. planking nailed against them (Fig. [90). Thesurplus coal may be out at the bottom through the opening in the battery, but is more frequently sent ilown the man -ways ; the loose coal is alloweil to remind undisturbeii until the bi-east is driven to the limit.
Working Seoma Lying ne&r Together. — In the South Staffordshire coollield, when the distitiin between two seams does not exceed 6 feet, the general practice is work the lower one tirst by loagwall, carrying gob roads in the nrdiiiary manner. When the boundary is reached the roads are ripped down into the upper' seam, which is then taken buck longwork towoi'ds many cases it is found that by such procedure t>' only makes a greater percentage of large done if it bad been cleared olT 6rat. tion is less, a& the undercutting is
Text Book Of Oual-Jiininu,
In the aouthem piii-t of the WarwiL'kftiiire coulfield all the seams rome together, being eepai'ati'ci by a small thickneAs of parting, amounting to na little as z ft. between each seam. The method of working has been described by Mr. E. F. Melly.* A pHir of dip ronds are (liiven in the lowest of the seams to be worked to a distance of not lens than 500 or 600 di-ift is then cut through all the foitr seaniH (ithown by dotted lioea in Fig. 191), aiid they are each opened out by level headings to a diittauce of from 1 50 to zoo ydf. on each side, crocK-cuts at each end, and generally one in the middle, connecting the four (leaQis for ventilation. In thin way, eight different stalls, or working places, ai-e at once made, each of which may be partly holed every day, so that 50 to (io tons should be delivered to the flat, A B, fivsm wich one, and to this point an incline rope, which takes fi-oni ( 5 to zo tulis iit a time, dehvere the empty
Each face follow-behind the i-tlier, luid as oiJy a very short
pai-ting exisltt bf tween the .seain.s, there is considerable breakage, U8 the faces cannot jjoBaibly proceed at a greater speed than, say, 2 yds. per week, and aw the distance at which the face of one seam lies unothep is alwiit 10 yds., the coal in each case has only five or six weeks iu which to settle down or deteriorate before being worked.
The main flat, A B, in made to lait a long time, generally two or three months, and the faces adjoining the road are ftllowci to hang Ixick 11 little, as making a new Hat is i-ather an expensive bnsiueu-s.
Spontaneous Combustion. -Some setime of eon! are particularly liable to combustion, the fii-st signs of which Ri-e given by a peculiar ttmell, termed "tire stink." This i desirable state of afliurs is produced by three agencies : (a) o tion of the organic conHtituent ; (6) iron pyrites; (c) p The firnt is undoubtedly tlic main one, but is assisted mi by the other two.
(a) Oj-idaliun qf the Oiyanir Cmulittieiits. — Richter'st ei| tents satisfactorily deniunBtrated t!io high impoi-tance of '
N. S. I. Jtxxiii. isi: and Brit. Sue Min. Stud. x. i t ilHutlHT'i!/ {Fvil. d-e.}. Dr. I'erey. 1S75, p. 199.
METHODS OF WORKINii
iu.-tioii. anil it unity be looked upon as being the most eHeetive of the three. OokI absorbs oxygen, one part combining; with the carbon un-l forming onrbonic acitl aad wati', while the other entei-N into combination with the coal, and proportionally incretiseK its weight. This alone would fix careful attention on this nctioa, as it is found that, before combustion, ocnl so inclined emits large quantitieti of carbonic acid gas. Heattag rMults from the absorption of oxygen, and absorption if fuToured by heating, moiatuie, fine division, find absence of tight ; everything thus combines to favour decomposition.
(6) iron PyriUi. — This substance on decoiii[)osing yii'lds, first, ferrous sulphate, and, secondly, feme sulphate ; the former mslces its appearance in the form of colourless fibres, protruding hei-e and there from the face of the coal, while the Utter is of a brown colour, and ia more frequently obeerved. These products may suffer further decomposition, sulphuric acid being sometimes formed, and as their volume exceeds that of I he originnl pyrit, disintegration of the coal is effected, together with a small heating in close proximity to each lump of pyrites. The hunt generated is quite incapable of commencing a fire, but it may help, in a gi-eat degi-ee, the action of other agents. Fenic sulphate is reduced to ferrous sulphate by contact with nmall particles of carbon, and hence may act us a carrier of oxygen the organic constituents of tlie coal.
(e) Friction /rom SllppUigi. — Pressure from the roof on pillai-s cracks them, and grinds the irregular sides of these fissures together, thus producing heat and a considerable quantity of fine coal. Now, small coal does not absorb more oxygen than lai coal, but it does so more rapidly, and the temperature rises very quickly. Really solid pillars never fire, it is only when they are being cru bed that combustion occurs. The heat acting on the small coal produced by the grinding action, may also subject it to the process of slow distillation, and produce a quantity of bituminous mutter, which, on the addition of further heat, suddenly bursts into fiame.
— The oxidation of iron pyrites cannot looked upon us the primary agent in producing combustion. The amount of heat that would be given out by the oxidation of the quantity of sulphur in any coal can be easily estimated, and, on calculation, it is speedily recognised that this heot could not prmluce the iBsuIte attributed to it, even if the pyrites existed in isolated noilules; another argument in favour of this is the very slow niitiue of the process; the heat produced is twnsequently disipat*d, and only a small heating of the jwrticles takes fice.
TttMonn be little doubt that the decomposition of iron pyrites
"iir.i to spontaneous combustion ; owing to the
mIui.'i'iI, it allows the coal to be more readily
Tkxt-Book Of Coal-Mining.
[lermeiited by diirrents of oxygen, niiil, by the heating — small though it miiy be— favoiire the action of such currents.
When the first agent U cooKidered, every circumEtimce seeing combine to render the action siicce&iful. Keating, moititure, and absence of light are all conducive to the oxidation of the orgtuiic coastitiientH of coal ; it is in seams most free from pyrites that pontaneoiiH combustion takes place. The constitution of the coal seems to be of great importjtnce ; it is only in bituminous varieties that this undesirable state of things is found.
Little om be added to what hnn been already said on the heat prodnceil by friction ; the principal argument in favour of this view is the one already givenviz., if fire be found anywhere it will be in thf ciiicks of pillara. No doubt this is pei'fectly true us regards some underground tires, but spontaneous combustion is frequently found occuiTiug in heaps of coal above ground, and this coal may contain a very small percentage of pyrites. To account for the fire under such circumstances is impogAible, unless the oxidation theory in a4lmittd ; and, in the opinion of the author, this action, in tlie majority of cites, is the primary agent, although either of the other two in conjunction may greatly facilitate it.
.—This, enn only be done by the landing up and removal of all fine slack and refuse. A vigorous cuireut of cool ail" must be circulated through the workings, cooling the surface of coa] over which it sweeps. The piiictice of reducing the quantity of au* passing cannot be too Htrongly condemned ; such procedure iiitreaset the risk of combustion, because sulficient air in always left for oxidation, and, owing to the small volume, the air gets heated highei' than the euri'ounding stIata, aiid consequently aids, instead of impedes, the risk.
There is a point at which a vigorous current of aii' i;< inadviuable ; if combustion has broken out the quantity of air should be reduced, but until that point is reached a diminution in quantity only acts iletriuientally.
In longwall workings, close and effective stowing of the gob with roof stone is the best preventive ; if sufficient material is not available to completely fill the excavation, the pack should ake the fonn of squai*e cogs, and be arranged draught-board 'aahion. In thick seiims, as there is pi-actically neither roof nor tides to timber to in the workings, the only method of dealing nith a fire is to isolate it by damming ofi' the affected ai'ea.
If rt fire occur-s in a fast road, or in the gob in a thin seam, an attempt should alwuyt lie mate to dig it out. As an additional safeguard, lines of water mains are often laid along all the principal roads, these pipes being connected to the water Ijehind the tubbing in the shaft. High pressure water is invaluable at collierieK liable to BiwutaneoHS combustion ; if a lire is attacked vlgoi-ously at its commeiicement it is often miistei'ed, hut when it attains fair jiro-
3IETII0DS OF WOItKING.
'73
poiliuiiis, it may not oiily CKcnsion enormous expense, source of contimial ti-oiible and danger.
Bibliography. — The following is a list of tlie more important meiuoin deitliiig with the subject-matter of thie chaptci- : —
Ktti. INST. SCOT. : on a Xeireantle CoUierg. J. T. Uohson, L 41 ; A ComiHtriKO't belwtta the Sloop and Hootii and Jjoiutirall MethoiU of' tl'orkiHg, J. H. RoniildBOD, i. loi ; IMaiU of IjmgiBall Wurkingn. 3. Hogg, iii. 328 1 Same Xota on Suhsii/eneu ami Drair, 3. S. Dison, vii, 114 ; l/ongicaU Wvrlingi in the Edge Stunin nt Kidilrif OoBiertH, U. Johiutone, x. 204 : Workiny Thick Cool fieam hi/ LongteaH at Uaigonie. F%fe, Robert McLaren, xii. 65 ; A'of on Shale at OiMiank, Alex. Fanldi, xll. 130. SOC. tKD. UtN. : Milhode d'exploitation el mtiUrial de tranipurl dei miner rfM Betiga, 3. B. Harsant (a* Serie), t. 365 ; A'wte *ur Ferilatimi dtt ameha lie heuille jmiiuanUs el Irit iirfiW' it flontbroiru (Rilogtie). H. JonlcDweW (2" Srie), v. 353 ; hcenditu iliiiit Itn houilltref. Procidit eniploi/f pour let prvener et let teiinlre, M. Nesterowki (2* Sio), vii. 839 ; Nate tur la mahode dej-plottal'ion employ a " La Bnlanee '' caiirju da PAoniu, njinw iTAuhiM, M. Bidaobe {2" SfTiel, Tli. 351 ;. Etudet ur I'aU&athn et la eembiutian ipontaH/e de la haaiSe t-rpotfe a fair, Henri Fayol (3° viij. 487 and 611 ; Salt mr let iaeendiet dam let hevUtiret, M. Dnrand (3° StrieJ, zii. 43 ; Xole tiir Iti mmtremti'lt de len-ain procoipiii piir tejjio'gallon den monet. H. Kayol (3' Serie), xiv. Soj. K. B. 1. : On Mlnei and Mining in the Xorlh StafforihhWe Coalpbl, J. Hedley, ii. 342 ; The effect produced vpon Beds of Coiil bji irorliiiy aity the oeer or iiwlertging Seana, George Elliott, iv. 141 ; Ttir Workiw} of Thin Settm of Qmii, Kith ObitrvatioKi en Longvall and Hard ami PiOaT Wurk, G. C. GreeDwell, iv. 191 ; On the Workiwi and VenlUalioa of Coal Mints tn the eouuliet of S'orthutnberlaud anil Ihirham, John Wale*, vii. 9 ; Oberralioi m PlUar Wofbhff !„ the Northamberland ami Durham CoUieriet, S. C. Crone, ix. 17 ; 0ih- Mode of Working the Ten Yard ( bal 0/ South Staffbrdtkire, H. Johnson, X. 1S3 : On the Method of Working Cital. bg L-mgiraO, Gmrge Fowler, xix. 37: Working Cool by lAtngirall at Annriteg Oolliery, Xotlingham, Henry Lewis, xxi. 3 ; Prevention of Spontaneoiu Combtulion of Coal at Sea, T. W. Btraning. xxv. 107 ; fMugirall Worlliigi at Eritt Hetton QMerg, W. O. Wood, xxv. 2U nnd xxvi. 64 ; Mininff at Saarbmeken, A. B. Sawyer, ixviii. 9 i fWw Sgilaia of Warkinn the Mmn Coal nf Moira, W. S. Gresley, xxili. tSi : Xoten on the WaT-nclthire Coalfiebl, E. F. Melly. xiiiii. IS'- ha:i. gbo. 8OO. : Tht Method of Working 'Hearing itinet" nl J.,e]/eelt. StafordMhire. W. J. GrimBhaw, jd*. 155 ; Oh Sinking of Sarflfe oudiuj to the Working of Coat Mine; w. J, Gritnshaw, xlv. 455 ; IjmgioaU SyHem of Awtiny (TW, W. J. GrimBhaw aiid H. Phllllji., IV. 312, 330 and 341 ; Tlie /ipatl Sgitem at Averrign P/l, Wenl Leigh, 3. HiltOD, xvi. 270 ; Warking Coal hg /tmg-. W. B. Unrfortli, xviiL 303; Kateeon Oo-d Mining,!. 8. Borrow*, iSqia, BWT. 800. ms. BTCD.: Mpdifil [Ay-a-nll :„ y„rl.-l.!re, E. F, Moll. i. 306 ; foal Minina t- "mtl, II 1 1 1 i- 1, |v. co ; fW
M!n,n.j th .Vort* rf i i..,n,,-aU,n Santl.
WaUs. A. C. of Coal lgi..y
together, 3. 3, 'if I'sderground
Hoghea, ix. A. H. lUdruBTnn,
ii. 101 : U 1&8; 'oml
Text.Book Of Coalmining.
I'iOar H'orLiHg in the Xortimi C'oolfUlil. H. K, llnlman, i: Double StaU Method of Working. M. A. 8. Iteiimajiie. x. 29 ; uf Goiirft ailh Blatt Furnace Slag. C Z. Bunning, x. 5S ; Worl-iig hen tinimt of CimI Iv'im lix/tltier, B. F. Hellf , x. T04 ; Coat arid Coal Mining in Belgium, W. it. Qretiej. X. 133 ; Longvmll at Cdj/Hen ColHerg, R. B. LiBhman, x. 184 ; Loagwall Workimj with SprciiJ S'ferenee to Ihe Jrraiigetuent 0/ labour, H. F. Bulman, i. 189 : JCftet vf Co,,/ irorkig an the Siirfaee, B. W, Dron. xi, izz, H. F. Bulman, ui. 34 Hnd I10, and xiii. 103, J. A. Locgden, zil. 127. W. 8. Gresle;, Xiii. 57 ; A Sonth'i Viiit to the Sorth Slagordthirr foaljielil, A. W,
Onuebrook, liii. 137.
R. issT. M.K. : PiUari nf Coal, 8. H. Paddow, i. 170; Laofitnill .Syalem of Minimj, J. W. Harden, i. too ; What it Ihe bat intern 0/ Worbiitg ihiei .' 0. J. Heinrich, ii. 105 ; Firet in Muiet, Iketi- Cautft I hbJ Jlraiii of Enlngaithinii Ihetn, R. P. Bothwell, iv. 54 : OutiiiU! of AthrticSe 3lln-ng In -iU Countu, Fti 3. P. WetheriL. , V. 401 ; <hiil MiHlag la the ConHelltville fhte Beglon o//iiniyii-nni"a, J. Knltou. xlii. 330.
VALKS. INBT. : The Stetp ifeonure* of South , G. Hobson, i. 214 ; The iMtLomirk Sgetem, R. BedUogton, li. 135 ; The Working of l%in Seauu of (hat, JL Cossham, ii. 255 ; On the large proportion m OmI \ml !h WorkiKO. A. Bassett, ii. 180 ; The LonguU Syttem, T. Hedlej, liL 148 ; Tie PUliir and SliiU, Double Stall, anil Loagatill Sgrteuie of
Working Coal ii
Abrrdarf, J. Williams, iii. 232 ; Cbinparafirv Sgttenit of Mining iH the Korth of England and South Walee, G. Brown, w. 10 ; Th* 1 dlfffrent Vahode of WorUnti the Souih irWw Steam Oxd, Geoige WilUnaon, xi. 139: The Working of Sleep Seam; M. G. Johnson, xii. 36j : Worlimi Thin Seavii in Iht Siuhloek Diolriel, J. McMnrtrie,
1 varioHj Melhoda t
I York,hir,
U of Working Coid !: , .. „.
MamiuU, i. IS i On retalU of different SItthodt of Oetting Coal, R.
Miller, i. 37 ; bn dlgerenl
Od illfereiaMelhodi of Working Coal.G.rovitt,l. 64: On Lmtgaaa
t Mtthodt of WorHng Coal, P. Cooper, i. 44 j
wd ItM Modifiealiotu, C. Hodgnjti, ii. 134 ; On the Mahod of Worldnf the Xnatone Seam at Normanton, leith tone TimuTlit un Ihe ITiiu ' - of Deep Coal, W. B. Garfnrtb, viii. 29. :A?f. IK8T. : Oh Cleavage Planee. and their tnjtvenee on the EeonmHieal
Worki-ng of Coal, G. G. Andrf , ii. 132 ; Mimng in North Statkhir, J. Woian, vii. j8 and C. Gordon, vii. So ; On i% Free : a Con tideration <y' carefal SpeeuU Paehing at a Preventipe, B. Splice, viii. 38 -, Method of WorHm Coal at Whilfeld CoUitrg. H. Wright, viii. 59; The Erection of Storming; icilh a tiiea to Uelola jiarl of a Mine OH Fire., A. B. Sawyer, . tco ; Gob Firei and Pit Stopping; R. Oswald, viii. 198.
Uhaiteu Viii.
Haulage.
FrimitiTe Kethods. — Doling tbe present no brsneb of the varioafiOperataonsinood mining has improved tnor than haalage. Id the olden times, carTTing the mino on the shoulder of men or women was the method aniTenaUy emiovei, aad is stOt tried out in place* where dTilisntion ii* imperfect. Tbe practice JK, however, adopted in one instance in our own country, where the conditions ar such that any othertem woald be impracticable—viz., the ironstone mint of the Forest of Dean. The eui-liest improvement consisted in the introduction of sledges, which are now employed to a limited extent, for liauling coal from the working plarae in thin netim: to the raadwavs, as it ia impKicticable to lay a line of tramway nlunj the face. In the thin seams of the Somenetshire coalfield, where the coal is 14 to 16 in. thick, roadii 4 to 5 ft. high ore carrieil up to the face (it distanceeof about 40 yds. apart, and atongthse tnbsare brought. In the face tbe coal is loaded on to an ordinary plunk about 1 3 in, brood, and 6 ft. long, one end of which is fastened to a piece of chain having a book nt the end farthest from tbe plank. The chain is pawed between a boy's legs and the hook connected to a ring on a leather belt faitiil round his waist. The plank is dried to the way-end, and itM load placed in the tub waiting
At this point, it may be stated, that it is a great advantage to have only one loading. Every time coal is emptied from one tub to another, breakage rCMults, anil, in Addition, it coHts money and
Bails.- — At the present time, pinictically all the railii used are of the dange jiattern ; bridge and angle designs having been abandoned. The sections employed have gradually got heavier, owing to the more permanent nature of the ways, and the desire to make haulage work as smoothly and with as few hindrances as possible. There can be little doubt that the wear of a rail is largely influenced by its composition, but the shape of the section and dispositioo of metal in the different parts is of greater moment. Using heavy rails does not necessEtrily ensure long wear.
Text Bouk Of Coal-Minlsg.
The deagning of aectioDs has of late received considerable attention, eqwoally in the United States, and several papo-s on the subject have been oontribated to the Amer. Inst. M. These rer to the heavier secdons employed on railways, bat are none the less ime, if to the deagns in use in collieries. The chief points brought out are. that the head should have as broad a wearing surface as possible, and should not be too deep. If too much metal is in the head, the temperature at the finish of the rolling process must be high, which produces a metal loose in structure that rapidly wears away in use. On the other hand, if the raO is finished by colder rolling, the compactness or physical hardness of the metal is increased. It is evident that the smaller the section the deeper wiU the efiect of the compression of the rolls penetrate, and the finer will be the grain of steel.
The American Institute of Civil Engineers appointed a Committee to draw out some standard rail sections, and a report of the progress made, has recently been published.* Ten different sets of designs were prepared, the fcdloing dimensions averaging as nearly as may be to the individual sections, if any wide deviations which appear in one set of sections only, be neglected : Head, 1 2 in. radius, top comer in., lower comer in., vertical sides, percentage of metal 41.5 ; Xeckt in. top and bottom fillet radii, sides either straight or 1 2 in. radius (there appears to be a
diversity of opinion on this point), percentage of metal 21.0 ; Bfucj 37.5 per cent of metal, width same as height of rail, sides vertical, with in. top and bottom comer rstdii, angle of head and top of base alike, 13 degrees (about 4 J to i). The width of the head is 0.54 and the depth of head 0.287 of the total height of rail. Fig. 192 shows a section of rail weighiiig
30 1-to til© yard* signed on these lines, which
the author is employing
largely on main roads at a
colliery where the total load
of coal and tub is 25 cwt.
It replaced a rail weighing 39 lbs., in which, however, the
ement of material was bad. The disposition of the material,
CoThditions in Manufacture of Steel RaiU F. A. Delano, xvi. 594 ; )U and Speqficatione for Manufacture R. W. Hunt, xvii. 226 , A System of Hail Sections in Series, P. H. Dudley, xviii. 763. and Min. Jour. 11. 319, March 14, 189 1.
Haulage. 17;
encKigh Titbodt wmtiag mbti ea pMlHp Mad bMd para wWi tt is not wanted.
Sir. P. H. Dodkr' yrtitn to pkn tk &w tf (he mdii ft* tfae Bides of the wb above iht aaoUt, sv toH*b th* loiv portiiia of the Tob tbkfar. far tli Mkarnm immbm : — To Mora uemihf eqoaliae th bmt flf tte werioa f tlw buv And the bead, permitting txMat wrBmg ; ta knr the iMtnI uda better equalisjn Che sonia of the Botatl betwea the faaae and keMi, and chewing the teniaitj tope r— Mt ; eA tbs tcrndBiiey of the w€b to bend tae base the nil Hikder hear; Infie. '
The ioOomiog aped&eatittmt is raDonmended when ordvnag
Tbe lectioa of nil. wfaca railed, ikaO caolbiin lo the template foniished ; with an aQowance in hdi o( meh andet sad inch over permitted
Tbe length nO iteU W fECC : lariuioa in length of ooe quarter
otaaiacb logw sad ihwlet win be mOautA.
Ibe nih osM be free frail all mcchsakat maA (laws, shall be sawed qnaie al the eadi, asd the barn nude bv the fva carefully chipped or Bled ofl, patlieolaHT ander Ifae head and on the top ot the
iSe tails ihaU be aaoeth ua tbe hfadi. itnigbt In all directions, and wjthoal aoy twist or kink*, [anienlar attention btaag given to having the ends sithoDt aiij drop.
The steel to coQtahi as liigfa a percentage of carbon tlie are wiUin ia pot in.
Id the worktog places the lightest weight poBsible of rides kIiouIiI be employed, just strong enough to cany the loaded tiilw.
Length of Bsila. — Id the workings, the usual length is 6 Ft., or som<-tiius 3 ft. when a. longer length is iiiadiiiiaHiltlo. TUtt length should be such that the weight ts small, in urtler that the workmen can easily move them about, nn it is hem that tlii< greater quantity of rails are lost by falls. For Inyiiig tliu iiiiuii reads no purpose is serred by iihort rails, and for su<-h Hitiuitiuiift, their length nearly approximates to those emiiluyorf on Murfiim railways.
GtiTige. — Tbe most general gauge is 24 in., although it vnritw from 18 in. to 30 in. With narrow gauges the openitlon irl' tipping the tube sideways ie facilitated ; indeed, tlio objtiHiim a narrow gauge is the ease with which tub are ovcrtiii'iied.
Hethoda of Iioyiiig Bails. — Two (unsidcrntioiiH havii Ui Ihi home in mind here. In the working ploceti, eii{)(H-iHlly wlmi'n Ui longwall system is used, rails are being fi-eijuently tukon up Hnil relaid in another position. This bujipt'iiii evtiiy tiiun llio fnui' advances, and as a result, the way in tiut put down with iiiiidli ngard to evenness of road.
Amer. lost, H. E. j
t IIM
Text-Book Of Coal-Mining.
FlOS. 193 AND 194.
On the other hand, greater care is taken in laying the rails in the main road, because the line is a permanent one, and must be kept in good condition, in order that resistances to traction may be reduced to a minimum. Care is taken to make the gradient as regular as possible ; the rails are kept perfectly stitdght, or, if curves are necessary, they should be bent by a machine similar to those used on railways. At many large collieries an experienced plat-player is employed, who superintends the laying of the main roads.
In laying curves, the gauge must be a little wider than on straight lines.
Fi8h-plating. — To obtain a rigid and straight joint on the main lines, side strips of steel called fish-plates " are fitted on
each side of the web (a a. Fig. 193) where the rails meet; holes are punched through the web and through each fish-plate, and bolts placed in them and screwed up tight. To allow for expansion, the holes through the rails should be oval, and to prevent the bolts turning round when the nuts are being screwed up, either the holes in one fish-plate are punched square, or the bolts made oval for a short distance under the head, and then round afterwards, or one fish-plate is punched with holes of a pear-shaped section (Fig. 194), and the bolt made of a similar form just under the head. The remainder of the bolt is made round, and, passing through the oval hole in the rail, permits the latter to moN'e a short distance.
It is important that the fish-plates should be rolled to correspond wiUi the slope of the head and top of the base of the rail to ensure lrfect fit
Sleepers. — T6 give the road a solid foundation the rails are laid on transverse supports called '' sleepers," which may either be constructed of wood, iron, or steel.
Wood — The length, breadth, and thickness of wooden sleepers depend on the gauge of the road and the weight of the load ; f nau 3 in. to 4 in. deep by 6 in. broad is a common siie. Tlie wood employed is generally Scotdi fir or larch ; the former is cheapest in first cost, but the latter has greats lasting caiipacitT.
To secure the rail to the sleeper, a hole is generally punched through the base and a flat-headed nail driven through it into the wood. The objection to this is, that the hole weikkens the rail to a tt great extent, and breakagee ctften result at the point where they are punched. For this reason a hooked nail called a is pieienred. One of these is driven on each
o o
Haulage.
'79
side of the rail. }[ere a point must be noticed ; the book on tbe (log is nt right angles to the other part, while the base of the rail is sloping. As a result, the dog must not be driven vertically downworda, but on a slope {a, Fig. 195), in order to obWn as large a beui'ing sui-face as possible between the hook of the dog and the base of the rail.
The objection to dogs is, thiit they do not prevent the rail mo\-ing longitudinally like a nail does when put through a punched hole. Tbe diificuHy is completely overcome by cutting a small notch out of the base of the riul where the sleepers are to be fixed, and to prevent these being opposite each other and weakening the rail, those on one side of the base lead thoee on the other aide, from 1 in. to in. (Fig. 196). The notch is not more than a j in. deep, and is taken out of the thin edge ol the
KiG. 196.
base, instead of through the thickest part, as is done when holes are punched for nails.
/nni. — Wrought-iroB nleepeis have been largely employed. They consist of a flat strip bent round at each eud, to grasp the base of the rail, and then a block (o, Fig. 197) is riveted on at such a dititance away that it clutches the other side of the rail.
Sleel.')( late years the use of light steel sleepers has become generaL lu one form, Cotquhoun's patent, the rails we fastened by punching two holes iu the sleeper, one on each side of the base of the rail. A steel , or chair, is passed tluxiugh these holes ; the inuer end firmly grasps the base of the rail and
the whole is secured in position by a wooden ' lers
weigh about 14 lbs. each, and as tiiey w of comigated steel to give axtr
i8o
Text Book Of Coal-Mining.
narronnMB of the clasp, joints cannot be made on the sleeper, and fish'plates have to be employed.
Bagnall's aleepei* is made extra wide, a made on it. A centi-al conve corrugatioi
nd rail joints may pii-sses from end to and, although the sleeper Ls narrowed in the to reduce weight, found for two conigalions, one on de of the central I coiTugation (Fig. 199). The jaws, or chairs, four tn number, thrown up for the purpose of securing the mils, are strengthened by corrugations at the back ; the sides and end of the sleeper are turned down, thereby preventing lateral displacement, esjiecially on cui-ved hnee.
In Hipkins's sleejier, the edges ai-e also turned down all the way round, but the top is flat. Instead of providing four small chairs at each end, only two are thrown up, but they are large ones, and each is strengthened by coiTugations.
The author has employed Bagnall's and Hipkins's, with satisfactory results. Being of steel, they are very light, weighing only about I z lbs., and ai'e cheaper and stronger than wrought-iron ones.
Switches.— At junctions of i-oiids, switches oi-tiu-n-outs have be employed. For permanent situations these ai'e best constructed by the blacksmith and platelayer, eopjnng those adopted ou railways, employing guard or check rails on all cui'ved portions (see Figs. 254-256).
In the working places, and for tempoiiiry purpose.s, where turnouts are moved from time to time, a more rough and I'eady arrangement is requii-ed. An oiHlinary form consists of a movable rail about 6 ft, long (a h. Pig.
h. This i-ail can either occupy the position, a h, or that shown by the dotted line, a' b. Where the i curve LI not a sharp one this device acts admirably, I but in quick turns it is I
s.sful, .
throws a certain length of straight rail where there should be I J curve.
The more genei-al practice is to employ castings for a poition of 1 1' ie switches. Middle beds and wing pieces can be bought of any , idius and to any gauge. This construction is very handy, easily id and removed, and generally applicable under any conditions.
HAULAGE. i8i
PlatsB.— To i-eadily tm-n tubs about at jiinctiona where the Space 16 limited, the rails are made to teiininate, and a plate of wrought ai' cast-iron about 3 or 4 ft. square plaeed in the gap. The tub cau readily be turned about in any direction, but to guide it into its proper way, with a minimum of trouble, an angle-iron guard is usually secured to the plate by means of set pins, and the rails leading from it are opened out for a short distance (Figa, 201 and 202).
The continual passage of the flange of the wheel over one spot on these plates gradually wears a groove in them, especially where tbei'e is a lot of traffic, as at pit bottoms, whei-e they are
Kiti
iisuaily employed. To i-eraove an entire pliite takes eoiifiiJemblB time, and when i-emoved, the iron is good for nothing but scrap. To obviate this, looee wearing pieces should be introduced. These consist of two wedge-shupetl platas (a a. Figs. 203 and 204), level with the top of the plate, which is recessed to receive them. The sides of the recess are inclined towards each other, so that the wearing pieces are in a manner dove-tailed, and when ilid into position iu the front end, are secured there by naila, b b, jiii-ssing through them and the main plate. When worn out they cnn be replaced iu two minutes.
Turn Tables. — As the labour of turning a tub on plates is considerable owing to the friction, revolving tables are substituted. Tliese consist of a circular frame and top plate, which, in its commonest form, runfi on four wheel rollers.
Tlie movement with the above is comparatively eaaj', but baa been rendered still more so by the employment of boll bearings. In Hudson's turu-tuble, a
.'ries of balls, j in. Fio. 205.
diam,, are an'anged in an
annular groove (?i. Fig. 205) and on this the tup plate, c, rests, being pivoted on u pin, a, in tlie centre. A very simple automatic catch lucks the ttbje in any desii'ed
Textbook Of Coaisuxisg.
At Lye Cross Pit, South Staffordshire, the line of nik tinted on the tile top an packed np in. at the end to remove the waggma, and a etop a tt eAed to yewn t the tabs mnniag over it, bat ae ananged that bj-digfat pteeaeie on a foot lerer die waggoee ate ideued. A standpast and lervr are ako attached to the otiter edge at the table, the fever being ananged to work the atch aad alK> paO the taUe nNUtd. Tbe adTantages aie, teee of tartamg, the antoaatie calth, and the fact that oa hibneatkn l e qnii ed; iinhm tmataUeB at the otdnar; wheel leUer tjpe ue wdl giieoeJ, the lafaoar of tttniBg the tnfae on theet m
TUBS. — Thegenenl &ieh|*Mliee tstOBakethebedj-nctanpiIar, and cena to act it eher ot weed, wiDOgfat-iiwi, or steel. This boafy leelB on a fa uu o ewk , geoenllf of wvod — ahnoet inariablj oak — or MetieK of iron. To th faameaie attichtd tlw pedertah forcing the beatings for the axles of the wheris.
— If wood is emplojed in the body it nny be tim, haA tw fBflar. The latter is the ebeapwt and —' nost OBDnnliaJ, bat dm seens pivfenble, as ite wearing capacity ia groat. Ue advantages of woods tabs are their low first coot and the hb with wUcaalliepaiis are Msda; llxii itinaitiinlagii in llwihipi aumnft fi leoaiis j Thejr ate nsnalty ujusti acted eottii tbeadeand end boards to the le qni red ieiths, patting an angle-pieee of sheet-iton at ead comer, and holtii the buaifc bit. The bolte iooU have katf-nnd hoHb paced on the ooiaide of the tab. with the nats inaide.
Wtoaght-ifonudstedbadieiaiekigfypb;ed; with Oe latter metal the wit is les$, bat conoaon is br tofitd than w&h wroaghtitai. Vith teetangoler tabs the hodf is genenlfy made of three plates, two Conning the ades and ak and the ethothe bottom. The latter shoaU ahnTS be iMde ltij'
iiin lij miNiiil ihiiiaii iiilii llm liib nea the bottom and sides is made with angle-inm, which ihonU have oneqaal ndoK, say 3 in. bj 2 in., the to ee aide being played TeetiallT. Bydoti pcvriBtadat the point whete the angle-inm aids. A small qaantitj fina coal eoBe cts in thevners,getewet and rots the (late. If the ane-iran is made so high that this fmaDaccamalabandoca not teach ahoee it the
A band of iat sti steci imm toond the tcfi of tike My. aad the joint should always be nmde al one of the ends, aercr at tke . Rirata sontetimes eoaie oat, and the end ef the bond prajacte. If the joint be made at the ade eerioos injaij any he ieaBn, ti*te bare snap heads pJsBcd oatmdt, e down on the inside.
tana of tab empknvd on the Continent is sfaaorn in
JiH.
ini=
Fig. zo6. The advantage of this special shape, is that tlie carrying capacity is increased without increasing tlie height, for, by bending ia the sides at the bottom, practically a distance equal to half Via. 206.
the diameter of the wheels is added to the body of the tub, and yet the total height above the rails remains the same. With the Continental thin Beams this is importajit, although, of course, the cost of manufacture must be considerably more than an ordinary rectangular-bodied tub. With this constnietioii equilibrium is very stable, as the centre of gravity is low. They are made entirely of steel, the ouly wood employed beingthe buffers, which are situated at each end, and run right across the plate. In general, seven plates are used in
the manufacture, two on each side, one at each end, and one in the bottom. The side plates are riveted together, and the end plates secured to the side and bottom ones by angle steel. The frames or Eeet are channel steel (the jtedestols lying in the grooves), and are bolted to the bottom plate.
Pranoes,— The body i-ests on a frame, either of wood or iron. The forinei' consists of two longitudiuni pieces rtmning the entire length, and either connected by two cross baulks, or by two iron strips. These bearers pi-object past the body and form buffers, which shoidd be lined up with the object of preventing those on two Gucceetiive tubs getting interlocked when passing round curves, as, if they do, derailment inevitably ensues. The buffer end is geDernlly widened out by adding on the inside two pieces of wood and placing a Via. 207.
wrought-iron hoop around, but the better practice is to employ a cust-steel or malleable cast-iron shoe (Fig. 207).
A still better plan in to use iron frames ; they coat 11 little more, but wear better, and are a little tighter. Here the buffers are formed by a strip of wood running aci-oss the end of the tub, and cross-buffering n 209 show a tub body and irau fj-ameworlt e Pit, South Staffordshii*.
Height. — The height of a tub is governed by the thickness of a seiim, but they should not be too deep, or the breakage of coal is great. In low seams, if the tub be decreased in height and the space between it and the roof increased, there is neither the incentive nor the necessity to break the coals to get them into the
Figs. 208 and mployed at fell End
Tjixt-Book Of Coal-Mining.
tiib. To remove the neoeBatj altogether, one end of the tub is frequently made hinged, or loose, when the ooal does not have to be lifted over the top at all.
Sise. — The only advantage of large tubs (canying 20 to 30 ewt.) is that the useful weight (load) is large compared with the weight of the tub. The disisulvantages are, they ore awkward to move about, requiring large horses to haul them, and when derailed, several men are required to get them on again. The latter objection can be removed to a certain extent by the employment of small hydraulic lifting jacks, which can be readily carried about. The best size, perhaps, is one carrying from 12 to 14 cwt.; they are easy to handle, capable of being put on the rails by one man, and with any ordinary gradient can be moved by a pony.
Wheels and Axles. — Wheels may be constructed of cast-iron, cast-steel, or forged steel, the former being rarely employed.* Their
t
i:
Figs. 208 asd 209.
xr
Df
size should be as large as possible, with a view of reducing friction. The height of the roadways governs the diameter of the wheel where rectangular-bodied tubs are used, but by adopting the Continental form already referred to, a large wheel can be employed in a thin
seam.
An improvement of considerable value has been the introduction of £yre's solid forged steel wheels, which are perfectly weldless, bosses, body, and rim, being forged out of a single steel bloom. For the same strength as cast-steel wheels they can be made much lighter, may be either fast or loose on the axle, wear very well, and are practically unbreakable.
At the present time, axles are made of ordinary round bar steel, which is rolled to such perfection that it requires no turning. While the diameter should be as small as possible to reduce friction, strength is of far more importance. Weak axles are a constant source of loss.
This remark applies to ordinary casting. Chilled cast-iron wheels are used at many collieries with marked success.
r
Haulage. 1 85
Two entirely different methocfe are used for coDnecting wbeelii tuid axles. In one case, the wheels are loose and turn freely oa the axle, in the other, they ore 111101/ fixed on the axle, and both are forced to revolve in tlm same direction with the same velocity. The looe wheel and nxle are eniployed on Tehiclen travelling on ordinary roads, which are verjuneven and where motion takes place in anything but straight lines, and as the roads in older collieries nearly approximated to theee conditions, loaee wheels were at one time Inrgely employed on underground rHilways. Their advantage, and the only nne they posseas, in the small resistance they offer in pang round curves. Naturally a wheel on the outside rail passes o\-er more ground than one oa the inside, and if both wheels have to travel at the same velocity, a grinding action )>etween them and the rails must be set up.
At the present tune, collier roads more nearly approximate to surface railways, and as a i-esult, wheels fast on the axles are becoming more and more employed. On the stnught, there is less friction than with loose wheels. Their great advantage is their absolute trueness of gauge. Loose wheel-- are kept on the axles by cotters, and washers have to be placed against these to prevent excessive weaj-. No matter how carefully they are looked after the gauge is scarcely ever correct, and the cost of repairs to looee wheels, if cotters and washers are included, is much greater than with fart wheels.
IlTawbars. — Tnb are MniiMd together throug'h dnwbaH, which are preferably riveted to the bottom of the tub. Indeed, the connection between iron and iron should always, wherever possible, be made by rivetji ; if Iwlts are used, sooner or later they work loose. In the construction of tulis, two points should be observed ; strong dranbani and strong axles. Notliing is gained by making either too weak, and one breakage will minimise all the gain resulting from the decreased first cont.
Where tube nm in sets, drawbam, similar tboee used on railway waggons, are employed : the coupling chains are always attached, and ready connection can be made. With some haulage clips, links on drawbars cannot be used ; in such <ases, a (Hece at flat steel is used with a hole through each end.
FedeataU — Two types are employed, one for loose wreck, the other for fast ones. The
genera] desifu of the for- Fioa. xio aso an.
mer is shown in Figs. 210 and 21 1. With fat wheel*, as the axle cannot be threaded I through a hole in the pedestal, the bottom part of the casting is omitted, and a wrought-iron guard-strap passed around. To allow of automatic lubrication this strap is bent 00 one side and leaves the under part of the axle exposed (Elg. 112).
Text-Book Of Ooal-Mixisg.
Tt) weight, the are best mde of ae will be noticed, sre cond out whererer poebl.
LabricBtion. — A great deal depends on efficient lubncatiou. which with loose is nearly imposiUe, except at great cost. With them, the tub ha to be turned orer asd liquid oil poured into the bearings. This not only means eoDfidcfable labour cost, but the waste of oil is great.
In some cafie. the tubs are nm over a pit full of oU, and in doing so depress a pietou. which shooUt np a jet of oil on to each bearing. Al! the waste drops baf k again.
Numerous fomu of self-oiling wheels and pedttals ha¥e been designed, the majority of which have have bein described by Mr. Emerson Bainbridge,* bat none of them are sattsfactor; in practise. So long as they are new and ju loidced after by tlie oCcwla, good
Fio.
Fic. 113.
results are obtained, but the rough work of oollieries is unsuited to delicate appliances.
A recent improvement of the Hardy Ick Co. shows promise. The top part of the pedestal (a, Fig. 113) is of thn ordinary type-, but underneath a steel dish, stamped out ot ane> sheet of metal, is fitted, this (he axle in position, and at the same time preventing any du!<t or dirt getting into tJie bearing. This 8tel dish, h, is shaped to bold a piece of hair-felt, which is soaked in ml. A considerable number are in use at Xnnnery Colliery, and it is stated that one application of lubricant every two or three weeks is sufficient, while a fresh piec of felt is required about every live weeks.
For wheels fast on the axle, by tr the greater numtier of lubricators consist of revolving crashes, or star diacK, which supply I small iiuantity of oil to the hearing as the tubs pass by. Brushes eoon wenr out, and for such reaaon the latter arrangement is preferable. Two wheels, one for each hearing, are placed in a semidi-ctilar trough, and are generally arranged both to rsTotve and tiarel forward a short distance. They are seated
N. B. I. XXT. 315 : sxrii. S.
Haulage. 1S7
on springs, and fad thus acconinioikte themselves to varying heights of the axle.
The adv-aotage of this class of greauiers is that they caii be put. dowD anywhere, and are qutt automatic. In a long haulage plane, they can be placed at intervals whei-e necessary, nnd considerably reduce both the power required and the cost of lubrication.
In the paper before refeiTed to, Mr. Bainbridge states the cost of greafing tubs at eighteen different collieries, varied from 0.075 per ton raised. Oil gave the worst results, no doubt owing to the quantity of wai. With grease and corrugated week, the co.>it raried from 0.075 o.aSgrf. per ton. It will be noticed that tbtH result in over one halfpenny less than the maximum, and shows that some efficient method is very desirable. A low cost may, however, mean that the tubs are btuUy lubricated.
Haulage by Horsea. — Even where mechanical haulage is used on main roads, horses have to be employed to bring the produce from the working places. They are connected to the tults, either through the medium of a pair of shafts, or a tail-chain joined to a stretch-bar, to which two side traces are Ettch of these systems has its advantages. With downhill gradienLi a horse cannot hold back the loud when connected to it by a chain, and, therefore, to prevent the tub running away and overtaking the horse, the wheels have to be " lockered," which is dono by pushing a short bar of iron through the spokes, and preventing the wheels turning. This is very objectionable, especially on undulating gradients, and causes considerable wear and teai-. Shafts are dangerous to horses, as they catch the and hamper movement, particularly so in narrow and heaiHlytimbered roads ; they also prevent the liorse getting out of the way of the moving ti'ain of tubs if the weight overpowers thp animal. Up bill thei'e is no difiereuce between chains and shafu.
Ferdinif. — The chief item of cost in horse haulage is that lUie to feeding, as not only may an excessive charge be incurred, but the condition of the animals may be so reduced as to unlit them for pei-forming the maximum amount of work. The problem is to keep them in the best condition at a minimum c-osi, which oin easily be done by a proper selection and mixing of food. It may bo stated that, however concentrated nutritious elements are obtained, small quantities never aiibrd eatisf action, as hunger is not appeared until the stomach is filled, and, ti~ fore, in addition ti) foods supplying waste of tissue (onto Ac.), gome bidkier body has to be given. This is ib" bay and straw are found in the feed.
Some prefer to give hay in its uncut state, t where the horse may nibble at it as it prefera, 1
up with straw into the state of chat)' and mj
TEXT-BOOK OF COAL-MDs'ING.
The latter jirocedure eeems beet, llorses going out of the workiogR into the etAble are hung-, atitl bolt their food. If the Oiangeicontains hard com only, this being small in bulk, ja rapidly consumed, pa&ses into the stomach without being properly masticated, &nd the animal does not obtain the nourisbnient it should do. Hay is then attacked, and, being in its natural state, baa to be piled from the rack, pieces are droppeil on the floor, tr4uipled under fooi and lost, thereby occasioning waste. On the other hand, if bay and straw be ciit up and mixed with the hard com, the uianger contains an increased ; then, if the borae takes its food voraciously, the iirst pangs of hunger are aoon appeased, the remoiniler is consumed in a leisurely manner, and the full benefits of the nutritious matter are obtained. In addition, waste is minimised with propei'ly constructed mangerK.
Regarded from the standpoint of cost compared with benefit, ' bran is ijuite out of place as a food. Its chief use is as an appetiser, and foritii corrective aud laxative projierties. Sometimes it is given as a mash at week ends, when a horse has to stand in the stable all the next day, while others mix a small quantity with each feed. As it seems preferable avoid extremes with such ' regular bodies as those of colliery horses, the latter course is generally adopted.
Respecting the different varieties and mixtures of hard com, every one interested in the munBgement of colliery horses should i-efer to a paper by Mr. C. Hunting," in which the cotiatituenU of various foods are fully described, and the whole question gone into. It was long considei-ed that onts alone were sufficient. yir. Hunting points out that this is correct to a certain extent, ns they contain more proportionate quantities of nutritious elementA, ' but for very hard work, such as underground hoi'ses have to do, tlie consumption of muscle is far in e.Ycess of the waste of any other tissue, and food containing a heavy proportion of nitrogenous or flesh-forming material must be given. If the choice were limited to one article, oats are superior, but an equal weight of a proper mixture of beans and maize gives better results than oats alone ; bot.ter in a double sense, because not only is its , fleiih-formiug capacity greater, but it is considerably cheaper. Peas are often used as a substitute for beans, as they run a little ' cheaper, but are very heating, and should only be used with care,
Mr. Hunting strongly advocates the use of a mixture of green food during a short time in the summer, but some discretion is in its administration. Under no circumstances should it Ije sent down the pit when soaked with rain. It should not be allowed in-bye, where a tired horse may gorge itself when waiting I at a aiding.
A horse's stomach is i-relatively small compai-ed n-ith its bulk, j
Haulage.
.Sy
m that it cannot i-etaiu sufficient food to maintain the iiniinal futlong intervaU. Mangei-s sliotiUt therefore be estahliBheil at the adding to which the horses tmvel, so that tliey can eut small quantities while waiting there.
Coat of feeding. — At a colliery where the hoi-ses ai-e on iin avemge 15 hands high and So in number, the cost of feeding during the years 1885-1892 haR varied from a maximum of 12.25*. yer horse per week to a minimum of 8.G6., the avemge for the whole of the time being 10*. s.Sgirf. Twosamplea of feed are given below : —
Lb.. piTdlJ.
Lh..pnJv.
Beans
Muzg
OUs
Hay.
Clover
O.S49
Straw
S-?S9
I'otul
Cost and Life of Hortea. — Figures I'elating to the purchase of horses at the eami> colliery for a period of thirteen years give the average cost of each one an 1 4*. The average life for the some period practically amounts to about eight yean), but the percentage of deaths from accidents to horses employed being i-amber large — 6. 19S— during the last six years, the life may better be taken at nine years, which is the figure given by Mr. Hunting in the paper ah-eady referred to, where the life of horiies, on an average at twelve colherics, amounted to that length of time. Mi-. Hunting gives the average number of each year for twenty-one years: hoi-ses, 4.70 ; ponies, B per cent. of Corn CuUiri'j and Ostlers. — At the colliery under notice,
(YeedB are all prepai-ed and mixed at bank by two men, and the
TSt per hoi-se |jer week equals e.zijGd. Two men ai* employed cleaning and attending the hoi-ses down the pit, both on the day and night shifts, and during the daj-time one of the men goes round the different parts of the pit and sees that the horses are supplied with corn and water, while the other cleans out stables, kc. The cost per horse per week is is. 9,5 id.
Shoeing. — With pit horses rough shoeing is done, old scrap iron being used up in many cases, but against this has to be set the trouble and time the blacksmith is put to in going into the workings, often a considerable dbtance, when a horse casts a shoe. The average charge may be taken as dd. per horse per week. In two most interesting papers by Mr. J. A. Longden* the Sliot'w'j of FU //orsH, Urit. .ScK.-. Jlin. Stud. iv. 104; Ches. In9t.i1.373.
following directions are given: Kever pare the sole or frog, and only cut enough of the hcam oS a.t the lower end of the hoof to allow the shoe to bed properly ; above all, reduce the weight of the shoe to the lowest possible point, and do not employ "calkins" on either heels or toes. Three nail on the outside and two on the inside are quite enough for the fore-feet, and they should never be placed near the heels. He gives the ,caHt of shoeing ponies at Clay Cross and Blackwell Ctdlieries, Derbyshire, at 3.23d. per horse per week.
Taking the average of many years, the total cost incurred for each horse per week is as follows :
Keep 10 3.891
Repaire to harness o 2.53S
Cutting ajid preparing feed . . . . o 5.296
Oatlera ' 9.153
Brushes and carrrcombs . . . . o 0.218 Veterinary scion and medicine . . . o 3.058 Shoeing o 6.000
'3 S'64
Arrangement 0/ Stables. — Pure water and plenty of ventilation are essential. The stables at Lye Ctogb Pit are shown in Figs.
314 and 215. Each horse has a stall 7 ft. long by 6 ft. wide, and a corn manger made with specially shaped bricks, 4 ft. long. A water bosh is placed between each two stalls, and a 3 in. mainpipe with down branch pipes delivers water to each bosh, which has a hole and plug in the bottom to allow of easy emptying.
The stables at Eppleton Pit are most elaborate. Each pony Stands in a distinct arch, 5 ft. 6 in. wide by 6 ft. long, the brickwork between each stall being 18 in. thick. A passage is provided behind the mangers with communications to each stall, which the horse's food is introduced, thereby not only facilitating
cast out of furrdct iiai£. til sni Li Hi'-'-Tiir-iic - ia~ s.#i T-r-tatL-T
each stJiIL wLm. ±. r:* mrs. iz.. -.iir -n:* luajuiHi —
down into altar 'ejstL Lrii. .r: ir vuin :n-::i!iL .c
bricks. Wser zrrrjL zt-.n pr.nfei -sui:! r.i" " y, iLrj one is pUcei it ra"" t-r-ii zt&Lr -te.tjtlzi:**. TTit iticjs* drink on ccir rCTrr v. tzii -tir: zr-.ci -.it* :ii :urr-.
life, there car. be =i: w.c:: :c -f':c:l:cl7 .c i-iiiLUj'i jiul-. with. At y;k" *xZieras. stciL .'""it t-jh _L':r!r-s: lji-: itkeep is so akrse ari ":Lit .".-i' irsL": -fiij. fr';t " "Liik: haolage cooLpkK? r.'>c £tT-.ii:r_--i.j "v-jii z:**iis:;LZJi2L. ziraz. -zisciallv where tij? rn.ii=c_-* t?* zz, zl' :c -j.t j.il.L ±z. iz--c-kr.:ir
of this ia. E:T.r*l CJ yjT J l-'-n.LZ,* -l-r S.i-T". .r '--g'
4407 ton* az. xTtsTkjp: L*rjLZjvt :c : ji*. T4.r -u* '" :rr Mc>, :r 4.4dL per toe per
Upon the r*vani:cr?iii: :r: zrhLr- v j-.h-: TJLr -;j3:>?>*i :r -.ri-rTwiae of hor*e ZAzliL -tcTLTij :t*e-i.'Lr. it'--t-l r:is.i-. :r the inclina&:*i ie ?.':z"7 r, "iitT aiLirij.- :r zz-J, Tr.ri pe:- formcri by a iorae ia *gri..- r-? :i:c*.'< m -„:;t* *.-.rrr -.Lt :i:i.-iitions are nrrngfL iJiii ":.ia rrbiirr". lti -i-r Ija-L Lj-r
the remainfaz -c ri- -j-r i". 4:1 LiA:l i:i .r. .: : ir. :2. its: horses are ecDi o'S'ri: v. Jiii,-.! rjL -Jiir ;-.-Vii..->7. r-i-.jL 'l- "Axbz 42 jonmey- a 'iij. vtjL :--"ji-.e ".riTr..-: f r i:.:!:?. Ti.r: load of cfaL: taicr: -sw.;! "irr ir v,:- ' ..'.r -.-r-u. -TT-r*:* c: ej-iL
horse for this -l-.- '.rr. .n-r V,- '.l 2 ZLl',r — Lilf
the distance :ri.Trrllri:. T--t TAi-r ' — r'iiirrlT - ::.iii:-x tL.e foregoing;? ct i; 2cc /"i* l-cj:. i:. : z-~i:/:::::t.-/ .rr!. Li-rse serves this iistAiJce. -Af i: .-ri.-TVr -e? :.iV. -.rivrll::: .77 tons led 2.;i niilr-. .r rs v-r-- .-rti : iii-r. A ->::*:itr ill"i=*rition isaifop!*ii r-Ti:--r.',rf: -v.::r. ':.'Tr i i r-r: rijicej 5? iiit.t* per iav. travels .75 l'. 1 .fe.: 0: -.r. i-.'l sri bet:.-' 7 mcl*. The a.<*efal effe"- r.-.rr - :'::..- 2 77 iil-rs. cc i:.*:* toe* led I mile. At '.rJ.- 1;:. v.-.:: -.l-.r v-nv-r :i-*-;r..>r ..is. wi> led bv Lor-efe -ari,- tc r - . r ::r Tii -er-il to a cost per mi. ter l.:.* ,: :r : -T/.r:. :ir aTrij iistinoe
TEXT nOOK OF COAL-MINISG.
of time they bet-ome worthless, and the cost of uji-keeii mntur. A little consi deration will expliiiti the i gmdienta have such influence in haulage on lailn, I thftu in surface work with ordinary carta. With well lubricated bearings and wheelH on mile, the resistance to motion is slight, and a horse easily moves heavy loads under favourable circumstances. Down-hill gradients are therefore favourable to u good perfonnance of useful effect., hut where the inclination is against the load, the small i-resistance is against Itu'ge weights being moved, as the load ha a greater tendency to run bade than if the surfatM on which it rolls was rough liie an ordinary road. In the former case, the friction is so smiill that the horse has practically to contend with the full weight of the load divided by the gradient, while in the latter, the greater friction reduces the stain. Mechanical haulage therefore becomes a nocesdity with heavy gradients, as even where tbee are in favour of the toad, the strain of returning the empties becomes so great that the advantage gained with the load is nullided.
SELF ACTIITQ INGLIITES.— With miue liaving the necessary inclination, gravity sujipliea the motive power for the haulage, and self-acting inclines, or jig brows, are employed, the principle of which is that the loaded tubs running donii-hill will haul the empty tubs up. A certain gradient is necessary, as the weight of the full set has to overcome the friction of the two sets, the drum and rollers, plm the weight of the empty Bet and rope; the latter ia variable and greatest ut the start. Koughly speaking, a gradient of i in 36 is required with wheels and axles of ordinary size ; but the length of the road plays an important part, owing to the greater weight of the rope, therefore, or the plane gets longer, the gradient must also increase, to overcome the increased resistance. A flat paii has to be provided, both at the top and the bottom, to make up the sets, and it is advisable that the gradient at the top of the incline ahould be greater than it is at the bottom, as the set then easily gets into motion.
Arrangement of Hails. — Nothing gives better results than two lines of rails completely from the top to the bottom, which ia only poasible when the roof is sufficiently gooil to allow of a double way being kept. If it will not stand such a width, tbi'ee rails are carried up, with four in the middle where the tubs pass each other. These are the common arrangements, but rails may be arranged in many different ways.
Where the roof is so bad that a double road cannot be made, even in the middle, two lines of I'uils are used, one inside the other. The tubs run on the outer line, and haul up a dead weight travelling on the inner gauge. At the point of meeting, the rails of the outer gauge are raised up and those of the inner depressed, and the dead weight passes underneath the tubs. The weight of the balance must be less than that of the full set, but more than
that of the e
Haulage.
The working cac
'95
alwaj's made at the
Fio. a
e empty one. The working capacity of such au ai'mtigement is one-half that of a i-oad laid with a double liiie of railti. For inclineK where intermediate landings are worked, thia ariimgemeat gives excellent results, and in many cases, under such eondttious, an much mineral can be jigged down with this system by any other.
In litall roadti going into the working plate, the common practice in steep mines is to make a full set going down uue i-oatl haul up the empty set in the nest adjoining roadway. Where the inclination is great (above 35 ) the tut have to be placed on special carriages to thi-ow the coal into a horizontal portion. If this were not done the load would be emptied as it passed down the incline.
Blooks or Stops. — Arrangements 1 top of inclines to prevent the tubs prematurely running down befoi-e the set is made up. The common form of blocks is shown in Fig. 316, but whei'e the inclination is steep, the top part, a, is across the whole width of the rails, and the two wheels of the tub against it. If the sets are always jigged on the same side a balance block can be used (see Fig. 237). Mr. A. E. Sawyer" describee a good block rt arrangement which ia opened and ' '" shut by hand at a distance, the working of which will be easily imderslood fi'om Figs. 217 and
Drums and Pulleys. — In permanent situations, and on long inclines, drums similar' to those on winding engines are fa.ste&ed on a shaft, the empty rope coil- '-'
tng on one and the full rope on
the other. A brake has to be provided to retard the descent, and to keep the velocity from getting too great. These drums occupy a coiiBiderable amount of room, and in confined situations pulleys become necessary. These may either be fixed on a vertical or horizontal axis, and may be made for working with a chain or rope. Chains are very convenient ; they can be easily added to, if the plane lengthens, or are shortened with equal ease. They can also be transported much tier than wire ropes, but they are
Text-Book Of Coal-Wining.
heavier, mora liable ta breakage, iind require & steep nation, owing to the greater friction. If ropea are t either a clip, or a C pulley ivith aeveral coils on it (see p. 207) may he uiied, while for chains, the throat of the pulley may either be fitted with Y gripe or feet, and in the latter case several tuma are parsed round it. For fia, aig, short inclines, with only
one or two tubs jigged at a time, hdihII hand jigwheels are employed (Fig. [19), which can be readily ' moved about from place to place, aod are usually secured to a prop. Brakes.— All-round onflM are prefer'able on email wheels, the brake - ring being of cast-iron, and the strap of wrought-iron, Some material, such as a wooden curb, should be placed between; in the smaller wheels, a lining of hemp rope, attached to the brake-strap by bohs, gives excellent results, but care should be taken to counter-sink all the pin-heads.
Mr. Malissard Taza describe.4 an ingenious fan-brake on a selfacting incline plane at Bilbao," which consists of four radial blades, about ft. wide by 16J ft. diam., two band-bi-akw beiog also provided for safety. The fan-brake works slowly at first aa the tubs move away, gradually increasing in speed until the journey attains the rate of 10 ft. per sec., after which motion is uniform, owing to the resistance of the air. The advantages are : absence of continuous friction of brake-strap, with wear and tear, uniform velocity, speed capable of any regulation and variation by addition to, or removed from, the arms of the fan, and less attention while the journey is running, none being required except on the arrival of the waggons at the top of the incline.
Hollers. — In every system of haulage small rollers should be placed at intervals, to keep the ropes and chains from dragging on the ground, as, if they do, not only is the resistance to be overcome much greater, but wear is rapid. The rollers employed are small cylinders on a spindle, and may be either consti'ucted of cast-iron, steel, or wood. Caft-iron ones possess no advantages, and rapidly wear out. For surface and exposed situations, wood is not to be recommended, as it cracks and split under climatic influences. Underground, the same objection does not hold good, and wood is often employed, it being contended that it is better that the rope should weaithe roller than the roller wear the rope ; the latter may happen if steel of a hard nature is employed.
Haulage.
"9S
Junotions. — In steep mines, where intermediate hanging-on places ai's worked, the continuity of the raila him to be interrupted (It such, places. The branch roads pass dwfty level, or nearly so, and at the joining place an iran plate is laid, which is bridged over by rails that can be lifted in and out of position (Fig. 2IO).
The alteration in length of the jigging-rope is either obtained by adding on a. piece of chain provided with large links opposite
each intermediate liuiding,* or by employing u number of short pieces of chain, which lie at the side of the jig when not in use. Each length ts provided with one piece, which can be joined either by shackle connection or by a specially shaped pair of links t (Figs- 221 and 321).
TrftQSmiSBioti of Power. — One of the firat <|ii6fitions to be considered in mechanical haulage is that of the position of the engines.
(let) They may be placod underground, and the steam genernted there also.
The objections to placing boilers underground are the great danger of the fires igniting 6re-dainp, or the coal in proximity to the boilers or flues, and the insecure foundation affordeil by the general i-un of strata.
(2nd) The engines may be placed underground, and steam jnerated at the surface and conveyed down the shaft to them.
This practice has, in some few institnces, caused lires, by the smail coal which accumulates on the pipes becoming so heated as to burst into dame. A loss, which increases with the depth and the presence of water in the shaft, results by the radiation of heat from the steam-pipes, however well they may be coated with non-conducting composition. In some instances the loea may tach from 8 lbs. to 15 lbs, of steam pressure, whUe better results
I m Mixo, A. R. Sawjfp '
J, p, 162.
ig6
TEXT-BOOK OF COAL-MINiyC.
show Dot more than 4 lbs. or 5 Ibe. Putting aside the incoiire nience of using steam, if it can be cheaply generated — as, foot iDBtance. by the want* heat from coke ovena — a good perfoimanco of useful effect is given.
At Bi-oomhill Colliery, Northmnberland," steam is conveyed to a pomp 1414 yds. fi-om the boilei's at bank. All pipes art. coated with a non-conducting composition: the loss by condensation is 21.06 jwr cent. The pressure at the pump is 13 lbs, below that ill the boiler at hiink.
Mr. Baure f states that experiments at Bezenet CoUieiy. France, with an engine situated underground, 1 200 ft. away froni tlie boilers, with pipes about 3 j in. diaui,, showed a loss of tS per cent. Two received's were placed in the length of pipes, one at the top of the pit {206 ft. from the engine), and the other at a further distance of 984 ft.
In carrying steam large distances, the pipes should be covered
with a non-conducting composition, and rest on sup-
Tio.jiij. ports fitted with a roller (Pig. 223), so that they can
move ely to and fro. Stufling-box expansion jointB
should be used thivnghout, at intervals of from 40
to 50 yds. Tlie seci'et of the success of transmission,
seems to be due to providing two fixed points in
eitcli length of pipe, and forcing expansion to take
place equally in both directions. In horizontal lengths,
tbu pipes are oljimped half-way lietveen two espansion
jointtt, but where they are on an incline, the
fixed points are placed near-er the lower end. In
addition, steam should never be turned out of the pipes. With
these precautions little difficulty is experienced from expansion.
but the greatest nuisance it getting rid of the condensed wattir, for alt bough steam traps, or sepamtors, may be placed in the range, they only colkcl water out of the pipes, and it has to be still discharged into the roadways. The recent invention of what is called the " steam loop" promises to entirely remove the above complaint.
At Elemore Colliery, Durham, where the length of the column is 224 yds., expansion joints are entirely dispensed with ia the shaft. The arrangement at the surface is shown in perspective In Fig. Z24, the part mai'ked A being a knuckle-piece, the pipe going
N.B.l. XKiv. 159; xixvi. [J. t Soc. Imi. Mia. (z- Strie), \iv. 297.
Haulaoe.
through two I'ight angle bends. Tho dotted line represents a chain passing over wheels, holding a block of met&l weighing about lo cwt., which checks the too sudden fall of the pipes in the shaft during contraction. The horizontal length of pipes in the drift is 40 ft., calculated to allow for a movement or spring of from II to 12 in., which is the greatest amount of expaJiBion when carrying steam. At every third pipe (each g ft, long) in the shaft, support girdei-s are fixed below the lliuige to allow one foot of lilide. If it were not for these, the pipe column would bulge on The column of pipes is free to move in a vertical dii-ection, and the whole weight ia Kuppofted by 11 pair of larger girders fixed at the Main seam level. The advantages of the iimingement ai-e, that expansion joints are completely done away with, and the trouble attending them, OS, for iiistani.-e, the leakage of steam, which seriously affects the roof and sides of the mine. This is most noticeable at the beginning of the week, when steam is beuig got up, and when, owing to coatiiict ion, steam finds vent at the expansion joints (where such are in use) imtil the column in thoroughly heated again.
(3rd) The haulage engine may be placed on the surface, and the ropes carried down the shaft.
This is the practice most in favour, and is unquestionably the best. With any uiethod of haulage, whei-e the i-ojie travels at high speeds, and in continuous from the engines to the end of the plane, pei'haps the ailvantages are not so apparent. Kopee working in the roadways of mines ai-e apt to get injiu'ed. and are more liable to bi-eak in tlie shaft and cause damage; but with any of the slow speed endless rope systems, where the shaft rope is only used to transmit power from the surface to a series of pulleys situated near the pit bottom, and is not lialile to injury or breakage, moat satisfactory results are obtained. It adds the wear and tear of another rope to the expense, but such a rope can be placed in position in a very short length of time, compered with tliat necessary to tis pijies, either for steam or compressed air. Tlie cost of excavation for engine-houses underground is always moi-e than on the surface, as the men work shorter hours and get more money.
Transmission of power with wii-e ropes for very long distances or circuitous routes is not to be recommended, the useful effect being small, and the wear and tear considerable.
ComjireMed Air. — Transmitting power by compressed air has fllreuily been described. The great advantage of employing this agent is that a certain quantity of pure air is delivered into the mine, which is practically of no benefit whatever, if it be done at or near the pit bottom, where main haulage engines are genendly placed. In cases, however, where enginea have to be worked at considerable distances away from the pit bottom, this method is very advantageous.
igS TEXT-BOOK OF COAL-MINING.
Etectrieiti/.—lhin subject has also twen considered. It I employment offers advantages for quick speed haulage at point* I ft long distance away from the shaft. The convenience ana eae with which it can be applied ai'e its chief recommendations. It ' is not too much to say that a man could lay a greater length of electrical mains in one day than he could pipes in a week. In non-fiery mines, no possible objection can be brought against this system, and by employing every safeguard possible, its use ould not lead to danger in any way.
Difibrent Syetems of Haulage. — Having decided on the I position of the engines, the different Bystms of haulage that are in use may now be considered. These may be divided into four heads : I
(a) Direct ffaitta/je, where the gradient of the road is sufficient to allow the empty tubs to run into the workings and to draw with them the haulage rope.
(t) Tail-rope Si/stem, where a second, or tail-rope, of lighter make has to be used to haul the empty tubs and the main rope into the workings, the gmdient not being sufficient.
(c) Kndlett Chain .Vystem, where an endless chain passes from Uie euginefl along one cade of the i-oad, round a pulley at the far end, and back again on the other side of the road to the haulage engines ; the empty tubs are attached to one-half of the chain, and the full ones to the other ; the former proceed towards the workings, and the latter towardit the shaft.
(rf) Endless Rojte System, the difference between this and the one last named that a rope is employed instead of a chain.
DZBECT AOTin'Q HA'DIiAQE.— This iiystem is employed for hauling out of workings to the deep of the pit bottom. It requires a single line of rails, and a gradient against the load sufficient to allow the empty tubs to run back themselves, to carry with them the rope, and to overcome the friction of the drum. As with other machinery, the engines should consult of a pair. Only one drum is retiuired, which should be capable of being thrown out of gear and of running loose on the return journey.
Sixe of Engines Bequired. —The number of tubs in a loaded train, or " set," is regulated by the size of the engines and by the pressure of the steam ; the size of the engines depends on the quantity of coal which has to hauled each day.
To illustrate the methofi of calculating the size of engines required, it will be best to awume some case. Resistance to traction is due to three causes — (i) Friction of axles on pedestals and wheels on mils, pi-oportiooul to weight; (i) Imperfections of road-laying — i.e., bad joints and crooked ways, proportional to weight and square of velocity ; (3) Resistance offered by air currents.
The former has by far the largest effect. With a well-lubrited
turned lude and large-sized wheel rolling on a smooth rail,
J
Hadlage. 199
friction is small, but colliery tub axles are generally rough, unturned ones, and can seldom be kept perfectly liibricat-ed ; it, therefore, is generally considered that an allowance of g'sth of the weight should be made for friction.
Let it be aasumed that 75 tons an hour have to be hauled up an incline 1 500 yds. long, Laving an average inclination of i in 20 ; that the tuba weigh 6 cwt. each, aud carry 1 3 cwt. of coal ; that the pressure of steam at the engines is 65 lbs.; and that the average speed of the is 8 miles an hour.
Eight miles 1 40S0 yards, so that the speed per min. 'Vy - - 234.6, and each journey takes 7 minutes, to travel one way. The time in and out will, therefore, be 14 minutes, and allowing 3 minutes at each end for chiuiging makes 20 minutes. Three journeys per hour should thus be got out; but there ai-e always delays, and it will be best to rely on, say, ai.
Ah 75 tons per hour have to be delivered, each set contains 30 Ions of coal, and as each tub holda 12 cwt, there will be 50 tuba in each journey. Fifty tubs weighing 6 cwt. each 1 5 tons, therefore the gi'OSs load is 30 15=45 tons; but as the incluiation is 1 in 20, the net load will be 2.35 tons=! 5040 lbs.
For this, a plough steel rope in. circumference, weighing lbs. per fathom, will be sufficient, and its total weight will be 750 " 7i 5437-5. say, 5440 lbs. The net load on the engine will be J- 277 lbs.
As the gross weight of the set is 45 tons, the reKistanee due to friction (taking this @ 3'gth) 1.5 tons, or 3360 lbs.; for the rope, frictional resistance ia iltz lbs.
The total load on the engine is, therefore :
Due to set . . . 5040 1
'"1* 277 t =SSwlbs Friction of set . . 3360 f "Se ">s.
If it be decided to have a drum 6 ft. diam. aud a pair of engines having a stroke of 3 ft,, as the pressure of steam is 65 lbs. the sLEe of the engines can he found by the rule ;
Area of cylinder (a) x pi'essure x twice the length of stroke load X cii'curaference of drum. In this caine :
6.3.i4i6.88S "- 6s X
which is the theoretical area of the two cylinders; to overcome internal resistance and friction of engine 35 % of this amount should be added — i.e., 147.83, so that the area of the two cylinders becomes 578.01, or each of them 389 aq. inches.
The diani. is, therefore : V.-Vbi' p'actually 1 9i inches ; or, to avoid being under power, say, a pair of 20 in. cyl. by 3 ft. stroke.
ioo TEXT-BOOK OP COAL-MINING.
The quantity of material a pair of engines of given dimensions will haul in a cei-tain time caii be easily determined by applying the converse i-essoning to the foregoing.
MAIN AND TAIL EOPE HAULAQE— In this method, a lighter rope, called a tail-rope, has to be employed to haul back the empty set from the shaft to the workings, such addition being caused either by the gradient being undulating, or not Ruffident to allow the tulw to rwn bick of themselves, f. 225 illuBtratea
t'm. 225.
the theory of the system. Two (drums are employed; on one, a, the main rope is coiled, und the other, 6, contains the tailrope, which passeH from it to the extreme of the plane round a pulley, e, is finally attached at the bock of the eet. As this rope only has to haul the empty tubs back again, its size is much less than the main rope, but it lius to be twice as long.
Devioea for throwing Drums In and Out of Qear. — Each drum on the engine is altei-nately thrown out of gear and allowed to I'un loo!<e, hut should be pi-ovided with a brake to prevent it travelling too fast and paying out slack rope. This can be accomplished in several different ways : either the drum may loose on the shaft and driven by clutches, oi' fixed to the shaft and a sliding-carriage employed, throwing them in and out of gear. If clutches are employed, they may be the same as those used for, and described under. endlesKrupe haulage. With drums running loose, und travelling at high speeds, wear is oonsiderahle, and they should be bushed with some metal, such as brass, which allows them to turn with little friction, and is capable of renewal. Allowance for wear should alxo be provided on the shaft, which has to he nicely turned. This arrangement possesses an advantage, inasmuch us both drums can be placed on the same shaft, while with a sliding carriage they must be on separate ones.
Sliding carriages ai-e genei-ajly ed by an arrangement of levers, even with compound levers a considerable amount of force is required. At Elemore Pit, the sliding carriaeB (Pig. 226) are moved by an endless screw gearing into a cog-wheel, on the same shaft of which is keyed an eccentric. with its link going to the carriage. As the screw is turned, the cog-wheel and shaft revolve; consequently, the eccentric draws its link forward, and pulls the sliding carriage out of gear.
Haulage. 201
Uetbods of Working Branofaes. — In branch, or sulxirdinate roads, H return pulley is necessary at the far end, and a. separate length of rope h required for such, both ends of which reach to the junction with the main road. Joints are pi-ovided in the main-roiid ropes, and the brunches are worked by diwconneeting poHions of the main-road ropes, and attaching the ropes of the branch road to them, connectionK being made by ordinary socket and Hhackles.
Three methods are adopted for changing the rope* under normal conditions ; such cases where the rope overhauls itself — that ia to aay, where it rtiDs in-bye without the aid of engine-power — are matters of detail, and do not a£fect the main systems. In two of these, the ropes are changed when the set is at the branch ; in the other, when it is at the pit shaft.
Pig. 337 illiistrateB one method of changing when the set is near the branch end. A shackle connection is provided in the tail-rope, and so arranged that it arrives opposite the branch at the same time as the set does — that is to say, it ought to do ; but
FiCIS. 227 AND 218,
here, as in every other method, it is found advisable to have a winch, with a chain and hook fixed at the way-end, to winch up the main rope to meet the branch rope, as it often happens that they do not quite face each other, which is not at all surprising, considering the great length of rope in use. The main road tailrope is then disconnected at the points a and b, and the shackles of the branch rope, a' and b', attached in their plac. As soon as the engine ha again, the empty set leaves the main road and goes into the branch one. A slightly difl'erent method is illustrated in Fig. ;i8, the changing also being made when the set is at the branch. The end a repeat-ea b, which is then brought on a little further by the engine and connected to i'. Here the tail-rope always remains entire.
In the other method, the ropes are changed when the set is at the shaft. Joints in the main rope ai-e so arranged that when the set is out-bye, all the shackles are opposite the different branches (Fig. 219). Suppose there me three bmnches. A, B and O, B lieijig ready for an empty set. The full set, which is standing at another branch end, say A, having been hauled to the shaft, A's branch rope ia disconnected from the main rope, and B's branch I'ope connected to it. The engine is then started and
Text-Book Of Coal-Mixing.
the empty set at the shaft hauled out stopping nt the bi-onch end.
n-bye into the branch B - Nothiug can be more aimple auij espettitious than this method. To facilitate matter and save time, if it be desired to bring a set out from C, the rope can be partially changed while A'a set is i-unning.
In the latter Gystem, no stop takes place from the stall to the completion of the journey, as the ropes are changed at the branch at the same time as they are at the shaft ; while ill the other two methods, a stop has to be made nt the branch end, or in ftU two stops are required, as the ropes have also to be changed at the shaft. Where time is an object, the advantages of the third method ate Belf-evi-
The rope is automatically disconnected from the set when it reaches the shaft either by a knock-oft' link (Fig. 230), oi' preferably by the arrangement shown
in Fig. 231. Afl drawn, the hauling rope which is attached to the short length of chain, a, will pull the set along, but at the detaching point at the out-bye or shaft end, a hori-across
the i-oad, catches the lever, 6, moves it backwards in the tUi-ection hoWn by the an-ow, lifts up the link, c, and detaches the set, which n to the shaft.
ENDLESS CHAIH".— This systom differs from the foregoing in the fact that a double line of rails is necessary; that a ch&in
inclined "
Haulage,
employeil tmveUing over the top of the tubs, and, an the name implies, is endless ; that the speed is small, not more than three miles au hour ; and that the tubs are attached singly at equidistant intervals, depending on the quantity recjtiired to be hauled.
Attaohment of Tubs,— Where the gradient is small, the weight of the chain resting od the tubs in Rufficient to drag their along, but for steeper inclination a Y-shaped fork, catching a link of the chain, la firmly riveted to the end of each tub {a, Kg. 206).
Driving Pulleys. — For giving motion to the chain, two different forms of pulley are adopted. In one, a Beriea of Y-shaped jaws, with the groove at the bottom just wide enough to take the link edgeways, are aiTauged at intervals around the circumference. The chain only posses half i-ound the pulley, the necessary grip being obtained by the links of the chain catching in the forks.
In thin system, as with the endless rope, it is alisolutely necessary for efficient working that Kmall guide (" leading-on ") pulleys should be just before the chain (rope) i-eaches the driving wheel, so that it may be accurately led on in the proper place.
Fig. 231.
;s. J34 ANO 2J5.
Instead of fixing forks in the throat of the pulley, a series of pieces of stjuare iron (a. Fig. 332) may be placed alternately on opposite sides. This iron is Itent back at the top to clip the rim, and at tbe other end poftses through a bole in the throat of the pulley and is secured on the underside by a nut.
With the ordinary form of fork, nu allowance is made for the lengthening of tbe links of the chain due to wear. When ever}-- thing is new they are at iwirect iiitervals, grip the chain, and prevent any sUp. With wear, the links lengthen, and do not properly lit the jaww. This inconvenience has been ovenome by an arrangement due to Mr, Briart, which consists of a series of Y- Bhaped grips of stel screwed into the periphery of the pulley (Fig. 353). As the links of the cliain lengthen, the gi'ips are unscrewed, so as to increase the distance between each, thus fitting the altered length of the links of the chain.
The better plan appears to be to use a senes of bloclcH of steel, called " feet," arranged at intervals around the circumference of the pulley, and coil the chain two or three times round to get the necessary grip. These feet are of an inverted cone shajie in section (Figs. 134 and 335), with the object of preventing the chain from
TEXT-BOOK OF COAIMINING. ! betw
climbing, and, owing to the i-eceee between each, the circumference of that part of the pulley on which the chain works is in plnii hke a polygon, preventing any possibility of slip. They also tuke any wear, effecting considerable economy from this source. They are secured to the throat of the piilley by bolts with coiintr-sunk heads, which may either pass through holes in the feet, or, preferably, through a ulit running down the centre, a£ the latter allows a little adjustment.
Taking up Slack. — It is just as essential endless chain as with endless rope that means should he provided for automatically taking up the slack produced by lengthening during wear. This is a point often neglected ; indeed, the common practice is to allow the chain to extend until it is only kept on the pulley with great difficulty, and then to cut out a piece. Far better results are given by any of the tension ai'rangements described under endless rope haulage.
Working Branches and Currea. — I'he chief advantage of the endless chain is the ea.se sniiill amount of labour with
which branches and curves tan be worked. With branches, all that has to be done is to arrange ii series of pulleys one above the other on a vertical shaft, each one working a chain. Even with the most regular output, the coming from uny branch is seldom the same as that from its neighbour, and liijidrances may often occur in any one of them. If all these pulleys are keyed on the upright shaft, the stoppage of one branch means the stoppage of all. To allow any of tbem to remain idle while the others are working, only one, and that the driving pulley, is keyed on the shaft ; the others are loose, and arranged to be thi-own in and out of gear by clutches, similar to those used in endless rope haulage.
When the tubs approach a junction or the dehvery end, they are easily detached by aiTanging a small guide pulley close to the roof, and passing the chain over it (Fig. 236). At this point the chain is lifted out of the fork on the tub, and detached without any manual labour, and if the rails ni'e aiTanged on a slope, the tub still continues moving under the iuHuence of gi-avity, passes under the upright pulleys, meets the ch!\in again further on, and automatically re-attaches iteelf. Curves are worked 011 the same principle ; the tubs detaching and attaching themselves, and
Haulage.
Os
gravitating i-ound the cui'ved poi'tioD- With an endless i-ope automatic detachment eiiu secured, but in only one form of clip can the tubs re-attach themselves.
Ueans ofUimmiBing Breakages. —Unfortunately breakages are common occurrences with the endless chain. The proverb ie quite tnie that u chain is not stronger than ite weakest link." The result of a breakage on a steep incline may be very disastrous, as the tubs run downhill, sweeping everything before them. To prevent this, it is usual to apply on the loaded road a balance-block arrange-fig. 237.
its journey each tub depresses the end. b, and pas.ses over the obstruction, but immediately they have gone by the block falls into the position shown, and stopH the tubs running back.
Wliere the inclination is not steep, the amtngement illusti'ated in Figs. 238 and 239 cnn be employed. In their normal position two blocks, a a, about pins at b. lie across the mil*, as shown in plan, but are pushed aside by the wheels of the tubs up a small greased plane, c, to descend again immediately the tulw have gone by, and bo block the ruad.
The chain is carried above the surface of the road on the tubs, that is, so long as it is entire ; if broken it trails on the ground. If, therefore, a series of Y-grips be arranged in the centre of the way, they do not catch the chain bo long as it is whole, but directly it breaks thev come into action and tirmlv hold it.
EKDLEBS BOFE HAUIjAQE : — Briving Appliances. — The methods employed for di'iving mny be divided into (n) clip pulleys ; {b) conical wheels ; (c) grooveil wheels.
(a) Clip Pidki/8. — The general construction of theee are that the rope is conducted into a groove, in which ai'e placed nlidtng jawB, which are pushed downwards, causing them to grip the rope firmly and prevent slipping. Tliey occupy little space, are convenient, side friction is entirely avoided, and as the rope only passes half round the pulley the bending action is not great.
A good form of clip pulley is Barraclough's. One side of the pulley is entirely sepai-ate from the other', connection being made by bolts, while any required distance between the two parts can be maintained by set pins, placed at intervals around the circumference. By such means, the pulley can be altered to accommodate any sUe of rope in a few minutes. All round the circumfer-
Text-Book Of Coal-Mining.
ence are a series of taper pockets opposite each other, inside which work two sliding jaws (n, Fig. 240), which are hollowed at the bottom and sides to receive the rope. Thei jaws are seated on springs, b. When the rope enters the piilley, the weight forces the jaws down the taper sides of the throat, and so narrows the distance between the jaws, causing them to grip the rope, while, as soon as the weight is taken off, the springs assist to release and I'believe the rope.
A pulley employed in Scotland, both for cable ti-always and mine haulage, is that shown in Fig. 141. The ordinary arms of the pulley terminate in a hoiizontal and vertical flange, a and b, to which are respectively bolted the taper throat rims, c and d, a.
Fig. 240,
piece of wood, e, being interposed between. It is stated that no injury whatever i.s caused the rope, and Mr. D. Ferguson gives some figures which seem to bear out that view.
It is, however, difficult to see how any cUp pulley can woi-k without flattening the rope ; their very principle of action is to grip or wedge the rope, and the greater the load, the greater the wedging. There are, of course, good and bad clip pulleys, and probably the latter predominate, at any rate, they are responsible for a great deal of prejudice. At a colliery with which the author is connected, one of the best known forms of chp pulley waa originally used for driving rope haulage, hut was removed and replaced by a taper C pulley. Considerably more than three fames the work is now being obtained from the driving ropes.
To avoid the flattening action, a pulley has been designed having a serpentine groove in the throat, and so long as this
' Min. last. Soot. rii. 145.
Haulage.
remains in the curved state, and does not wear alraiijhl, fair results are Raid to be obtained.
(6) C Pill/- — Toavoid the flattening of the rope, C pulleys are employed, which originally consisted of a pulley in the ahiipe of a C. around which the rope was coiled several times to give the necesBary grip and pi-event slipping. Here flattening is certainly avoided, but another disadvantage is introduced in Ihe shape of side friction. On their adoption, it was Found that the pulleys wore in rather a peculiar manner ; their dished form was hoou lost and the diameter of the coming-off side became less than tha going-on side. Seeing that the pulley wore in this way, it soon became the practice to construct them so, and now the great majority are made slightly conical, the diameter of the going-on side being largei' than the coming-off side.
The throat of the pulley is made parallel (Fig. 241), but loose wearing Begment8,o, are bolted in. These wearing segments save large sums of money. Apulleyeoatsfromis to jao, while the segments can be obtained for In addition, the segmenta
Fig. 14a.
can be changed in a short time and are easily handled ; pulley changing not only reijuirea far longer time, but considerably mot's men. Another point is that pulleys should always be purchased in halves; in such state they can be transported and got into place with half the expense they otherwise would. Loose wearing segments and pulleys in halves have materially reduced the cost of modern rope-haulage.
As to the amount of taper necessary, experience is the only guide, but the heavier the load the greater it must be. If properly proportioned these pulleys work very smoothly ; the rope practically does not sUp downwards, but follows a serpentine path from the time it goes on at the top until it comes off at the bottom. Side friction is, to a certain extent, avoided, as practically none exists between the successive coils, but where the rope leads on the puUey there is a small amount against the upper coil, which is an objection. Also, to obtain good results the speed must be rather slow ; practically, it would hardly be possible to go more than three miles an hour.
Je) Grooved PuUeyB. — In order to get rid of aide frictioa 1 prevent the slipping which token place on taper C pulleys.
ao8
TEXT-BOOK OF COAL-MINrNG.
a series of ijnrallel grooves are put in the main driving pulley, and a similar pulley with one groove less, placed Bome i distance away, the rope being wound from one to the other, each coil having a separate groove to work in. As each coil only passes half round the circumference, and as the second pulley is not a driver, but a follower, the rope has little grip, and consequently several grooves have to be employed on each pulley. To meet this objection, the rope is frequently taken from one pulley to the other in the form of the figure eo. but although thia reduces the number of coil, the rope is bent backwards and forwards, for it passes under and over the pulley. This not only injures it, but shortens its life, as compared with a rope always coiling round a wheel in the same dii-ection.
Another method to lessen the number of coils, is to drive both pulleys, which is the common procedure on cable tramways. No matter, however, whether both pulleys are driven, or whether one is a follower, they only work properly when the grooves are of equal diameters. When new, thi condition is possible, aa the pulleys can lie turned in a lathe. The gi'eatRt stain during working naturally conies on the first groove, which is therefore subjected to more wear than the second, while the latter also wears far more than the third, and so on. By such action the grooves not only increase in depth but do so unequally. From the time the rope piiisseB into the first groove, to the time it leaves the last one, no slipping can result. It is also evident that when the wear iu the grooves has progressed to such on extent as to make a difference in the diameters of the first and the last one, the speed of the rope is governed by that of the groove having the smallest diameter (the going-on side), and a point on the circumfei-ence of the largest groove will obnously travel faster than this. As it is impossible for the rope and part of the pulley to travel at different speeds, a grinding action between the pulley and the rope ia set up, and the latter rapidly wears out. To show the extent of the wear iu the grooves, it may be stated that after thi-ee years' wear, those ia the leading driim of a cable tiaiuway line measured respectively, a J in., ag in., 2 j in., 2l in., 3 in., and 4TTr in-
When the grooves ai-e fixed together as in oi-dinary pulleys, each groove tightens one coil of rope on the other, until when the last groove is reached, the strain amounts to so much that it has in actual cases sometimes broken the pulley, or in other's the rope.
For such reasons, instead of the second set of groovea being made in one solid pulley keyed fast to the sliaft, a number of separate pulleys running loose on a bearing are employed, thia being the form adopted at Lye Gross Fit. A pulley 7 ft. diam., having five grooves, is keyed on to the third motion shaft (a, Elga. 243 and 244), and four loose pulleys, 6, are threaded on a shaft 15 ft. away. The in-going rope, c, is led on to the underside of the first groove on pulley a, coils half round it, and passes on to the first
loose pulley at b. and then back again to the Becond gi'oove or pulley' a anil so ou, until it finally leaves the last groove on a ami passeij away ut d. By such meanH the wear on the dri\-ing rope if
reduced to a minimum, for the second Bet of loose pulleys can move at varying velocitieD, and go accommodate themselves to the difFei-ent speeds required by the unequally sized grooves of the solid driving wheel. The objection is, that as only one pulley is driven, a large number of grooves have to be employed where the load to be moved is a heavy one.
The Wider Diffei-eiitial Pulley, iidopted at Bell End Pit, completely gets over ftil
Briefly desttribed, it consists of |i-ic. 345,
a aeries of loose rings (a, Fig, 34S)> threaded on to an ordinary pniley, these rings lieing grooved to receive the rope. Both pulleys liave loose rings, and both are driven, the second pulley having one less groove than the first. The flange, d, on one aideof the pulley is removable, and secured in position by 11 aeries of bolts, e, indiornbber washers being provided at 9 and A to prevent the bolts becoming loose during working.
The peculiar [>oint appeal's to be, that all the grooves are loose. At first sight it would be thought that at least one fixed groove must be provided to obtain tite required grip ; but this is not necessary. The explanation appears to be that the pressure of tba rope in the groove of each individual ring, is traiisferred to the underside of the ring, hence the friction is just us great there as
2Io Text-Book Of Ooal-Mining.
it would be under the rope if the pulley had solid grooves. E&ch ring adjusts itself to the unequal strain on the rope, or weai the groove, and constantly accommodates itelf to these conditiooB j whit in motion. The fatt that the ropes equalise themselves on the rings gives each wrap its proportion of duty, and there is no necessity to secure any of the grooves. It is essentially a friction drive, with each ring accommodating itself as explained. The rope never moves on the grooves, aa is proved by the fact that when it is at work the impression of the rope is left in the oil at th bottom of the rings, which concluEtvely shows that noslipping takes
FlOB. 346 AND 247,
place. The bottom and sides of the ringa are thriroughly lubricated by automatic grease-cups, inserted in a hole, 6, in the under-- side of the rim of the pulley, a groove being provided opposite each hole, as shown at c.
The complete design of what may be taken m the most modem type of endless vope haulage plant, as adopted at Bell End Pit, is il!uBtratd in Figs. 246 and 247. It consiRts of a pair of 16 in. cyl. engines by 2 ft. 6 iu. stroke. On the crank shaft is a pinion, a, 5 ft. diam., gearing into a crown wheel, 6, 15 ft. diam. on the second motion shaft. This is provided with three hearings, and od , it is keyed a, pinion, c, 3 ft. diam. gearing right and left into crown wheels, d and e, 7 ft. 6 in. diam., each key on to third mob'
Haulage. 211
ehafta provided with two bearing, one of wliich ia carried on a special bed-plate, while the other is situated on a prolongation of the right-hand engine bed-plate. The two third-motion sh&fts nverhanK their right-hand bearings, and on the outside is keyed two Walker diffei-ential piiUejs, f and jr. The object of this is, that at any time required the loose rings can be tuken oB', cleaned and oiled, or anything done to the rope without interfering in the slightest degree with any portion of the engines. To take the outw&rd thrust, an adjustable strut, A, connects the two thirdmotion shafts ; this is made in halves, connected by right-and leftband threaded screws. Such arrangement takes oil' a great deal of the strain, which would otherwise come on to the right hand bearings.
Arrangement for taking up Slaok Bope. — Successful working is influenced, to agreat extent, by the armngement for taking up " slack," and at the same time putting enough tension on the rope to prevent any slip on the driving pulley. Eopes lengthen with use, and, in addition, the varying inclination of the plane
Flu. 248.
Fici. 249.
inHuenoes their tightness, or otherwise. Tension carriages should always be placed at the lowest end of the road ; the full rope is led on to the driving pulley, then to the tension pulley, and passes away as the empty rope. Naturally, the pulling, or full rope, is always tight.
Sometimes this tightening pulley is firmly connected to a screw — it may just as well not be applied at all, What is wanted is some arrangement that gives and Utes, and automatically accommodates itself to the varying load. This may be dune in many ways. One form is shown in Fie. 248, which, however, is nob recommended. Long experience has proved that the life of ropes is considerably decreased when the wires are nltemately bent in opposite directions. The better plan is to carry them half round a pulley on a carriage, which can be either weighted and travel on iin incline, or it may be ou the flat, with a weight attached behind by a length of chain, this weight exei-cising a direct pull on the waggon ( Fig, 149).
The heavier the load on the i-ope, the heavier should be the weight on the tension wagon, and viot vera. The weight giving
the best reeuItR is easily deteiiuuied by expeiiment, and when once found, need not be varied unless the load on tbo rope increases. The pnlleyn on the tension waggons are often made amalier in diameter than the driving wheel, but the far bettr plan IB to make them tlie same sixe. IndeI, every main pulley around which the route coils should be of equal Hize throughout — one pulley should be a duplicate of another,
Clutches for Working Branches. — It lia been often stated that branches canuot be worked with such ease in the endless rope system as with some otliers, but it is difficult to see why such an opinion should \ie held. Indeed, the number of bimiches ma}' be unlimited, if each pulley is able to be thrown in and out of gear by a clutch aii-angement. In some cases, the ropt: along all the bmuches and main roads is made in one continuous length, and a stoppage auyu'here stops the pit.
Numerous clutches are in use. In the ordinary forms there may be a cone siding into a conical box, or a series of lugs on the pulley fitting into a sliding coupling box. The efficiency and life of the I'opes (which mainly afl'eet thij cost) depends on the speed at which they are run, and the freedom, or otherwise, from jerks or Etiwus, and neithei' the cone nor claw clutch should he used, if the duiiitiou of the ropes is to be secured. Supposing the main rope to be travelling at its normal speed, and a. branch thrown int gear ; with the ordinary clutches.the brunch rope has inly taJie the speed
Fjo8. 350
that the main rope is travelling at, a very serious strain is thi-own upon it, and often something hivaks. On the other hand, if it be desired to throw a branch out of gear, it can seldom be done without stopping the main rope. Cone clutches often " jam." and cannot be got
Fiaker'a Clutcit.— To overcome these disadvantages, friction clutches have been designed, a very successful one being that invented by Mr. Henry Fisher. It consists of a driving drum, firmly keyed on to the shaft. Around the ijeriphery of this drum is arranged a series of segments (a a, Pigs. 250 and id left-hand bciwb. b. An anungfr-
HAULAGE. aij
ment of severe is provided, by means of which tliese sci-ewa can turned. If they are turned one way, the segments together juid grip the di-iim; if the other' way, they open and leave the drum. The numljer of segments is generally thi-ee, sometimeti four, and in the centre of each Ls nn obtoug hole, in which is inserted a sfjuara pin, c ; the other ends of these pin:j pass into the arms of the diiving pulley. The drum, being keyed to the aloft, is always revolving; the driving ridley ia loose, but attached to the friction segmente tbi'ough the pins, e. If these segments are tightened on the drum, practitly they bet-ome part of it, and Evolve, carrying with them the driving pulley. The amount of friction, or grip, is determined by the amount of i-otation given to the screws, and can be so regulated that sufficient pressure is only exerted to drive the pulley under its normal load. Should a tub come off the rails, or any excessive load be thrown on the rope, the cluth gear should Blip. Strain is therefore totally avoided.
The same thing takes place when a branch is thrown into geur. When the segments are first tightened, considerable slip takes plai'e, the branch moves off at fii'st very slowly and gradually increases in speed as the inei'tia of its load is overcome, until it travels at the same i-ate as the maiH rope. As Hoon aa it does tliis, a very good plan is to slack the segments on the driving drum until only juat enough grip is given to drive the bninch rope.
The only drawback is its cost. It is very carafutly made, tde fi'ictioa parts are bushed with copper to get more adhesion, and there is a lot of fitting work. Its economy and advantages are indisputable, but it is possible to purchase economy too dearly. Itlany other friction clutches exist which do not, perhaps, give such satisfactory results, but their cost is no much smaller {hat, except in the more important situations, their u.'ie is recommended.
Bever and Darliru/'a Clittch.—lti this form, what might be called a brake flange is attached to the driving wheel. Inside this flange is an inner split ring. The bearing surface of the ring and the brake flange aru each carefully turned. On the driving shaft is a collar, which can be slid up and down, but is forced to revolve with the sliaft as it travels over a long key. To this collar is attached an arm, and to one end of the arm a wedge, which, when the clutch ia out of gear, only juut enters the slit in the plit ring. To throw the clutch into gear, this collar is moved towards the driving pulley, and in doing so the wedge is driven into the split ring and expands it, causing it to grip the brake flange and so tuiD the pulley. The principle is exactly the same as the Fisher and Walker clutch, but na the pressure is only exerted at one point its action cannot so perfect.
K'tmston' C/i'icA.— This is the same as Bever and Dorling's, except that the split ring Ls expanded or closed by the aid of one right-and left-hand screw instead of a wedge.
ai4 TEXT-BOOK OF COAL-MINING,
Brakes for Bran ohes.— When a branch road is tlirown out'l of gear, if it gradient is a, steep one, the tubs may moving, even after connection with the maio haulage hue bees f broken ; this only takes place when the inclination is such that I the road is nearly self-acting.
Even when such motion te in the same direction as in general (that is, towards the shaft) such continuation is objectionable, as, unless the rope were required to stop, it would not be thrown out of gear. Where the gradient is in favour of the loail, an oidinaiy band brake is usually arranged, so connected that it is put o the clutch is thrown out of gear.
Where the gradient is against the load, and the tubs haven i tendency to run back, a most ingenious brake is applied bjr 1 Walker Bros., and has been working with great success at Lye. I
tiG. 252.
Cross Pit. Four brakti blocks (a. Fig. 252) arc arranged at intervals around the pulley, ajid are pivoted about the points b. Each is provided with a right-and left-hand strew to allow for adjustment, and to take up wear. These bi-ake blocks are not at right angles to the lirake rim, but slightly inclined to it, and are pushed away from the wheel bo long as it turns in its normal direction, indicated by the arrow, but are kept up to their work by the pull of a small weight. When the branch ia thrown out of gear, the moment the wheel starts to run back, the arms carrying the brake blocks try to take a position at right angles to the brake rim ; but as this is shorter than the inclined distance, the blocks are wedged against the brake rim and prevent the pulley from running back. In the illustration, as long as the pulley turns in the direction indicated by the ai'row, the brake keeps otT, but immediately it attempts to go the other way the four arms endeavour to take a position at I'ight angles to the circle a a.
Bopes Under and Over Tuba. — Two systems of endless rope haulage are in use. In one the rope ti-avels over the tubs, in
Haulage.
other under them. The advantages of the Former are, the route is always carried above the ground, and is not on it, causing frictioD, wear and tear, and lees life to the ropes, and all the macbineiy is overhead and can be easily inspected. The dis- Bivantages are, that the tubs cannot loaded high, as is the practice in some districts, without attaching to the tub means for carrying the rope, which not only leads to complication, but introduces another possible cause of failure. This disuilvantage may be, and is, avoided by attaching the I'ope to the sides of the tubs ; but, inasmuch as the ptiU is not in the centre of the load being moved, frequent demlments result. With the rope over the tub, curvefl are not easily worked. If any exist, they should be made as sharp as possible, and a gootl large guide pulley placed at the bend. I'mctically, ©very curve with the lupo over the tubs requires an liddttionul man, as it is not safe to allow the tubs to work round without supervision. For a day, perhaps, everything may go right ; but one accident eotits more than a man's wages for a week. If the rope is under the tubs, any amount of curves may be worked easily ; but here they should be made as large and of as wide a sweep as possible. Rollers are placed all round the curve, and the clips easily pass round these, if the roiUrt art large in diameter, mid placed near together. For good working they must be the largest ttize allowable. Automatic detachment of the tubs is 0. veri' simple mutter when the rope travels underneath, but over the tubs it is only possible with fine form of clip.
Arrangement of Tubs.— The tubs may be connected to the rope either in sets or singly. On the branches, one tub at a time is attached, but on the main line, from two to four tubs have to be massed together. Where the tubs are run in sets, from ten to twenty are attitched to each other, and only one of tliem connected to the rope. Such a train i-efjuires an attendant, and the chief advanljige of this system of haulage is lost — viz., regularity of delivery. Where only one or two tubs are attached at a time, tha delivery to the shaft bottom is a model of regularity ; the tuba come and go with scarcely any attention.
One or Two Road Systems.— The endless rope system pi-oper requires two lines of rails and a wide road. Where the roof is a good one this is not a disadvantage, except, perhaps, in the closing years of the colliery's life. The nature of the roof in some mines prevents the doutJe line system being applied. The difficulty is oven'ome by I'unning the tubs in sets, and arranging pass-byes at intervals. An attendant travels with each set, and waits at th siding until the train travelling in the opposite direction arrives there ; they pass each other, one proceeds towards the shaft, and the other in-bye. Connection between the set and rope is usually made by a sci-ew-cUp attached to a bogie carriage (Fig. which the train-man rides.
Another plan, which avoids the inconvenience and expense
ai6 TEXT-BOOK OF COAL-MIKING.
running sets, is to provide two roads each laid with a single line of rails. In one, the full tubs travel out-bye, while in the other, the empty ones pass into the workings.
For steep gradients, where the load would be too great for a single rope, two may be employed. At Newbattle Colliery, Edinburghshire,* such system is adopted, each tub being connected to two ropes. Although an elaborate arrangement of friction
clutches were applied to allow bbe ropra to automatically adjoBt themselves, and each take their share of the load, yet such were found uuneeessary.
Boils at Junctions.— At main stations, where branches are worked, the usual arrangement of switches and crofisiugs is employed, and as the ropes are either above or beneath the road, no provision has to be made to prevent their being injured.
For junctions, with FuiS. 155 under-i-ope haulage,
OaiJ, several methods are
used; two of the more general ones being shown in Figs. 254 and 255.
In Fig. 254 the empty tubs are t&ken utf the rope as soon as they have passed the switch at A. and are then run back The full tuba shown
"V
to the jiinc;tion as : ira the working! pass at y the illustration.
ndifAted by the
mce on to their proper road,
HAULAGE. :;i7
The better plan is thtit of Fig. 255. It is moi-e compact and easily worked. The illustmtion eaplaina itself. In both these figures it will be noticed that small breaks or spaces are left in the d'tossing rails, and in these the rope generally works. Unless some such provision were made, the rope would receive serious injury from the flange of the tub's wheels as they passed from the junction to the main line, as each wheel would have to roll over the rope as it lay on the top of the rails. To prevent any chaDce of this happening, not only are i-ecesses provided, hut the rails at the junction are raised some 3 in. above the general level, ujt shown by Fig. 256. Just before reaching the junction, 11 short length of inclined rail is fixed, followed by level i-ails at the junction, and then another short inclined piece is inserted, throwing down the rails to their original level. At the junction, the haulage ivpe is, therefore, below the lower flange of the cross rails, and tube joining the main engine-plane can do no injury. When a tub on the engine-plane reaches the junction, the clip, which carries the rope a uniform distance above the floor, lifts the rope out of the groove and lets the tub pass without obstruction, the rope falling back into the recess immediately the tram has gone by. Check and guard rails oi-e used at all junctions, as shown by the figures.
For over-rope haulage, no better plan can lie adopted than that of raising np the empty road for sonke distance before the junction, until on arriving there, sufficient height is gained to allow of the construction of a bridge, over
which the empty tubs pass 'lO' 257-
either straight on or into the . brunch (Fig. 157), and beneaO) which the full tubw from the branch are taken.
The illustration explains the arrangement, which is preferable to having the crossing on the some level; there is no chance of collision or derailment, and, owing to the height to wliich the empty tubs are raised, they run freely round the curves, and require scarcely any attention,
CLIPS. — Tubs ai-e attached to the i-ope in many different ways. A good clip should be capable of easy and ready attachment and detachment, should not injure the rope, have few wearing parts, and act equally well on a downhill or uphill gi'adient.
Clipa for " Under " Haulage : Screw '. 7i;).— The common form of clip consists of two plates connected together by a screw, and attached to a hook, through which they can be joined to the draw-bar. This certainly holds the rope, but is neither easy to attach or detach.
Sntal/man't f'/tp.— The principle of this is the same as that of the screw clip, but the gripping action ia obtained in a much easier and readier manner. It consists of two plates (a a, Figa. 358
ii8 TEXT-BOOK OP COAL-MINING.
and 259), connected together by a. bolt, i, in the centre ; a lever, c, 1
turniiig about a point, '/, is proviiied, its shorter arm being enlarged, ]
in the Bide plate, and, as a result, tbe lower pare of the plates I
can either grip or releiise the rope. Adjustment for wear cai
easily be made by tightening the Iwlt, b. A very powerful grip ii
obtained, the rope is not damaged, hs it gripped for several J
inchee, attachment is eay, and the clip passes 1
Tia. a6a freely round curves. It is, however, rather cumb
some, and cannot be automatically detached.
Fisher's Clip consists of a hook having a hinged I piece, a {Fig. iGd), at tlie fw aid. which Can be I doubled back and locked by a sliding collar, b recess is provided to receive the ropo. The hoolc ' is placed in the draw-bar, the clip grips the rope by defecting a small portion of it. It is essential that tbe hole through the clip should be the same size as the rope and of softer material, so that it wears itself instead of tbe rope. To allow this, the recess is provided with bushes, c, of soft iron, which are kept in position by rivets, and are easily replaced when worn.
With Fisher's or any similar clip, it is absolutely essential that the rope should have a wire core, if not. it stretches too much, and the clip wilt not hold. The liook part is made of a very good quality of iron, and is the weakeKt part, so that in the event of the tub being dei'ailed, the hook straightens out and the rope is not damaged. This dip acts eijually well uphill or downhill and round curves, and can be easily and automatically detached in the same nay iis any other clip which is locked by a sliding collar.
Clips for Over Haulage. — The common method of attaching tubs to the rope is by means of a chain, one end of which i hooked on to the drawbar of the tub, the other end passed twins I
Haulage. ;.9
round the haulage rope, and then hooked back on to the chain pasKiDg from the tub; as soon as the full weight comes on to this chain, the coils get quite close together and form a compact fuHtening. This attachment is not by any means perfect, although a very convenient one. On undulating gradients, two chains aj ne before and one behind each tub, but both must not be tight at the same time, as in such a case, if the rope was suddenly stretched, the tub would inevitably be lifted off the rails. Wire ropes are in the habit of twisting, and when they do, if the above attachment is used, the chain twists with them, winding up whatever slack portion there may be ; consequently, on reaching turn pulleys, or any bend, where the rope is raised higher than its normal position, the tub is overturned, and all siicceeding tubs are overthrown until the rope is stopped.
Wurd and JJoi/is Clip. — Many of the above disadvantages are overcome by the clip employed at Handweil Park Colliery. It is exceedingly simple, consisting only of a hinged lever, to the bottom end of which is attached the chain fn,tened to the tub. (Figs. 261 and 262). The lever works about a pivot, a, and immeiliately the weiglit of the tub comes on to tlie end, b, tlie rope is gripped between the top end, c, iind the curved plate, il. The lever is hinged, which allows the clip to fall into the guide pulleys when passing round curves. It has
and hnn given every satisfaction. It is easily attached
and detached, but this cannot be done automatically, and on undulating grailients two clips have to be used for each tuli.
Rutherford and Thompton't Clip. — The great advantage of this appliance is that it automatically attaches and detacheK, enabling curves and junctions to worked on the gravity principle, in the same way us with endlei chain haulage. It does away with one man or boy at eacli junction, for with an ordinary clip some one has to be employed to take off empty tub.=i anil put on full ones ; while with this one, all that is necessary is that some one should be in attenilnnce to space the tubs, and to lift off the clip from the empties, and attjich it to the full ones.
Figs, 263, 264 and 265, which are respectively fi-ont and side eIevatio:u< and plan, show details of the rope gripping apparatus usually employed, which is composed of two Y-forked jaws, a
mounted and geared together as ehown by Fig. 265, so that they
can oscillate about the two pins, 6 b', iw L-enters. Aa soon na the
clip cornea into the same Hne an the hauHug rnpo, the motion of
the liLttr turn the forks
Figs. 263,
slightly about the ceiitreii, h b', and ciiuses them to close on the rope and grip it firmly. The stronger the pull, the tight the grip, heuire the clip is well suited fur heavy gi'adients ; and as it is attached to tlie tub through a rigid rod, which iti hooked over the top while the other end passes into a small bracket on the front, and as the jaws can move either back warifs or forwards orks well on undulating
gradients.
The rope ca of this clip. 01 it iigaiii, with us a chniii if the Y on ftn not tixed to tli
1 be lifted out dropped into
as much ease lifted out of
ordinary tub, tub fl
detachable, an armagemeut employed to prevent them being
itccidentallj lifted ofl' when the rope is discoimected.
Automatic DotaoherB. — Little difficulty is found in automatically detaching any of such a type as Fisher's, where the grip on the rope is determined by the position of a sliding collar-, beoiuse if this collar is lifted up, the clip is released. If the i-ope and clip be conducted into a groove, having sides ai-mngeU on an inclined plane, and if the rope is kept down as the clif passes through, the collar ia lifted up.
At Nunnery Colliery a very simple iippliance is used to perform this action. At the detaching point, two strips of iron are connected at one end by a cross piece, and are pivoted about pins near the centre. Figs. z66 and 267 show plan and elevation of the arrangement. The apace between these two strips ia wide enough to allow the rope to pasa through, but not the collar on the clip. The end, e, of the two of iron cannot be pressed
HAITAGE. Mt
down because ibe other end, a. is onder the rope, coiuequeiitlj tbe coll&r of the dip has to sHde up the inclined pWie and is gradiuJly lifted, releasing the rope.
An apparatus of more elaborate, and perhaps more eutv ch&racter, has been designed br Mr. J. ¥. Lee, of Castle Bdett
Colliery. It consists of i which the rope und the lovi each side is formed of n
groove having inclined Hides, out of tr part of the clip cannot be lifted, an angle-piece (Fig. 269). The continuation
of the jawH is made hy two lovum (a, Fig. j68) kept up by a weight, li, but wlien the priwture bncomc* vsncwivn they may be piuhed down, the object of thin Mng the leimn can accommodate their height to nnit the varying {xwitionN of cotlara ou different clip. The rope and lowtn- ]Mrt of thn clip jwa* underneath the jaws, which taper toward* the jioirit uf oiit ; Mm
collar passes up tbe indicecl plane and is lifted, thos detAchinj the tub. To prevent any cfaance of failure, the collar of the cli] is provided with a flange.
At Skelton Park Colliery* the rope are attached to a simpli hook beneath the tubs, as the gradient is slight, and the weight L sufficient to haul them along. They are detached by ai apparatus, consisting of a lever (a. Fig. 270) working betweei split rails, and depressed by the passing tube. This turns thi shaft, d, raises the lever, b, and life the rope out of the hook, c At the same time, a slight divergence is made in the line of rails causing the hook to move aside from the rope, which then drop when released by the lever, 6.
With Butherford and Tbompeoa'a clip, detachment is obtaine(
by an appliance which consists of a holding-down pulley (a. Figs 271 and 273), and of two inclined guide-blocks, h, one on each side of the rope, the spaces between tbem being such that thi rope can rise up, but that the forks of the clip catch the under side As a tub and its clip come to the detached the rope gradually gets higher and higher, tending to lift the clip out of its socket but is prevented from doing so by the two guide blocks, h b, whiel catch the top of tbe forks. Ultimately the rope is lifted com pletely out, and the tub runs away. With a clip having a ver tight grip, a jerk is thrown on the rope by such action, and prevent this extending down the road to the tubs further in-bye a movable holding-down pulley is placed a short distance awa; which checks vibration in the following manner : — A shaft (a. Fig 273) is fixed across the road above the rope and on it are keyet three arms, one carrying a holding-down pulley, 6, the second having a weight, c, at the end of a lever, while the third, d hangs downwards. The action of c is to keep the pulley firmly 01 the rope, and that of (2 to lift the pulley when the tubs an passing, this being necessary, or the clips would catch it and break
The tubs which are travelling in the direction !irom ato b, push aside the arm d which hangs down before them, and on doing 80, turns the shaft, a, round, and life up the pulley and weight, which fall again immediately the tub has posted.
At curves, where the continuing raid in on a downhill gradient, the tubs run round and attach thenilves to the rope aguiii immediately this comes low enough to grip the clip, but where the gradient rises out-bye other means have ta be employed, as the rope tends to get further away from the clip. It is impossible to deflect the rope far enough downwariU with a fixed guide pulley, as these have to be placi high enough to clear the clip. The movable one just described is inadmissible here, as the tubs being detached from the rope, are only moving with the force due to
Kic. J74.
the inclination of the road, uid would not have sufficient power to lift the lever and weight. The ingenious appliance shown in Fig. 274 has been designed to meet such CBes. A pulley, a, is fised at such a height ns will allow the tub and clip to pasa beneath when it is in its normal position. This pulley not a fixture, but it is suspended from a shaft, b, fitted with guide blocks, and connected by crank levers, e d e, andj A, and the links, ft c, ej and h t, with the rails forming the ixmd at this point. There are two seta of level's, one on each side of the raits. The rails, for a distance of about 12 ft., are carried on a platform hinged at the point, A, and by means of a bidanceweight take the inclination shown at i i. The tubs when detached from the rope, run down the slope, I k, pass beneath the pulley, a, aud continue by the momentum they have gained up the slope, i A ,- their weight, however, over-kuJances the counterpoiBe, The platform descends about the centre, k, takes the position, 1" k, pulls down the link, h i, moves over the two cranks, and depresses the guide pulley, a, and the rope to such a distance that it is caught by the clip, and the tub consequently move away. As soon as the tub lias gone ofiT the platform, the counterpoise i*ui:es it again and the guide pulley, HO that the whole apphance in automatic. The points d, g and k, are fixed, the remainder movable. At the momentof
attaclinieut of the tubs to the rope, the difl'ei-etit pai-ts of tlie apparatus occupy the position shown by the dotted lines ; the travel of the pulley, o, m about loui.
Threading the Bope. — It is rather a difficult matter to put on the first I'ope of a new Rppliaition of endless rope haulage. As supplied by the manufacture, ropes are very carefully coiled and should be unwrapped from the outside, care betug taken that no " alack " is payed out, or the i-ope will at once Idiik and spoil iteelf. If a new rope is replacing an old one, the threading is an easy matter, but one requiring care. First of all, the old rope is cut through, and one end of the new rope attached to the old one, but in between the two ends a swivel must be placed. The object of this is to take out alt the twist in the new rope ; uuless this is doue, diiBculty will afterwards be experienced in the working. The coil of rope is placed on a turntable to which some moderately strong brake power can be applieil. The engine is then started and the old rope moves away, dragging with it the new one, the iattei' following the former, and occupying its place. When the two ends come together, they sboiUd be strained as tight as possible, which is done by attaching blockti, and, at the same time, the tension pulley is braced up as close as nin be, as the ropes invariably stretch in use.
tjnlesa an old I'ope is available, horses have to be employed ; their raovementa ai-e very irregular, and there is considei-ably more chance of damaging the rope.
CompariBOn. — If a good representative of each type of haulage is taken, the cost per ton per mile is about the same in all of them. To a great extent, the cost depends on the number of junctions and branches, because attendants have to be provided at these |)oints to attach the tube. In comparing the cost of one system with another, it is usual to reduce the cost to a unifomk distance hauled of one mile — that is to say, if the cost is twopence per ton per half mile, a simple proportion gives fourpence per ton for one mile, but although some uniform distance must be introduced, yet it does not givn a fiiii' coiiiparisan in every insljince. Take, foi' example, su endless rope or chain plane, exactly a mile from the beginning to the end with no junctions. One man at each end should perfoiin all the labour of taking olf and putting on the tubs, and the cost jiei' mile, on the one mile length, would be very small ; but if, in another case, there are four junctions in a similar length of plane, each of these jimctions will require tlie services of an attendant, and the labour cost will show very much higher than in the former case, providing the same quantity is hauled, and yet the two planes may be exact of each other, and both be laid out with the same care and labour saving appliances.
Another point to which attention should be directed is that in published statements of costs, many estimates entirely overlook
Haulage.
aJS
some part of the first coet of the plant. Hauliog engines cannot be worked without steam, and the extra amount for additional pullejB, dttings, pipes, caused hy adding haulage machioeiy, ehould be charged against the plant. Then again, the stores' charges for the machinery should be noted.
The moot ireful experiments which have ever been mnde to determine the cotit of different syatema were those carried out by the North of Kngland Institute." This was, however, many years ago. The endless rope system was then in its infancy, while little improvement has since taken place in either the tail rope or endlese chain syatemH. This report sti-ongly brought out the merits of endlesB chain haulage, so far as regards its ease and coiit of working, but friction clutches, automatic detachers, improTed driving pulleys, and the other siniilur labour-saving appliances of modem endless rope haulage were then unknown. At that time, a life of one or two years in a haulage rope was considered a very good performance ; at the prestint time seven to nine yeare b by no means an unusual occurrence. At many collieries the rope cost per ton-mile does not exceed o.id.
The great advantage of the endless rope system is the perfect regularity of the delivery. The tubs come one at a time at regular intervals, and are easily dealt with ; in addition, the full tubs going down inclines assist in pulling the empty tubs up. Both thee advantages are common to the endless chin system, but the disadvantages of the latter is the enormous weight of the chain and its liability to break, especially on long planes. For surface work, the endless chain possesses one advantage, inasmuch OS it is little affected by the action of the weather, but underground this advantage disappears.
. With the tail rope system the tubs work in seta, and, therefore, travel at a high velocity, fifteen to twenty miles an hour being often reached. The delivery is intermittent ; a train of from fifty to sixty tubs is brought into the pit bottom at a time, and men have to be there to deal with the set; on its arrival, all is hurry and confusion for a few minutes until the empty set has been despatched to the workings, and then the men have little to do. Should a tub become derailed when travelling at this speed the damage done is considerable. With an endless rope, travelling at only two or three miles an hour, thero is little possibility of derailment, and even if thifi doex occur, the damage done is slight. With the tail rope system, less length of rail is required, but a larger pair of engines are necessary than for endless rope, because in the former case they have to he powerful enough, to deal with the iimvieil load up the heaviest gradient, have to travel at a very high speed, and derive no benefit from the counterbalancing effect of gravity on undulating gradients. TTieir action
12S Text-Boor Of Coal-Mtmng.
is intermittent and they require an engineman always ia tittendance.
With the endless rope sysUm, the constant attendance of lui engineman can be dipenHed with by arranging a clutch gear at the bottom t/f the pit, where the main strap rope terminntea. This point ia the principal junction of the pit, and men have to ba there to attach and detach the tubs. If a signal come*: from the workings to stop the main i-ope, one of these men can easily turn the wheel which disconnects the clutch gear, and the engine on bank may continue running. The author is not aware where the werviees of an engineman have been dispensed with at a hauling engine, except in the instances of two of the coUieioes under his charge. By spending £100 on a good efficient clutch gear oue engineman looks after three continuously mnning engines — i.e., hauling, fan, and shop machinery, and not the slightest hitch has ever oceuned. The only objection to this system is the possibility of some accident happening to the shaft rope, but an experience of eight veal's does not support such contention.
The author luiw at work every system of haulage ; but the one that stands pre-eminent is, undoubtedly, the slow moving endless rope, with the tubs attached at regular intervals. This appears to bo the common experience, as nine out of every ten systems which have been put to work during the lest ten years are endless rope, with the probable exception of the North of England, and even there tliis syBtem U mpidly gaiuihg ground.
An endless rope can be employwl anywhere, although to obtain the beat results the roads should be laid out to suit it. The only objection against it is that a double road is necessary to obtain its advantages to perfection, and that double roads are expensive to maintain where the roof is bad. As previously pointed out, even this disadvantage may be, and is, removed by employing two roads, each laid with a single line of rails, one for the full tuba and one for the empties.
LooomotiTes. —At best, haulage by locomotives is not to be . recommended, as neglecting the dangers of and the difficulties of ' dealing with the smoke, steam, kc., the system has the disadvantage of being intermittent in the matter of supply. The engines have to be small ones, and are not only very expensive in up-keep, but are very liable to derailment. Locomotives worked by steam have been applied in English collieries and In the American anthracite mines. Locomotives worked by compressed air have been tried on several occasions, but have never given satisfaction.
Electric IiOComotiras.The first locomotive worked by electricity was applied in i88a at Zauckerode Colliery in Saxony. The current is conveyed along the roof of the roadways by a iron conductor, and is transmitted to the motor by a conducting piece which slides along the iron. The locomotive has worked most satisfactorily ever since its application, and performs the work
Haulage.
more cheaply than boi-see which it replaced. Altogetbev, there are four electi'ioal locomotives in German mines, and Mr. K. Eilera* states that the coat of tramming with electricity is at Stassfui-t and Jauekerode, 75 per cent., and at Hohenzolleni Colliery, 67 per cent, of what it originally was when horses were employed.
At the present time (1892) the only electrical locomotive employed in English mines is that introduced by Mr. G, B. Walker at Whamcliffe Silkstone,t where the engine doea not depend for its grip on the friction between the wheels and the rails, but gets direct pull on a fixed rope. The latter is tised at either end and lies parallel to the roud, aud is passed over a api-ocket wheel or friction clutch geared in a suitable manner to an electric motor on a trolley. The road is 500 yils. long, the inclination averages 4 in. to the yard, and the rolling load is approximately 4 tons.
Several instollationM have been made in American mines, and Mr. H. C. Spaulding} states that the Tliomaon- Houston Co. have recently couatmcted the largest in that country. The locomotive is 60 H.F.. weighs 11,600 lbs., is 3 ft. gauge, and has a maximum apeedof i o miles an hour. The armature speed 1020 revolutions per minute, and the locomotive is 3 ft. 3J in, high, 3 ft. 6J in. wide, and 12 ft. 610. long.
Bibliograph7.The following is a list of the more important memoirs dealing with the subject-matter of this chapter : —
JJ. E. I.: Ihe CuutjiaHrr of f'nal Vfjlergrouml, N. Wood, iiL 239 and Appendix, v. 6s ; Coni'ryanet of CiM. VaiUrgroaml, John Dflliah, xvi, 53; t'nilrrjiTound Haulage at Felloa Gillieru, D. P. Morisou and J, Nelson, xvi. 117; Jirport of Tail Rope Cotnmillte, xvii; Detcriptioii of Foarletn dijcreni Mtthod4 of Lubricating Cotd TiAt Or CoTce. EmeTBoo Balnbridge, xxv. 115 and xxvii. 8 ; A nne Mtthod of Hope Haulage, J. I'eose, xxviii. 335 ; Some Htmarki oit KmUeig Bopt Jiauiai/t, W. Jackson, xxviii. 243 ; IIhU of literal at the SIcttttM Park aak LtUHptey Joiner, A. L. Steaveoaon. xxiL ro5 : The tediag and JUaHoaeme'it of CoBienj Harici, Charles Hunting, xxxii. 61.
eoo. IND. MtN. : .Vote tur bt traction miciiTiiijiie p/ir cordele tt corde-queue iittluUie aiLe mine4 dAniikt il la foue Sainle Marie, G. VniUemin (2* Eijrie], iv. 429 ; Erponlian de 187S .- De divert tyitima dt trartioa nirnmiffue ijpliguei. 011 pourani t'opptiijueT, aiu mines, P. Holter Bene), ix. 139; Trainagc mieanique,pitt Julei CItagot, Minei de Blatay, E. Suisse (3- SiSrie), 1. 455.
BRIT. soc. MiN. BTUn. : Tail Bopf- Buidage, J, Wroe, i. 328 ; Daerlptionof impnirtd CoUiery .llabUi. J, P. Kirknp, iv. 127; Shaelitg of Fit Bomrn, J. A. Loneden. iv. 107; Ooiivaiance of Cbiil underrn'ouud ba Ettttriatu, 3. A. Longden, ti. 114; Eltrtrit Hatilaijt at Jiaacktrode ColUery, H. W. Haghd, viii. and U. 79 ; Haulage of CaaJt, Emma /¥(, Toauelti/ CoUierg, F. R, Simpson, S. 171 ; Underground Haulage, HUlorieal !Solt, df.., H. F. Bulman, xi. 166 1 Endleti Hope Hauiagt at Cattle Edeit CaUierj/, W. Bell. xiii. 63 ; Endlei Hope JIaidagt at SoittK DerweM (Miery, H. W. Ungbes, xiii. 113.
22S Text-Book Of Coal-Mining.
MIK. INST. SCOT. : Fift SytUmof OtU Chain Haulage on Indine$, R. Andrew, ii. 122 ; Haulage by Endlt$$ Ropes and Chains. M. MoFarlane, ii. 256 ; Haulage EaerienceSf J. Hyslop, iii. 30 ; Tail Hope Haulage at Eamock Oouiery James Gilchrist, vi.. 206 ; Cadzow Colliery End* less Rope Haulage System D. Ferguson, viL 78 ; Description of Haitiage Exhibits at 106; A Syitem of Endless Rope Haulage at Newbatde CoUiery, A. M. Grant, ix. 211 ; Haulage by Self- Acting Endless Chains D. M. Mowat, x. 152; Pit JPonies, their 'Feeding and Afanetgement, J. B. Hamilton, zi. 260.
80. WALBB. INST. : The comparative merits of Large atid Small Trams for Colliery Use James Broaden, vi. 173 ; Trams, Thomas Boms vii. 164 ; Underground Horses W. D. Wight, xii. 28 S ; Endltss Rope HaulagCf James Colquhoon, xiii. 123; Endless Rope Haulage at Clifton Colliery f Nottinghamshire H. Huxham, xiv. 33 ; The Hasard Collieries f Belgium, M. W. Davis, xv. 192.
ENO. AND MIN. JOUR. : Improvements in Winding (Haulage) Machinery, 1. 8, July 1890; Oravity Plane at MouUon Hill Mine, Quebec, Ii. 143 and 325, Jan. and March 189 1.
CHE8. INST. : Pit Ponies, J. A. Longden. ix. 273 : Etidless Rope Haulage at Clifton CoUiery, Henry Fisher, xii. 123.
MAN. GEO. SOO. : Underground Haulage at Astley and Tyldesley Collieries, G. H. Peace, xvii. 354.
AMBB. INST. M. E. : Wire Rope Haulage and its aoplioation to Mining, F. C. Roberts, xvl. 213; Electricity and Haulage, F. A. Pocock, xviii. 412 ; Electric Locomotives in German Mines, K. Eilers, xx.
V, STAFF. INST. : A few remarks on Underground Haulage, J. R. Haines
BEV. UNIV.: Note sur le drainage automoteur par chaine flottante des mines de FUols, C. Blanchart (2* 8e), vi. 142 ; Note sur un system de plancher mobile en fer applicable A V exploitation des taUles chassanies par plan indint C. Raicfant (3* Srie), ii. 8a
ANN. DBS MINES : Note sur quelques details de plans indian6s avtomoteurs, M. Villot (8 Srie), xvL 409.
Chapter Ix.
Winding.
TnE material havuig been brought to the pit bottom, the neTct thing is to convey it to the eurface. This is done hy placing the tubs in a Kuitabte apparatus called the aige, to which one end of a rope in connected, while the other is attached to, and wound round, the drum of an engine at the surface, On reaching the top, the full tubH are taken off iiud replaced by empty ones, and the cage then descend.
Fit Frames. — As some support has to be provided for the rope, a pit frame with pulley attached is used for such piirpose. At modem collieries with large winding machinery running at quick speeds, one stroke of the engine means a considerable hft of the cage, Hnd unless the head-gear pulleys are placed a good height above the surface level, and the engineman is very careful, the cage may be brought up against the pulley, and over-winding take place. In addition, the great majority of collieriee are provided with screening appliances, which are inclined so that the coal may run down them, and, as the trucks into which the coal is loatled stand at the ground level, the landing place has to be some dietance higher up. A further height is therefore given to the pit frame, and it is quite common to tiud the head-gear pulleys Oo or 70 ft. above the ground. These erections are constructed of different materials. On the Continent, towers of masonry are employed, but such procedure has never received favour in this country, nor, indeed, a very extended application anywhere else. The material mostly in favour, until recently, was wood, wroughtii'on was afterwards employed, and, as in every other branch of engineering, the use of steel is rapidly becoming common.
Before describing the method of constioiction, perhaps it would be beet to refer to the general method of design. The structure, as a rule, consists of six main p&vtB : (i ) two vertical upright legs (to carry the weight to be lifted) ; (2) two front vertical legs (for affording support to the cross timbers carrying the guide ropes] ; (3) two back lege (to pi'event the whole structure being dragged over by the pull of the winding-rope going to the engine). These main legs ai'e braced and connected together by 1
TEXTBOOK OF COAIJiUXINO.
pi£<cs, aildetl to gire gennU KtalnJity to the whole structtira. There is nothing [larticalar in the four Ih of the front fnm work, except that ther eDcIoee a wider since at tbe ground lei thiin the top, the object of such being to prei'ent them toppling over side7s: hut the poitioa of the back legs ie of considerable importance. Their bottom ends have to be placed at a distance from the front legs ss will efiectually prevent any chance of the frame being pulled over towards the winding-engincL The proper poeitioa of these legs i-s very easily determined, although iu uiany initancee they are placed anywhere but in the right positiuii. Oftn they aie carried so far towards the windingengine that additional vertical supports have to be provided underneath them ; no advantage is gained by this, it only introduces nn element of inKtubitity, as the legs may not be strong enough even to carry their own weights The strain on the pit frame, both as regards direction and amount, is the reeoltant of two forces, first of all there is the weight — \ii.. the weight of the tubs, coal, cage, and the rope hanging don-n the shaft, which a monng, or live load, and, therefoi-e, throws more strain on the structui-e than if it were an inert mass. The other strain is tliat ooming from the winiling-route, which has to desert sufficient power to lift up the weight hanging in the shaft at a certain velocity. The direction of the iniU due to the weight in the shaft is always vertical, but the dire-tion of the one due to the winding-rope may be at any oiigle tu the vertical, its direction being determined by the height of the head-geai*, and the height of the drum above ground level, and its distance from the centre of the shaft.
The relative position of the back ls to the front oneK is determined by the principle of the parallelogiaiu of forces, and may either he worked out by calculation or graphically. Supposing rt b (Fig. 175) is the ground level, e the pulley, and d the drum of the winding-engine ; e fc is the direction of the force acting
due to the winding-rope, and which tends to orertum the structure. Under ordinary circumstances the amount of force acting along c d must be ecjual to that along c b. Take the distance c A as being equal to the amount of force acting in that direction, and lay off along e a, distance e e, eiiual to c 6. From e, a line, e/, is drawn parallel to c 6, and another line, b/, is drawn pamliel to c e. The direction and magnitude of the resultant force will be given by the line of, the diagonal of the parallelogram. In the case under considertttion, the hock-
Winding.
stay should I'each the ground at. the point ij, where the Umgoiial cuts the line a b ; but, even at the best regulated i-ollieries, accideiitB happen, and the cage may be drawn violently against the head-gear, or, even without doing this, it is possible for some larger power to he applied along the luie e d than that due to the weight hanging down the shaft. To be on the safe side, it iit preferable to lay oA' along e d a distance a e' eqiiiil to twice o h, and hf ai'e drawn parallel to c t' and e d respectively, and the parallelogram constructed as before. The point '/, where the diagoDitl c f' cuts the line a b, will Jetermiae the length of the base of the pit frame. In an actual case of over* winding, the weight of the pit frames reduces the likelihood of their being pulled over, and adds to their stability ; ijideed, it is very probable that unless a detachmg-hook is used, either the head-gear would be smashed or the rope broken.
Wood. — Where wood is the materiid used it ia genei-ally pitch* pine, which should be free from sap and knots. The height and position of the back legs having been determined, the strengths iif the required timbera are found by calculation, and depend on the height and load to be carried. In side elevation, the front legs are vertical, their position with respect to the centre of the shaft being determined by the size of the pulley, because they come dii'ectly under its centre, while the throat of the pulley has to allow the rope to pass down the axis of the shaft. In end elevation, the width flt the top is determined by the diaVance between the centres of the two cages, because each pulley has to lead its own rope on to the centre of each cage. If to the distance between the centres of the cages, be added the distance between the centres of the ptdleys' bearings, the length fi'om centre to centre of the two main cap-pieces is obtained. This given the width at the top. The width at the bottom is determined by the amount of inclination given to the legs, which is usually i in 9 or 10. The main legs, both book and front, are bniceil and connected together by horizontal and diagonal struts, and often too many are intixwluced. There ia no necessity to add one more than is absolutely necessary, as they only weaken the erection by biirdening it with additional weight. The structure often reste on two main parallel sills running from the bock to the front legs, but such practice is not recommended. These siUs rest on brickwork, and dirt iind soil accumulate around them, with the result that they are the tu'st part of the structure to get ratten, and, no matter how carefully they ore painted, decay cannot be pre~ vented. The best plan is to put each leg into a cast-iron shoe (eimiliu' to Figs, 276-278), resting on a pillar of masonry, and held ill position by tie-bolls. Fart of the timber is buried in the shoe, and at the point where the iron ends and the timber first becomes exposed to the atmcHphere a crevice exists, through which moisture and damp can find its way. Unless this is prevented, the timber
Winding.
'33
will rot quicker than if it was on wooden sills. To prevent this, the joiDta should be mott carefully filled in with putty and painted, and then a strip of sine placed all round.
Iron or tSteel. — Fit frames have gradually increased in height, and the tendency has also been to i-aise heavier loads at quicker speeds. It has, therefore, become difficult to obtain timber of the required size and lengths, except at great expense, Aij a i-esiitt, wrought-iron erections were first substituted, to be replaced in their turn by steel. The position of the various parts should be the same us if wood were used. On the Continent, a design is employed where the legs are composed of tubular girders braced together by channel section atjiya, but the general English practice is to construct the legs either ot box or lattice girders. A fine example of the latter design is one of the pit frames at Soudwell Pai-k Colliery, the construction of which is shown in Figs. 276 to 278, which are respectively side, front, and back elevations. The general construction and dimensions are given on the illuetrationB. All the main struts are of lattice girder work, which coniiists of four angles, one at each comer, connected by diagonal pieces of flat strip ; the pulleys are carried by girders, which ore of box construction iu section, but the sides are lattice work to allow for the adjustment of the pulley carriages. The plates shown in the front elevations are open at the bottom.
As the legs have to bear less weight at the top than at the bottom, iC is common to make them taper. With a lattice girder, if it tapers, every set of cross-pieces binding the comer angles together is necessarily ot a different length, which increases the c ist of manufacture ; to remove this disadvantage, the legs have lately been made parallel throughout. By doing this the weight of the girders is slightly increased, and they arestrongernt the top than required, but as the cross-stays in each ginter are of exactly the same length, each one can be cut and rivet-holes punched from one template, instead of the innumerable sises whicli ore required with taper girders. The economy of construction, therefore, far outweighs the extra cost of the additional weight.
As a lattice girder is rather expensive to make, and as of late years it hiis been possible to roll very long strijis of either iron or steel, the box girder form of leg has been adopted in many coses. The one at St. Hilda Colliery, South Shields, may be quoted as an example. It is 75 ft. high and commences at the bottom with a section 1 3 in. square and finishes 15 in. square at the top. Each member consists of four plates, bound together by angle pieces at the corners. In the main struts, the four plates are y", in. thick, and the angle iron is in. by 3J in. by in.
Pulleya. — At one time chains were employed for winding, but, except in the rarest instances, none are now to be found, ropes either of flat or round section being employed. Upon the type ot rope used depends the shape of the throat ot the pulley, such
Text-Book Of Coal-Minixg
pHi't being the only VAruibk one, their genei'al design being the same either for round or (lat i-opes. They cotiwifit of a out-iron losfi and rim, connecter! together by wroughtiron ipokes (Fig. 179). Tlie shaft, or "gudgeon," is composed of wrought-iron, having turned beiinngs. With n view of reiiuting friction, the bearings should be as smuli nnd the [ridley as large bh poEfiible. The large diameter of ibe pulley introduces another advantage, nfl it reduces the bend of the ro{)e, and it is, tlierefore, not uncommon to find pulleys having a diameter of 18 to io feet. Beyond such size there ts a difficulty in making the pulley sti-ong enough to stand a beavy load, and at the same time keeping its weight within bounds. It is very necessary that these pulleys should be as light as possible ; if ot, with quick winding tliey liave a tendem-y to spin after the ropes ceaKe running.
When flat ropes are \ified, the groove in the rim must be made perfectly flat, or the rope will be unduly strninetl. With round ropes, the bottom of the groove will be semicircular, of a sufficient size to Buit the i-ope. It is essential that the throat should be made wide enough to allow the rope a certain amount of play, for, as each successive coil is wound on the drum, it is obvious that the poaition of the rope in constantly changing with respect to the vertical plane of the pulley.
SKIPS AND CAGES.— At onetime the mineral was wound from the in what werecnlled skips, which were attached to the winding-rope through the medium of chains and swung loose in the . The Mines Regulation Act, 1872, made it compulsory that guides should be adopted tn all xliafts over 50 yards deep ; and at the pi-esent time practically all shafts are provided with guides, and the tubs placed in a framing, calk
Shape and Construotion. — The shape of the cage ia determined by the sine of the tubs, and the number on each deck. A common procedui'e in dealing with large quantities ia to place two tubs, end to end, on each deck, and to have four decks. If the
3S
tubs are gmall ones, four may be placed on each deck. Then an to material. Everywhere cages ai-o now constructed of steel. Kach time a winding takes place, a, certain useless dead weight has to be lifted, conRisting of the weight of the tubs, the cage, and the rope hanging in the shaft, and it, therefore, becomes imiwrative, with deep shafts and heavy loads, tu use material having the greatest strength and the least weight. Every second saved in the time of winding is of impoititnce. Nothing is gained by having cages too heavy, while everything is lost. A heavy cage
knocks itself to pieces, while the cost of a light one is so small, that the gain in output, which results from quicker winding, more than compensates for repairs and renewal, A good example of the modem colliery cage ia tliat illustrated in Figs. 280 and 781. It holds two tuba on each deck, each weighing 7 ewt., cairiee $2 cwt. of coal, and weighs iUelE only 30 cwt., so that tlie iisef"' load 1847.2 percent, of the total weight. The horixontal '' composed of angle stel, 3 in. by 3 in, by j' in., tio-' vertical angle pieces and one flat strip on ead' ening plate, 9 in. deep by in. thick, rUDa horizontal frame, and the three uprights n diagonal struts. The author lia.s employ
36
Text-Book Of Coal-Mixing.
"1
W
similar construction, only lighter, carrying 22 cwt. of coal and an 8 cwt. tub, the weight of the cAge and bridle chains being only 1 1 1 cwt. ; the ufful load is here 53.0 per cent, of the total load.
Means for Keepiog Tuba on Cages.— When the tuba are placed on the cage some means hax*e to be provided for keeping them there during the procesa of winding. Thi£ is done in a variety of ways, but by far the commonest, and perhaps the beat, is to employ a bar of iron runningalong the side of the cage, each end of this bar being bent back at right angles. In ite normal position it hangs as at a (Fig. z8i), and locks the tubs, but on arriving at bank it is rotated, the ends desci'ibiiig the arc of a circle, shown by the dotted lines, and taking the position drawn at i, allowing the tuba to run ofl' at one side, to be replaced by others, the bar beijing then pulled down again.
In some instances this bar, instead of being at the side of the cage, runs alongthe top of it, and when in its ordinary position the ends hang vertically under the influence of gravity. The liar b. Fig, a8z) works about thecentre, a, and is provided with a stop. On reaching the surface, the baiikismAu piitihee the hanging piece, e li, to the Ipft hand, and a tooth in it catcbex the stop, a b, and holds it in a horizontal position. To release, the end b is lifted, and the catch drops to the id so keeps the tubs in the cage, forms of rope are used at collieries — flat and round. The advantage of the forinei' is that as the rope is wound on the drum, each lap coils successively on the one below it, and the vertical plane of the drum and pulley therefore coincide. A certain amount of counterbalancing also takes place, as the drum varies in diameter. At the commencement of the wind it is small, bub as the coils are wrapped on, it increases in diameter, until at the end its maximum size is attained. These conaiderationa influenced at first, in a very marked degree, the choice of rope ioT winding purpoees, and flat ones were largely adopted. Eitperience has not, however, justified the selection, the above-named advantages being found to be more imaginary than I'eal. Even with the deepest pits, it is possible to place the winding machinery at nch a distance from the shaft that the angling, caused by m round rope coiling on the drum, is scai-cely perceptible, or, at any rate, is not very objectionable, and it is also possible to perfectly counterbalance the weight of round ropes by several methods, which are described further on. Excepting on the Continent, fl ropes are becoming a thing of the past. They cost twice as mnci as round ones, and only wear about half as long.
Ropes are constructed of three materialshemp, iron, and
d/
vertical positio
Winding.
37
Btel. In English collieries, hemp has never beeu uHed to miy large extent, and at the present time, not at all. On the Continent hemp ropes are numerous, and iron or Btel ones rare ; aloe fibre is, however, employed instead of hemp. It is ditficult to understand why this class of material is I'etaiiied, for tin strength is so small, that a very large and heavy rope has to be employed. The engineers state tliat it great advantage is the non-liability to breakage, owing to the perfect reliability and uniformity of construction, but statistics do not bear out this claim.
Wire BopOB. — In the early days, no doubt, some steel ropes did fail in nn unaccountable manner, but at the present time their manufacture has reached a high degree of perfection, especially in Englaud,
Wire ropes were first constructed of iron, but are now made almost entirely of steel. No advantage is gained by using the former material ; it does net wear well, and its tensile strength is so small that heiivy ropes are requii'ed. Most manufacturers supply steel in three qualities — -Bessemet', crucible, and plough. The latter is about 50 per cent, stronger than the former, but only about lij per cent, stronger than crucible steel, Crudble steel ropes can be purchased in all ordinary sizes from £:i2 to ;£4i per ton, while plough steel ropes cost from j£$4 to j£66. For all situationK where a rope is worn out and not spoiled, the latter are worth the extra money. Every rope put to work should have a record kept of its performance, that is to say, the number of tons that it either hauls or windtj. Statements ore sometimes made that a rope has lasted so many years. Unless the number of tons is known, such on assertion is valueless, because a rope in another position might have lasted only half as long, and yet have dealt with more tonnage. On inclines, or places where a rope is subjecteil to severe shocks and stniina, it is not advisable to use plough steel, because the rope may be broken and spoiled before it is anything like worn out, but for slow-moving rope haulage, or, especially winding, the highest priced ropes ore the cheapest in the end ; in the first place, owing to their great strength, a smaller weight is required, and in the second, their life is much longer.
Ropes usually stretch when first started, and probably get more brittle with work. They should be carefully manufactured, and carefully and thoroughly examined. The bct signs of the limit of work, ui-e the wearing and occasional breakage of the wires. The principal causa of failure is due to oxidation, especially with stei-l. Unless ro|
never lost, no mutter what ntatjjdtUUKji Oi construction. places. The grease n fat and quite fret i importance, shoold 1
Text-Hook Of Coal-Minixo.
well greased, while the inaide goes rusty. A simple bill effective roite-greasiBg tippumtus cousifits of a cylindrical case made in two balvee, and provided with two handles, which are grasped by the attendants, one on each side. Brushes are arranged in the top part and clean ofT the old grease, while the rope runs though & bath of oil held in a cup just below ; the grease is thoroughly iiibbed in by some loose felt, also saturated with grease, which ia situated lu the base of the cylinder.
The drums and pulleys should be as large as feasible, a good rule being that their diameter should never be less than a hundred times that of the rope. The angle that the rope makes with the pulley should be as small as possible. Ordinary ropes consist of six strands, of seven wires each, twisted round a hemp (.'ore ; but for special cases where small diiima have to be employed, the diameter of the wire is deci'eased, and more wiree and strands used to make up the rope. Except for such pnrposee, no advantage is gained by this construction, as although the tense strengtli of the wires is increased, they are apt to break after a little wear. After a thin wii-o has worn a little, only a small <iuantity of material remains, while the same amount of wear on a larger wire ia scarcely perceptible.
For ropes wttli hemp O0t8, if thd circumfei-ence in inches S(]uai-ed, the product will practically be the weight in lbs, per fathom. In deciding on the sice of rope the weight to be lifted is hi-st determined. For a winding-rope such load must include the weight of cage, tubs, coal, bridle-chorus, and the rope hanging in the lihaft. Each manufacturer issues a card giving the breaking strain of different, qualities of ropes, or if tlie particulars are forwarded, he will readily advise a suitable eue. The breaking strain, however, is not the working load. For shaft work the safe toit is token at oue-tenth the breokiiig Btmin. and for inclines one-seventh. In the former vtiee, men have to tia\-el on the rope, Fw.s. 2S3 A.sD 2S4. and forsuch reason a higher
margin is allowed.
the strands of a rope utn laid in the oppoailt direction to the twist of the wine in ench strand, with the result that the wear on the crown of the strand great and tb Kir. readily break there ( Kg. S&4). Lang' PaUtU. — In England the first successful change from tlhe old construction was introduced by Messrs. Cradock, in iSSo. In lAng's patent, the wires are spun in the strands in the mim diretioD as the strands are laid in 285). Tlera ia, ttilargersorfaoe expoaedtofriioii. In wcH'Uiig RMnd
Winding.
Bry maimfacturei There seeiiis, howev
drums, &c. the wires are bent obliquely, and the greatest
amoual of wear is obtained. Lang's rope wears out ; it ib only
under' the meet exceptional circumstances that wiik break. Fig.
z86, from a photograph,
illustrates the gradual re- Fios. 2S5 ano 186.
duction that takes place in
the diameter. This coii-
Htmction has increased the
life of the ropes at least 1 00
per cent., and uo greater
argument can be adduced
in its favour than the fact
that a:i soon
Cradock abandoned their patent t-ightR e
menced unking ropes of this constrnction.
to be still some " unknown quantity," as the author's experience
of Messrs. Cradock's ropea is that they give better results than
those of other firms made on the same principles.
Locked . — With the object of inci-easing the wearing surface, locked coil ropes were introduced in 1885. A series of coils of wii-e are spirally wound upon each other, all of which, or sometimes only the outer one, are composed of special section wires, which when closed together, interlock, and present a smooth unifoi-m working surface. The rope in external appearance resembles a bar of iron, but is exceedingly flexible, and has little tendency to twist. At , there must have been some defect in the manufacture, as the outside coils slipped on the inside one and the ropes broke up soon. At present, their chief disadvantage is the impossibility of splicing kio. 287. Fiu. 288. and difficulty of capping. Recently, flattened stranded ropes have introduced, and can be spliced with readiness, but have not been in use long enough to establish any data as to their economy or otherwise.
Attachment to Cage. — The end of the rope iM to the cage chains through what is known ns the capping, which existfl in many diffei-ent forms. The old plan was to employ two semicircular collars encircling the Tope, these being prevented from slipping or drawing off by rivets, which passed both through the rope and capping. The driving in of these rivets necessarily injured the ropes; to remove this disadvantage, a capping with collars driven on (Fig. 287) was adopted. A better plan is to employ a conical socket (Fig. 288). In attaching thb, the rope is first of all threaded through the thin end and draw.
Text-Book Of Ooal-Mining.
difitaiice beyond. The ends of the strands are opened, and bent back on themselvea, part of ech strand being cut away, and in every instance are secured with thin binding wire. The end of the rope is now conical, and ia drawn into the socket. Aa an additional security, a conical ivedge in often inserted in the place origiaally occupied by the hemp core. Except under sbnorraal conditions, it is impoBflible to draw the thick end of the rope through the Bmall end of the socket, except by splitting it. If properly constructed of suitable mnteiTal, such could scarcely happen, bub for very heavy loads, collars are shrunk on. At the point where the rope leaves the capping the wires are subjected to auipping action, and often break. It is, therefore, advisable that carefid inspection should be made, and a plan is adopted at many cotlieries of re-capping ropes at regular intervals, whether they appear to require it or not. In wet shafts, the wires rust inside the capping, and such action cannot be detected. To prevent it, the capping is often run full of lead.
Cage Chains. — The cage is attached to the capping through the medium of chains, usually eix. in number, one at each corner, and one from each centre of the two longest sides. The two latter are often allowed to be slack, and only the corner ones kept taut. There appears no reason why such should be done, as if six chains are required, all should do a propoHion of the work- It is argued, that the object of the central chains is to take the weight if anything happens to the comer ones, and, no doubt, it is a difficult matter to keep six chains of such a length that all take an equal bearing, but the difficulty is overcome by providing the two central ones with adjusting screws, which enable any slack to be readily taken up. These cage ur bridle chains should be of the very best quality of iron obtainable, and should be regularly taken off every three or four months and annealed; to much depends on them, that no precaution should be neglected. As a rule, each pair of chains is conne(?ted to a larger link at the end furthest from the cage, and each of the three larger links are in turn connected to a still larger link, which is fastened to the clipping by a bolt. With this method, if anything happens to the main link the cage is detached from the i*ope. The better plan, and ]rocedui-e in the North of England I the Continent, is to connect the link ' joining each pnir of chains to a compound plate, shown in Fig. 189. The breaking strain of chain made from the best qualities of iron ciiu be found by an easily reraeuihered rule ; — If W breaking strain in tons, d diameter in eighths of an inch: -. The
Winding. 241
safe working loiul fur ishfifta should not lie mDi than one-tenth nf the breaking strain.
Uethod of Taking Off Strain, — Wlien the eage in resting the bottom of the shaft, and ia siuMenly lifted, the sti-ain on the winding i-ope is much greater than that duo to the lond, eBiciftlly if there is any slack chain. Messi-s. Crndock have imblished ti table showing the result of some tests, very caiffully made by n dynamometre, from which it appears tluit the exti-a sti-ain may amount to over twice tho real load, as will be seen from the following extract :
Cage and four full tubs weighed b_v much „ lifted gentl; ,, „ with 3 inches of slack chain
The extra strain has an injurious eft'ect on the rope, and lumeroits devices have Iteen projKtsed from time to time to reduce t. The author, in visiting Mnriemoiit Colliery in Belgium,
obseiTed a at Lye Cross I centra] one, n the cage, is m
t-'r tCjiI' -j. z. L :''-i:_vti tnc. . ': -jtrti "Lifoi . iir, A-e.
T- v.. j::
-V r.ez. rcvir
k- Live ScirL. placed the
l:.*r t"-- v.iLr. :Lr ::..-;.:: ! ir. a vr-nicMl y-I&ne and ir-.ir. i: :: .-.i:.:::.-. a'*v .. -. U : ->>v:aei the ::-L-.j ::vrTr:.: :: c::i.:.:'e>-::.- uiu.h. and a croiMMry ;,;-:.:::-:. r::':. :':.. vr:.::\i! v I'liir.-ire.r described. Ii ;- 2fi:':>r a .iiri'.:!: ::.::- r :... e-iiinaie dednitelv
some might inciiilt, and the t-ost of either or Ixith of tlieni id small.
GUIDES. — The cures are not allowed to liwmg free in the slinft, but ftre kept in the proper direction hy guides, which amy either he wood, iron mils, nr wire ropes.
Wood guides are usiiall; made of pitch-pine, aw joined together in lengtlui, and are secured to cross baitlks by HCi-ewis. They are uusuited for quick wiiidiug, are costly to fix and keep in i-epoir, but they are rigid, and their first cost in small. For deep shafts and heavy lands, the small tiilvantnge iu cost is fioon counterbalanced by the cost of the up-keep. With few exception, they are a thiii of the [Mit.
Bails. — To obtain the rigidity of wood and to avoid i-apid wear, rail guides firmly to buntone have tieen subutiluted. It is obvious that the ordinary form of chair employed on i-always oaiiuot he used, im the head and neck of the rail have to be left clear, in oi'der that the sliding attachment on the cage may pass freely along. As a rule, the flange of duch rails is made broader than tfae onliuary eoiistriictioii, and
and 294), and prevented from moving laterally by two pins, ii f>, the heads of which are bent i-ound to gi'ip the foot of the rail, and counter sunk iu tlie ' chair to pi*event the guide shoe, c. catching them. The two pins pass through the clair, a, and are bolted at the far end to the cross buntous of timber, f, carrying the whole structure. At Horlot, near Liege, luil guides are fairtened together by fishplates at the baek, bolted to the rails; the buntons in this case are not placed at the joints.
Rail guides are not only expensive , but require a lot of attention. Mr. Cli. gives the following statement of the cost, whei-e the niiln weighed 5S to the yd., wt'i* each y yds. long, and were and bolted to oak buntons set 5 ft. apart. In the walling, the buntons were set in cast-iron sockets ; in the tubbing, iron circles of U section rebtied on the ribs, and these carried
gii-ders, to which thf rails v
attached. A space of
0.078 in, was left open between the ends of the mils for exptuution, and the bolt-liolea iu the mils and tish-plates were made
Textbook Of Coal-Mining.
a tor each yrd o!
Out iFhrrt Shaft irai tubbed.
(a) Cirdf'.— Cost of each circle complete, placed in pit, including
all bolt* and vraaben, and erecting
(b) JtaiU — % £$ 14!". per ton, (4rdj. reqoireQtc
Fixing in shaft
Total eoit per yard
II .oi " S o 9i
(a) Bvutont. — Oak buntons 6' lo}' waebera. and fliiiig in shaft Rails and fish-plates as above
6'x8", wilh 8 bolts and
Un the Continent, tlie common syfitem of fixing rail guides in that due to Mr. Al. Briart, which consists in dividing the shafta hj a single series of biintonB dt Vw. 195. H steel girders, which at
Mariemont are 14.96 feet long, 0.82 feet deep, and ars placed 9.84 feet apart. The utmost care is ezerciiied in getting these buntons ia the same vertical plane, and pre- ' lus to being fixed they are notched to receive the raiLt, which are each 19.66 feet long, thus giving a slight play between the joints. To secure the rails to the buntons two steel glands (a, Fig. 295) are fixed, one on each side of the rail, which they firmly grip, a bolt, b, passing from one gland to the other. To prevent any chance of movement, a block of castiron c through which the bolts pass, is placed between the raili and ia famished with a slight projection, which lies in ft corresponding groove rolled in the flange of the rail At buntona where joints occur two sets of these glands and block aie fixed one and one Mow ; but at the intermediate liuiitons odIj one set at the top of the girders ia used.
Winding.
In paii8iiig through tubbing, the buntonii are ciimeil in shoes bolted to the internal flaDges,the girders being wedged in poeition -with wood keys (Fig. 296).
Wire Hopes. — In the majority of (aees, rope guides are employed, but differ from ordinary wire ropes in the fact, that instead of consisting of a number of wirt twisted into Gtrands, and then into a rope, each stand consieta of only one wire, but such wire is of large diameter. At first guides were made like ordinary ropeti, but when a little wear had taken place and a wire broke, the projecting piece wan caught by the shoe of the cage, and the rope "stripped," causing frefjiient stoppages. As rope guides have only to sustain small weights, wire of high tensile strength is not
Rope guides are cheap in first cost (they can be bought for jji6 ji ton), are easily fisetl, require no attention except oiling, and their near is almost unlimited. They must, however, be kept taut by proper means. At their upper extremity they should be capped like a winding-rope, and connected to eye-bolts in the head-gear. At the bottom they should pass by tbe side of a bunton, be held there by a staple, and weights added to thai lower end. Instead of weights, screws are sometimes used. In deep shafts expansion and contraction regularly take pliLce in the guides owing to the variation in temperature, imd the length alters considerably from a hot day in summer to a cold day in winter. If screws are used, the guides require constant attention if they are to be kept tnut, whereas, if they are weighted, they are always tight, as the tension is always tbe same.
It is a difficult matter to say what weight should be applied to Vuin ami 2oti.
each I'Ope, and for this reason it is not advisable that such weight should be in a solid block. Tbe proper weight is a matter t experiment; it varies from 2 t 4 tons. In addition, one large weight is vei-y awkward tn deal with. A series of single weights, therefore, appears preferable, and are best constructed as shown in Figs. 397 and 298. Each one is provided with two handles, a a, has a hole throtigh the centre, h, and a loose wedge-shaped piece, e, which when removed iiUows each weight to be without moving any of the others. This pi weilge-shaped in plan, but also in cross sectior out of place when the weight is in a horizoi blocks weigh about 200 lbs. each, and can be b
hits:
24
Text-Wxjk Of Coal-Mining.
Conductors between Cages. — The only objection urged against wire guides, is that the clearance between the cages has to be more than if a rigid conductor was employed. For deep shafts this is, no doubt, true, if the guides are connected to the cage on both sides : but a method is used which entirely removes the disadvantage, and allows the cages with wire conductors to be safely worked with as little clearance as if rail or wood guides were employed. In ordinary cases three conductors be fixed to each cage; in the special method, two conductors only are fixed to each cage, both on one side of it, but in between tike eagm aiut unconnected to either of them , two other ropes are suspended. These latter ropes are often flat ones, and at the point of meeting are lined with steel strips parsing from oce to the other, while the cages are lagged up on the inside. The result of the whole
Fii;. 299.
Fig. 300.
arrangement is, thiit from the top of the shaft to the bottom, the cages are on opposite sides of the central conductors, and cannot possibly catch each other when passing.
Guide Shoes. — ?>ome connection has to be made betwem the cage and the guides, so that the former shall travel c o rrec t ly along the latter. If the guides are of wood, the shoe need not encircle them, and the form shown in Fig. 299 is employed. With iron mil guides, which are also rigid, the common form of shoe has already been in Fig. 293, but with a view of reducing resistance, rolling lias been substituted for sliding friction, and at Anziu Collier}', France, the guide shoe is composed of two wheels, one on each side of the ndl guide (a n. Fig. 300), revolving on a pin to the side of the cage.
For wire ropes, which are flexible, the guide shoe must go completely round them, or any oscillation would throw the slipper off* the guide. A common mistake is to make the shoes very mueli stronger and heavier than necessity requires. If the guide properly hung, and the ceuti-es of the shoes set to the
L£i ue
Winding. 47
gauge, very liltte strain is thrown on them, iiud only & companilively
weak coiinecLiou is re({iiired. It is ailvisiible timt renewable
biiohes should be provided for tbe paits gripping the rope, as nil
the weur takea place there.
A good form ia shown in t'n-- 301.
Fig. 301. It consists of n
base plate, a, bolted to the
cage by two pinB, b b, and
has cast-iron bushes, c,
divided into halves, these
being fixed to the baiie plate
by a. Bteel strip, rf, which
encircles them. This strap f
is kept in position by two
pins, e f, also bolted to the
sides of the cage. By taking out these two latter pins, the busheB
can be changed whenever desired without removing the base plate.
As an experiment, the author tried brass bushes, but the I'esult
was by no means satisfactory. The first cost was much more than
tliat of cast'ii'on ones, and their life was considerably less. If the
guides are kept well lubricated the wear is slight.
Guide Troughs. — While the cage is travelling in the shaft a small itmount of oscillation is not objectionable, as there is seldom leas than from 2 to 4 in. clearance at the wmei's, hut when pausing through tbe timber framing at the top, or at intm-- mediate hanging-on places, where the clearance space is small, additional means have to be provided to prevent the cage from deviating from a definite line. With rigid guides nothing is necessiU'V, but with wire ropes the general plan is to place a trough opposite each guide at the Kios. 302 point where they pass through the frame. The 3°j' usual construction is to rivet two strips of angle ii'on to a plate at the back ; the angle pieces are belled out at the top and bottom ends of the trough, and the back plate is bent outwards to avoid any chance of the slipper receiving a blow when it enters the trongh as it is gradually guided into the paper groove. The troughs are held in position bytwo bolts which pass through the timlier framing.
Where the banking level 11 considerable instance alive the ground, it is by no means a occurrence, when storms prevail, for the g to be blown out of the troughs, and if this liappenA during winding n serious accident may Mr. A. B. Bouthnll h
r getA over the difficulty. 2 and 303), with a projection
siOe, is placed in tho iitlti trough, h, which is recessed to t-eceive the projection. TIuk block is free to move upwards, Itut is prevented froui dropping completely out of the trough liy a stop-plate, c, placed iil the lower end. In it normal pQfiition it agninxt Ibis stop-plate, and the guide passes tliroiigh II hole in the centre, iind is always locked in its proper fmsition iit the trough. Wlieu the slipper of the cage reaches iliis block, it lifts it upwards, but on the descent of the cage the block, by the action of gravity, drops into iu former position.
Engines. — For winding purposes a pair of engines, with the ci'unks set at right angles, is the only form admissible. There are, however, two wayx of placing these engines, either vertical or horizontal. VertiotI engines ore becoming things of the past, ' In the first plaee the cost of foundations is great. The drum of ' ft winding engine may weigh nnythiog up to 80 tons, and if such a mass hns to be placed 30 to 40 ft. above the ground, and revolved at a high velocity, the struc-tiu* carrying it must be correspondingly lai'ge. Vertical engines were designed to reduce wear in the pistons, it being considered that if a laie cylinder WBS horizontally, the lower half would wear very fast. For the same reason, with hoi-ixontal engines it was usual to employ bni'k piston-rods, but both in this case and in the former one, the evil has been proved by experience to be more imaginary than real, 1 and Of a result, both vertical engines and back piston'roda are ' being abandoned. At Harns Navigation inverted engines are applied at one pit — that is to say, the drum is placed below and the cylinders above. The cost of foundations is reduced, but it would appear that no real benefit results, as the second pair of engines at the same colliery are placed horizontally.
The design and strengths of the various parte is more a matter for the mechanical than the mining engineer. The stroke is usually made twice the diameter of the cylinder, and the connecting rod throe times the length of the stroke. The valve*, both steam and exiiaust, sliould be of lai'ge proportions. In winding, everything is sucnticeil t*) speeil. The engine should be simple, entity biuidled, and, above all, over ite work. Op large engines, the double beat, or Cornish valve, lias until recently been the one generally adopted, owing to the ease with which it is capable tit bung moved, but modem improvements in the design of equilislide valves have largely brought such class into favour, proper size of engine to do a given amount of work may be found by apply'ing a veir elementary formula of mecbnnics, mple as the problem is, the determination of the requii:d is oftn moi-e n matter of guess-work than of reasoning. In '"g a load, an engine has to do two things. Everyone isiiwat greater expenditure of force is required U] move a load than to keep that load in motion when once started. The ; work that a winding engine ha-' tu do, is to get
Winding. 249
corlain velocity tiniformly actielenLted from iest, and to raJite the load the distimce passed over during the time this velocity is being obtained. Mr. Hobert Wilpioti suggests a formula, based on such reasoning, which, if followed, will be found to be sa,tiafactory.
W the neigbt to be set in motion ; one cage, coal, number of empty tubs ou cage, one winding rope from pit-head geax to bottom, ooe rope
from bank level to bottom.
i' greateBt velooit}* obtained, uniformly accelerated from . gravity =31. a.
' time in socondti during which u is obtained. L- unbalanced load on cngioe. R ratio of diameters of dram and crank eiteles. Psacerage pressure of steam in the cylinders. N number of cylinders.
H - space passed over by crank pin during time I. C~%; constant to red uc angular space passed through b; crank, to the
distance passed through by the piston during tlui time f. A area of one cjUnder.
f addition for friction, lie, of engiuea varying from 10 to 30 °/o of A. l! ajea of cylinders with margin for friction allowed. D diameter of cylinder required.
1, Where the load is balanceil :
2. Where the loud is unbalanceil.
The symljols will retain their significance, and the formula will remain the same as before, with the additiou of another trm to allow for the variation of the lengths of the ascending and deBcending ropes. In this case : — -
A, - reduced length of rope in i Af-increaseil length of rope it is weight of rope per foot in
V. s. a. V.
To show how this fomiulsi applieil, periiaps the best way will be to work out an example, aiming that 1200 tons are to be raised from a depth of 420 ytls. in 8 hours, that the tubs weigh 7 cwt. each, and carrv 1 2 cwt. of coal, that four tubs are raised on each cage, which weighs 30 cwt.. and that the pressure of steam will be 70 lbs., the diam. of drum iS ft. and the stroke 5 ft.
1200 tons in 8 hrs. 150 tons an hour, and as each journey carries 48 cwt., nearly sixty -three journeys have to be made in each hour, and each journey must not occupy more than 57 seconds. As numerous small stoppages always occur, it woidd be best to assume that winding and changing has to take place in 50 seconds. If changing is performed in 8 seconds, the actual time of winding will be 42 seconds, and, as the shaft is 1260 ft. deep, the average speed will be 30 ft. a becond. The maximum velocity will be at least 40 ft. The time /. in which this velocity is obtained, may safely be taken as Ith of the total time of winding 6.
The rope should be of plough steel weighing li lbs. per foot. If the load is balancetl L 48 cwt. 5376 lbs. If the head-gear is 60 ft. high. 18.322 lbs. In the time f. the dram will probably make three revolutions, therefore 8=3x5x3. 1416s 47.13. 'R 3.6.
/07S.b 3X4, sav 30 ince.
Position of Sngine House. — In nearly every case the direction of the inset governs the ftosition of the winding engine, the driun shaft being geneitiUy at right angles to the axis of the inset and cages. The choice, thei-efttre. appears to be limited to two positions, either A or H <Fig. 304 K Such, however, is not the csise ; the cashes may still Iv kept in the same line fay placing the pulleys obliquely, shown by dotteil lines, and, by doing so, the enanehoae may be situated at. say. either C orCor practaoally anywhere ; indeed, by putting one piUley over the other, tlw eniriue may be pLiceil at right angles, D, to the axis of the inaetb
Drums. — The winding mpe is coiled on a dram, wliidi maj bt of various forms. The first di'is'ion is produced bathe tjpsof rope adopted.
The ropes ai-e llat oneand coil on themselves; the of A narrow cylinder of >uia11 diameter fitted with side. Its weight U small and its i-construction
The other main di\~ision is caused by the emplojOMBfe of rojH-s. It lia> lier-i\ xritfil to make i-ound ropes cofl
Windixg.
ami euijiloy a drum fiimilftr to ihiit used fur a fliit ro]>e, but tlie experiuieiit diil not meet with success. TLree types of <lruni> fojround ropes are in use: (i) The ordinancylindi-icnl foi-ni. parallel throughout ; (2) Theconicol; {3) The BpinU,
The pam.llel form is obviously the simplest, cheapest, and least liable to accident. Its only disadvantage is the side friction resulting i,-,, ,g. from the angling of the rope. The . successive coilatie side by side, and as 'Wff//// they lap on the drum are constantly /'m//) moving relatively to the centre line w of the pulley. An attempt is made to equalise this strain, by placing the drum in such a position that at the commencement of a wind the rope is at the same distance on one side of the centre line as it '\s on the other side at the conclusion— that is to say, the centre line of the pulley coincides with the centre line of half the drum.
The result, however, is that at first the coils do not lie against each other, but have spaces between, as the rope tries to get into the some plane as the pulley, but after the central point is pa.sHed, the rope still tries to keep in the same plane as the pulley, and the successive coils not only lie very close against each other, but a grinding action is set up between them.
This disadvantage is removed in some case by turning; shallow grooves in the circumference of the drum for the to coil in. It then winds evenly and grinding is avoided. A far cheaper plan, and an equally satisfactory one, is to make the drum aliyiitli/ conical, instead of cylindrical, a slope of 1 in 10 bein' sullicient. The tendency of the rope to gel into the same plane as that of the pulley, is thei'eby counterbalanced by its disinclination to climb the slope, and each coil winds evenly iiguinst the other. With either system, and a cyUmlrical drum, it. is impiissible to avoid aide friction altogether. What is done is to make the side friction of one Up equal to that of another, and not throw all the grinding action ui">" or two coils.
To obtain the ad\-antage 'cueing, which is discussed
further on, conioaJ i5 "led — that is to say.
of counterbalancing the slopo of
25 'I'Ext-Book Of Coal-Mixing.
tMyin olT. For this reason, their use has been absmdoned. lu their place spii'al di'umH have been substituted, which consist of a combination of a cone and a cylinder. The cone is very steep, and ou its nide is aiTniiged a spiral groovA, usually made of semicircular iron troughs. The rope commences to coil at the smal end of the spiral, and gradually ascends the cone, finally wrapping on the cylindrical part, the latter being added to reduce the width of the drum and the angling of the rope. An each groove has to be placed at such a distance from, the one immediately above, that the rope going from the lower spii-al misses the troughs of the upper one, a considerable amount of space is occupied, and unless several of the coils took place ou a cylinder, angling would be very large, and, in addition, for an}' great depth, the irise of the drum would be enormous.
Several objections may be urged against spii-al drums : (a) As pointed out further on, counter balancing is not perfect ; (b) Their enormous weight and cost ; (c) The disadvantage attending banking. The cage at the bottom of the shaft is attached to the rope (filing on the sntaller diameter of the drum, whilst tliat at the surface is coimected to the larger diameter. Wlien the cages are moved to change the decks, thu drum has to be turned sufficiently to wbid up on its auudleat diameter an amount of rope equal to the height of a deck, whilst, at the same time, the cage at the Hurface is lowered a considerably greater diatnnce. because the to which it is attached is coilett on the lavijef diitneter of the drum. After the engineman hwa put the bottom rage in position, he has to lift up the top ciLge again to discluirge its content the result being that tiuie is lost in banking.
Brakes. — An efficient brake ou a winding engine is an absolute necessity. In cases of emergency, very power'ful ones are Inquired, and ti> meet the case the bi'ake-strap is connected through a lever to the piston-rod of a small engine, int which steam can be admitted. Such un appliance acts on the "all or none " principle ; full power has either to be exerted or not. If steam be admitted to tlie cylinder, the power appUsd to the brake is due to the area of the piston multiplied by the pressure, and as neither the steam pressui'e nor the piston area can be varied, tho power exerted is always constant. Immediately steam enters the piston such power is applied to the brake-strap, the I'esult being that when a steam-bi'ake is thrown into action the machinery is subjected to very severe shocks, and consequently such appliances are only used in cases of emergency. As a rule, winding engines are protHded with two brakes, one applied by the engineman's foot, and the other by steam, the latter only being used on rare occasions. Sevei devices have been designed to increase the poweiand leverage of font bikes, and to do away with those of
ISnni'a Jli-n/.r.—'Tlie brake-strap does not encii'cle the drum,
WINDINd. J53
but consists of a block of wood (B, Fig. 305), about 24 in. long b_v 6 in. broad, in which n series of holes are bored and hUed with sand. This block of wood i8 placed at one end of a long lever, the other end being moved up and down by a rod connected to the arm of another lever controlled by the enginenian. The block being small in area, and fitted to the rim of the drum, only requires a very small movement to free itself, and the length of the lower lever being nearly equnt to the length of the engines, it follows that a large amount of power can lie applied. At
Vm. 305.
Bickershaw Colliery, Lancashire, the leveiife is about 200 to i, and aa there are two blocks on each drum tlie power exerted by the enginenian i.s multiplied to a great extent. The action of the Rand in the holes is to keep the brake rim free from grease. Bv the aid of an adjusting Kcrew, A, the brake can tightened in a few minutes and any wear taken up in the blocks, which are usually I'renewed about every four mouths.
TyldenUy CoHieri/. — A pair of 32 in. cylinder engines are here fitted with a powerful strap-brake, moved b}' a toggle-joint le\'er. The engineman exerts pi-essui'e through his foot-treadle in the direction of the an-ow W (Fig. 306), pulk down tli.' bell lever, A B moves the toggle-joint, D E F, and gives motion to the lever, F G H, working about the centre, G, the end, H, Wiun attached to the strap y " half round the brake-ini.L in each pait is shown by ' oQ the brake, the ' the instant nitely larga
Text-Bch1K Op Coal-Mining.
has desiiil & speciA] valve and gearing (Fig. which any vniiutioD of power to be applied, as the pressure of et
the brake-cylinder is made
if Btoam in I
proportion to the amount of force exerteil by thvJ engineman on the e trolllDg treadle. The p sage, I, leads into cylinder of the steambmka,ff which is fitted with npistonl and piston-rod, the lasts being connected by n linfcj to the lever applying tho brake. Steam is adinitt4l| on one side of the piston T only, and enter's and leaves the cylinder by the same passage. The valve-box. (I, is fitted with two valrea, fi and c, both connectedJ by gearing to the lever tol which the foot-treiidle, /M is attached, and couti'rolled by the link, e. The valve, b, whi(| fidmits Hteftm through the passage, g, is kept cIot;ed by n Bpring, d, which just balances it against the steam in the boiler. Ilhe relief valve, e, unless the brake is in action, is in equilibrium, free tofl open or shut. W
When the treadle is pressed down, the steam-valve is relieved OtM some of the pressure which keeps it closed, and steam enters thai cylinder until itn pressure is sufficient to again close the valval iLgainst the force exerted by the treadle, so that the greater the force exerted on the treadle, the greater the pressiu-e must the steam i-each liefore it closes the steam-valve. At the same time, us the treadle relieves the steam-valve of bome of the spring pi-esiiure which tends to close it, it brings an equal force to bear on the relief-valve, e, to keep it closed ; any increase of steam pressure in the cylinder beyond that intended iit once escapes through the relief-valve. Thus, if the force exerted by the treadle 1 to reUeve the steam-vtitve. is to the extent of what amounts toa one or two lbs. per sq. in., the Mteam-viilve admits steam intofl the cyhnder until the pressure there is one or two lbs. perscj. in., as the case may be, and then ctoaes. The treadle at the same time exerts sufficient force to keep the relief-valve closed until the steam in the cylinder has reached the one or two lbs. pressure, and then allows anything beyond that to escape.
CounterbalanciDg. — With an ordinary cylindrical unless some means are taken to connteibalance the weight of t
rope hanging in the shaft, the engine ix Hiibjecled to a. Tfuiation in the load, especially in sleep shafts. If
w weight of cBpe and imply ttib9 6a70 Iba.
c weight of coal— 4480 lbs.
weight of rope hanging down pit 6000 lbs.
At the commencemeDt, when the empty t-ittK nt the pit, the weight to be lifted will be ;
In the centi-e of the run, half i' woulil have been gilded to the descending load and subtracted fi-om the ascending one ; the weight
on the engine is, therefore :
At the end of the wind all the descending cage, and the weight on
)B IB acting in favour of the le engine becomes :
Dm-iiig the complete opei-atiou the load vfiries from 10,480 lbs, against the engine to 1510 lbs, in favour of it. At the coinmeucement of winding the engine WB.<itea a deal of energy in setting this mass into motion, and as speed !s the main object, the euginenuin cannot cut otf steam when mout desirable, but must go on, and tioally has to i-everae the engines in ordet' to bring them to rest. An enormous amount of energy is therefore lost in the latter part of the run, and such loss obviously increaaos with the depth of the pit.
Supposing, now, that by one of the uiethorls of counterbfdancing, the weight of the rope hanging ilown the sliaft was balanced. It this new factor be denoted by r', the weight to be lifted at the commencement of the run will be:
in the centre of the wind it will be :
The weiglit tl smaller at the b will be cleurly t decrement in
TKXT-iUMJK OF
two forcM are equal and oppout at Uie beginmng.
Having jit-oved the great advanta of eounterbaloBcing, the meana by wliich mich is secured may now be considered.
Taperin'j Htita. — A tapering rope enables winding to take place from greater depths than is possible with ropes of uniform xec-tion ; the tlieory of taper ropes to obtain imiform strength throughout, thinner at the cage end where the weight is least,' and thicker at the drum end where it i.s greatest. Their thickness IN mich that the section at any part is capable of safely bearing the loud on il at such point. With tapering rope, a Emallep initial deity weiglit is thrown on the engine, as their section at the largest \imai will lie less than that of a rope of uniform unction throughout, because a smaller weight has to be supported. Tho ililTerenoe lietween the initial ainl final load is also smaller, but it incriwsos more i-apidly, because the largei' diameter is woiinil oil the drum in the ascending portion, while in the iliiiM!onfliiig portion the larger section is being unwound. These ropiw cost more than ordinary ones, and owing to the difficulty of uianufiu'tui'B cannot lie made so perfect.
Flat HoptM. - This means of winding allows of a certain equalixation, for the radius of the coil of the rope continuea to incnwse, while> thitt of the descending rope diminishes; conse-i qiiently, lui the resistance decreiu'es in the ascending load, the leveriifje inoreaMS, anil tis the iDci-easesin the other, the leverage diminisheH, Tho variation in the leverage in a couatant quantity, and is equal to the thickness of the rope. If the diameter of the drum -be madv small enough nt the commencement, n remarkable uniformity in the load may olitained, the only objection being; the line of Hat ropes.
Cimioal mid .''final Driimg. — Reenlta analogous to the prorediuft may be obtained by using round ropes coiling on conical druuin. Tiiey may be either smooth, the successive coils lying side by side, or uiay be provided with a spiral groove. If aconicaddnua was oonatiiieteit to give perfect equalisation, the sides would be so sleep that tho rope would slip ufl'. For such reason scroll drama werA which are open to the objections already stated. It) addition, tlie load is seldom perfectly cotmterltalanced. To tibtain satisfactory wear from a rouuil rope, it must be coiled on a itrum of Urgv diameter. Such condition limits the siie of the smaller diameter, vrhich is ustially made so large that if the final diameter was of (he dimeasious to give perfect toonter-
? of the drum would be
For this
. and to prevent the gnat latotml displacement at tbe winding rope from the ci-ntn Une of polley, owing Uinr iMmrilT lai width, iuch dnuns are onwDy uade fbraevnal coils to taW pkm on thr spiral, aad the remainder on the flat IWI Ay* * f'yf.— With cyliadrk*] drraas, parfM*
Winding.
Ss7
counterbalancing con be secured hy sevemi meUuxlB, but all have given way to the endless rope eystem, which ia preferable to all other'a if tbe shaft is free from crosH-timbers. It consists of placing benentli the cages a tail rope, equal in diameter to the winding rope, and after conveying this down the pit into the sump, where it forms a loop, it is returned uud attached beneath the other cage. When first introduced, it was considered that a pulley must be placed in the sump for the toil rope to pass round, such pulley remaining stationary under ordinary conditions, but free tu move between guides and be lifted out of its bearing in cafie of accidents. In the majority of comes no pulley whatever is uued. All that has to be done to keep the tail rope from twisting, b to fix two beams side by side across the pit in the sump, lietween which the tail rope pasaeK, and another one below put across in the opposite direction, the latter passing through the loop in the rope.
It is perhaps preferable to use a guide pulley in the sump, as old winding ropes can then be used, otherwise a special rope has to be employed, a& old winding ropes are not sufficiently flexible. The balance roie is connected ta the bottom of the cage by an ordinal'}' capping and bolt passing througii a. cross-hearer.
By this system jierfect counterhidancing is obtained, as a factor ia introduced equal and opposite to the winding i-ope, and gives equality at the beginning and the end. The one solitary objectioD urged against it, is that a greater weight ia put on a under part of the winding rope — viz., the capping, but if properly constructed and put on, the capping is quite ao strong as the winding rope itself.
MeinkJce'g Syalem.* — A balance rope is employed in this method, but instead of attaching it beneath the cage it is connected to two auxiliary ropes, which may either be coiled on the same drum as the winding or on auxiliary ones. The auHiliary rope passes over separate pulleys on the head -gear, and the balance rope is equal to the weight of the winding and ausilinry ropes. Perfect counterbalancing results, and no additional weight is thrown on the capping of the winding rope. This, in conjunction with the fact that the tialance rope may be led into any position in the shaft and based oS, are the advantages, but as it is much more coniplioAted than n tail rope benejtth the cages, the latter seems preferable.
Sxpanaion.For economical working uteatn must UMed expansively. With a (nlinMously mntiing engine thei-e is no engine, working under i;iling.
the problem is not so i.n;; is
sacrificed to speed. 1 1 : lart
25
Text-Book Of Coal-Mining.
quickly, should travel at a high velocity, and be quicMy brought to rest ; it is also essential that the engineman should be capable of putting either full steam on or against the engine, whenever required, and, above all, the machine should be simple. Under these conditions, regular expansion is quite out of the question. Of late years several most ingenious automatic variable expansion gears have been designed, which give satisfactory results. They are so arranged that at the beginning of a wind the engine takes full steam, and they only come into operation when the machinery has attained its maximum speed. The general type consist of " trip gears,'' that is to say, by some arrangement the
Fio. 308.
valve is made to tiip off the lifting lever, and close before the completion of the stroke.
Mtisgrave Gear, — In Fig. 308, A is the spindle of an ordinary Cornish valve fitted with a dash-pot, O, at its upper end. With ordinary gear, the valve would be lifted by the lever B catching the projection 0, but here a bell crank lever, D E, capable of turning about the centre, F, is interposed between the two pieces. Fastened to the upper end of the frame carrying the valve is a pin, G, and spindle, H, on which is keyed an eccentric, K. By means of the link, L, and the rod, M, a rotary motion can be given to the eccentric about its axis, H. At the beginning of a wind, the lever B (moved by the eccentrics of the engine in the ordinary manner) raises the valve through the bell crank, the spindles rising and falling with the lifter, as if no expansion gear was
Winding.
present. As sjieed increaMs, the rod, M, which is in connectioD with the goverDor, is moved in the direction shown by tlie arrow, tiiriiiK round the eccentric, K, and depresses the end, D, of the bell crank. The lifter, B, then trips off the other end, E, of the bell crank, and allows the valve to cleo suddenly, any injurious shock being prevented by the dash-pot, O. The lifted*, B, continues its upward journey without the valve, and on its return, the spring, N, pushetitfae bell crank into gear again. Fig, 309 shows the attachment of the gear to the engines. It h worked by a dead weight governor, a, driven by a strap, b, from the drum shaft, c.
In the case of a new installation, it is only necessary that the maximum speed at which the engines are to run shall be determined, and then by a proper relation between the pulley on the drum shaft, and the pulley on the governor, the point of cutofTcan be readily fixed. This gear has been applied in numerous instances to winding engines, and the author has insfiected its working on several otrasions. At Tj-ldes!ey Colliery, Lancaliire,
the drum makes twenty revolutions, and a cut-off of Jth commences at the fourth revolution. The gear doe not come into operation until the maximum speed is obtained, and is thrown out of action by the governor towards the end of the wind, when speed falls. Its advantages are, that it has no complicated parU, ia out of the eiigineman's way, and comes in and goes out of action without interfering with any of the parta handled by him, and, at the same time, allows full pressure of steam at the beginning and end of a wind, or at any other desired point during the ascent or descent of the cage ; indeed, so far as the enginemau is concerned, he is in just the same condition as if the gear were absent.
Gnmfje Gear. — A gear is applied by the Grange Iron Co., which is similar both in principle and ai-tion to the one just described, and gives the same results. The only ditferenoe is in tha n ment of the parts. The lifter raises the valve tlirouuh rocking lever, under one end of which a tli'l . pu.ihetl or withdrawn by a couibinittio:! go\'emor. When the wedge is puMhed rocking lever (which Uikes place when ih. obtained), the lifter drops off the other enl to close at some intermediate point in the 1-
26o
TEXT-BOOK or COAL-MIXING.
Sulser Gear. — This arrangement lias beeii applied to i enginett on the Coutineut, and is most ingenious, eJthough rather complicated. Fig. 310 is a diagrammatic sketch. The shaft, a, driven hy bevel geai-iug from the crank shaft, and revolves at the aame lipeed. Un it are keyed two 310. eccentrics, only one, that working
the steam valve, being shown in the sketch. By the revolution of the spindle, a. a motion to and fro in the direction of its length is given to the eccentric rod, b e. As this falls, it catches a projection, a. oil the bell crank lever, a e/'jh,the fixed points of whieka are e and A, and the valve Ls lifted. On a second shaft, J b fixed an eccentric, which 1 be rotated by the governor in ths ] direction indicated by the arrow. The rod of this eccentric i connected by a screw to b c. In ordinary working, the apparatus I stands as shown in the sketch, and the valve is regularly closed and ( opened. When speed increases, the spindle, k, and its eccentric ia rotated, and the tr, b c, pushed outward, with the result that tho projection e trips ofi'rf, and expansion results.
Condensation. — Expansion to obtain the best results must J be in combination with condensation, except where very high 4 pressures are used. Unless condensation is employed the ratio of expansion can only be small, because the exhaust steam must have a pressure greater than the atmosphere. Xo satisfaotoiy solution of the problem was obtained owing to the complicatjotx resulting, until the idea of using independent condensers applied.
Ad independent condenser, as its name implies, is not fixed to, I or moved by, the engine or engines whose steam it condenses, bub is worked entirely by an engine of its own. To be a success, it should take steam from several engines, and run continuously. With it a constant vacuum is always retained. Many suchappUancea are in use, but it can scarcely be said that any are working perfectly satisfactorily, although many are giving good results. 'l"he chief difliculty seems to be to deal with the enormous volume of steam which comes from the winding engine at intermittent times. Winding engines are necessarily large, and run rapidly, BO that when they are moving, especially if expansion is not used, the volume of steam discharged is very Urge, far more so thau is general with continuously running engines. TTie condenser, therefore, has a. difficulty in dealing with these sudden rushes, AnotliH' point is, that either a targe quantity of water must be availalde, - or some means introduced for cooling it. At Anzin Colliery t'
Winding.
hot water fi'om fclie condenser is cooled by being piuuped to tbe top of a wooden frame and then allowed to fall through tbe air. A series of horizontal trays composed of brusbwood are arranged beneath each other, and the water in falling from one to tbe other ie split up into small drops, tberaby largely increasing tbe -cooling surface.
An instance of the work such an apparatus may do is supplied by an independent condenser and air-pump at Itickershaw Colliery, which is kept continuously working by a subsidiary engine. It takes steam from two pairs of hauling engines, having i6 in. cyl. 3 ft. stroke, fifim a. fan engine with lo in. cyl. by 5 ft. stroke, and from a pLiir of 30 in. cyl. by 6 ft. Etroke winding engines, and maintains a t'onstaut vacuum of 10 lbs.
Compound Engises. — Moat economical results are obtained by what is known a.s conipoundiug enginisi — that is to say, the engine is supplied with a high and a low pressure cylinder, and expansion takes place in each. Tlie steam from the high pressui-e cylinder passes into the low pressure one. The object of using two cylinders is to obtain a higher degi'fie of expansion than could take place in u single cylinder, with good results, nJi; tbe difference between the initial and final temperature of the steam would be too great. A pair of compound engines would, therefore, contain fonr cylinders, and as simplicity is essential in winding machinery, auch tyjie has never met with favour.
Quite recently, however, it lias been suggested that winding engines should be caustruct in pairs as beforo, but instead of both cylinders being high pressure ones, one .should be high pressure and the other low pressure, steam passing from the former into the latter. This is the type known as the twin compound, but tbe difficulty encountered with it was that sometimes it could not be got to start. Such failing was fatal to any application for winding purposes, as engines of such description are practically doing nothing else but starting and stopping. The first solution of the question was obtained by Mr. Wm. Oalloway at Llanbradacb Collieiy." Successful woi'king followed on the introduction of a reducing valve between the stenm pipe leading from the boiler to the high pressure cylinder and tbe pipe connecting the high and low pressure cylinders, in such a manner as to maintain the presBure in the intermediate pipe, irheri the engine tens not at work, U Ikeuihr HJMfllfl at the same average as the steam in th*t assume when the engine was working, eteam passing through Ihs ] quantity necessary to accon valve was introduced in t with the high preasurs si
Text-Book Of Coal-Mining.
the intermediate pipe itself, for the purpose of enabling the reducing valve U) be properly regulated.
Special Methods. — Blanchet'a Pneumatic System. — The employment of round ropes is limited to a certain depth, as a point is reached beyond which they will not support their own weight. Taper ropes have theoretically no such limit, but practically ey have, owing to the method of construction. To dispense with ropes altogether, Mr. Blanchet successfully applied at Epinac, France, the principle of the pneumatic tube.
The Hottinguer shaft was intended to reach iioo yds., but, unfortimately, after attaining 711 yds. no workable coal was foimd, and, although the pneumatic has been ubed for winding on a small scale, it was never carried out in its entirety ; but sufficient experience was gained to prove that the idea could be a practical success. At the same time, the results did not show that it was superior in economy to the system of employing ropes, if counterbalancing be adopted. The expense of the installation was enormous. One tube 63 inches diam. and about
in. thick was placed in the shaft. It was made up in about 20 ft. lengths riveted together with buttjoints and counter-sunk rivets. At first, it was thought that the tube would have to be bored, but such was found to be unnecessary, although each length was hammered to a perfectly cylindrical form upon a mandril. A diagrammatic representation of the scheme is given in Figs. 311 and 312, the former showing the cage at the bottom of the shaft, and the latter at bank.
The piston is made in two parts, one at the top of the cage and the other at the bottom, while the former is subdivided into two portions placed at such a distance apart that uj . ''—mf in passing the doors through which
SmJy%BmA the tulis are changed, one of them
sliall always be in an uncut positioii of the tube ; this ensures the pressure remaining constant when the piston passes the doors. The lower part of the piston below the cage carries a parachute, p. The cage holds 9 tubs, one above the other ; the load of coal carried is
Ttibe atmospJteric du puiU Hottinguer. Z. Blanchet. Soc. Ind. Uiflu (2 Serie), iv. 57 and vii. 273; T. W. Bunning, N. E. I. xxiiL 8i Pneumatic Hoisting, H. A. Wheeler. Amer. Iu8t. M.E. ziz. 107.
Figs. 311 and 312.
a.
t
m-
Winding.
nearly 5 tons ; und the total weight of the piaton, cage, tubs, anil coilI is about 1 3 tons.
When the air is exhausted above the piston, the latter coiumenees to nsceud, wliile for descent, exhaustion ia stopped, its connection with the exhaust engine severetl by nieauB of doors at C, and ail' allowed to pass upon the top of the piston through the regulator. c. To remove the tubs from the cage three double doors, /, are provided in the tube, both at the top and the bolton, these correeponding to three levels of the heaptead. Three movements of the cage take place to change the nine tubs, and to keep it steady while such ia proceeding, three double sets of stops, a' ai-e introduced, and con bo thrust into the tube or withdrawn by means of one lever. When the cage is conhned between stops a' of the two sets, decks i, 4, and 7 cud be handled, while if the cage be confined by stops a' of each set, tubs 3, 6. and 9 are discharged.
At the bottom of the shaft, the equilibrium pipe, E, goes from the bottom of the tube to a point Buflicieutly high to be above the piston during the whole time the tubs are being changed. When the cock, e/f in thLs pipe is dosed, the pressure of air on the bottom keens the pistol up against the top stops, and when the cock is opened, and the main inlet and outlet valves, A and e, shut, the air below ratified, and the cage falls on to the bottom stops. At the pit top, the two pipes, A andB,ai-e provided with stopcocks, c and t ; the first is in connection with the atmosphere, to allow the ciige to descend, while the latter is in connection with the exhausting engines, and is used to move the cage if required while banking is being performed.
When the cage ascends, the doDrs,/,y and e, are shut, but when it arrives at the top, it is made to stop, first, by automatically shutting at k the connection with the exhausting engine at C, secondly, by moving the valve I, and admitting some air from the atmosphei-e. while if tlie ascent still continues, the valve u is lifted and the tube opened to the at mas ph ere. To avoid all shock when opening these valves, the lop pail of the piston caiTies a spring buffer, a. In the descent, when the cage arrives near the point whei* it bos to stop, it automatically closes the escape valve at
The apparatus also serves to ventilate the mine. During the descent of the piston, the valve A is shut and e opened, and sJl the ailcontflined in the tube is forced to hank, but during the ast'eut of the piton the valve e slit and h opened, so that un amount of uir equal to the contents of the julie ia exhausted from the to be di.sclmrgi'd inti) the iitiiiiwphi'ru when the piston
uds. Eoepe Sy
quires a large li.'il amount to i I lie with
rEXT-BOOK OF COAL-MINING.
the drum relatively small in diameter and in width, the ascending rope is sometimes arranged to ooil on the space from which the <descending rope has been uncoiled. This is not often employed. It is inconvenient when repairs have to be made in the shait and only one rope used ; in ordinary cases the second rope is coiled on the drum, here it cannot be, as there is only space for one. In addition, the wear on the laggings is also great, and the centre part of the drum is soon cut into a deep groove.
To i*emove the objection to the weight, <S:c., of large drums. Mr. Fredk. Koepe designed the S3rstem where they are dispensed with altogether. The first application was made at Hanover Colliery, in Westphalia, and may briefly be said to consist in the substitution of a single grooved pulley in place of the ordinary drum.
The winding rope passes from Fujs. 313 AM) 314. one cage over its head-gear
pulley, round the " drum," and, after passing over the other head-gear pulley, is connected with the second cage (Figs. 313 and 314). The winding rope simply encircles about half the periphery of the drum, in the same manner }is a driving belt on an ordinary pulley. There is a balance rope beneath the cages, so that the arrangement may be likened to an endless rope, the two cages being simply points of attachment. The drum pulley usually consists of the two outside cases of an ordinary cylindrical drum, bolted together and securing between them a band of hard wood in which a groove is made to receive the winding I'ope, the depth of this groove being generally equal to twice the diameter of tlie rope. Instead of being placed the head-gear pulleys are angled towards each other, with the object of reducing side friction.
The system has been in successful operation since 1877, and results show that the single winding rope lasts more than twice as long as the two ropes fonnerly adopted. Experiments made have determined that with a rope passing only one-half-tiu round the driving pulley, the co-efticient of adhesion between steel ropes and wood rim is in practice 30 per cent., which would admit of an excess of 105 cwt. being placed on the present ascending load at Hanover Colliery before any slip can occur. The first application of this system in England was at Bestwood Colliery, Nottingham,* but after seven years' working it was abandoned (in
k
Ches. Inst. xi. 267.
Winding.
65
189a) owiog to the slip which took place when the winding ro|)es were oiled. At this colliery such slip was most objectionable, because winding took place at an up-cast shaft which was cased in all round. The enginetuan could not see his cages, but had to rely entirely on the indicator, On the other band, at Sneyd Colliery, North Staffordshire, where the second application of this system in this country was put down, its working has been, and is, most Eatisfaclory.
The merits and demerits of the system are fully explained in an elaborate inquiry by Mr. L. Tmsenster,* and later particulars of the results obtained at Hanovei' Colliery are given by Messrs. Mahlet, de Goumay, and Suisse.l
When the cages reach the landing-place and rest on the stops, the weight is removed from the rope, and sufficient adhesive [lower doe.s not east on the rim of the motive pulley to enable the load to be re-iitarted. This can be guarded against, either by dispensing with sto{>s at the top, as iii done at Sueyd Colliery, or by continuing the rope piist the cages by means of cross-beads, above and below each cage, connected together by croes-piecee pDKsing outside ; the bridle chains are hung from the top crosshead, and when the cage rests on the stop.s the weight of the winding and tail rope still remains on the motive pulley. Tliis was the arrangement used at Bestwood.
The great objection to the Koepe system, and the cause of its abaudoument in a few instances, is the probability that if one rope broke botJi cages would be precipitated to the bottom. In Germany a brake block has been placed over the pulley, which, in case of the rope breaking, is automatically wedged against the pulley, and prevents the rope from slipping.
A recent installation in Belgium entirely removes this objection. Instead of one rope, two are employed. The di'um has two grooves, and there are four head-gear pulleys. Bach rope posses from one cage, over its head-geai' pulley, round one groove in the drum, over the other head-gear pulley, and back to the other cage. Eia-h rope passes half i-ound the drum — in fact, the arrangement simply consists of duplicating the Koepe system. The only difference is in the attachment of the ropes to the cage. It is obvious that it would be a very difficult matter to keep both rows exactly of the same length, while, if they varied, niid one became longer than the other, the shorter rope would have all the weight, and the longer one would in oil probability be thrown out of the groove on the pulley, and might caoifp & wigitsvt accident. To prevent this, the rojies, imtteoU f ' '— nected to a tension nppnratUR pulji an eijujtl oa t
' Itev. VnltM
Text-Book Of Coawhixing.
are termLiuitd by an ordinary capping, b b, through which is paaBed an ordiunry chain, c. This chain is eadJess and jxtasefi round a polygonal drum, d, ou the top of the cage, but the sides of the polygon are rounded to tit the links of the chain (Fig. 316)- This pulley can turn on an axis, and readily permits the chain to adjust itself to any variation in the length of the ropes. Two small crosa chains, e e, connect the main chains, n o, so that iu case of the breakage of either of the ropes the other one holds the load ; and, finally, in case the chains, a a, should break, the cage is supported by a, flat meUd rope, having one extremity attached to the capping on the winding ro{>e, n'liikthe other is connected to the cage. Instead of employing round balance i-opes beneath the
cages, two flat ones are employed, the strands of each being laid
in altei'nate directions. By diHiig this, it is claimed that aDy
tendency to twist is entirely removed.
I Prevention of OTervinding. — Unfortunately, overwinding
I aometimes takes place, and the cage and it-i cuuteuta are lifted too
I far, and dashed violently against the timber at the top of the pit
I frame. To prevent the rope being broken, and the cage dropped
bock again down the shaft, detaching hooks areemployed, Tbeea
may be divided into two classes ; those which simply detach the
rope from the cage, and those which detach the rope, and, at the
same time, prevent the cage from falling. The former vevd first
employed, but ae additional means bad to be provided for holding
the cage when released, which involved the introdnct'
another complication, they have entn'ely given way to th*"
where one instrument serves purposes.
Winding. 267
Tliere are many elhcient disecgaging appliances in use, all of whicli perform their work well, and only differ from each otliei' in mutters of detail. Perhaps the best known ones are King'ti, Ormerod's, and Walker's. In all of them, detachment ia eD'ecteil by pasBing the rope through a circular hole in an iron plate, w through an iron cylindei-, the she of which is sufficient to allow a portion of the book to pass through in its working state, but not to allow it to fall back again when disengagement has taken place.
King's hook consists of two outeide fixed plats, enclosing between them two inner movable ones, which can oscillate about a strong pin passing through both plalett and framework. The upper end of Ijoth these plates Ls made of uuifortn width, except near the bottom, where two projections n, Fig. 317) are tisej,
which prevent the hook from pLssiug patirety through the hole in the disengaging plate. The winding rope is attached to the top shackle, d, and the cage to the lower one, e. Whun the two movable plates are placed on the central bolt, li, their upper part (lose in opposite directions the connecting pin of the winding rope shackle, and entirely overlap it, and in such position are secured by a copper pin, e. In case of overwinding, when the hook passes into the ring of the disengaging plate, the two projecting pieces, a a, are forced inwards, thd copper pin sheared, and the jaws at the top forcibly separated from each other, releasing the ejiackle pin, d ; at the same time the two projecting pieces are foioeii outward,/ /; and prevent the cage dropping
iTrnMraTa io0i toWM to the foreguiug one. The only
frictioii, and unless they are regularly taken npait and oiled, there ia a probability thai the platen will tinaly rust together.
Wal/ur'a hook acts on an entirely different principle. In those just described, the weight is utilised to prevent displacement, while here the load is always endeavouring to detachment, but prevented from doing so by a hoop encircling the hook. Its construction will bo Fius. 319 Asu jao. understood from Fig, 319,
Two levers,af(, are pivoted about the c-eutre, h, and kept from opening nndcT oi-dinary conditions by the colliu', e, held in position by the co])per rivets, rf, which iilso secure an addition I saf eguii rd , eonaistiog of a tongue pHGKiug from one jaw to the other. When the hook enters the plate, the collar is pushed downwards, und the two rivets slieared ; the upper [tart of the jaws open, release the winding shackle, >tnd lock the cusptinsion jaws on the disengaging plate (Fig. 320).
Safety Cages. — The apimratus just described do not safeguard the cage in the event of the i-ope breaking. To perform this operation, innumerable devices have been designed, none of which bave, however, met with perinniieDt succeBa in this country, although many are working on the Continent. These safety cages usually depend on the action of a grip, which is kept away fi'om the guides so long as the weight of the cage is home by i the rope, but immediately fracture occurs, a spring, which bas I been kept iu compression, is released, and the grips clutch tha I guides and prevent falling. The objections to such appliances J are numerous. At modern collieries, the velocity of the descending 1 cage approaches that of a. falling body, and there is always a I danger of such appliances coming into action when not wanted. Then again, the result of suddenly stopping a cage travelling I at such a speed would be that, unless the safety appamtus was exceedingly strong, in all probability it would bi-eak and release the cage, while it' it was strong enough, perhaps the guide ropes would be broken. In either case, if men were travelling in the cage, the probabilities are that the shock would ' great that they would be thirtwu out; indeed, instances a record whei'e with a detaching hixik the velocity of the ai cage has been so great, when detachment has taken place, that n bave continued on in obedience to Newton's first law of n and have been seriously injured by being dashed violently a the top of the cage, even after the latter had stopped. The It safeguard against ropes breaking is to employ noae but tboW* the very best quality, and to give them careful treatment a regular and etlicient inspection.
Winding.
Automatic CoiUrivaiicea.~~TietBciiing books do not pi-event overwinding; they only reduce the damage done, and often prevent loss of life. In addition, they do not xafegiiard the (iesceading cage. Two classeaof automatic coiitrivanceB are used. In one, some projecting lever is fised above the pit's mouth, which when struck by the cage, puts on a brake ; these are not any more effective than disengaging hooks, as they come into operation too late. Iti the other type, an instrument is so arranged that, providing the enginemnn shut off steam at the proper moment, he is in exactly the mme position aa if no stich appliance existed, as it does not come into nctioo ; hut if at a determined point in the wind the speed is greater than it should be at that point, the eteam is cut off from the engine, j.,
and a bi'ake applied.
Tie Visor. — In this appliance, which lins been in use by the Wigan Coal and Iron Co. for some time, a shaft, , E (Fig. 321), carrying two beaked cams, E', performs one revolution to each wind, such motion being obtained by the bevel gearing and endlesB screw, shown at D and D'. each side of this cam is a tappet, F, which ia engaged by one of the beaks, if the engines are going beyond the pi-oper speed, such engagement being performed by the aid of the governor and levers, H and G", Usually two governors are provided, weighted for different speeds. What takes place is as followa : when the engine is travelling at high speed, the rise of the governor lifts up the lever, M, and throws the two tappets. F, into the path of the beaks, E', on the revolving shaft, E. If the speeil decreases at the proper moment towards the end of the wind, the governor falls and throws back the tappets, F, consequently the appliance does not come into action, but if the engines are travelling above their pi'oper speed, one of the beaked cams catches the tappet, F, and raises it ; the arms, F*, cross head, F*, and bar, F*, are raised also, and the pawl, C, disengaged from the catch bar, B'. Immediately this takes place, the brake is applied and steam shut off. A somewhat similar appliance has been designed by Mr. C. H. Cobbold,* which also acte through a governor.
Grimmia'a Apfiratua.- oth the appUanoes just desci-ibed ai-e
Kc
t Ihid.. ix. Mi-
J70 TEXT-BOOK OF COAIMrNING.
open to the objection that the engine receiveR n great shock by ihe sudden application of the bmke. lu Grimmitt's appliance, which has beeu very recently introduced, this dilHculty has been overixime by employing n pneumatic arraDgement, which buoys up the brake lever for a few seconds after such has been cast loose by the uppnratuii. A-i air escapes from a regulating tap, the airveeset and lever sink lower and lower, gradually increasing the pressure of the curbs on the brake wheel.
Catcbea at Pit Top. — At the great majority of collieries, Home appliance is used to hold the cage while the changing of the tubs takes place.
Kept. — The common form consists of a series of legs, usually four, arranged in pairs on two sides of the cage. They are pivoted on a shaft, and are readily pushed aside by the cage on its upward journey, but have to be moved out of the way again to allow the cage to descend. Such form is shown at d, Fig. 334. In another form, a series of projecting bolts are arranged in the main timbers at the top, which ore pressed outwards by springii. and can be moved back by levers. Such type is not so suitable for heavy loads as ordinary legs, as the wear is considerable, and a greater strain is thrown on the framing at the pit top.
Hydra-ulie Kep8 the ordinary form of legs, if the cage is at bank, it cannot descend without being lifted off the props, n£ the banksman cannot withdraw these while the weight is on. Fiiis. i22. 3J3. Asu 324. is used, and each deck
changed independently, seven reversals of the engines have take place, each deck requiring two, and the final lowering of the cage another. This not only occupies time, which is so valuable in winding, but nausea considerable wear and tear of the machinery and consumes steam. In addition, slack rope is payed out on to the bottom cage, and as this is iLsual 1y quickly drawn lip, a very injurious shock is given to the rope. Several devices, all coming from the Continent, have been designed with a view of securing the cage
Winding.
firmly while changing is going on, but to i-eleaee it again for descent into the Bhaft, without the preliminary lift of a foot or 60, and conBequent reversal of the engine.
Franti'fi" appliance used at Oamphausen Colliery, Saarbriicken, consists cf fowr plunger cylinder, e {Fig. 322), provided with stuffing boxes and pistons, joined together by wronght-iron tubes. Each plunger is provided with o double lever, g, having its turning point on the piston itself. One end of this lever projects under a fixed pin, t, while the other serves as a support to the bottom of the cage. The rise of the piston and double lever is cauEed by water in the accumulator, K. The ascending cage, B, lifts the front end of the lever, g, upwards (Fig. 323), which by reason of its own weight falls into the horizontal position immediately the cage has passed. AVhen the cage rests on the legs, it is supported by the water in the piston, connection between the plunger cylinder and accumulator being cut off by a tap. When the cage haa to bo lowered, this tap is opened, and the weight of the tuba and contents presses down the plunger, drives teck the water in the ai.-cumulator until the lever, ij, takes the poeition shown in Fig. 334. As soon aa the cage has passed through, the accumulator again forces the piston and lever into the higher position, and the tjip above referred to is closed.
At Oamphausen I Shaft, a somewhat different arrangement in in use. The Kitt. 325.
four pistons, p, stand obliquely and have at the top an end, c (Fig. 325), turning round a bolt. When the hy- . draulic apparatus is not these legs, means of the lever, h, and the connecting rod, t, can be pu-shed backwards and forwards just as in the ordinary way. A still greater variation consists in using an air vessel, W, Instead of an accumulator. This vessel is filled with water up to the middle, the upper spice containing air at a prefisure of two atmospheres, which serves the same purpose as the weight of the nctmmulator, but by reason of its elasticity work.'' more advantftgeonsly.
The disadvantage of such apparatus is its complicated nature, liability to get out of order, and the fact that in cold weather the water freezes. The lattc overcome by employing
glycerine in the rams and 1
Stavxi Props. — Tbeee im 'ent of lever,
without any compUnMdifll ' *aine object.
TEXTBOOK OF OOAlMISING.
With thm oalj one re\-ers&l of the engine takes pbce, tint U inuuediateljthe cag is brought to bank, the diracttoo erf nkorement being always aftnrArds lowering one. Tbe appuatas ooBsists of two shafts, s aad b (Flg&. 316-318), fixed in bearings; tbe legs, c, lies. ii6 Asn 327. upoa theagB
on another shaft, d, which can swii about, bnt ia t- tached hralnk to tbe aUft, The sfaaft,<i> counted to & bj- a (qgo-jaiiit lever.faBd/. to tide in a hociaotital dinMioa, H the two Wms, c and fcecvnt mdi motioB, hot tbey aDow the aig to pass throw when eoanag to bank, for, 'bmg loose on tbe shaft tber rotate aboot tbor axia, and taka tba pontka abovB bf tbe dated Han, dntfiag bade TTTiTn ttirJT waliaj. m iiiini iiitbi When lowmn is dedrad. tbe haakiMaa pdk ow a Invr, bovh ibe bak g in tbe direc t iMt *bowa ky the anow. aad ivtataa tbe ihafl ii lUa Kfka 1/. nnta tbe pout A V a little above tl atnt Gas jontagdaadi. TiMiiliarehr thir tiha |dani thn rd tba rn don the iit, M t£*
pme, dide on an
nn havicj sofia of
TteaatbMbaa ratttmrfStA Omfy
aVweandnaraateoB he id ito I
BMcwf wbaw be faai aa il a epe at ion, it is rjiiwid ea (Aot
Winding. 273
this, the cage is only moved once, where otherwiae it would have to be moved throe times. It means more labour, because with ordy one landing, one set of men will do the work j with several landings, a set of men will have to be employed in each,
Hilda CoUiery. — The general method of caging two deekw at. once is well at Hilda Colliery, South Shields, where the detaib have been carefully thought out. The inset is divided into two stages, and all the tubs from the workings arrive at the top level and run down a gradient of In. to the yard, either to the shaft to supply the top platform, or to a drop cage, by mettas of which they are lowered to the bottom level to supply the bottom deck. Apian of the an-augment of the rails is given in Fig. 319. The empty tubs from the top deck gravitate down an inclination of 3jin. to the yard to the point, a, and are carried by the momentum they have attained for a short distance along a b, and up a
Fig. 329.
slight gradient, h c, sufficiently far to clear the points, b. Their direction of motion is reversed, and they then run along the line marked " empty tubs," indicated by the ari-ow, and deliver themselves to the point, d, where they are made up into sets and hauled away to the workiugs. The full tubs for the lower decks, after being dropped by the cage, e, gravitate to the shaft, and the empty ones towards the cage,/, which is connecteil by a rope to the drop cage, e. As the weight of the latter and the full tubs is heavier than that of cage/and its empty tuba, when e is lowered it lifts up f and the empty tubs to the top level, where they are automatically released Ivam the cage, and gravitate away to join those at d, which have already come from the top deck.
The following automatic catches are used for keeping the tubs on the cages during their ascent or descent : (a) During lowering, the tuba run in from the direction shown by the arrow (Fig. 330), the axles being caught by the cath, c, maintained in position by theweight,u7. On reaching the bottom the weight strikes the floor and lowers the catch, allowing the tulis to run off (Fig. 1 (b) When raising tubs ; the position at the bottom is Bbov
Kg. 33J ; on raacfaing the top cnnked lerer a strikes fanAr at the side which libents tte tab (R i33)-
FliW. ijo, 331, 131 AX 333.
Oifiom CeOiery, — Vr. Hcmry Rsfacr hasdeagnMl an uranencut in wfaidi the nils (a. Fig. 3), are pivoted aboat point,
Flos. 33 iXD 335.
fi 111 - ' to tko battoM <tf Ite ea. Ik tha OIw bottoB put of the cacB is akawm. tka TCrtieal a igB atrta boag caJnad tkasaka dnc
Ctei. IKL XL SU-
Wikding.
end of the mils are two feet, and at the other, two levers, c", projecting below the bottom of the cage wlien it is suspended. WTien the cHge is lowered, the feet rest on the props, d, ftiid raise the mils at that end of the cage, while at the same time the lever, e', restA on the pi-ope, d", and lowers the rails at the other end, the result being that the tubs gravitate away. Before the rails are inclined, the tubs are held on the rails by the stops, e , which presB against the axles, but simultaneously with the rails, a, being inclined, a foot,y, attached to the stop, e', rests on the prop, ij', and raises it to the position shown in Fig. 335, and allows the loaded trains to run away. The prop g is pivoted about a shaft, t, and 18 connected by a rod, n, to a lever, q. When the axle of the firat loaded tram presses against this lever q, the prop g is withdrawn from under the footy, and the stop takes the positioa drawn in Pig. 334, in time to prevent the empty tubs running through the cage.
In addition to the tub-releasing gear, the empty trams are run on the cage by the aid of a movable platform, A, connected with an oscillating cylinder, k, to which air or stam is admitted by an ordinary-three-way cock, r. Siraultaneously with the inclining of the mils on the cage, the foot c presses down the tappet rod, a, and gives motion through the crank lever, I, to the connecting rod, m, which opens the tap. r, and admits steam to the cylinder, when the
platform. A, is raised to the oage {Fig. 335). As soon as the cage is lifted from tlie props, steam is discharged from the cylinder, and the platform. A, falls to the horiEontal position. The oivillating platform seems to be on unnecessary complication, as the rails might easily be arranged on a permanent incline.
Fowled — At several of the collieries in the Nottingham district, Fowler's apparatus is used forsimultaneously changing all the decks of the cage. Fig. 336 shows the apparatus in the position when the cage has just arrived at bank with its load of full tubs; the platformBnan contain the empty tubSt while hhh are ready to
) inclination as the rails on the
Text-Booe Of Ooukieisg.
Winding.
Bell Eiul Bell End Pit, where the shaft only cntaina one cage, the author ia employing a combination of several armngemeutA. The cage doubt -decked, and each is changed independently. The rails are set at a permanent inclination, and the tuba are kept on by a hinged arm, but at the landing-place are released by an automatic arrangement described a little later on. At the bottom, the lower dealt is received on a set of Stauss props, the tub is released and gravitates away to a platform. The cage is then lowered without reversing the engine, and the top deck tub i-pleased, which then runs to the same platform. The full tuba are now on the
bank.
The platform refeiTed to is attached to a hydraulic
ram and pivoted about a f n il rf g , . point slightly away from — r TTjli- - ' .i VA— its centre (Fig. 338). When '
the tubs are on, it therefore takes a certain inclination limited by a stop. The curved guard, b, prevents the tubs running through, and the inclined surface will uot allow them to pass out during the lift. The hanger-on pulls the lever, a, the platform and its conrnt8 rise a distance of about 6 feet. On arriving at the top the platform auto maticIy stops tlirough catching the lever, d, and cutting off the pressure, and is tilted in the direction, wheitthetubsrun away on the top landing, e, and gravitate to the point where they are attached to the haulage ; the platform then descends, ready to receive another consignment of empty tubs.
The relensiug gear employed is di'signed by Mr. W. B. WilK* The inclination of the rails is such that tlie tubs will
inty run forwards, and the, cage by the mechanism -1: arms, (((I, revolve insui! and the angle pieces v.- pnveuted from rising
s h.jld t
released from the MI341. 1-ho L All of tlie oige, ilie tub, but are
ns
Text-Book Of Coal-Mining.
Fios. lijg. 340 i
t rations), while they are kept in theliproper place by a spiral spring, b, attached to lerai-s, c c, projecting outwards. On the cage being drawn out of the shaft these jevem strike anst and lift two matches, d (Fig. 339), wliicli fall back into place uain, and on the retwn of tho cage push the levers, c, into the position shown Ity the dotted line in Fig. 341, and release the tub. By the time, however, that the cage rests ou the legs the levers, c, have completely passed the catches, il, and the arms, a, woidd be closed by the springs, b, but by such time . the L parts of the arms are locked beneath the bottom of the tub, and remain there, until it lias passed out, when they immediately close and prevent the f iirthei' passage of the aecoad , tub.
At the surface, the cage is lifted until its bottom deck rests on the StausB props, and the motion afterwards is always a lowering one. The tubs are automatically released by a similaiapparatus to the one at tha bottom,
JioBcoup Colliery. — At No. 5 Pit the clinging operations are perfomiod with extreme rapidity ; at the bottom with the aid of a balance platform, and at the top with Btauss keps; and, by the peculiar amingement are carried on independently of each
e reaches the bottom it is received upon a platform, p (Fig- 342), counter-bale need with a weight, w, equil to that of the empty tubs and the cage. The two empty tubs on tho bottom deck ai-e then replaced by full ones, and the extra weight of the load they contain causes the cage to descend with the pbit- , form, until the second deck is level with the inset. The tube oil ] thia deck are then changed, and the platform and cEige descend again, until the top deck is level with the inset, when the empty ' tubs are replaced by full ones. The descent of the platform u governed by a brake, a, regulated by a hand-wheel, b. A catch, c, is also pi'ovided, whicli locks the platform at the proper levels, by engaging with the stops, e. This catch can be lifted off by an arm, d. It wilt allow the platform to ascend, hut not to descend until I'eleasetl. Immediately the cage containing the full tubs lifted by the winding engine, the counter-balance brings back the platform to the level of the inset, ready tn I'eceive the other cage.
Winding.
a;y
The changing at the surface b carried out as follows, The bridle-chains are made very long, and before the top rage comes to bank, the bottom cage reaches the baJauce platform just described. At this point the engine is steadied, and the top is lifted until its lower deck remits on the Stauss props. An amouiit of stack rope is, therefore, payed out on the cage at the bottom by such operation, but through the bridle-cliains being long the rope itself is kept straight, and does not " kink " ; indeed, not so much is lot out as would be
expected, for befora the top t'lu. 342.
cage is actually raised to bank, the empty tubs on the bottom deck of the cage below ground will be replaced by full ones, nnd the platform lowered, thus taking up a length equal to the height of one dock. At the surface the bottom deck is also changed Erst, the cage lowered by moving the „.,.j,. g 8truss props, the full tubs on the second deck replaced by empty ones, the cage again lowered and the top deck changed. The engineman has only to attend to theoperations at the surface, tlie tubs at the bottom being changed with the balance I platform, and by the time I the top deck is changed at the surface, all the olack chain and rope has been taken up, and the engine starts away upon receiving the signal from the bottom.
At Auxin Colliery a balance platform is also emplcBd, but to remove any chance of the rope kinking when the slate rope is jiayed on to the cage, n short length of aloe rope is insei-ted between the bridle-cluuos and the capping of the attml rojie. As this is quito soft and flexible, no hann o&u i-Mult.
Fencing the Pit Top. — To allow the empty tubs to run an, and the full ones olf the age tt awnUe fencing has to be employed at the pit top. "" ' "
oppofiit the ends of ibaet the other two aides. ""
I fencing I
' ' I of Gliding gates
K erected o
b these
38o
TEXT-BOOK OF COAL-MrNING.
gates aad lift them upwards when the cage arrivvE at bonk, hub ne soon as the descent commences the gates fall to the ground and secure the top of the shaft. As the cage travels at consideruble speed when it strilcee the fence, it is advisable that the latter sboidd be made as light as possible. The preferable plan appears to be to employ three strips of iron connected together by cluins ; the top one is longer than either of the other two, and reese on two props in its normal position. On the arrival of the cage at bank, the bottom piece of iron is first Kiu. 343. lifted, then the second, and finally the
Vj The problem is rather more complicated
if winding goes on at an up-cast shaft where fan ventilation is employed, because, unless some special means rm adopted when changing is taking place, the pit top is open to the atmosphei'e. '
/'fmbetion Colliery. — At the up-cast pit, the entire distance from the ground level to near the top of the frunie is cased in, aa shown in Fig. 343, by two rectangiiliir sheaves of wood, each forming a compartment in which one cagg travels. As little play as possible is given Iwtween the aides uf the cage and the framing, each cage practically forming piston. At the banking level, small rectangular openings are made, of just Bufficientr size to allow the passage of the tubs through them ; these openings are closed on the inside by a vertical trapdoor sliding in two grooves, which 19 opened by the cage as it ascends, and on the outside by a safety trap-door, balanced by a weight which is lifted by the on-setter. By this method, the loss of air is reduced to a minimum. The bottom deck of the cage is made solid, and to prevent any loss of air when standing at bank, it ia provided with a second or false bottom, about 18 in. below the one on which the tubs rest. By this device the top of the pit never becomes open to the atmosphere, even should the engineman raLse the cages a short distance above the proper level. To provide a perfect joint, and reduce shock, the inside doora hare n gutta percha band i-unning along the lower side.
Homer HHl CoUierf/. — Another method of covering commonly
employed is well illustrated by that in use at this colliery. The t is closed by a pymmidal covering, [at the upper end of which ia a. amall movable shutter. The pre§sure of air on the outfdde of this pyramid, owing to the vacuum beneath, is considerable, and it is, therefore, counterbalanced by weightH, lo (Fig. 344). When the cikge in nearly at bank, the capping on the winding-rope first lifts the small abutter, a, and it does ao easily as ita area is small. This to a certain extent takes off the pressure on the main casing, and as the weight of the latter is also counter-balanced, the cage
lifts the covering vertically upwards without any injurious shock. As an additional safeguard, springs, h b. iire placed at the four comers.
Tub Controllers. — To pi-event the tubs running into the shafts, ordinary blocks |Fig. 216) lue generally employed, but possess many itiiad vantages. The;' have to be ujieneU by hand, and when once open wQJ allow Uif m 'er of tubi to pass by. Automatic
' are eoiitrolled by a projecting
Text-Book Of Coal-Mlning.
6tuiJ, (( (E. 345), which Btand up between the r&iU and catolies the axle of the tube. This stud ie attached to a lever, b, piloted about a centre, c. One end of the lever is weigbtud, to, while tht ' other is attached to a foot treadle, il. The weight always keeps tbi lever in Eui;b a position that the stud, ii, blocks thi way, unless tlu banksman depresses the treadle. This apparatus has two objec tiona : (a) aa the stud engages the middle of the asle, this may g bent ; and (6), the bimksman has to keep bis foot on the tre until the tuQ has passed by.
For empty tube the foimer is not of much importance, as little ' etiiiin is thrown on the axle, bat for loaded tubs the objection is fatal. The latter is scarcely any inconvenience, as the apparatus is very compact, the treadle can be placed anywhere, aud the banksman, having the use of both hands, is left 4uite free.
To the apparatuK used at Bell End Pit for regulating; the p
control the delivery of tubs in aud out of cages, or for intermittent delivery from inclined planes or platforms without the need of attendants for scotching and releasing the tubs. The apparatus Can be opened from any distance by the person i-requiring the tuba, Rnd all the other movements are self -controlling.
To open the controller, the shaft, a (Kg. 346), is twisted and loves the tongue, b, causing the sliding bolt, e, to project under the lever, d, and lowering the stop end at e, until the axles run dear, when delivery by gravitation commences. The succeeding turn the star wheel /, in the direction shown by the narrow, u pass by, until the cam [loint, g, comes into contact with ths t; the sliding bolt, c, at c', and withdraws the same, causing lever, d, to fall into its proper position and stop the delivery of until it is reopened in the usual way.
To check any tendency there may be for the star w tnivel beyond its right position when driven by the tubs, it is provided with a square boss. A, upon whujh
erthe
Winding.
2S3
presses. A b mull roller, k, is fixed over the aliJing bolt, i; lo jirevent any tilting op of the latter when hivy loads ni-e pre6.siug against the butter atope.
£other when used on cage decks, or on inclined platforms, two (uutrolter hose m-a tijced between the raiLt, so that the buffer atopB come into contatrt with the tub axle us close to the bearing of the wheels aa possible ; by doing eo, there is little risk of bending the axles b; the shock of stoppage of the loaded tuba, and, as an additional preventive, elastic spring buffers are also used to equalise the bearings of the ftxlen against the topK. lu Fig. 346, the box mechanism shows an aniiugement to pa two tubs each time. To paiis one only each time, two cam points, g, are used to one atai--wheel boss, while tor passing three tubs, a star-wheel with six points would be ued with only one cam
SlgnaUing — Nothing conduces tn rapid winding more than efficient signal*. Two aystemsai-e employed. The ordinary method consists of a wire carried down the side of the shaft, one end Ijeing attached to a lever and the other to the mechanism working a bcLl. For small depths this system works very well, but where the line is a long one, the power required to ring the bell is considerable, and although balance aiTangements are used to take ofTthe weight, the banksman has still to exert a large amount of foi'ce, which necessai'ily takes time.
Instead of these mechaniciil signals, it has now become common to use electrioil ones. Undoubtedly, when such wei* Gi'st applied, they wei*e by no means suitable for the rough work of a colliery. The great mistake matle consisted in making them far loo weak, and not introducing sufficient Hnfegitards ; in adJition, the men at collieries were quite unused to such appliances, iind if anything went wrong, an electrician had to be sent for. At the }>resent time none of these objections hold good. It has long been i-ecognised that signals suitable for dwelling-houses are of no use whatever at collieries, and a special stronger type lias Itcen designed. The working and keeping in order of such appliances have ceased to be a wonder, and many collieries at the present time simply purchase their stores, and lit up and keep the signals in order themselves.
What are known as single-stroke bells are generally employed, that is to say, the bell only makes one stroke each time a signal is given. The elements of auLt-BSsful working jirinciiuJIy he in having largft-sized battery cells, which ale almo-t universally of the Leclonch type, and pi-oper wire in the shaft. One of these wires should undoubtedly be insuhtted. Sometimes both wires are suspesdBd from a point on the head-gear and hang free in the .tAtml*- nntliin Mm covered. This on-angoment possesseii it is chip and requii'es little iu-'.> not ilainaged by pieces of
iS4
Text-Book Of Coal-Mixing.
coal, ix., E&Uing down the shafts as these simply wire &nd do no harm. Sooner or later, however, leakage cmrent takes place. The better pl&n, although the dearer to ctHnmence with, is to employ a properly insulated wire and cany it in grooved boarding down the side of the haft. No staples or iron should be employed to keep the wire in the groove, which should preferably be made slightly smaller than the diameter of the covered wire, and then the latter lightly tapped into place, the whole being finally covered with a light wooden lid. The insulation prevents leakage, and the wood casing any damage to the insulation.
Bibliography- — The following is a list of the more important ' s dealing with the subject-matter of this chapter : —
Iht ScToO Drum,
and Cnloadiiii/ Dedxd Cagtt. D. P. 31 Orison," xiui. 39; Baiaiiu Cold from gnat dtpdu hg Almo*phrric Pre*tre on (Ac of £, Blandul, T. W. Bonniiig, xziiL 81 ; Tkt apiaUioH of ComttrbfUamang anJ ExpaMion to Winding-Enmitrt, J. Daeliali, zzv- 301 ; DofTioa of a niKditg-Engiite wilA Sdf~eating VariMe Rtpau- *um, Wm. Pb xxvL 109 ; fsiproptd Ezpaation Otaring far tViiidUg-Eiu;tHa, J. DBgliah, nil. 3 ; Haf'tif Boat*, Wm- LogU), xzis. wi. r. SOC XIX. STUD.: Loiidiag and Cnloadiiu/ of DrdfJ Qiga, E. F. BoTDler, iv. 132 ; Guiila in J*itr, U. Bramwell, vL 6 and 5S, and J- A. Longdeti, Ti. 44; irimdiiig'llopti md tAeJr Altadmtut rA Caire. P. U. ChstM. ViL 47 ; Xoltt on tlu Koept &,tl,n WtaiiiiQ, H. W- Hoghes, ri. 177.
8O. STAFF. IS8T. : Jn Improotd ArrangemtiU for Sltant Bratet, T. Fkifield, ii. iiz; -JKliKa Coifing otui Banking Apparalta, W. H. WilU. ir. 31 ; WinAHg-EwgiMt, H. W. Hughes, ziL ai-eoc
. ise. MIX. : A'ote nr U eieralmait du pniu Bobert, H. Robert (3* 8£rie), ii. 295 ; Tht atmotplitru! da puiit HoUinmr. Z. Blaacbet (s* Srie), ir. 557 and Tii. 273 ; Gaidagt da puitt it u'w.
de Beanzat, et Chanselle (a* &<rie), vi. 697 : (bmparum d..
morfs* Ow'Jaije, Bapjnrt iTuit Cownattian, MIL Fine), Griot, DesioTeam, et ISarietta (z* Serie), \i, 750 ; JfarAiwt iextraclion ttnuiJna. '" , . — -
du arti fl T f
tmrtTKri .1 rErpoiilioi Lgon. M, Griot (3* Serie). iiL 365.
HIK. ISST. SCOT- : Winding, J, S. Diion, I. JT ; Cotf.wy Ska/i
G. W. Smith, i. 301 : EUrtrie Stgnidt for CoHirria, C. McLaren Imne. ii. 47 ; Sfmu'f' CoM-Eating Afiyarattti, F. J. Rowan, x. 137; A Ing DitUtHce Elrdric BeB. J iiean, lii. 41.
80. WAt-KS i>'ST. : Haftty DtlacluHg Hook; itc-, S. Hamble. ziL 45, Appen-'l dii by Hort, Hnxham. liL 191 ; Wirt Ba, T, H, Da&i ztL 305.
CUES. ISST. : Coal Winding in Detp Shaft; A. H. Bloke* vt 248 ; Sl Arting Arraagnani for Vnlooiding and Loading OMitry that, T. G. Lees, xi 209; Soipe Pa/an .Sj/ttem Winding at Saaad Cdilirria, Robert Wilson. xL 267 ; Coiinlfr-haladng tie ITcwK q/ Winding Boprt.C. Meinickc, liii. 333; Tke Alcatlon of iUaiida .lytUn of Ealanr* Hoptt la H'iMUfig tciik Flat Sifft. J. C. Jeffoson, ziv-230.
Winding. 285
AJCEB. INST. M. E. : EquolizcUion of Lo€ui on Winding-JCngines by the Employment of Airm Drumi E. M. Rogers, xvii. 305 ; Pneumatic Hoisting, U. A. Wheeler, xix. 107.
N. 8TAVF. INST. : Some Arrangements for preventing AeeidentM at Level Landings in Cage Di and Shafts, A. R. OAWjer, viii. 204; On Economy of S!eam practically obtainable in Winding Engines, B. Woodworth, ix. 158 and 219 ; Hie Holding Pincer of Olands on Wire Conductors, A. R. Sawyer, ix. 270.
BKV. UNIV. : Note sur Vinstallation d'un guidonnage eutiirement me'tallique (Systeme Briart) L. Donekier (2® Serie) iv. 211 ; Systeme extraction par cables sans Jin, L. Trasenster (2 Serie) v. 8$ ; Note sur direrses dispositions de puits d'extrtictioH affected a Vathrage par amxrreiU micaniques, H. Glepin (2® Serie) vi. 107; Note sur guiaonnages mallimtes etablis aux fosses tP Havre, Ch. Demanet (2 Serie) vii. 549 ; Note sur un nouveau systime de taquets de retenue pour cages extraction, A. Stauss (2 Serie) xviii. loi.
ANN. DBS MINES. : Itapportfait au node la Commission aur la rupture des cables des mines, L. Aguillon Serie) xx. 373.
EmjAoi des Cables Continus pour P Extraction dans les Mines, V. Watteyne and A. Demeure : Annales de Tra\'aax Publics, Belgique, xlviii.
Chapter X.
Pumping.
The amount of water met witli in mines is dependent o depth and pu the nature of the oferljnng strata. Shallow minesfl are always more troubled with water than deeper ones. TheM suheidence caused by extracting the loaterial cracks and fissures thel ground above, and affords means for the ingress of water. EveiJ when the depth is gi-eat, if the strata overlying the coal seams contain large quantities of water, as is often the case, the workings ' naturally release the water, and it flows into the mine. In Eome cases, a series of impervious beds are found to exist between the water-bcai'ing strata and the coal measures beneath, and the water met with during sinking may be tubbed back.
Pumps. — Numerous types of pumps are used for unwatering mines, but they may be broadly divided into two classes — bucket , and plunger. If the engines are placed at the surface, with the former type the water is lifted during the forward stroke, while with the latter it is forced at the backward stroke.
Bucket Pv/mpa. — Suction pumps in mines are similar to those used in oi-dinary wells, only better designed and on a larger scale. , They consist of a pipe, called the working ban-el, a (Fig. 347), into which a well-fitting piston, p, having a valve or valves opening upwards, is worked up and down by being attached to the pumprods. The lower end of this working ban-el is coimectod to a suction pipe, containing a valve, c, called a " clack." The lower end of the suction pipe is called the " snore piece," or " wind bore," and ia pi-ovided with a number of holes at or near the bottom, through which water enter the pipe, and which prevent, to a certain extent, any large piece of solid material entering the working barrel. The combined area of these holes should be larger than the area of the suction pipe.
When the piston, or bucket, makes its up-stroke, a 1 created in the working barrel, and the pressure of air forces v through the suction pipe and clack into the working barrel. On. J the return stroke the clack closes, and the bucket valve opens, J
Pumping.
allowing the water to pass to the upper aide of the bucket, t raised to the Bitrface on the return stroke of the engine.
Pluiu/er Pumpi. — In this system tlie water, instead of lifted, is forced up by the action of e. plunger. The arrangement of thiK, and the necessary valves, is Bbuwn in Pig. 348, where the piston, n, is just commencing its upward stroke, and is sucking water through the valve, 6. On the return, the valve c will open and b close, and an the plunger passes water is forced through c to the surface.
/follow Ptutujers. — With bucket pumpa, lighter rods can be
employed than with plungers, but wear and tear is large, and the maintenance charge is heavier. Pliuiger pumps have one dixadvautage ; unless the column of water is solid at the commencement of the return stroke the ram falU suddenly, and the pipes receive a severe shock. To remove the difficulty; md to combine
the advantages of both systems, hollow i ' " '
they consist of a hollow plunger, a (Pig. 3 a valve, b, which is closed during t the return, being prevented going ' plunger may either work tlirou rising main, or, preferably, th where it may easily be tightened
Text-Book Of Coaiminixg.
Stoclu or TroOB.— The pipes through which the water is delivered to the eurface are called "stocks," or "trees," and, in Gombi&ation, form the rising main. The consiEt, us a rule, of autiron pipee, geoenlly 9 ft. long, shorter lengths of 3 ft. and 6 ft. being used for making-ap pieces. They should be ns long ha poMible, without making them difficult to handle, as hv doing sty the Dumber of joints is reduced, there being less liability for lur to entr. They should always be cast standing: if not, the probabilities are that the metal will be thicker on one side than the
The thickness depends un the taze nnd the pressure to be with' stood. A cubic font of weighs 6; lbs., and as it pontaius 144 in., the pressure per s(|. in. due to each foot in depth is .434 Ibe. The common mle, and one erring on the right side, is to allow a pressure of I lb. tor each foot in ileptb, or to find the total preiwure in Ibe. per sq. inch due to a column of , its vertit height in feet may be divided by 2. Indeed, some allowance is absolutely necessary in determining strengths, because it is well known that the pi'CGsure experienced in pumping sets is variable during dillerent parts of the stroke, and exceeds that due simply to the weight of the water.* The necessary ti ' ' the pipes is by the formula :
nhere d - internal diam. in inches, t - thickness P the pressure in lbs. per sq. inch.
The weight of any length of pipes is found by the fi
where to weight per lineal foot, D the outside diam. inches, d — inside diam. in inches, and c is a constant for cast iron, and 2.64 for wrought iron.
Of late years, wrought-iroti and steel pipes have been s' tuted for cast-iron ones. For the same strength their fi considerably lees, and they can be made in longer lengths, tuul yet be much easier handled ; 1 5 to zo ft. lengths are by no mean uncommon. They have additional advantages in being cheaper, and not so liable to fracture.
Joints. The trees are joined together in \-arious diSerott ways. For moderate lifts, the common practice is to face and turn in two concentric V grooves in each flange. A sheet of lead it placed between the two flanges, and when the bolts a together, this lead is forced into the V grooves. The better f for heavy pressures is to employ what Ls known a
9 Kxmna. 11 etterplRtt
Consnlt. N.E.I- xii. 9; and Brit. Soc. Mic. .iii. 107, andvilL
female joint. One flange is provided with a projection and the other with a corresponding recess. An india-rubber or lead ring is placed in this groove, and the flanges screwed firmly together.
pipes, one of the beat known joints i
For wrought-] Williams's patent. Each pipe terminates in a short cone, a (Figs. 350 and 351), and is provided with n loose flange, ft. The joint JH made by introducing a double cone-shaped annulus
, c, and screwing the flanges tightly together. An india-i-rubber ring ia fitted upon each ferrule. The advantages are, the small amount of time taken to make a joint, and the pipes can be connected at small angle', whereby, in many CRses, the trouble and expense of bends is avoided. They possess an advantage over screwed wrought-iron pipes, as they are not weakened by having threads cut on them, and when galvanised, no part is subjected to coiToeiion, as is the case when galvanised pipes are screwed.
Supporting Pipes in Shaft. — The ordinary plan is to provide a main buntoa of timber running across part of the shaft, upon which two smaller piet£ are tixed at i-ight angle;), one en each side of the pipe under a flange. These short pieces are hollowed out to fit the pipe perfectly. It is difficult to see how such support can be improved, and it is invariably employed where there is plenty of room. It, however, requires a considerable amount of space, because the main cross-piece has to be fixed on the outside of the pipe, and as it has to bear all the weight, is necessarily large.
In a shaft where room was valuable, the author applied the method shown in Figs. 351 and 353. A bearer, was fixed at right angles to the brickwork of the shaft. Wrought-iron pipes were employed, as the flanges on them took up considerably less space than cast-iron ones would have done. One of these timber pieces was fixed immediately below each joint of the pipe. A wrought ii'on gland, with two screwed pin-ends passed round the pipe and through the timber piece, and was firmly bound against the tube by nuts screwed as tight as possible, A main bearer similar to that described in the preceding paragraph was " ' ' s bottom of the sliaft, this supporting, in a great
neasuve, the weight of the Spear Bods. — The bnci
plungers, are connected to ore killed " a|>ear
oyeil. Since those
30
l-EXT-BOOK OP COALMINING.
above have to support their own weight and the weight ot all ' below, the iipjier i-ods must be made projjortionately large. With pill nger-pu Dips, the roOK must be heavy enough to force up the column of water before them. Wooden i-ods ai-e pi-eferably made of pitch pine, except at the surface, where they are exposed to changes of teraperatui-e. Pino is more readily obtained in long Mtraigbt lengths fi-ee fi'om knots. J
If i-ods of sufficient sectional area cannot be obtained, they ara 1 made up of two pieces, the joints of the one coming into the centre J of the other set. Single rods are sometimes jointed hj' cutting I
' J53-
the ends slanting with a, hole in the middle, the connection bein, made by an iron plate on both sides and bolts passed through. An oak wedge is fi nally driven into the hole in the centre to mie the joint quite firm (Fig. 354), but this bus the disaIvantage that the wood is likely to split. The bolt are not passed through the core of the wood, but alternately on either side. A common joint is to cut off the ends of the rods square and to bolt connecting, plates on all four sides.
Compound rods are often put together by two pieces side by side, which may be cut so as to lit into one another {Fig. 355), or they may be simply in contact with bolts at intervals. Often the rods are connected by side ii-ons, with the bolts outside the timbeis.
Iron rods ai'e built up of various sections fixed together bolts or rivets, usuaUy the latter. A general form is composed
Pumpinu.
3 , and two flat strips. one o mpoutid girder is euiploj-ed. riiis is usually very simple.
Two
two channel pieces, liack U Bide, but every section of ei
Omding the Bods.- beam iire placed ucross the shiift with ci-oss-piefeK (Fig. 356). Rubbing Uiardsare tised to the aide of the HCtnal rod to tiike up wear. Oatiihes are alsci tiled, the object of which is to prevent the rods falling down the shaft should a breakage occur, and to stop the engine exceeding its stroke.
Counterbalancing. — In deep fihafts, the weight of the rods becomes very great, and is more than that required by the plungers ; in addition, a more powerful engine is needed to lift
Pnt- 357.
them To remove this disadvantage, bnionce-bobs are placed tit one 01 more point-i at the surface or in the shaft wherever possible
Connectiona to Bods — Owing to the eaae with which bucket Ufts can be lengthened, it is common to lind one of these at the bottom and plunge higher up the shaft. This neceasitatea attaching the pluugent to the main spear rods by some form of connection. In general, water from great depths ix not forced or lifteil to the surface in one operation, but in a number of staea, each of which is called a lift It is, therefore, common to find the main pumping rod going direct to the bottom of the shaft, with plungers attached to it at intervals. Tliese connections are oftD mode by the method illustrated in Fig. 34S, but the better plan )E to fork the main rod (A B, Fig. 357), instead of placing the
ia
Text-Book Of Coal-Mining.
plungers at the side. The phiogei' ix then fixed iu the line of tbv fl rods, the latter being coutioued on either side, joining again I Etfterwards. I
Talves.— The simplest kind of valve is that in which a flap works on a hinge. This is the type used on the buckets of suction pumps, but it consists of two Baps instead of one (Fig. 358); clack-valves are constructed in a similar manner, but instead of fixing the hinges of the flaps, they work within guides, and the whole is free to move upwards a few inches, thus giving a greater area of water passage at the commencement of the stroke.
A valve largely employed for pumps of moderate capacity foi lifts of 3 to 500 ft. is the single beat nne (Fig. 359)- The spindlsV is fitted with alternate discs of india-rubber and sheet-ir lift of the valve being determined by the amount of compreasioa of the india-rubber discs.
For lifts up to 300 ft., india-rubber disc valves give good results
Fio. 360.
Flo. 361.
An india-rubber disc is fixed over the centre of a grid, and on the I
1 mter rushing through the holes ts lifted at the edges, and itnme*<l
Ldiately shuts again at the return stroke. In the ordinary con* J
truction, as the disc drops in the same place each time, it is booh J
r eut away by the bars in the grid. To remove this disodvaatage,
Messrs. Evans and Sons fix a small brass collar, a (Fig. 360), in
the centre of the disc, b, and place it on a spindle. Instead of the
DBBsagea through the grid being vertical, they are placed at an
inclination, with the result that the water flows obliquely, and
turns the rubber disc slightly at each stroke, causing it to drop ia. '
a diffei-ent place each time. In their later construction of valTS.J
the holes through the seat are made vertical.but the disc has teeth.|
cut all round its circumference, such teeth Iwing inclined; tlM
action is exactly the same ns in the former case, but the cost has
been reduced. Such a valve is superior to a metal one up to
certain presHures, especially where the water is gritty and dirty.
For heavy pressures, nothing gives better reault* than the Cornish, or double beat, valve (Fig. 361}- TheKchnve been applied
Pumping.
>93
to pumps 9 in. diam., working under 700 ft. head, aitd have given satiirfactioD. For larger pumpe, inGtad of employing one valve, which would be very unwieldy and often get broken, multiple valves are used, that ie to eay, several double beats are ari-anged in a cluster. At the Bradley pumping engine, where the plungers are 27 in. diam,, there are seven such valves working on gutta-percha beats in each clack box.
QuadTBnta. — For any type of horizontal engine Gxed at the surface, quadrant have to be employed to change the direction of motion. If two Uft are used, quadrants are placed on opposite ides of the shaft, and so connected that one is making the up stroke, while the other is making the down stroke. In such ease, the quadrant consists simply of en L-piece, as one balances the other ; but where only one lift is employed, the quadrant is made of j_*hape, And a balance weight placed on one end. Instead of using wooden quadrants, wrought-iron or steel
Suspended Lifts.— When water is met with iu sinkings, even in Htnall quantities, pumping has to be reported to, owing the limited space. Tins is not only a diHicult but a very ejcpensive operation. With the ordinai-y sjiear rods and engine at the surface, there are several methods for dealing with pumps during sinking, which may be divided into two distinct type : (a) The trees may be permanently fixed in the .shaft aa sinking proceeds and pipee added aliove the working barrel ; itch system requires a telescopic suction, or a telescopio pipe above the working bairel, and owing to the difficulty of securing the lowtr ])nrt of the pipes, is not to be preferred to (6) whei-e the Uft is slung by ground spears, and pipes addeil at the top of the lift.
With this suspended lift the first thing to do is to make one part of the shaft into which the suction pipe is dipped lower than the other. An ordinary-snore-piece is employed, a (Fig. 362), above which the clack-piece is attached, followed by the working
g down eaA ndeof Uie pampand theftmrrjattlteamfBtr b pullflT tf slueli mre connected to polleTB. nft tfae KiTfMe, and witk the aid of ropes, the wbak aet can be krwered or raJMd immiilj nqmiea. For addhicwal acuuiit, olfaflr wroqgbt-irai gUadft ate added, wUeih not only toad j tna lift, bat fltnogtbeB the spean. A frat beam, or clar ring, y, m aln fixed to >tady the , and pcvnoit any mtanaaat, which would be Ukdr to tak place throngb the np-and-down watiaa vl tfae pump rods. Other cnm-fieet h, are plaoMl to aan at gwiiiai for the $pear rods. The ropes from the puUejra OD the gnaml ure wound od bhwU engineB at the snibce. Kpee an added at the top as reiiured.
Tbe heiglit at wfaicfa the woriiiig barrel can be fixed abov the water dends on smeral areniBBtance. Tbeoretaeatlj, the diMance is 34 feet, becanae tlw pressure of tbe atmoefdiere wiH balance a ""li""" of water of tlut height. Tbn are, bcnrever, several disturbing caaaes. Tbe joints are never perfectly airtight. Tbeie w abo a certain amount of function between the water and the sides of the pipe, whii-b increase if bends ar fffesMit. In actual pnctioe froin 37 to 30 feet is about tbe limit.
8tu lifts are expenrivB both in first cost and in To a great extent they hare bem superseded by direct-acting steam pninpH tJung in the shaft. Hie types of pamps employed are a little further on. Three ranges of are required — steam, eiliaii.', and rising main, all of which are iieucdiy of wronght-iion. The steam-pipe w sup- Fia. 36J. plied with a eliding joint, and a sliding
f1 ri suction ha$ also to be employed, as the B H i El ll n whole nirangement is only mored bodily B H I II 11 H every 15 to 18 feet of sinking. ,BJ IL WTf fgl At Denxby Main CoUiet-. Yorkshire,* H PTI 11 11 H pumps were suinded by two ropes bBIII II K worked by a team rnib, and the eteant, B HU U U Q exhaust, and deliver-pipeswrenllcLunpedL J. S together and fastened to the ropes. ""
t" 5 I J cUmpK were formed of two pieces of i I 2 5 J- about 4 in. by 1 in, (Fig. 363). hent together between each pipe. With arrungeineiit nenrly 1 00 yards was sunk in one lift, but as this
ire,*
opes '
VUtL, J
m
this "n
Pumping.
95
not Gul&cieiit to get through the wnter. n think ivac plnred nlxnil 6a yards from the top.
At Cunklon Sinking, Yorkshire,* a large quantity of water waa BucceaaFutly dealt with by piilsouieters, wliich were all of No, lo size, and capable of pumping 50,000 galloiie of water per boiu'. They were suspended on oue side of the shaft by heavy clmitis, to which the steam and delivery pipes were clamped as at Denaby Main OolUery. At a depth of something under 30 yards, which is the limit of the pulsometer's power, a tank wan Hxed in the shaft, and a man stood on a pliLtfm-m iidjoining, to regulate tba flow of water und see the two lifts kept piice with eiich other.
At the worst period. 1 50,000 gallons per hour were pumped with two lifts of three pulse' meters each, iii-ningl one above the other.
With BD ordinary cast -iron snore-piece, breakages through shot firing are common. At Gauklow a very excellent form of wind-bore was employed. It consisted of three wroughtirou plates (ft a a, Fig. 364), the bottom one blatik, the other two with a hole the site of the suction pipe through them. The lower Range of the wiat-iron pipe was bolted to the top plate, and the three flanges were fasteneil together by a large number of covered with iron ferrules, which being loose, withstood the shows. the whole forming a grating or cage.
Oornish Pumping Sngines. — This type of engine, which is still lai'gely employed for pumping openitionit, is illustrated in Fig. 365. It consists of a single cylinder, with its piston-rod contteed to one end of a beam, the pump rods being attached nfJuH' It, ia single acting engine, Kteiisi being admitted
Text-Book Of Coal-Mining.
Via. 366.
to the upper eurface of the pifitou, causing the engine to moke its in-Btroke. An equilibrium valve is then opened, and steam pMsee to the lower eide of the piston ; the pressure is then equal on both sides. The weight of the pump rods causes the outward stroke. Communication is now opened between ihe lower side of the piston and the condensed', a vacuum formed, and steam re- j admitted to the upper side of the piBton. This engine was designed by Watt, and remains at the present time as he left it. J The valves ore opened and closed at the proper time by tappet J rods, regulated by a cataract. Any number of strokes per minute 1 can be obtained, although from the massiveness of the machinery, r speed must necessarily be slow j in addition, a pause is made between tlie successive strokes, during which the valves, or clacks, have time to close, thus reducing any chance of shock. It is a large 1 piece of machinery, very expen-l sivo in itself, and also to work, hut when once in operation,! requires little attention, has ft J very high efliciency, and its weazfl ing capacity is almost unlimited, I Bull Engine.— To reduce thefl cost of the machinery nnd ( tions, the Cornish Bull engine Fig. 366} is often employed, it the cylinder is placed directly over the shaft, and the piston rod connectil to the spear rods. works in esaotly the same manner as the Comiah engine.
Davey DifferentiBl Engine. 1 — Pumping engines have fre- J quently been called " profit enters," and attempts are always being I mode to reduce both their fii-st and working cost. It is question- A able whether the working cost of any engine is less than that of the Cornish type, but its first cost is great, and it is liable to accident, especially in sinking, when what is known as a " riding column " often occurs — that is to say, some obstruction geta in one of the valves in the cla-k ; the whole weight of the column of water is thrown on the engine in the retum stroke, and the load act in conjunction with the steam pressure, instead of opposing it. Id nine cases out of tn this means that something Jms to break, although to reduce the risk, stops, previously alluded to, are fixed at intervals, to prevent the engine going too far either J on it out stroke or on its in-stroke.
Pumping.
To remove the digger Mr. Henry Davey has designed a gear, whereby a, differential motion is communicated to the slidevalve which is connected to a, lever, one end of which is worked by the engine piston, while the other receives an independent motion from u subsidiary piston controlled by & cataract. The action of the gear will be readily understood from Figs. J67- 370, and the following description given by Mr, Davey.* The diagrams are not drawn to a scale, but clearly show the action of the gear.
The main slide-valve, g, is actuated by tbe piston-rod through a lever, h, turning on a &xed centre, which reduces the motion to the required extent and raveraes its directiou. The valve-spindle ia not coupled direct to this lever, but to an intermediate lever, I, which is joined to A at one end, while the other end, m, is joined to the piston-rod of a small subsidiary steam cylinder, j, which has a motion independent of tbe engine cylinder, its slide-valve, i,
K108. 367, 368, 369 And 370.
being actuated by a third lever, n, coupled at one end to I, and moving on a fijced centre,;), at the other end. The motion of the piston in the sultsiuiary cylinder,j, is controlled by a cataract cylinder, k, on the same piston-rod, by which the motion of this pofiton is made uniform throughout the stroke ; the regulatingplug, g, can adjusted to give any desired time for tbe stroke.
The lever, I, has not any fixed centre of motion, as it% outer end, m, is joined to the piston-rod of the Buboidiary cylinder, j ; the main valve, y, consequently receives u diffei-ential motion, compounded of tbe separate motion given to the two ends of I. If this lever turned about a fixed centre at the end, m, eteam would be cut oiTin the engine cylinder at a constant point in each stroke ; but as the centre of motion at the end, ni, shifts in the opposite directioa with the movement of the piston, j, the point . .. .- dependent on the position of the
'98
Text-Book Of Coal-Mising.
nfaB&rjr piston M the moment wbeo tbe slide-v*h tiam*. ' ' ' cot tbengme-Gtrok, tbesalsdiuTpistofiisnic
" I, u Bbown by tbe ftmnre in tig. 367, and
tk iiHtanw oi m li load, af iHnctzBted in tig. 36S, the engine- {Bton, nng lesB reacstutce to txMeaaater, moves offnt a higher ipccd, Mxm orartakM the safaradiuy pistM) moving m mo- Muit qieed under Uw oontrol of the estwtact ; ibe clneing of th win nlve, y, is GaiiBeqaeaiUy at-tJilMMled, closing an earlier cut-off. With a heavy load, as in Kg. 369, tbe engine-picton, cneaantcring gator resiBtaDce. mores off more lowly, and the eabadiaiy piston has time to advance fnithcr in it stroke before h is oTivteken, letardii the '""'"g of the main valve, g, rang ft to cnt-off latCT. At tbe end of tbe engiDe-strobe (Elg. 370), the rdative pceitMBs becowne reverend from Fig. 367, in rcadinesB for the conmeneemcfit of the ret ui-n -stroke. A letardingear is alao ayplitd, by mtawi of whif b anv paoEe that m raqnind between gaeeeadn strefcee is eaalv obtained.
It IB BOW muty yean since this gear s&s brooght out, and long experience has proved its perfect idiabilitY. Opinions difTer as tbe relative econcames of the conponnd engine, with which this aRaagomeait is connected, and ti of the Cornish engine; bnt <aie if agTd on tbe ment of the nlve-gcar, and it is beeoiwing quite oomman to find it applied to the Comi&h engine. Mi. Diavey mentions an intMnce daring siofcing operations where dw botton-duk f ul a1, uid 96 yards cS 1 $-iaeh ralTimn wu ruling an the backet, and tbe engine continued walking without anv iajoiy whatever. The totid wiHghl on th engine in the outward itnAe was 7 or S ton, and in over to save the cylinder covers tram being carried away, steam bad to be admitted on tbe tippoBt fide of the piston, rewrsiiig the ofdiuary working of tbe engine, and fonning a cofbioo in frocl of the piston. TbiB was entiivly accomplislied by the itntomatic action of the differential
Diiot-acting Steam Pumpa. — With any type of engine fixed at the etirfacv tlie Gi co is great, both for the engine itself and for its pit work. As coosidecabie power is required to lift tbe great weight of tods hanging in the shaft, the engine has to he made larger than if such were absent. It has consequently become common, intttead of cmploving such type of engine, to fix the pumps at the bottom of the shaft and force tbe to the sutface>. The disndvantiigiv here are — conveving steam underground, the difficulty of dmliug ith the eshanst-#i&m, and the liability for the itself to be " drowned,' if tbe lodge, or aump'room, is not large.
Theobjectionsto introducing stim are here more than counterbalanoed by the couwniniav of tvsing tbe ptimps, for their portability and tlif we with whMt they may be wu-ked is considerable. Uw akhaxwt stfonu nv)<l with the Uiger pumps, can be got rid
Pumping. 299
of by aeperal devices. The liability to (Irowniug (iiii, to ii certuiii extent, be avoided by fixing the pump in a (.'chamber, and only allowing an mutb water tu pa:: into it as the pump can eah*6. This is usuaUy done by a self-acting tap and bull arriiageinent.
8uch pumps am be applied to lifts of a thousand feet, as the water is always flowing in the same direction, the movement during the reversal of the stroke being kept up by an air reservoir. The coat is low, breakages are rare, and the space occupied by them in the shaft is email. To lessen the difficulty of working the engme and keeping the room for it ojien, they are constructed loug, narrow and low.
Am with the other type, they ai-e capable of being divided into two classeebucket and plunger — and in addition, may be single and double acting. For clean water, the bucket pump with cnp leather is the best up to 400 to 500 ft. head, as the packing is easily replaced— any ordinary mechanic can do it — and its cost ia less to commence with. For gritty water and high hfta the plunger types are pi-eferable, as they are outside-packed, and any leakage is easily detected. Double acting purnp are certainly preferable to single acting ouw. The latter only deliver water at each alternate stroke ; their capacity ii< half that of a double acting one, and the column of water is brought to rest after each stroke, and has to be started agiiin. In all case, the stroke should be made as long as possible, uk to olitain a given piston speed fewer strokes are required ; the direction of motion is not changed so often, there is less wear and tear on the i-alves, and leac shock to the different parts,
Among the many escelleut pumps liefore the mining public, those of Messrs, Evans it Sons are in great favoni'. After considering several types, the author adopted tbowe of Messrs. Evans' for bis work. They fti strong, well -designed machines, perform the work they are stated to do, and iire easUy managed by any ordinary attendant. Tbey will i-estai't themselves if stopped by want of steam, and requii'e little supervision. It may appear invidious to single out one particular fiim, but thiu is done because it is impossible to give descriptions of even a portion of the many pumps which ai-e at work, to which the I'emarks made above may apply equally well.
The steam end of Evans's Cornish pump consists of an ordinary piston fitted with Tonkin's valve, which is a steam-moved one, consisting of a smaller plunger inside a larger one, the latter carrying a common slide-valve. The steam-chest b placed on the side of the cylinder, and the bottom of the the same level as the bottom of the cylinder ; the whole of the condensed steam is carried out at every stroke of the piin. and the necessity for drain cocks avoided. Thero iu no extraneous gear whatever; the pumps will start at any point of the stroke, there being no dead centre, and they can be worked by compressed air. Th
dovUc NctiBC planner |KtiBp, with tke pnmpiui half m ia Ftj. jji.
AH Om pump fwcte of cyttmlnakl fonai, and the various foniom it mtomnmafd thai tkmy out ba without neceesi- Uiaf m tiiity aw Tbs vh-lioxee are coostmcted vanr Wmt fnBnm, nvy valre is easy of access, —J —y W I M ftk tk wad w iaiw d wham Rcpiired.
niJMry lont u( dinsk MtiD rtcam pumps, the BHOB w a Mtnfy lafifwiting obs. To bum them wm-k more MWotyr aM nmbrty, taA Aa, chaps, with more economy, tr wMfc aMal: sack lTp kw tfa> Miraatagc of compact-
Ai tw tli mill iif laifc ijiKaihi iViiJiiin f
Fc 371.
FwiwaffyjiiiMi— .Aiu idHblallv, wgvnar le aQ ndMn. IVt Aa atgn-
Pumping.
pose. Messi-8. Evans construct one ia which two vaan ai-e placed ID the same Btraight lioe as the steam cylinder, nhich is of the oi-dinary pattern. The lower pump-ram is twice the diameter of the upper one, and ouly one auction valve ia used. All the water fii'st passes under the lower i-am, which on its downward stroke delivers half the water into the rising main, and half into the upper end of the top plunger. Wlien the rams rise, the lower one euuks in water, and the upper one delivers that water which has passed into it during the Fiu. 371. downward stroke. Au air vessel Li placed in the vertical delivery pipe similar in construction to ig- 375-
At Denaby Main Colliery a special type of pump was designed by Messrs. Itoiley Co., which consisted of three hollow plungers. The upper pair and b, Fig. 372) are atattouary, and over them slide barrels, which are connected to the steam piston. Prom the lower end of these barrels projects the bottom pluuger, e, which workii into the third barrel, together with the two stationary plungers, and ia secured by means of connecting rods to the steam cylinder ; thus, there ai-e two smaller barrels in connection ivlth the larger ram, moving between the larger barrel connected with the smaller rams. A series of valves, <l, constituting the delivery valves, are placed iu the junction between the smaller barrels and the large ntm, while the suction valves, e, ai'e placed at the bottom of the large barrel.
As the bottom plunger rises, the water follows it into the lower tTel, while at the same time the water iu the upper hollow plunger is forced into the rising main. On the down stroke, the water in the lower barrel is forced through the lower plunger and valve into the upper barrels and plunger, and thence into the rising main ; the discharge of water is therefore continuous. One of the ujipt-r pKuigtrs, b, is open at the top, and form- . 1 iiritice for the water; the
oiiji-i ..iLojian air vessel, which is
a suitable sniffing valve,/,
[pump and below the discharge valves.
V to b' token in with evei-y up-
&c. — For successful workigement of the suction and jnaJe as large as possible.
Perhaps the best
,lo;
TEXT HOOK OF fOAlMiyiXG,
aiTUDgenient is tliat shown in Fig. 373. The suction pipe is attached to the end of the pump, nnd its lower length is provided vith a foot valve, b, which always keeps tJie pipes and cylinder charged with w-nter, and pi'event the pump, on being started, from having to free both itself and the suction pipes from air. For gritty water, a strainer, c, is introduced in the suction pipes, and sei'ves to prevent any coarse matter passing into the pump. A retaining valve should be placed between the end of the pump and the commencement of the dehvery main, fio that when auy t'epaii-s are necessary, the pressure of water is off the pump. For charging the suction if at any time it Inseo wati'. a sliui-t lenh of pipe, a, with a suitable valve is inserted between the suction nml the delivery pipes, of conree,.
Fiii. 373. VIGB. 374 A.SD 375.
n
J/
beyond the retaining valve. Where the suction pipe is long, iti is just as necessary that an air vessel shoidd be placed on it' as on the delivery side. This is best done by carrying the suction pipe upwards and inti-oducing a tee-pipe, d. This chamber CRU easily be extended by adding ordinary pipes and putting blank flange at the top.
Air Vessels. — IHitt acting steam pumps always work better with nir vessels, although their utility is much qiieetioned. Water I'eing an incompressible fluid, some elastic medium haa< to be introduced to i-esist the shocks due to and startiDg the column. Sometimes a pump works just as welt (or rather as badly) with an air vessel as it did without one, but this is not the fault of the air vwset ; it is more probably due to its improper position, insufficient sise. and lack of attention. In the pinto, tlie air i-essel sliould be so situated that the air in vrater tends to louie liack into it and not to flow post it.
n
'ig- 374. but, water has iictually
very good rough arrangement is shown perhaps, the best is Fig. 375, whei'e all the to flow right through the air vessel.
Then as to its size. What may appear to be a large chamber Is fitted on to a pump, but it muet be remembered that it ia only charged with air at atmospheric pressure. With a lift, say, 300 feet, the pressure per square inch would be roughly 150 lbs., and immediately the pump starts to work, the water will compress the air iu the air chamber with this pressure, and necessarily reduce its bulk; therefore instead of having, say, 10 cubic feet of air in the chamber, the volume under the above load is reduced to i cubic foot. It is also suggested thut the air enters into mechanical combination with tiie water under this heavy pressure, just in the same way as it does in mineml waters, and that, eixiner or later, unless it is attended to, the air chamber gets completely tilled with water.
Neglect of counteracting these causes has io mn.ny ciuea made air vessels quite useless, and has given them a bad name, but with proper attention they will do everything that is claimed for them. They never work well, unless means ai-e adopted to keep them properly charged with air, and the air ho introduced should be above atmospheric pressure. The better plau, although it entails a little expense, is to employ a small force pump, worked by the piston-rod of the pump, which delivers a small quantity of air into the air va-wel (vith each stroke.
Coadenaing Arrangements. — Where the diameter of the tfteam end in not double that of the water end, the exhaust steam can be easily got rid of in several ways. If the steam eud is large, and the pump eud small, the volume of exhaust steam is great that the water is heiitd too much. Often the exhaust is turned into the suction pipes simply with ordinary pipe connections ; but a far more ,
euccessfid arrangement is Holman's condenser, ns applied by Messi-s, Tangyea to their steam 376). A vafutimoE from S to 10 lbs, is easily obtained, and buck pressure removed. The apparatus consists of one or more do 11 bio-lien t valves, and the
am i- --'-H ' .innulor sti'eiims to
et t ! I -"'ng to tl'S pu'
. Hayward, Tyler pliance is to dis- 3 iKi..;.-,ible in ID he operated
correspondingly rapid. Where
valve has to be introduced,
inked into the atmosphere
Text-Book Of Coal-Miking.
whenever required. 'When the pump is tirat started, before pipes are thoroughly filled with water, some such device lutely necessary. Any ordinary two-way %'alre will perfonn the operation.
CalculatioTiB oa to the Sise of Pumps. The size of a. pump to perform a certain amount of work is easily obtained by a simple method of reatwning. As an illustration of how such is done an actual example is given. At a collieryunder the author's charge, water was raised by winding it in a took ; and by measure' ment it 'n-as found that, aftr allowing for slip, 10,000 galls, ui hour had to be dealt with, or 166 galls, per minute. The first> point to decide is the piston speed ; many authorities say that tl may be from 200 to 300 feet per minute. There is no doubt that such velocity can be used, but no pump makers, who, after all, are the best judges of the capacities of the machines, would recommend such speed for regular working. By common consent, a good and safe velocity may be taken at 100 ft. per minute- If 166 gaUs. have to be delivered every minute, and the piston speed be 100 ft., 1.66, or, say, 1.7 galls, will be delivered for each foot the pomp works, if it is a double-acting-one.
One gallon of water contains 277.75 cubic inches, therefore 1.7 gall. X 177-25 471.315 cubic inches of water have to be delivei-ed for each foot the pump works.
is the area in sq. inches of the required water column.
If the piston-rod of the pump is put at 3 in. diameter, ita a: will in., and this added to the area of the water column makes the area of the required plunger to be —
diameter at required plsnger /iJ*i y.6S in.
The height to which water had to be lifted was 400 ft, ; the pressure per sq. in. will, therefore, be : —
400X. 433 173-2 IbB. .-. total pTeBsnre 39.277x r73.2 6So2.6 Iba.
The steam preiure available was 60 lbs. per sq. is. The an of the steam cylinder, therefore, should be : —
One half of tliis urea should be added for friclioaal i-esistanct-. .-r., making the area 1 70.07 eq. in.
-. diameter of steam ojlinder:
/iZ£:?Z-,4.7.
or practioiiHy 1 5 inches.
Fi-om these results a pimp was put to work, having a steam cylinder 16 in. diameter, and in. rams, and has dealt with the quantity of water it was intended for.
In determining the quantity of water a pump of a given siie will deliver, the converse of the pi'eceding cBilculationa can easily be made. When the piston speed ia known, all that has to be done is to find the area of the rams, remembering that the area of the piston-rods must be taken out, as the water cannot occupy the pace that they take up in the pump chamber.
The quantity so found is the theoretical one, but ia never reached in practice, owing to the occurrence of what is known as " slip." Neither the suction nor delivery valves can be instantaneously opened or closed, and, as a result, the piston does not discharge its theoretical volume at each stroke ; a certain quantity is forced back into the suction during the delivery stroke, and another quantity escapes back into the pnmpchamber on the return .stroke. The amount depends entirely on whether the pump is in uHicieut working order or not. With the beet constructed vArieUes in good order, the loes or slip will not amount to more than 2 per cent., but it may inereae fi'om that to anything if the valves are worn, or if an obstruction geta beneath them and prevents their
Effect of Acid Water. — Water containing sulphates and chlorides has a most injurious eft'ect on the working parts of pirnips. Even when present in small quantities their influence soon mokes the working piii-t*f i-ough, which either cuts away the bucket leathers or grooves the plungera. Fi-ee sulphuric and hydrochloric acids are contained in many mine waters, and are specially objectioimble. To prevent this action the working ports are generally lined with gun -metal with satisfactoi'y result. It is expensive, but there is no other alternative.
DrsinlDg Deep Workings.If the shaft is at the lowest point the water may eaai] be couveyeil fi-om the working places to it and raised to Uiesui but if the shaft is on a higher level
than the wotlBB tibA pi becomes a far more difficult one.
With small qwpMMhfcjlh 'm way is to loud the water into
speci&l tMflHHEH haft in the same manner as
to bt
lifted is not very l'|i workings by the
3o6
Text-Book Of Coal-Mining.
use of a Byphon, the principle of which is showd in Fig. 377.
the tube, ah c,is filled with water Rnil open at both ends, the
water naturally falls out of the end, e, which i& the lowest, and
ci-elites a viicuum at the
Kit!- 377-point, b. Now if the end,
sure of the atmosphere &t [lint point ivill force water ulongaS to fill the vacuum, jind a constant flow will |.iass from to c under I certain conditions. One I condition is that the veir- f tical height from a to fi, or the height A, must not be more I than that which the pressure of the atmosphere will supply. J This theoretical height is never reached, owing to the ] of the water in the pipes and the i-esisttuice caused by the I inti-oduction of certain valves which we necepeary for the siic- ( oessful working of the syphon. Pi-nctic© proves that it cannot with safety be more than 27 ft. The other condition is that the diticharge orifice must be lower than the inlet ; it is ttlso advisable that the gradient should be as uniform as jxssible, or air will collect in the bend, and the syphon cease to work. Indeed, where the pipes iire undulating, as thej sometimes have to be, . discharge cocks must be placed at each bend in order that the pipes 1 can be always freed from air. The discharge orifice should be as ' far below the inlet as is possible, for the velocity of efflux is represented by the pressure B — A.
Where pumps are used, a small pipe should be led from the rising main into the syphon to allow water to be taken out and the syphon filled, if any leakage has taken place. A clack of a very light construction should be fixed at the inlet end to prevent the 1 water flowing out when not at work, and a tap should also be I introduced in the drop-leg to i-regulate the flow.
If the height escels 27 ft. other means have to be adopted, the commonest of which is that where horses are used, a throwpump being worked by bevel gearing. This is, perhaps, the most arduous work to which horses can be put, and they are unable to remain at it for any length of time ; it is also slow and costly, . The horses are soon worn out, and something else must he employed. If power transmitted by wire lopes passes the place where the ' pumpa are situated, or any point near, it becomes a very simple matter to caiTy an ofi'-shoot to a pulley, which then takes the place of a hoi-se. The endless rope system is particularly suitable for such aiTangement. A cluth can be fixed to the pump, which can be set to work whenever reijuired.
Where compressed air is available, pumps can be driven by it
readily iind clieaply ; several are designed which work very Hatiefoctorily with such a power, and are tjiable of dealing with large (jiiautitiet; of water.
Hydraulic Power. — Whei-e pumping appliaiicaa ara fixed in the shaft, hydruiilic engines are oftn employed to pump from deep workings into the sump, the power to drive ihem being obtained from the rising main of the pumps. Their ikction depends on the principle that u small quantity under lieary preture is equal to a hirge qnnntity nt a small pressure, or having a head of water of too or 70D feet in the rising main, a small quantity of
this can be conveyed to the deep, and lift u larger quantity of water into the sump for a height considerably lees.
A common construction of such engine is employee! at Tees Hetton Colliery, Durham, and is tihown at Fig. 378. It comdsta of a motor cylinder of special design, provided witli controlling valves,andconnected through a strong base plate to the pump,which is of the ordinary type. The piston of the motor cylinder, n, is connected direct to the piston of the pump, c, and the latter is provided with a cross-head, d, whicli server to actuate the tappets on the tapped-rod, e. The small auxiliary valve. J, is operated by the tappet-rod, e, through the lever and valve rod, ;/, thus admitting the drive water to either end cf bbe piston, A. which, in its turn, engages the main slide v&lve, j, aadadtBita drive water to the motor piston, k. The latter Blivke until arriving
3o8
Text-Book Of Coal-Mining.
the delivery valves in the pump, and passes away to the main pumping engine. The controlling valves of the motor cylinder are composed of liguum-vitse, as this wood requires no further lubrication than is afforded by the water. The pressure on the motor piston of the pump was roughly 230 lbs. per sq. in., and by means of this pressure, 7000 galls, per hour were forced to a height of 156 feet.
MooTB Arrangement,* — An hydraulic engine of a totally different class is that designed by Mr. Joseph Moore, where two
columns of water are substi- Fig. 379. tuted for the ordinary solid
rods connecting the steamengine to the pump. The action will best be seen from the diagrammatic representation (Fig. 379V A cylinder, a 5, at the surface, having a piston p is driven in the ordinary way by a steam engine, and each end of this piston is connected to each end of a smaller cylinder, c d, situated underground, having a piBton, q, and connected through a piston-rod to an ordinary double acting pump. The pipes and the cylinders are all full of water. When the surface piston p moves from a towards 6, water is forced down the pipe e and moves over the piston q towards d ; when the piston p reverses its motion, the piston q is also reversed.
The success of the appliance is due to an arrangement whereby the stroke of the rams is adjusted, as without some such appliance, should there be any leakage in one of the power pipes, the plunger at the bottom would make a shorter stroke in one direction than in the other, and would work towards the end, and, unless there were some regulator, knock off the cylinder cover. It will be noticed that the pipe g h connects the two power pipes e and/. In this pipe are two valves, j and A;, opening in opposite directions, the former closing against pressure from pipe and the latter against pressure from /. These valves are opened by tappets, m and /, set apart a few inches more than the length of the stroke. If the pipe e leaks, the piston q will not make as long a stroke as it should do, and stops short of d. In the return stroke, when the piston q has travelled as far as it
Min. Inst. Scot. xii. 168.
Pumping. 309
safely ghoiikl do, nnd before the piston p oa the Hiirface has completed its stroke, the projection catches the tappet I aud opens the valve k. The pressure of water m J in now free to lift the valve J, and to run into e, immediately etiiuiliaiug the preeeure on both sides of the piston q und stopping it. The water displaced by the remaining part of the stroke of the pistol p, pofises through the valves from one power pipe to the other.
The power pipes are kept charged from a tank placed above the level of the highest point. There is a valve opening inwards on each of them, and when the piston p makes the return stroke, enough water is sucked in to make up any leakage. A considerable number of these engines are at work, and it is stated that diagrams taken from oue working at the Shotts Iron Co.'s Collieries, Edinburghshire, show tiiat 66.26 per cent, of the work shown in the indicator diagram of the steam-engine iit got out of the pump.
Electricity. — The use of electricity in mines was lirst called into requisition for pumping, and by far the larger munber of installations are stiU applied to sudi a purpose. An electric motor can be readily connected to a pump, either by gearing or bells. Tlie convenience of electricity is such that in all installations of the last few years, scarcely anything else has been employed in pumping from deep workings. Innumerable instances could be quoted of its success, hut for our purpose we may beat refer to the fim ptimpiD);; pliint and its additions, which were put down by Mr. Brain, at Trftfnlgar Colliery, Oloucestershiro.* This commenced working in December 1882, and attained such succeHS that thi-ee additional plants were ei-ected in May 1887, and are now doing the larger part of the underground pumping.
The last installation consists of a double thi'ow 9 in. plunger, by 10 in. stroke, situated 3320 yards from the generator, and 1650 yards from the bottom of the shaft ; the pipe main is 7 in. in diameter, and at a maximum speed of 25 strokes, the pump lifts 1 20 gallons per minute, 300 ft. high. The current is conveyed to the motor by a copper conductor consisting of wire, insulated and carried on earthenware cups. The E. M. F. is 320 volte, aud the current retjuired is 43 amperes, The cost of the engine and the electrical plant was 644 ; the weekly cost for maintenance, including 1 5 cent, for depreciation and interest on is 17*. or .oojrf. per horse power hour. The effideucy attained throughout was only 35 cent,, but the engine, which is uu old encloses 6.49 horse power, or 23 per cent, alone j tacluduig losM in the engine the efiicicncy is 45 per cent.
With the nil! of luxTum ">ifmdary batteries, in which
the current of clertricitj' nud caiTied about, small
lunntitiraof watratiu be, and have been,
3Io Text-Book Of Coal-Mining.
dealt with in miuef. Thee accumulntors cnn he placed or carriage iiind lake luiywhere required. A motor aud pump on a second carriiige n.re also arranged, and accompany the accumulators,
Pulaomater. — Wlien describing the methods of dealing with water during sinking, reference was made to the which is also largely employed for draining deep workings. lb consumes a great deal of eteam, but its advantage is that it will piunp nearly everything that will go through the valves. No matter how gritty or dirty the water is, it works nearly as well as if it were quite clean. It peculiarity consists in there not being any steam cylinder, ' piston, piston-rods, or bucket, as is usual in the , ordinary form of pump. , Its construction is shown iti Fig. 380. It consists of two pear-shaped water chamljers, a a, the air chamber, h, the suction passage, c, and the delivery passages, d d, which communicate with the discharge pijw. Steam is admitted to either of I the chambers, a, through the pipe, e, but the direction is controlled by a ball- "alve, f, which is capable of oscillating, and closes each passage alternately ; g y are the suction-valves, which ai'e of the ordinary flap form, and are prevented going too far hy the stops, h h. It should be especially noticed that the delivery passages, d d, each of tfae
water chambers just above the auction-valves.
The action of the apparatus is as follows :— When the two chambers, a a, are full of water, if steam be admitted through the opening, e, it will paas into that chamber which is not closed by the ball-i-alve, /, and rapidly depressing the water loitfiout cavaiiif/ niiy agitation, will force it through the delivery chamber, d, into the rising main. This action continuBB
3"
until the wnter is depressed to tiie top of tiie passage, d, wlien the Rteam attempts to rush through thU opeoiog. and in doing BO violent}'' agitates the surface of tbe water. Immediately this takes place, instant condensation follows, and a vacuum is produced in the chamber. This sucks over the ball-valve, and diverts the live steam into the other chamber, depressing in tiu-n the water there. While this is |!oing ou the vacuum in the first chamber sucks up the water through the pipe, e, and Utta the suction-valve, g. When condensation takes place in the second chamber, as it will do as soon as the water is lowered to the top of the discharge orifice, d, the boll-valve is an sucked over, and live steam diverted into the firat chamber. The suctionvalve then closes, and the water is discharged as before ; first one chamber and then the other is filled and emptied.
Dams.It is often necessary to put in Btoppings, called " dams," to prevent water passing from one part of the mine to another. On the Continent wooden dams are most in favour, while in this country masonry is generally employed. The advantages of the former are that if the wood la perfectly dry when put in, the moisture expands it and makes the structure more water-tight, and any movement in the sunvDunding strata is not so liable to dislodge or crack the wooden dam, as it is a masonry one. Osving, however', to the convenience and ease with which bricks can be obtained and pnt in |H3sitiou, their' use is becamin}; coinmon, even in districta where wood was formerly employed.
Id putting in permanent dams the first thing is to select some spot where the strata is of an impervious character and quite fi-ee fi-om ci-acks. Dams are invariably wedge-shaped, with the broader end towards the pressure. If this be heavy, two or three wedges ai-e built, one against the other. In preparing the ground, nothing but the pick and chisel should be employed ; the sides, floor, and roof lU'a carefully dressed to the required shape, and covered with Portland or other cement, to obtain a hard and proper sui-face to receive the masonry. Ciood hard burnt bricks should be employeil, and the lime should he of an hydraulic character.
To pass the water' from one side to the other while building is going on, a pipe is invariably btiilt through the lower part of the dam, this being fitted with a r&lve at one end, wliich can be closed when tbe work is finished, A second pipe of smaller dimeusiona is also btiilt throuc'h the dam near the top, and its inlet end carried into a oi " the roof, the object of ibis being
e the remoi-al of dam, which is a poJnt jj ude of the dun is s§|fl| puddle-
r fi'om behind the
'mportance. Tlie water
tarred sheets or well
, and prevent leakage
Bibliography. — Tto following is a. list of the more important memoirs Jealing with the subject-matter of this chapter ; —
VIS, INST. SCOT. : Jiomt Practieat Rendu of Hydraalie Pumping, D. Johnstone, iii, 157 and vi. 1 11 ; Ok the SiieHg Power o/iA* Common Pitn nml of tome of the SAoci ichidt oeeur in Famping, J. HoCrsRtti, iv. 2395 On an Improved Arrangement for IVoriing l/ndergromut Jngu laeaal of Hgdraviie Presture, Robert T. Hoore, v. 390 and lii. 168; Air Vegaelt, Dngald Baird, s. 251 ; Air VatcU, Allan Andrews, xl. 113.
soc. IND. MiN. : Mtmolrc uar ta nouvt'U madiine (JVmtijsnwnt inlirUtirt <fa MoalceiMJet-miiiei, M. Audemar (3 Bfirie), i. 437 ; MaehixeM d'uUement A VEipotition de Parii (1S7S), Cb. BaUson (3° Srie), Till. Soi ; Xole lur le noueeaii batander diijuiiibre de la pompe au puiW de I'Onilaiiie, M. Griot (3" Sriel, iii. 349.
so. WALBs ISBT. ; Pumping Arraiu/emenli at the RruUliKk CaUieriet, rtt, , J. McMurtrie, zi. 66 ; A Shurt Dacription of the PutiomeUr ad Hydroirope, Hort, Huxlmm, xi. 85.
C'HBB. ISBT. : Draiaiag and VealHatiag, iCt, at Stavrlg Cbllirriet, Job. Hamble, ii. 350.
AMBS. INsr. U.E. : The Worlhinnlon Oiiapaand DitpUx Pretlure Arnip, R. W. Hunt, iv. 317; Famjiing Eaginet, John Birkinbine, v. 455.
FBD, IKBT. : Firtier tC Weiton'i Pump for CiMirry Pui'poiei, G. B. Walker,
AitTij, J, K. Guthrie,
; Pawping Appliaiuxi at EUringhai
Simpson, xix. !0i ; The Difftrtnee hitwta. tlte Slatieiil attd Dyitaatieal J'ttuure of Water Oulamnt in Pumpt, K. Bainbridge, xxi, 49. r. BOC. MI. 9TU0, : Varialloa of PreuurB in Pumpf. H. F. Bulman, iii. 107 and viii, 138 ; Notes on the Erection of a Large Ham Pump, E. F. Melly, viiL 40 ; Eleetrieity applied to MiaiiigV. Brain, xi. 48 ; ffudrauUc Paviping, W. Walker, Jnn., xi. 132; Electrical PaOfiing Plant at South Fbntop Collier-/, 3. R. Biteon, xiv. 83.
Chapter Xi.
Ventilation.
XmpDrtanoe. — It is most importiuit that miQea should be properly ventilated. All coals give ott', to n more or less greater , a qiiautity of ileleteriouu g&ses, which have an injurious effect on the human life, even if they are not eiplcwive. In addition the breathing of men and of other animaU, and the burning of illumiDants, render lur impure. It, therefore, becomes necessary that ft vigorous current of cool, fresh air should be circulated through the galleries and the working-ploraB ; indeed, General Rule 1. of the Klines' Regulation Act, 1S87, makes such a current compulsory, but even if such wei-e not so, it really pays to have good ventilation, as men are not only CApnhle of doing a greater quantity of work, but they do it with greater comfort nd ore tar more contented.
The quantity of air required in a given mine depends principally on the volume of gases produced hy the con]. The quantity of gas given off does not always increase as the workings become more extensive, us it principally depends on the ai'ea of freshly coal surface. If bord and pillar working be adopted, a quantity of gas will be given olf while the exploring work is being done, but as the pillars are large blocks of coal, up to 50 yards square or more, the comparatively narrow (s to 5 yards) places driven to form the pillars, cannot liberate the whole of the gas. When the siicond or bi-uken workings are proceeding, wider places are driven and the coiJ is got more easily, so that more coal is being worked per man jier shift, and more gas is king, lis the workings get more ih fj-'ned out, and coQse<;|uently best plan is, therefoi'c, to make the output and to increase "Nxediiig. It is often )uld be I'egiilaled by the output increases, I the better plan ia ;e 111 the Rorinage litiry in the world.
liberated. With long 1 extensive, a greaUrr ait of fuc more guB will be given off "" the amount of air prop thf current, if explontl stated that the
Oases met with in Mines. — Atmospheric aii-in its pire state is a miKture of two gases, nitrogen and oxygen, but, as generally found in Nature, it contains small quantities of another gas, carbonic add, and of aqueous vapour. The osygen is tha life -supporting element, the nitrogen acting simply as a diluting agent. Dry nir is composed of 79 per ceut, by volume of nitrogen gas and 31 per cent, of oxygen. In breathing, men and other animals take air into their lungs, and part of the oxygen combines with carbon, forming carbonic add, whilst the nitrogen is unaltered ; the same result follows the burning of lights.
Carbonic Add is known to the miner ai; black-, or choke-damp, or stythe. Its presence is common, and U due to the combustion of illuminants, respiration of men and horses, combustion of blasting explosive!, decomposition of pit timber, and often exudation from the coal. It is chemically composed of carbon and oxygen; ite -mbot is CO,, and it has a specUic gravity of 1.53. As it is con* siderably heavier tluui air, it tends to occupy the lowest part of the mine. In its pure state it has no colour, but bus a peculiar h&rp, but not soui-, odour and taste. Its presence is manifested by its indnence on the flame of a candle, as it will not support combustion. Il effect on human life is dependent the proportion present. Over 3 per cent. piduces sleepiness, while with 10 per cent, the motiou of the heart is temporarily suspended. On the Continent, outbursts of carbonic acid are frequent, aad an in ever}- similiuto of fire-damp. The blowers are generally found in the vicinity of faults. At Toulane Pit, Uochebelle, one blower filled 500.000 cubic feet of workings in less th&Q ten minutes, and disengaged over 400 tons of coal.
Carbonie Oxide is \'ai'iotisly known as carbon monoxide and white-damp. Its chemical symbol is CO and specific gravity 0.97. Luckily its presence is much less frequent in mines than blackdamp, as it is far more poisonous than that gas. As HttJe u i per cent, produces giddiness and faiutness. while over 2 per 4.-ent. may cause death, lude, per cent, breathed for any length of time is fatal. Carbonic oside is known by its sweet at delicate odour and dcKdly results. Caudles burn well in this gs, if aunhiiig, a little brighter, although their flame is not elongated until ijj per cent, is present. It is produced by imperfect combustion, and especially by spontaneous ignition.
SaipkartUed Ilydrtyfit is nut found in large quantitiee. Its chemical symbol is SU„and specidc gravity- 1.17. It arises from the decwtipostion of iron pyrit*?, or. to a smaller extent, from blasting, espedally if inferior cheap gunpowder is employed. It has an injurious eU'ect on life. not support combustion, iumI burns with a blue flame. Us jn-esence is immediately detected by a characteristic and ofleusive smell.
I.ii/Mt CarhtireU Uydroynt. — This gas, known as fire-damp, is the one commonly found in mines, and to which exiJosions are
Ventilation.
31S
principally due. It consists, in the pure stnte, of cnttioii and hydrogen, its symbol being CH, and specific gravity 0.552. The fire-dajnp of the miner is, more correctly spMJiing, a mixtm-e of several gases, the largest proportion being carburetted hydrogen. Other bydrocarbona, with hydrogen, carbonic oxide, oxygen, and nitrogen, are genenilly present, the quantities of such gases varying con.sideralily in almost every coUievy. and often in different districts of the same pit.
The coal itself is the principal reservoir of the ga.s, where it is held in the poros oi' cellu in ti state of more or less high tension. Difierent gases exuded from the coal have been described in Chapter Il.,whei-e the phenomenon of " blowers " was also referred to. Blowers are a more or less steady discharge of gases from the cool, continuing for a long time. Where this discharge is a violent and sudden one of targe quantity, only continuing a short time, it is known as an " outbui-Nt."
Carbiiretted hydrogen is colourlegs, and when pure is odourless, while tire-damp in often detected by its iimell. This gas, if breathed in a pure state, would soon catise death ; it quickly extinguishes dame or lamps if undiluted by air. When 3 to
4 per cent, is present in air, the gas can easily be detected by the elongation of the 6ame in a safety lamp. If 6 per cent, be present the flame is not only elongated, but a blue halo, or cap, appears above it. This halo m often of a brown colour, produced by the presence of carbonic add gas with the flra-damp. With 7 to
5 per cent, the mixture becomes explosive, and flame is propagated through the contents of the lamp; with 10 to 12 per cent, the jiropagation is instantaneous and the explosion attains its maximum amount ; with 10 per cent, the mixture no longer explodes, but instantly puts out any flame that may bo brought into it.
After-damp.—'UndBe this head is included all the products resulting from the ignition of an explosive mixture. When firedamp is exploded, the carbon combines with the oxygen in the air, and forms carbonic acid, while hydrogen also combines with oxygen and forms aqueous vapour, leaving a large amount of free nitrogen without the corresponding amount of oxygen. As a rule, carbonic oxide is pi-esent in after-damp, as will be seen fim the following analysis given by Messrs. Atkinson" of a aample taken after the Usworth explosion in 1885 :
Carbonic acid gai- " " e oxide
4-54 voU, 2.48 „
3i6 TEXT-BOOK OF COAL-MEflNG.
The proportion tif carbonic osiile is, howerer, unusu&Uy h.
If combustion be perfect, i cubic ft. of fire-damp will vitiate 59 cubic ft. of air. If an excess of air or lire-damp were present before explosion, such excess would remain mixed with the afterdamp after the eiplociion, but in no case can the air in after-damp contain IcKs than twice iis volume of deleterious or the J explosion would not have happened. After-damp is often respon- I sible for more deaths than on actual explosion, as often all that I escape the latter are suffocated by the former.
Coal- Dust. — The roadways of EOme mines contain accumula- I tons of very fine coa]-dii.''t scattered over the timber and resting' on the floor. Messrs. Fafaday and Lyell, in a import on the Uaa-f well Colliery explosion in 1844, were the fiKt to demonstrate the n effect these acctmiulations of dust may have in extending firedamp explosions. Although several persons investigated the . matter, it was not until 1876, when Mr. Wm. Galloway read J his fii-tit paper before the Royal Society,* that general attention. I wae directed to the important part that coal-dust plays in aggror-fl vating fire-damp explosions. Subsequent experiments by by several memben* of the North of England lustir- 1 tute.T a committee of the Chesterfield Institute, § Sir F. A. and particularly by the Prussian Fire-damp Commison, demonstrated that, under certain conditions, the pi-esence of coal-dust in a fine state of division is a source of danger in (liy mines in which blasting is carried on without sjimal precau-J
Upwards of 300 experiments were made by the Prussian Pir-| damp Commission at Xeuukirchen, near Saoi'briicken, and it v that the following conclusions were warmated by thafl
results obtained iff —
>TlosBBbuiicIancein the immediate] to more or less elongation of t Same projected by a blown-out shot, ithether tniaO quanlitiet of fire-damp h prr'ral in tlit iiirrouRiiing air or not,
2. (a) In ihecompleteabsenceof fire-damp, theelongatioDorpropagaUoBi'fl of name is generally of limited extent, however fat the depe " of dust may extend in the mine-ways.
Proc. Royal Society, March 2, 1876, adv. 139.
t Ibid, xx%'iii. 437 and 490, and xxiviL 42,
% N. E. I., XXV. 239, and xxviii. 85.
I Vol. X., with appendix>:eB.
I Bine-Book, " 8eabain Colliery Explosion," and Proc. Royal Institatlon.! l,PartI.i8Sz. J
% TtansUtion by T. W. Bunning. N. E. I., xxxiv. 199 ond 197.
A complete review of the litetatnre of the sobject with extracts tbeopinioiiB held by English authors, ia given by Mr. E. S. Hutctiiason]! paper entitled .Vofw on Coal-la GMUrg Explotioni, \axer. Inst. M, T
t English Commis!
a Accidents i
Min
Pinal Beport, 18E
Ventilation. 317
2. (1) There are, however, certain deaoriptiona of coal-dnat which, it
SDited b; q blowa-oiit sbot, will oat only continue to cniry on le Qane even to distances extending conaldenthlr beyond tbe confines oF tho dust deposits, bat will also give liie to ezplosire phenomena or results, the abnnn of any tract of fir f- damp, which in cbaiacter and eSecta are similar to those ptoduccd bj Borne other dusts in air containing 7 per cent, of ftie-
3. (q) All the phenomena produced bjr the burning of and propagation
of tlame bj coal-dust arc intensified b; the presence in tne air of small proportions of lire-damp. (&] Certain dusts which under favourable conditions appear to havs the power nf propagating Same 10 an indeliDlte extent in adnstladen area, the air being-free from fire-damp, will, if only sparsely suspended in air containing tire-damp in some propor' tion below 3 per cent., render such a gas-mliture susceptible o( explosion by a blown-out shot,
4. Special experiments in which the branch gallery, described as opening into the main gallery near its extremity, was charged with a fire-damp mixture (rel,alned by brattice cloth), demonstrated that a coal-ignition or explosion, developed in the complete absence of fire-damp, can communicate ignition to an explosive gas-mixture existing at a very considerable distance from tbe point of first ignition.
Special stress was, however, laid on the fact that the occur-enee of H town-out shot is indispensable to the production of any and all of the eirecte (of ignition, propagation of flame, or explosion) to which coal-dust can give lise ; and Mr. Hilt empha&ises the fact that the part played by coal-du8t is not nearly eo dangerous as it might iippear from a supei'ficifti exnininatina of the Saaibriicken experiments,
Messrs. Mallaid and Le Chatelier, in a review of the work of tlie Prussian Commission,* consider the phenomenon of tbe ignition of coal-dust by 11 blown-out shot to be follows :— In that part of the gallery reached by the powder-gascfi travelling at a high velocity and endowed with a high tempeniture, the dust is violently thrown into suspension and ignites. The gaseous moss thus ignited (conaidembly expanded by heat juid increased by the partial distillation of dust that has been thrown into suspension by the mechanical effects of the powder-shot) expands into the gallery, and extends to a distance proportional to the meclianical effects of the powder-gnses and to the ease in which tbe diist in auspcDsion is distilled. The mechanical eD'ect of this jet of flame on the dust in the gallery, situated at such a distance as to escape the initial action uf the powder-gasea, is small, and rapidly decreases until it is destroyed at a very short distance from the shot. They consider that the cxjitrinients of the Prussian Commission confirm these I'ln their previously
expressed ones,t that tbe conil ;ire aot> to speak
exactly, explosions; tbiit comi' '
eiTects entirely insignilicaot for 11. :. less
3"8
TEXT-BOOK OF COAL-MLSlSt..
than fire-damp e.xplodoDS, even for most esceptiona.1 dust : that the combustion produced at any point does not extend finitely over the whole area covered with dust.
On the other hand, the Royal Commisaiou on Accidents tn Mines considered that the most emphatic refutation of MessrB. Mallard and Le Chatelier's condnaon, "that the influence of firedamp upon the combustilulity of dusts, if not altogether nil. is at lesl much slighter than was at first believed," and confinnation of the established facte which it combated, wa furnished by tbd Stwrbriicken experiments, and, after a review of the wbolo subject, considered that the following facts relating to the part |Jayed by dust in coal-mine explosions may be regarded as conclusively established : —
t. The occnrreDce of a blown-oat shot in working places itJiere renriiUy inmmabU eool-ffiHt -uM grtat dtnaidaiux errH ih (Xc lataiatxiKi fire-damp, possiblv give rise to violent eiploxioiu. or may at aoy rate be followed bj the propsgatiOEi of flame tbroogh reiT ctmsidenble areas, and eren by the commimicBtion of flame to distant paits of the workings where explosiTe ga-mixtures. or dust-depoaits in associaiioD with non-exploMve gas-miitoies, exist.
2. Tbe oeoaTTeace of a blow-ont sbot ia localities iricre oti imaO ptvportioAi a/Hre-Jamp exist in the air, IM prtteat* or era* eoaparativiifi thpiitig iitfiamnmUe, or admaBif iKM-lnrmwiatU bml reryjiitt, dry aiuJ poromt diiMU, may giTe liae to explosions, the flame from which may reach distant localities whereeither gBKaccomalationsoT deposits of inflanuiiable coal-dust, may be inflamed, and may eitetkl tbe diiaivas insults to other
That tlie above coucluons nre true is now generally admitted, antl the importance of adopting sorae effecttial means for dealing with dustdepoKit beomes self-evident when it is remembered. that the meet observer cannot detect gas in the aircurrents with safety-lamps when tbe proporti() present does not exceed z per cent.
It is, however, contended, more prominently by Mr. Galloway and Messrs. Atkinson.t that coil-plays the prindpat part in colliery explosions, and that fire-damp most be rdated to a secondary position. The chief argument in favour of this view is that explosions are so often confined to the intake sir-ways and not to return air-ways. The intakes are where dust collects owing to the haulage of conl, while the returns are those along whi ga£ is carried off. It is also contended that gas explodes equally in all directions, while many explofdons in minee do not seem to pass into all tbe routes open to them, btit follow certain definite paths, such af. intake airu'a\-s where gB$ is absent but coaldut present. An explosion that took place in a coalhopper at Branoepeth Colliery, Durham, where no gas could be present, is also quoted ns an Argiunit in favour of this iheoiy.
Final Report,
KSm
I, London, 1SS6.
Ventilation.
3"9
This hopper wns used to store in for tlie use of the coke ovens. It was being clejined out, when the fine dust took fire at an open torch lamp. Several men were severely burnt and three lost their livci. It may, however, be taken more ob on instance of ignition than of exploBion, aa, although several windows existed in the hopper, none of the panes of glass were blown out, although they were much cracked by the intense heat. Only one sheet of corrugated iron was bui'st off the boK, and this was not blown away, but was simply dislodged and fell to the ground,*
The theory is supported by the fact that explosions happen in flour mills, and in the drying chambers used for the preparation of brown cool for the market. It has also been proved by large explosions which have taken place in flour mills at Anuapoliii, U.S.A., that in the entire absence of inflammable gas, the explosion beginning in a distant portion of the works may be carried through the entire building. It is also possible, experimentally, to obtain explosions with air and lycopodium, simply with the lyeopodium lying on the floor and not for;ning a thick cloud.
The great argument against coal-dust being the principal agent in coal-mine explosions, as pointed out by the Royal Commission on Accidents in Mines,t is the fui.'t that, if it were so, tw-y blown-out shot occurring in a very dusty and dry mine should actually be attended by a more or less disastrous explosion or coufiagration ; and that, looking therefore to the enormous nmoiml) of powder expended in sfaot-liring in IhU and other countries, and to the not inconsiderable proportion which blowout shots must constitute, in many localities, of the total number of shots fired, disastrous coal-mine explosions should be of more than daily occurrence, if this view were correct.
Messrs. Mallard and Le Chatelier maintain that all explosions of magnitude which have been solely attributed to coal-duft have occurred in mines in which fire-damp occurs ; that the possibility of coal dust, per w, giving rise to an important exploKion could only be established by the occurrence of an explosion in a mine in which the total alienee of fire-damp can be absoliitly demonstrated ; and by the fact that lignite mines, which are genei-ally very dusty, the dust being extremely inflammable, but which are at the same time almost free from fire-damp, have never yet been visitfid by accidents of this class.
In Chapter II. reference wa.s made to the experiments of Mr. J. W. Thomas on the gases enclosed in coal. Dr. P. P. Bedson has conducted similar investigations on coal-dust and has established the point that some dustin give off tonsiderabl vqIih ezploaive gas at a coinpai-atively low temperature gaaen in coal-dust resemble in many respects t'
Itojal Commission od Coal , 7 + Final Keport. p. 47. : A CoRiributioa to IM
3ao TEXT-BOOK OF COAL-MINING.
been obtained from coal. Tlie main points of difl'erence to I noted are, firat, the large proportion of carbon dioxide {CO,) compared with the amounts found by Mr. Thomas, and, i the presence of olefines and higher members of the paralSn of hydrocarbons.
In the final Report of the Austrian Fire-Damp " is atitted that the experiments made confirm those of NeunHrchen with regard to the danger of coal-duet, but also show that the dangers are greater than have hitherto been admitted. First all the Commission tested the different kinds of coal-dust so as to classify them according to their sensitiveness to ignition and i danger. As they considered that black powder and mil&rexplo- I sives are dangerous in fiery mines and that their use shotdd be I entirely prohibited, they confined their experiments to high explo- J si vee, especially dynamite No. i. The experiments were made in ' levels, like the one at Neunkiichen. Each kind of duet that v used was also tested in order tn determine the following factaf concerning it : —
I. Petcentage of volatile matter,
s. Hygroscopic moisture.
4. Quanti of maish gas in too grammes of dast,
5. Qiiaotit; of gas given out by 100 grammes of dast at ic
6. CompodtioD of gas given out by 100 grammes of dust al Instead of imitating town-otit shots, the experiments were
mostly made with ciirtridges of dymtmite lying loot, or with a slight covering of coal-dust. The coal-dust experiments were almost exclusively made without any admixture of gas. In one of the levels, 353 experiments were carriedout and showed that many notoriously dangerous dusts were less inflammable than other lees dangerous dusts. Coal-dusts were therefore classified into tive and dangerous kinds. To judge of their sensitiveness, the coal-dusts were all tested with the same charge of dynamite, viz. : 100 grammes (3 j ounces). The experiments showed tliat without any admixture of fire-damp, nearly all kinds of coal-dust were ignited by a cartridge of 100 grammes of dynamite lying loose. The following points wei* considered establislied : —
I. The degtea of inflammability can scarcely be deduced from the J chemical composition. I
I. The tenure of tbe coal la important. Hard compact coal wiU give 1 less duat than cmmbUog friable coal. The fineaess of coat-duet depend* J
3. Tbe sensitiveness of a cool-duit, and as a rale, its danger, ii with its diToess.
4. Tbe danger of a coal-dust appeals to depend more upon its phjoiaali'l qualities than upon Its chemical composition.
Scliluasbcricht des tntralcomites dcr oBterrejchlacben CommfaisiaK'l lUT ErniitlluDg der zwectttoaBsigsten SicbeTheitmasstreln gegOD i" Explosion scbtagendet Wetter in llergwerken. Vienna, 1891.
Ventilation.
5. A blown-out shot with coal-diisC as tamping, or a cliBive of djnamile Ijing free, will iite every kind of coal-dust. Most kind of ooal'dust were igniUHl with a charge at 100 gr. (3J oi.), and all without exception were ignited with a charge of 300 gr. ( 104 oz. ).
6, A coal-du!t which otherwise is not dangerouH and takes Rre witty difflcaltj, may give rise to a disastrous explosion if there is a little (ir&danip present.
The question coDtiniiin to be n. very debatable one, Mr. Henry Hall was appointed by the Home Secretory, itk 1890, to carry on a further aeries of experiments.* Tlie result of these experiments being still non -con elusive, a Boyal Commission waa appointed in 1891, to inquire into tbe effect of conl-iluNt in originating or extending explosions in mines, whether by itself or in conjunction with fire-damp. This inquiry is not yet completed, but a preliminary report t hns been issued gi'ing the evidence taken up to
Sir F. A, Abel J considers that, under extremely favourable conditions as regards the nature of dust, its pliynical condition and itA composition, and the quantity of dust existing and suspended in the air at the time of the explosion, in the entire absence of fire-damp, coal-dust undoubtedly has the power of carrying on explosions almost to nn indefinite extent in mines. He questions whether thei'e is practically any limit, as, looking to tbe great commotion set up by the rush of gas produced as the explosion orinates and as it praE'Sses, the motion of the air is such that particles of coal-dust must whirled up into it, and must continue to produce a mixture of sufficient intimacy and sufficiently highly charged with inflammable particles to develop afresh the conditions which existed nnginally when the explosion waa started, and in that way the explosion may be considered to be a continuous one.
Mr. A. H. (Jtokes§ considers that the Prussian experiments proved that coal-dust, without a trace of gas, in a pure atmosphere, is not dangerous. Ooal-dust in mines promotes, extends, and aggravates explosions due to lire-dainp, by reason of the rapid inflammability of its finely divided particles. The sensitivenees to ignition of coal-dust and air, appears to be in proportion to the intensity of heat at the point of ignition, and the size and impact of the initial flame has a very important influence in controlling the propagation of flame. The condition necessary to ignite a mixture of coal-dust and air appears to de[>end on the temperature, volume, and the way in which the initial flame strikes the current ; also that each atom of dust be surrounded by air so that it can get oxygen instantly, and that each atom be near enough to its
Colliery Guardian, 1890, Ix. 875-
Coal-dMl in Mine*. July 1891.
; Ibid. p. sj.
3"
Text-Book Of Coal-Mining.
neighbour to be able to communicate flame. He has not been able to find any reooril of an explosioD in a iliy and dusty mine in which gae had never been found. Id most experimentjU cases where coai-dust was fired, the atmosphere wtm thickly charged with ccal-du&t — in fact, so thick that no living being could exist in it : and this was a stat of afikirs which could ecaroely be found in any mine unless as the result of & seriooH explosion of fire-damp, nor one that a blown-out shot could create and Gre wiib its own Bame unless it were pointed directly into, and in close proximity to, an accumulation of dust. A mixture of air and fire-damp which cannot be detected by a safety-lamp, and which may be hai'less in the absence of <tiiit, may, if diist be present in sufBcient quantities, become an inllamiimble mixture, and be the means of carrying flame as fur an sui'U mixture extends. The current of ventilation in a dry and duty miiie may be charged with such a low percentage of fire-damp that the most careful observer would fail to detect the blue cap indicative of fire-damp in the ordinary safety-lump, yet it might be so charged with fire-damp that any unusual circumstances, such as a heavily charged blown-out shot or other violent concussion, might raise a cloud of dust and render the current at once an iaflamiDable mixture. A compuratively biiielII expla'don in a dry and dusty mine giving off fire-damp, may be developed link by link into a most extensive disaster. The most dusty atmosphere of a mine, in its ordinary working condition, could nut be ignited by the direct action of any blown-out shot, If the current of (ur be free from fire-damp, in no mine in its normal ntate, aud the ventilation free from tire-damp, would an ordinary blown-out shot raise suflicient dust to make the ventilative cui-rent an inflammable mixture such as would ignite from the same shot, flame and create what might be termed an explosion, unless such a shot be tired directly into a bed or considei-able accumulation of coal-dust.
Actimt of Moisture. — It may now be regnrrled as established that small amounts of moisture are sufiicient to prevent the possibility of coal-dust being ignited, and at many coUeries the main rotids ai-e regularly watered. In order to be efficient the water should be applied in such quantities bm will simply damp the dust and prevent clouds of it being raiHed by any means. If the floor be properly watered it is suflicient to prevent any deport of dust on the sides or the roof. As a large quantity of dust is formed in the tubs during the progress of hauling them along the roads, a quantity of water is often thrown over the contents each tub immediately before it leaves the working face.
Attempts have been made to render dust harmless by applying along the loadwaya some deliquescent body such aa salt, but although the result in some cases has been satisfactory,* yet t'
method has not racsived many nppHcatioiis, the use of water being superior.
In some cases ordinary tubs ai-e provided with a perforated pipe at the back, and the watr applied in the same way on in stroetn of townE. If such a watering appliance is to be used, st good arrangement is that suggested by Messra. Archer & RobRon.* A circular brush is aflized to the reiir of a tub, and is suitably connected by bevel gearing to the axle of the tub, so that when this moves along the brush is rotated. The spindle of the bnish is hollow, and water is passed along it and through holeti on the rim of the bona, and ia thrown by centrifugal force from the tips of the brittle brush in the form of fine rain or spray.
Many collieries in South Wales are fitted with watering appliances, and the methods used have been described by Mr. A. Hood.t At Llwynypia Colliery, water-pipes are caiTied along the roads, and a fine jet allowed to issue at intervals, the spray being carried along by the air-current Hound outlet holes call be used when e. deflecting plate is jilaced at a small inclination to the jet to drive it into spray. If'lat jets, however, give a better spray, but i-ound ones are less likely to be choked up with dirt. In some cases, even with the finest spray, the action of the watch* cause the roads to heave to a considerable extent, but at Yiushir Colliery, where two miles of piping are laid with outlet pipes at intervals of from 40 to 60 yards, little difficulty has been experienced from heaving. Of couree this objection depends
entii-ely on the nature of the roof and floor. The best procedure is to load up and remove the dust as much as possible before watering, as not so much water
ia necessary, and mud is not formed.
Watering certainly makes the conditions
more pleasant. At Fochin Colliery the
intake air had been warmed and a jet of
gteam injected into it with satisfactory
results. The warming of the intake aircurrent is, however, objectionable.
Mr. H. W. Martin has described the
method in use at Dowlaie, where a very
elaborate system is applied. J Two mains
are laid, one for wat-r, and the other for
compressed air. Out of these at intervals
small branch pipes of half-inch iMtrual
diameter ara ourisd to the roof, and tlien
across, when U tqjote totem bvaoonical
i by tht
through
Text-Book Op Ooal-Mtning.
ail luijusitnble spray producer, b. The aperture in this U kinda adjuatjible, so that in the event of its being clogged by any sediment it can be " flushed " for an instant. ITie adjustment ia made by a nut and screw. A regulating tap is placed in both the air and water' branches, and to prevent entry of water into the air-pipe, and r'ice vtrM, a small ball-valve on a leather seating la introduced into each pipe. The spray producer hangs vei-tioilly from the roof. An exceedingly fine spray is obtained, which ia carried along with the air, and effectually damps the finest dust lurking behind timbers. It also cook the air-current, the expenence at Knrris Navigation Colliery being that the temperature of the intake has been reduced 4 to 5 degrees. The presxnre of water should exceed that of the air, but it is only necesaaiy that it should be a pounds above. The spray producer is made of bra.s, ivnd is globular in form. It cnn be opened in a ifecond by unscrewing a nut at the bottom, when dirt is readily blown out.
The mixtui'e of air and water not only produces a vei-y fin spmy, but it seems to act further owing to the intimate mixture, and hence the discharge jets can be placed at gi'eater distances apart. There can, however, be little doubt that the velocity of the nir-current influences in a great measure the distance towhich the spray ia carried.
Laws of FriotioE, &o. — Befoi-e describbg how a ventilating current is produced &nd circukted through the workings, a short deecription should be given of the laws of friction and of the general rules relating to ventilation. The subject is such a complicated and extensive one that only the briefest summary is possible here. The finest series of papers in the English language ai-e those by the late Mr. J, J. Atkinson,* which, although written so long ago, still remain the i!tandard authority. To these, and others written at the same time by several of his contemporaries, the student is referred for detail of information ami reasoning. The principal points dealt with, and brought out by the above series of papers, have been summarised and elucidated by Mr. W. Fairley.t
Currents of air, either on the surface or in a mine, are produced by a difference of pressure, and would flow at a gi-eat speed if noresistance were encoimtered. If v tlie velo<:ity io ft. per second, (jf gravity, or 32.2, and A==the height from which a body must fall in order to generate this velodty, such height being the motive column.
The water gauge, which is the measurement of the pressure'
Ventilation. 35
requiretl to genemte this Telocity at which the air travels, ij regiatanee letre (ditent, would be a tnuoll one, uud may be detei'- iniaed by tlie fui-mula —
where lo the weight of a cubic ft. of air ut the teinpei-atiu-e of the upcast, and A the motive power. Now
i.jzSjK heig ht ot b barometer (h) 459 + '
and
From thifi formula it will be found, that if the air has a tinnl velodty of, say, 50 ft. a. second, the theoretical water gauge retiuired to produce it is only o-d inch. Fifty feet Hecond is a Telocity scarcely attained in minett, and it is equally rare that the water gauge only shows 0-6 inch. The ditTerence between the water gauge due to velocity, and the actual water gauge of any mine, k the metunUHtnent of the friction which the iiir meets with in passing through the air-ways.
The three main laws which govern the fiiction oF gases towing thi-ough pipes are as follows :
(1) The frictional resistance varies directly as the i-ubbing
surface ; this rubbing surface is found by multiplying the length of the gallery by its perimeter, or, in other words, its ciivumference.
(2) The presHure i-equired to overcome the friction varies
inversely as the area, if the rubbing surface and velocity remaiDthesiime-tbatiK today, if two air-ways be taken, one of which is double the area of the other, only half the pressure has to be applied to eiich stj. ft. of the large one es would have to be applied to the small one, to uveicmne tlie same amoiuit of friction in the two ways, pinviilod tiie velocity of the air and the extent of rubbing surfuce were the same in each,
(3) The frictional reastuuce vni-iea directly as the square of "' sty; o scipiently. if the velocity be doubled, the
b u. ioiir tiiues. The eKplanatiou of thia
' 'I. bf rt'iiienibered thntif the velocity
jiDiutity of nil' juisses through tli
i.iind ujeets every resistance with
From these laws the following foi'muln is deduced :
where p the pressure in lbs. per stj, ft., ii tlie area of the aiv-way in sq. ft., s the ai*ii in sq. ft. of rubbing surface, V the velocity of air in feet per minute, and A- is a constant called a co-eflicient of friction, and is equal to the ventilating pressure required to overcome the resistance that a unit of air with unit velocity would meet with in circulating round a mine of unit area and having unit rubbing surface. The value of this co-efficient has never been satisfactorily determined for the irregulai' passages of mines. Although it is geneniUy admitted that Mr. Atkinson's figures are not strictly correct, yet they ara freely adopted. He states that it aeems probable that for every foot of rubbing surface, and for a velocity in the air of looa ft. a minute, the friction is equal to 0-26881 ft. of air column of the Knme density as the flowing air, which is equal to a pressure, with iiir at 32° F., of 0.0217 Pr sq. ft, of area of section.
The difiei'ence between pressiu-e and power must be clearljr understood ; pressure ia the force per sq. ft. producing the ventilation, and power is the quantity passing multiplied by the I pressure. The qu&ntity is found by multiplying the area by the velocity.
By transposing and substituting values of the difierent .symbols in {6) near-ly every formula can be deduced to work out the problems met with in ventilating mines. Several of the more prominent results obtained may be summarised as follows :—
(i ) The quantity of air circulating in a mine is according to
the square root of the pi-essure. (3) In air-ways of the same sectional area, but which only
vary in length, the volume and velocity of air curreiitB
are invei'sely proportionate to the square root of the
(3) The quantity of air passing in air-ways of different areas,
other things being equal, is according to the square root of the area multiplied by the area.
(4) The resistance varies directly as the length.
(5) The pressure required to propel air through passages is
inversely proportional to the ai'ea, other conditions remaining the same.
(6) If any two machines are employed to ventilate a mine,
each of which when working separately will produce certiun quantities which may be denoted by a and h, the quantity
together
Ventilation. 317
(7) The quantity of air paaxing is according to the cube root
of the power applied.*
(8) Since the quantity of air circulating varies as the julie
rout of the power employed, and ae the number of revolutions of a fan also vanes aii the cutie root of the power employed, it follow!* that the (juiiutity of air circulating depends directly on the speed of the fan.
PBODUCTION OP AIH CUaHEITTB.— The problem of sufficient air, and of so oirrying it into every part of the mine that the noxious gases are eflectually removed, is one of great importance. By the law in this and in nuiuy other countries, every mine haa to be provided with two shaftti, or outlets ; one of these Merves for the introduction of the fresh air, and is called the "down-aist"; the other, for the egress of the current after it hoM passed round the workings, and is called the " up-cast."
Itattiral TeQtilatioa.— No matter what the respective sizes of the two shafts may be, provided that they are connected by a possaga and that the density of the air in the two columua is eigunl, uo current is produced. If, however*, the densities are differeut, the pressure of the one column of aii* will overbalance that of the other. The ecjuilibriiim in the two shafts is destroyed by the natural heat of the strata altering the density of the air. As a deiicent is made towards the centre of the earth, a proportionate rise of temperature is found—that is, after a certain limit is passed. This limit i8 found at a depth of about 50 ft., where the temperature of the rocks is on an average 50° F., this temperature remaining constant all the year round. From the mean of numerous observations, it may be taken that the underground temperature increases 1 ' for every 60 ft. of depth below the invariable stratum. Therefore, the deeper the mine, the greater the difference of temper'ature of the air in the two shafts, consequently, the greater the ventilation.
From thu) cause ventilation is produced without any artiticial assistance, and is called natural ventilation. It is, however, so inconstant as to be wholly unreliable, dependuig tu a considerable extent on the temperature of the outside nir, and thu dill'erence in the levels of the tops of the two sluifts. In winter, the current may flow one way, and in summer the otiiei-. For such reaaouB natural ventilation ia never to be relied upon, although it does iu many cases materially attsiEt the other means which used to pi-oduce the air cuiTent,
Furnace Vflctilation.— The oldest means of produong ventilation was to artificially alter the density of one of the
A most intcrMting paper has been coDlributed (o tlie Federated lostitutloD of Uining Engineers (vol. il. poj- 483) bj Mr. W. Cocbnuie on a Daplcx Anangemcnt of VeDtllatocs, ibo renulis obtained OKTcelng rGnuukably well with the theoretical deductions given in (6) and (7).
38
Text-Book Of Coal-Mining.
columns of iiii' by heating it. At firat, this was done by merely banging fii'e-liimps in tbe up-cast shaft, to be soon superseded by placing a furnace at the bottom, as by the latter means the greatest effect is obtained. FiUTJacea may be constructed on two main principles (a), either an open fire-place with all the air passing Dvei' the fire ; or (b) contracting the area above the fire, and forcing the greater part of the current through the bars. Neither of these methods, separately, gives the best result. In the former, where a sti-ong current is passed over the fire, its cooling action is so gi'eat that the combustion is feeble and a high temperature is not attained ; while in the latter, if all the air passes tlirough the bai-s, not only is carbonic oxide formed in large quantities, but the resistance or drag of the mine is much increased. A combination of the two gives the best results, and ia . almost invariably employed. I
No better ill ustmtion of a well constructed and efficient furnace '
can be given than that at Eppleton Colliery {Fig. 382). The 1 length of the grate is 6d ft., and its breadth 11 ft. ; the end of the fire bars are 120 ft. away from the shaft. An air passage and firing-hole in provided on each side of the furnace, and also an air passage along each side of the drift going to the shaft. This drift rises 1 in 2, and is lined throughout with fire bricks. With this lai'ge grate area, all the air passing over the fire is , thoi-oughly and, in addition, doors we provided at the front, ao that the quantity forced through the bars can be regulated. Doors on furnaces are, to a certain extent, ueceesaiy, especially on re-starting after cleaning. The cuii'ent, which is then small, can be foi'ced thiMiigh the fire, and as it inci'eases, owing to the temperature getting high, the doors are gradually opened, and more air allowed to pass over the tire. The advantage of the side passages is, that not only may firing be entirely done at the side, but the risk of setting the adjoining strata on fire is ' reduced. A good casing of sand is placed all round these arches ' as an additional precaution. At Eppleton Colliei'y, twenty-four tons of coal are burnt in t
Ventilation.
39
tweoty-four hours. During two shifts n number of boilers are at work underground, eo that the furnace doee not produce all the air circulated. While these boilers are at work one man per ehift ia employed for firing, but at night two men are necessary ; thia means four men per twenty-four hours. The quantity of air circulated is 303,000 cubic ft, per minute, with a in. of W,G., but only ) 20,000 cubic ft. passes over the furnace.
In fifty mines it would not be wife to puna the return air-current over a furnace, and it has to be fed with fresh air. As the temperature at the bottom of the nhiift in sufficient to ignite ga, the return air-current has fui-thermore to be brought through a passage called a " dumb-drift " into the shaft at some point above the furnitce where the temperature has falteu below the igniting point. Neither feeding the furnace with fresh air nor carrying the return air-current through a dumb-drift increases the efficiency of furnace ventilation, but, on the contrary, diminishes it, as not only is the tempeniture of the air-cun'ent reduced, but ft shorter column of air is lieatetl.
The amount of ventilation produced by a furnace varies as the square root of the diSFerence of temperature in the two shafts — that is to say, if the mean temperature of the down-cost be 50* F. and the up-caet 75° F., if the temperature uf the up-cast be into 1 50° the ventilation will be doubled, nh the diflerence in the first instance was 25" and in the second roo" ; therefore,
The objections to furnaces are the ilauger of introducing fire into mines yielding fire-'<lamp, the risk of setting adjacent coal on fire, the corrosive effect on all sliaft-fittings and tubbing, and to the face that no moi-e than a certain quantity of air can be got out of a given furnace, no mutter how much coal is used.
Furnaces are most objectionable where tubbing is employed, as the wood sheeting between the segments ia continually being burnt out. Lining with brick-work offers little protection, na when the fires are damped down (for repairs to furnace or drift) the tubbing contracts so much that a large escape of water takes place, which, in some instances, t-o cools the shaft that the aircurrent is reversed. Where tubbing is employed, it is practically impossible to stop firing. In some cases in the north of England, which is the home of furnace ventilation, a second funioce ia often built, aud when the first is slacked for the second one is started.
Steam Jet.In the early pait of the century, Sir Goldsworthy Giu'uey proposed that furnace ventilation should be superseded by the use of a steam jet. Steam at high pi'essure was to be c&rried in pipes down the shaft, and allowed to escape at the bottom through a aeries of jets arranged giidiron-foahion tarot
S30
tit* pH. Am it WM MOB foutjfl tint thw metboil cwfwmieBl, nor so capkUe uf prodociiig large rolnmes ajr, W % fttriMMf It* (ue abandoned, mad exc in of emwei t( ii a*vcr employed.
KMlUtnioal VsntiUtora. — From the eutieet times attempts wn nude tn prodtuw cnrrente of air hy mechanical means. The dnt fornw eoiimiitd of a species of pump, which, in its improved form, wprwnto the modem displacement mnchiDe. Other ottanipts wra made to circulate air by the rotation of fans, wlii4!h was nut with much success until about thirty, jrears hko.
'I'hn comparative eDiciencies of displacement machines and trifuRal ventitntoi-M have been exhaustively dealt with by Mr. Vinhninc' The chief disadvantages of the former ai* the heavy and cnnibrouM machine which has to be employed to produce Im'Ko ijiiaiititieM of iiir, and the defect that, if there are sources of lanka|(o in thii apparatus, the volume of external air thus let in wKul't ifierfaia ns the depression increases, and, thei-efore, the air drawn from the mine will diminish. The re-entry of air must ulwayH lit) considerable, as a shutter is employed, which is neither rigid nor oven, in contact with the casing.
lliourotlca) objections have been fully sustained in practit atiil lit tlio pi-twftut time displacement machines have been eotii superseded by
Km. .l8j.
of which numerooB and varied types exist. It would be <iuite impossible to desii-ibe the steps which ha'e led up to the latest deeigne, or even the whole of diet* desigiiB. Reference can only be made to thoae largely in use, and which give good
iisozJly consitits of i-!i;lit or ten r<;taiiiniLu Taoes, which
nher
:M
eavy
duce
es of
et in .9 air
must Edther
'tS
rNM i-v iSj. Bi*fc 1
Ventilation. 331
to a pair of bara and angleifoiui, which, in their turn, ni'e bolted to cast-iron bosses, keyed on the main shaft. As these bnrfi are caiTied past the bosses and interlaced, a very firm, simple, and inexpensive structure is obtained. The fan is enclosed in a casing, giving about i in. to i in. clearance on each side. Over the fan an arch is provided, giving about 2 in. clearance tu the vanes, such arch being continued round aii an invert, but towards the bottom the clearance is increased, and gradually expands until it ends in the sloping side of a chimney.
In its original form this fan diR'ered fi-om all others in one point : it was provided mth a siding shutter, a, which is really a continuation of the circle of the top arch of the casing. This shutter allowed the area of the discharge opening to be regulated and fixed at such an amount that the beat retiultscould be obtained. In many fans only one inlet orifice was left in the caang. On the other side a blank wall was provided, through which the shaft of the fan passed, and was connected to an engine. For mnrliiniits of small capacity such arrangement acted very well, but in th larger fans it was not only found that the ventilator did not gwt sullicient air, but that all thLs air, entering on one side, and doing so diagonally, threw a severe thrust on the shaft and its bearings. For such it was found preferable to give such fans a double inlet, that is to say, leave a circular orifice through ih* casing on both sides.
The use of the Butter is to regulate the outlet ui auil Uw special requirements of tlie mine, and its pruiier position can only be determined by experiment, as no theoretical calculations irill determine the quantity of air that any fan will produce frtim anv particular mine. If the discharge oiilice be too Inrgo, air will re-enter the fan, while if it be too small, the air will not gvl away fast enough. The use of the expanding chimney is tn roduca th velocity of the air as it leaves the fan. When the ail' ImvM tht> ranes, it is travelling at a very high velocity, but as it up the chimney, whose area increases as it expands, it gradually travels slower and slower, until at the top it is discharged quistty into the atmosphere.
From its simplicity, freedom from repairs, and high efficiency. the Guilial fan has been in marked favour ever since its introduction in 1862, and probably more of its type have been erected than of all the other fans put tgottftt The objection to the Uuibal is its very large sixe, foundations requirod,
being what ia If
33a
Text-Book Of Coal-Mining.
not enclosed in a casing, and air in discharged all the way round tl circumference instead of only at one point. As cooGtructed un< recently, it consisted of an arrangement of long and short curved blades arranged altei-natelybetween two iron discs ; one of these discs is provided with a central opening through which the tur passes into the fan, and is inclined towards the other disc at such an amount that the products of the angular velocity, multiplied by the sectional urea at any point, are constant throughout the fan. Mr. Walton Brown* has described several modifications, which have been recently introduced. In the old type the air J woH discharged into the atmosphere at a somewhat high velocity, f
but in the new fan its vi'locity is considerably reduced by I addition of a. tnimpet-shaped outlet which extends beyond t external evils of the blades. Fig. 3S4 shows the fan as constructed at the present time ; a and b are the curved blades, the former running down to the centre. The area of this outlet is more than double the area described by the external tips of the blades, conse<]uentty the velocity of the air is gradually reduced as it passes through this divergent outlet, and as the resistance varies with the square of the velocity, less power is required to discharge tbe air, and therefore less power is required to drive tbe fan, tbe result of which is to increase its ethciency. In addition, tbe blades ore brought in towards the centre, and tbe air strikes all ! them equally, but to give the maximum ai-ea for tbe
' lai
Ventilation.
enti'ance of the air, the long blades, a, are reduced in width as they near the centre. The disadvantage of open-running fans is their liability to be afiected by high winds.
Sehiele. — This is an enclosed fan, but is not placed centrally within the easing (Fig, 3S5). The moving pai-t is email in diameter, and the blades of
the fan. taper from the tip *'io. 383-
wideningtowardsthecentre. The air enters at each side in equal proportions, itnd the vanes revolve between a casing of such form that its sides follow the taper of the blades, while the circumference is arranged aa ii gradually increasing volute chamber surrounding the periphery of the culminating in the exit, which forms the widest part of the air chamber
Cockion. — The objections to the Guibal, as before mentioned, are its great weight, size, and the vibration resulting from its unbalanced nature. To remedy the latter defect, Mr. Coekson has modified the ordinoiy construction. The close-fitting casing, expanding chimney, and adjustable shutter are retained, but the blades taper from the centre to the circumference in such proportion that an equal area of air passage is obtained throughout the fan (Fig. 386}. Theeipending chimney is not so wide in one direction owing to the blades tapering, and its width is, therefore, increased in the other direction so as to obtain the proper area of discharge. This alteration has removed the objectionable vibration, such fans being practically noiseless, and as they are more balanced, can be run at a higher speed, thereby allowing a smaller one to be used.
Capell. — This fan (Fig. 387), is a departure from all others in its arrangement and construction. All sizes above eight feet
Text-Book Of Coal-Minikg.
diameter are constructed with a double inlet. The fan if both vertically and horizontally, into chambers. The i division consists of a stiff steel diaphragm, a, which entirely Hepai-ates the air received on one side from that of the other. The ti consists of a cylinder, 6, having a serieK of port- UMUiilly six blades, c, projecting inwards, J
curved with the convex aide m the direction of i-otation The i air first enters into this cylindncnl chamber, and is discharged through the port-holeK, d, at a very high velocity against the inner and concave side of the outer wings. It is claimed that to an extent the via vioa in the air is given up to the outer wings and
actually nswsta in driving the fan The velocity of the air is also reduced, as the wze of the external chamber is gi-eater than the internal one and when it leaves the tips of the blades a further reduction takes place as the air is discharged into a spiral volute cliamber, and finally passes, by means of an expanding chimney, into the open air.
Walker. — This is one of the more recently designed fans, and is more or less a combination of several types. It bos Guibal blades, chimney, and shutter, but it is placed eccentrically in the cosing
Ventilation.
like a Schiele. Its constniction is of the strongest type, and it is claimed bj the makers to be indestructible. It is built up somewhat as follows : In the centre is a. miJd steel disc, G (Fig. 388), which does not, however, reach tlie circumference as in the Capell. On each side of this are angle-irons, C, to which the vanes, A, eight or ten in number, are attached, itivets pass through the two angle-irons and disc, and through ench angle-iron and blade. The disc ii supported between two iron bosses, D, turned where the; oome in contact with the disc plate, and secured thereto by tiirntH) bolt driven into limered holes. The bosses are bored out and secured to the fan shaft by keys. The blades in the larger funs are&lsobraced together by struts, H, and strengthened by a gussetstay, B, and instead of being full width from the top to the boss, ', they are cut away, as shown at A, in the cross section, and. if , necesiaiy, removable pieces are attached by bolts, to partially fill up the opening. By doing o, it is claimed that the mininium amount of central obstruction with the largest amount of fan
powi
ed ii
The two fans last described seem to be the ones most in favour at the present time ; Iwth of them have high efficiency and both are cheap. Neither, however, have been in use long enough to determine whether theu-wearing capacity is equal to that of the larger slow running fans, which have been so well tried and
a the p
Walker's Shutter. — The object of this invention is to reduce the objectionable uoLse and vibration caused by I'notary fans. In the ordinary Giiibal, the edge of the shutter forms a horizontal line pai'sJlel with the shaft of the fsu, and faces the blades. A little consideration wUl show tluit during the revolution, as each blade near-a the discharge orifice, it has on it a large pressure, but as soon an the tip of the blade and bottom of the shutter coincide the delivery of air is abruptly terminated, the fan entei-s the fan casing, the load ia I'emoved, and a rebound necessarily takes place. The jerk thus caused, is transmitted to the fan shaft, iind as each arm acta in a similar manner, the result is, tliat the whole struck ture is in a constant state of vibi'atiuu, and injury to it must .necessarily follow.
Messrs. Walker i-eplace the horizontal edge of the shutter with an inverted V, thus, Each blade commences to discharge at the bi'oad part of the and as it proceeds on its journey meetit witha gradually decreasing arvii of discharge orifice, until at the top of the all egress of air is stopped. As a result, the pressure air is gradually taken off each vane. The length of the liikt gi-eiiter than the distance between two blades, so
it the following vane may be opposite the commencement of the de next in advance has entirely left it. le of the greatest improvements wltich fans of late years.
Driving by Straps and Bopes-IIigh speed fans, except rare instances, are not di-iven direct by engines, but through belt or better still, by a number of ropes working in grooved pulle3rs. "With a steady ruuninj; fan-engine high degrees of expansion can be used, as the work is unifonn, but such procedure causes a certain amount of shock to the fan, as the pititon receives full pressiu'e of steam at beginning of stroke. Then steam is cut off, and the rest of the revolution is due to the momentum obtained and the expansion of steam ali-eady in the cylinder. The fan is thus practically driven by a series of kicks.
Belts or ropes take up tliis shock. Hopes, although more expensive than belts in first cost, are, perhaps, the beat in the long run. If a belt breaks, all the machinery is stopped, but all the ropes will never break at the same time. The only mistake that can be made is to put too great a strain on each rope, by which wear becomes very rapid. These i-ojjes are constmcteil of hemp, and to obtain sufficient grip are generally made to run in grooves, whose exiles are inclined towards each other at an angle of 45°. The ordinary method of application is to have each rope in separate grooves. They are pulled very taut at first, but get less tight as the rope lengthens. Another method is to wind a sin rope round the two pullfys as many times aa required for I neieesary horse-power, and to put on a tension pulley to get t required grip and to take up slack.
The wear of a rope is due to two causes : internally, by t movement of the fibres on each other due to the bending o pulleys, and, externally, through the wedging and slipping i grooves of the pulley, both of which may be said to be dii
piportional to the speed. Bope drives have only been employed for about the past twelve years, and have not been in use suflicient time to determine theif wearing capacity; it, however, appears to unlimited.
Arrangement of Engines, &o, — To minimise the result o breakdown in the engine, it is usual to apply two I working alternately for certain lengths of time, generally a three months at a sti-etch.
This arrangement only provides relief in case of accident to t engine, and if the fan breaks down everything is stopped, late years it has become common to duplicate the whole of t ventilating machinery, and work each fan alternately. good arrangement for two ventilators, as applied at 1 Colliery, South Wales, is shown in i'ig. 389. Two Waddle 't each 45 ft. diameter, are situated as illustrated. The i are 16 ft. wide by zi ft. high, and in each one, at points a a are eight wooden dooi-s, working in iron frames (see cross st These doors open tovxirdt the fans.
To change fans, the one that bos been standing is started, 1 peed gradually got up to about 40 revolutions. The other t
Ventilation. 337
flowed lowii to 50 revolutioiiB, while the speed of the second fan is increased; immediately the revolutions of the second fan exceed those of tlie first, the lur doors i:i its drift open, aad at the same
time, thoiie going to the first machine shut. The first fan in then stopped, and the speed of the second one increaaed to the ordioor}' amount.
Determioation of the Uaefiil Effect. — The amount of useful efiect produced by a fan is found by carefully determining t-he quantity of sir put into circulation by it, and by measuring the water gauge. Each inch of water gauge is equal to a pressure of 5-3 lbs. per sq. ft. The horse-power in the air
33.°oo where q the quantity of ivir in cubic ft. per minute and W.G. water gauge in inchea.
While the air measurements are being taken, the 8]>eed of the engine is cai'efuliy noted, and indicator diagrams taken, from which the mean stenm presaure in the cylinder is determined. The H. P. of the engine
where j) the average steam pressure, dthe diameter of the cylinder, S the length of the stroke in feet, and R the number of revolutions per minute. The ratio between the horse-power in the air and the boi-se-power exerted by the engine gives the useful eflect of the fan.
It must be admitted that, in comparing fans, it i.s scarcely fair to do BO, without deducting the power required to drive th engine when it is not connected to the fan. The higher typo engine in perfect condition necessarily absorbs leas power to & it than a bodly designed machine in an indifferent may, therefore, hnpiteii that a good fan driven will not show such a high efliciency as a. \tet by a good engine.
Efficiency of Fans. — No matter whethf one, ruimiiig slowly, or email one, truvellinf
Textbook Op Coaiminiso.
dtwB Jafwrn dt on the efwed of the peHpboT, or t ' Hf. Tlw theoKtKKl iliuM iMiiiMi vbidi - -
ii datcnaiiMd bv the foamnh —
L H b aijwwwl in fnk of sir ataMa nqnire-d to overcome B of tlw mia and taagmtial weoatJ in feet per
i m paaotxe. owiujEr to
.tUfiprflwtefcitto iir oC tbemaehme
B lh prcac* of th Ihiiinli it. TW iboOTy of vent- r n i iE iBy aMafMd MtWtf Mr, Mtttoe,* the turd die* hm faBM till nil 1 1 nto bKA by Mr. A. L. K,t to Mek ttw aotimt luiutiud for the raksoaung
r. M w n aanBdUw pnj Metoia onfin in k train plate,
of Mr anflttf aaniA toaanfire a a thin [4ato
- r pto fmm thea
Ventilation.
obstructing ths passages ; then in a normal state ; and afterwards by cipentng some of the doors.
With the equivalent orifices of these five different mitiee, or conditioiiH of mine, plotted as ab6Ste, iwd the volumes as ordinatea, a curve is obtained, which
clearly shows the effective-ym.
nesB of each fan, and is called it " characlrristic
A [perfect fan (no\-ing without friction and giving the theoretical water gauges, pi-oduces volumes of air propmi-tional to its equivalent orifice, and its curve is represented by a straight Hne, B, Fig. 390, commencing from the origin, because when the mine is closed the volume of air is neceesftrily nil. Owing to the resistances of the fan itself which vary with the volume produced, the straight line ia never obtained in pi'actice, but a curved
£aiivUnt eriAtx in *f.lt.
The nearer jre perfect is
4 types of f
and the Midland I
TEXT-BOOK OF COAL-MINING. a Ca&inittiee. but nnfornxDmiely their refort is not xtt tamed
Oompazuon of Fnmaoes mud . — Mr. J. J. Atkiiwfm mpptmi have been the odIt peivoci to thenetioJly compare the rAtiTe efficiencies of fomAse ani meiciiucal TentOatian. After the \-sryins cizromssanres of difierent miiftes azkd the ccodiiioDs under wbkii fnrDaoes and fu prodnoe a Teotiladng current, he a formula from vhirh it appeals that the denth at which furnace action becivnes as coonomioBl in fue] as a ventilating machine, increases dxroctl j as the Txdimie manned by a given weight of air as doe to the average upcast t cmpaaiime roqizired for the p1ductioQ of ventilation by fumaoe action — that is to sav. invesraeSv as the average dmsity of tlie heated air in the upcitst. Tliis depth, couivte. nun decrease in the >e proportion that the fnetl per horae-power per hotir, required to drive the engine of a ventalaxing increases
By this f crmula the following tahile was calculated, the depths at which furnaces become equal to ventilating madhineR in paint of enanomy of fuel on the assumption that the fuel due to the temperature between the furnace and the point in the upcast ccilumn. whei the average temperature prevails is the flute percentage of the whole fuel as that which arises from the apprlicataan of ventilating machines. driven by engine power, produce the aune ventQataon :
Canmnbia. of Cm! AVERAGE TEMPEiLTrRE OF UPCAST ., COLrMXS. i
hoar per h w i pu m a
Ix'
S 95S 1044 1130
A table is also given showing that the avenge loss in eleven cases rf furnace action was 40 per cent. If ore ventilating' machines lose 40 and utilise 60 per oent. of the engine power, the depths that are necessary to render furnace ventiladon as eoonoxnical as such ventilating machines in the consumption of fuel are as stated above. It should, however, be noted tiuKt many engines at the present day do not <xmsume 4 lbs. of coal per home-power per hour, and hence the eoonomy of fan ventilatioia is more than that shown bv the table.
♦ X, E. 1, vi. 135.
Ventilation.
Ur, C. Cocksoii, itt'tev giving a <ieGci'iption of u. fan At Daii-y Pit, Wigan,* stated that the phint was erected to lake the place of two undergroiuxl furnaces, liaving a fire-bar ai'ea of 129 iiiare feet on which 12 tons i 7 cwt, of Arley mine mixture were unit per 14 hom-s, producing, with the fui-nnce very hai-d lii-ed, 142,570 cubic feet of air per minute, the cost for woh being ig, jrf. and for fuel £4 3s. 7., or a total cost of 2#. io</. per 24 hours, wliich, multiplied by 365, will be 1876 per aunum. The fan gave the same quantity of air as the furnaces when i-unning at 52 revolution;! per minute, burning 4 tone 1 ewt. of I'ough buzzard Black per 24 hours, and costing for wages, to. 6d., and for fuel, 15a. 4. ; or a total per day of j£i 5*. lod., which, multiplied by 365, gives a cost of 471 ler annum, or a saving by the uae of the fan on the two items of fuel and labour of r4o5 fier annum. Of coui'se, from this an allowance has to he made for interest, depreciation, stores, Jrc.
Many similar instances could be quoted if it were necessary, but it is now generally admitted that mechanical ventilation is superior to furnace ventilation, as it is more under' control, cheaper, more eftident, and capable of being easily varied in quantity whenever desired.
DISTRIBUTION OF THE AIB CUBBERT.— Having described the means of producing the air current, and the laws which regulate its flow, its distribution undergi'ound should be readily understood, It has been mentioned that two paths ore provided for the current, onefor the fresh airto enter and the other'for its return. The distribution into the workings is a far more diHicult point than simply leading it along two roads. To reduce resisUknee and allow large volumes to be i-eadily passed, it is necessary that the air-waya should have as large a section as possible. An the resistance varies with the square of the velocity, the only practicable way to pass large quantities is to reduce the velocity, which may be done by diminishing the rubbing surface, increasing the area of the airway, or better atill, by what is known splitting, that is to say, dividing the current into several parts, and providing a separate air-way for each, bupposing one current of 100,000 cub, ft, exists in the mine, and paseit down an air-way having an area of 100 sq, ft,, its velocity would be 1000 ft, a minute. If this current be divided into five, each of which contains jo,ooo cub. ft., the same totnl quantity will be pa-Ked through the mine, and if each of these ctimnts be jirovided v ' '
in area the y ' '" ' "
fifth of wlut the resistance ih reduced to onetwn
t the
sppi
1 at once lit to the
34Z
Text-Book Of Coalmining.
number of split tbat can be used at any mine. All the spIH however separate they may be kept ia the workiugs, have to u ' at the bottom of the upcast shaft, aod pass through it ; therefore, when the resistance of the shaft is equiil to the ubi of the reastance of the air-ways, the limit of advantageous splitting is reached.
To obtain the beet results from splitting the air-cun-ent it is necessary that every spUt should commence as near aa possible to the shaft bottom, and have a separate in-take and return, ojid that the splits should approximately be of equal lengths, to avoid the necessity for regulating doors.
StoppingB. — When the two main roads are being driven, one for the in-take, and the other for the i-etum, they are connected at intervals by cross-drivages, and those nearest the shaft are stopped up again immediately another one nearer the face ia driven. These stoppings are usually built of dirt or rubbisli, and a brick wall put on the side nearest the in-take current. Every care should be taken that this is air-tight, or a small quantity will escape tbrougli and pass away to the up-cast shaft without doing any good. The practice is sometimes followed of leaving a small hole through the stopping to ventilate the cross-road, but it is difficult to see how this can do any good, as the quantity of air which escapes through is so email, that it cannot effectively ventilate the road ; while the total loss occasioned by a number of such outlets seriously reduces the <iuautity pa.siiig into the working.
Doors, — Where tubs, men, or animals have to puss thi-ough these croBB-Poada, doors replace the stoppings previously ref en ed to. Generally two and often three sets of doors are emplojed, the object of which is to pi-event the possibility of all being open at the same time. The main doors which are of a pennanent character, should be built in a masonry abutment, carefully made and fitted, and provided with a latch. If tula travel through the road a guard should fixed to each door to prevent the tub striking the woodwork ; this KiG. iqi. usually consists of a curved
strip of flat iron, bent as shown in plan by Kg. 391. Unless this pi-caution ia taken, sooner or later the door will be damiLged, and leakage of air follows.
It sometimes happens that doors have to be placed in i-oads where haulage is carried out by mechanical means, although such practice is by no means to be recommended. Either special boys have to be kept to open and shut these doors at the projter time, or, what is still better, a self-closing door, illustrated in plan and elevation (Figs. 392 and 393), which is adopted at Hettou Colliery, canheused. The door is in two diviaons, hung by pulleys travelling OD rails, these being arranged at such an inclination that the
H two halves nm together' by their' own weight, and shut close.
Hinged to the edge of each half where it meets the other, atid
H about 2 ft, from the bottom of the door is a stout piece of angle
B steel, a a, about S ft. long, the outer end of which passes through
H an eye bolt fastened to a tre, c, this being placed as near the
H mils OS will only just allow the tub to piss. When a set reaches
the door, the firat tub en-
H counters the bars, a, presses I them outwards, and in doing ' 39 - - 393
1 closes again when the lat .t 11
m tub has gone by. As this Vi //
i arrangement is similar on 1
ever way the set is travelling.
A
and the motion being gi-adual
/ft*
there is a complete absence of
ebock, so noticeable when the tubs strike against ordinary 1
H
Bflgulating Doors. — If P7
all the splits are of equal / q, length and the aii-ways of Oi 9
equal urea, the same resist- //
W
ance is encountered by each, y
but as such condition scarcely C
ever exists, artificial resistance
split to the desired amount. If it were not, the shortest t
?
M
r
1
splits would take the largest
ti
M
ift
M
quantity. This regulation is J Elected by an opening in a door, such being covei-ed by a sHdinc shutter, which c&n G
be set at any point to give
the desired result.
Air Croaaings.— In splitting air, one current has to pass over,
or under, the other, but it must do so in a seitai-ate conduit.
This is ettected by what ore known lu air crossings. A temporary
Figs. 394 and 395.
l-EXT-BOOK OF OOAL-MINING.
s any movement in the ground. At Lyo Gross pit, aroeansed as illustrated in FigK. 394 and 395. Id the in-tftke D invert of miisonry and two de wall are built, girders put across fi-om one to the other And bricked in between with email ai'lies. The return way is formed by carrying two walls up to the roof, this being also capped by girders which run at right angles to tfaoae previously mentioned. The conBtruo-< tion is very solid, but is required' on acunmt of the movements the strata, which, if not pre-j vented, would result iu serioi leakage.
In fiery mines, should explosion happen, all stoppings constructed in the ordinary way would be blown down, the two currents intermingled and ventilation entirely suspended. Toprovide against such contingency, it is often the practice to drive the return air-way Kome considerable distance above the take (Fig. 396).
Lobs in Cu-culation. the aid of stoppings, doors, an di
lated and made to fallow paths at will, in order that ventilation shall be earned into t workings and perform its mission, The greatest care mi
roads,
Spite of all cautions
air that through down-cast 1 reaches the working face. It is difficult to believe how small t' portion is, but the following example given by Palmer" may be quoted, showing the great los.*. A ventilati] current was measured at several places during passage fro
Brii, Soc. MiD, Stud. xi. 46.
ivo
Ventilation.
the dovrn-cait sbufl to the workingE. It is Ktated that the doors in the setim in question were well fitting and doiihle, and that the stappingn were made &a solid as posedble, and well stowed. The first meeuiuremeut was taken 140 yds. from the shaft, and the quantity found to be 16,650 cub. ft. per minute. At 805 yards from the shaft the ijuantity was 12,550 cub. ft. ; about this point n Split of 3140 cub. ft. {Missed away to ventilate an engine and tmvelling ixiad. At 1470 yds. from the shaft the quantity was 7700 cub. ft., and immediately aftr this point a second split of 3510 cub. ft. paB.sed away to ventilate another district. At the face of the workings, 2200 yds. from the shiift, the quantity whs 1560 cub. ft.
It will, therefore, be seen that while 16,650 cub. ft. left the ebnft, oiJy 1560 cub. ft. reached the face. Fmiii the initial quantity, however, the two splits alhuled to, must be deducted, vie., 3140 and 3510, making a total of 6650 fiih. ft. Deducting this from 16,650, Itnves 10,000 cub. ft. and a very simple calculatiou will show, that no Itss than 84.4 per cent, of the aii' current was lost in itw paasiigi* from the shaft to the working face.
MEAStraEMEZTT OF AIB CUBBEZTTS.— la onler to determine the quantity of air pasting, the velocity hnn to be a.scertained. This, multiplied by the area in sq, ft. at the point of observation, gives the qiuintity of cub. ft. of air. The velocity may he determined by seveml methods, only two of which need, however, be considered.
In the first, some light body, sucli as smoke, is employed, and the time it takes to travel a measured distance noted. Even when exercising the greatest care, the results obtained are not exact, although near approximations are given. If the road a ot uniform area, some detinite quantity, such as one cubic inch of gunpowder, should be always employed.
AnemometeTB.— At the present time, the invariable practice is to employ what ai called anemometers for the velocity of the air current. The common form is known aa Biram's (Fig. which conaiBts of a series of vanes, placed obliquely to the Rxi like the sails of a windmill. An indicator, or counter, is placed in the centre. The axis of the vanes carries an endlete screw, which gear into a wheel, to which a pointer is canriectd. Another form much is Cosartelli's, which is very similar to the Biram, but usually mad with five dials, registering suits, hundreds, thousands, ic, and, in addition, a small lever or stop is provided, by means of which the counting mechanism can bu thrown in and out of gear.
With the two anemometers just deKcrihed the velocity is
natured by holding them in the air cutreut for a certain length
' noting the number of revolutions. Thb means that
re lu one man cikiniot hold a watch,
i lamp with two hands. Davis's self-timing
Text-Book Of Coal-Mining.
anemometer dispenses with the ui*e of a watch altogether, and registers at once the velocity in feet per second, and not the number of revolutions of the vanes. In taking observationa the instrument {Fig. 398), is held out at arm's length for a short time until the vimes are travelling at full speed due to the air current, a small button, (i, is pressed, and the pointer turns to the speed, and is kept there a locldng an'angement. Each instrument being graduated by no allowances have to be made. To return the pointer to zero, the small milled head b is screwed down until a is released, when a.s soon aa b is unscrewed, the pointer turns to zero, and the instnmieut ie ready to take another
Fi<;. 397.
observation. Two graduated circles e, travelling in a small dial, inform read.
Messrs. Davis & Bon have recently introduced s anemometer for measuring currents of high velocity (01 per second). It is called the " C'apell- Davis," ; shaped like those of the Capell fan. It differs from anemometers on the Biram principle in having the vanes I'igidly attached to a blank disc. As a result, the wind pressure bears equally on the whole surface, whereas in the old construction it might impinge on one vane more than another and distort one of the delicate
Messrs. Atkinson i Daglish conducted a series of experimenta with anemometers, and determined that they all required correc- ' tion, to bring the velocity they recorded to the true velocity at J
whiub the air u by the formula,
Ventilation. 347
travelling. The true velocity mny be iletermined
where u is a constant proportional to the number of linear feet travelled by the air per revolution, II is the number of revolutions registered by the anemometer, and h the losses of velocity due to friction of machine, this loss being determined experimentaUy by a whirliDg machine.
Instead of this formula, the correction is usually made by adding numbers, which are supplied by the makers, and which vary for every instrument and for diS'erent velocities. Anemometers are necessarily of very light and fi'agile construction, and easily get out of order. It, therefore, becomes oeceRsary if accuracy is desired, that they should be tosteJ from time to time.
In order to obtain trustworthy results, the places of measurement must be of uniform stjction and preferably divided, by a series of horizontal and vertical strings, into a number of Fius. 399 AMD 400.
the anemometer placed in "T" 1 I — "I
each for a certain length I'" V"!" I' 1 'I
of
Id
Lpplied to tiiH strument, it should be I.. |...t.|. -I I"' , ..I
placed in the current, and ' I
allowed to attain the full
velocity before throwing the mechanism into gear. For very accurate results the observations should be taken in each division. Mr, Murgue, however, states, that the ratio between the mean velocity and the velocity at any given point in the same section remains constant, whatever variations there ai'e in the mean velocity. It is only necessary, therefore, to find the rtio between the mean velocity, and the velocity of air at any one convenient point, and in future merely measure the velocity at that point.
For all ordinary purposes, the velocity can be determined by holding the anemometer out at arm's length and moving it slowly over the section of the gallery, following the couree indicated by the dotted line in Fig. 400.
Barometer and Tbermanieter. — At every mine a barometer iinil theiinometer have Xo be pWed. The former indicates the pressure of the atmosphei'e, and u& the volume of air varies inversely as the pressure, the ciaa or fall in the barometer influences the volume of air in ttetlAlL It is also intended if the barometer fi off the fact) of the el
e freely liU old goaves niny li
Text-Book Of Coal-Mining.
ground for this aaeertion, as the giis in coal esistA under such a pressure that the small variations occasioned by dift'erenoe in height of thd baromL'l*?r are unuppreciable. In addition, a barometer is by no meajis delic.vte enough to act as a forewarning instrument ; since such a light substajice as air or gas would be affected long before any indication of change is given by a mercury column.
The indications of the thermometer are vahiable, as they point out the expansion in the air current j for, as the volume varies directly as the temperature, a rise means that a smaller weight or quantity of air will entr into the mine in a given
Water Gauges.— For measuring the pressure pi-oducing i ventilation, water gauges are employed. A cub. ft. of water ait 62° F. under 30 inches barometriuil pressure, weighs 63.355 '-i so that the pressure per sq. ft. due to each inch in height is consequently 5.196 but in ordinary calculations it is usual to nice one inch of water gauge as being equal to a pressure of 5.1 lbs.
The ordinary form consists of a (J-shaped tube, with one end open to the atmosphere, and the other placed in commumoation with the return ah-way of the mine. As the pressure of air inside the mine is smaUer than that outside, the weight of the atmosphere depi-esses the column in one leg of the tube and mises it in the other. The ilifTereDce in KiG. 401. height is measured by a movable scale,
'%jjr, graduated in inches, and indicates thepressure producing ventilation.
The variations in the pressure which are j constantly going on with centrifugal venti- J lators cause considerable oscillation of the I liquid in the tubes, and, in addition, capillary attraction causes the surface of the wab to take a curved line. It is, therefore, difficult to take accurate obser-ations with the ordinary water gauge. The author has adopted a form (Fig. 401), the design of I wliich is due to M.es.srH. Atkinson i: Daglieh. 1 In it the two tubes are replaced by two large comjiHrtments, a and b, having sheet gliiss in from. These are connected by a verii' small copper tube, e, in the centra of which is a thi-ee-way cock. One compartment is closely sealed, and connected by I means of a pipe, d, with the fan drift, white I the other is often to the atmosphere. Owing I to eiU-'h I'omparlnient being of large nreu while the connection I betfveen the two is very Mmall, the column of the watts' renu '
JPt.
Ventilation.
quite steady capillary attraction is not noticeable. A mitvable Bcale serves to determine the ditTeince in level.
Considerable diffei-ence of opinion exists as to the pi-oper position to take the water gauge at, and in which direction the end of the tube should be placed I'expecting the current. The English Fan Coniraission take the gmifte 6 ft. from the entrance to the fan inlet. Thia appears to be open to the objection, where small high-speed fans are used, that the eddies produced by rapid revolution are likely to give false results ao near the machine. The general opinion is that tlie end of the pipe going to the water gauge should be placed at right angles to the air-current and pivferably covered loosely with a roll of felt plugged at the top with wood, to cause the air to pass through the cloth (Fig. 403).
Bibliography. — The following is a list of the nioie important memoirs dealing' with the subject-matter of thia chapter : —
N. E. t. : Obtemaliani en Iht greater /at'lity of Ventilatitill -Dip titan Jti'te H'orkir.g$, G. C. Greenwell. ii, 31 ; Tie Theory 0/ Ikr VeRtHation M!na, J. J. AtktDMD, ill. 73 and ill. 311 ; Notai on J. J. Atkinfon'i FaptT, T. J, Taylor, ill. 347 ; Tkt relative jiotitim of I'peatt Shiffli and Ion of Umptrtiture in Hume, J, A. LoDgridge, It. 147 ; On nrtaiii ehangn irAiak tekt plae* in (Ac nnn/i'tiDn tAt air ilurina ill ponogt through Ihi Shaft and Worting* qfa JBine, 3. A. Longndge. iv. 103: The romparativt amtumplion of Fuel bg VtnlUating FumaceM and VentUaliHg 3tachint4, J. J. Atkinson, vL 135 ; On Ike proportion in which Air in Minet diitrihutei itelf ovtr tevtrid SjdiU havmjf differtat , and fffirring different retitlatuvt lo atrrtitti of patiinff thrmigh Ihrm, J.J. AlkJiisOD, vj. 163; On the relative imju/rtanre of tirlain coMteii in prudticing dtanj/t* of DtHtilg in the Air of MintM on U lirogrfie* in circvlnliiy, J.J. AtUnson, vii. 11$ ; On the anat* of Ihi Variation 0/' the Dentily of Air areulalmg in Coal Mint*. T. J. Tnylar, vii. 119 ; Jtteitir of Iht rendli of lie KrprrimeitU chick Aai'c £mm made to tett, and of the 'adtnu Khieh have Imtn advaiicefi agaimi, certain argvmenti tmoged by tit Writer relative to the I enlilolion of Mint*, J. J. Atkinson, vii. 133; On Ventilating Fkrnacti and their tiaetidlti of ariion. Win. ArmalronK. fx. 75 ; On Ihe Conitnidi'on of Venlilaling Furnaeci, J. Dagliih, lie. 131 ; Or the various moilii of aeetrlaining Ihe VdiKrititt of Currentt of Air in Mine* in order to determine lie antilj/ rirrwiting in a given time, J. ,1. Atkinson and J. Daplish, i. 307: On Ihe deetrtuite action of Purnaoe Gaite in Upi Hiajli, J. DBgllab. xl. 19 ; in lie Vtntilathn of Mine*. J, J. Atkinaon and J, DuKsh, xii. 93 ; A Comparieon of the LanieUt and Ouibal tyilemn of Meehanieal ftnldaliOH, Wm. CocbiuiB, xviii. 139; Tie rconomieal adeanlagtt of Mechauical YeutilatioH, D. P. MoHMn. xlx. 113 : The medanteal effect of " Bloicn-ol " Sialt on Ventilation, Messrs Hall and Clsik, xxv. 339 ; On the ailrantagu of Centrifugal Action Matiinee for the Ventilation of Mine; Vi'm. Cochrane, lavi. 161 ; Ilrporl of Committee on ilreiaaieal Ventilator*, xxx. tj% ; Cn lie me of Soil for Imnnti Ihut in Mine; R, Steveneon, xui. 145 ; m*trvoUon* of Earlluh'oln in order lo foretell the itetie of Sudden Outburett of Fire-dawj,, 11.
Text-Book Of Coal-Mining.
Walton Brown, xniii. 179 : Aeamnt of ExperimmU matit al Cellury. Xeunkirchen, partiru/ar' iMote un tlie oonw/iwa™ arue teiUM (Wl-7'iuf and Gan romt in anOaa mU ShoU. T. W BoDIiiiiE, 199 KoA 397 : Aeeouat of BtperiatenUi in Fraaa poii tktfcniUt amiitrtion itoermtnU 0/ lU Eartk't CtmI amdike ut 0/ 0( Mit, M. Walion Brown. ititL 43 ; Jre*- nwl Solmm't fiilenl T. O. Boboii. IMtW. 99; q/" Oammittte amaiiiltJ (u inire into (Ic ditrvatiotu of Earik Tremort ipttk a vino ttf dtttrmiairg ikeir eoamrdion any) irkk tkt ittae of Oam ifiBW, XXKvii. 55 ; A CoKtrSmtion to oar Kiuneltdgt of Cm-Jhul. F. ndllips Bedson, nxvii. 34s- fiOC. IXD. JiUt. : Ettnt mr kt maeUna d-arrogt, D, Kargne (2" Sine),
n iz. 5 ; Atragt in n
*ii. 477 et CiMintMioii AvwtFaiM
twmi du rapport de la lotu-committia* dtt 1
so. WALKS. IXST. t On tic Condition of Minf,
and OMhinW of Oat. At G. ViIfcitMon.
iafifort dt la Commitnem
M. Tt,wi,m.i.
G. Wilkinson, zi. 119: Air FVittuM
a. 3OS1 Tki Wattria of Jliiu*, A. Hood, xii. 357 -. Ot
Damfimg I'a lima, H. W. llaitin, kt. t6j. 1S. ISST. COT. : Vnl3atiem Mit miiw'wa rwii'ifciirf J. C
Simnioo, L to ; fiipcnaawi avtft Fvrtimf aad
BiUk, V. ijSand 154. ISST. c. S. IFcD. Ab.) : JfanU
G. Efiglekfc hii. 466
KanwiBitd.ciii.46S.
HkU. Is. S75: Tk /Vcadk Fin- C
MnM* Syni'pii rfA 'WtJ tatf FntrnW, IxL 103.
urr. Boc. MIX. snn>. : Eift rimmiM wiA m GmAJ fw, A. B.
LMeli,i.49D; rkJUtrf* todlMv, A. IGdn. t. 168 1
L J. a iikwmm,
. Ventilation. 331
MAK. GEO. aoc : CktUrifugal Paiu : tlteir reiativt ideney and uitfnl tftet, C. Cockson, xvi. 381 ; Oh a nta Ventilating Fda, C. Cocuon, xvli. 229 ; On lAc feet of Ooaf omiitg on 8ddai 0AimU of Otu, H. Fletcher, kx. 173.
FID. ISBT. : WaddU PattKi (tSoo) Fan, H. Walton Brown, U. 173; On a Duplex Arranaetnent of Ceittrifugal VetUitating Maduna, Wm. CocbrBUe, iL 483 ; Kottt on Fan Oaagtt in eonntetion wilK Fan Toting and tie Adoption of Fantto Mintt ; and Chngiaruon iff Fan and firnaa at SUivrMU OoOierg G. H. Ckpell, lU. 196 ; Note* on llit Gate* endottd in Coal and Coni'Dit, P. FblUipa Bedsou ud W. HoConnell, iii. 307.
Ahh. Deb. Mikeb :
Chatelier (S° erie), i*. iVnuicniw du gritou, HH. liaWd et Le CbatUer [S" Srie) ii. 63S ; Ifemolre ntr TnA-OM de* mtnM dant U boiiin houilUr de Ui /fuAr ( Weelpkalie), L. SoobM (8> Serie), i. 143 1 Siir rinfiamabiUU du gritou par la aineellte proMnant du dux de Saatr, tteport of a Conuolseion (S* Srie), xviil.
Chapter Xii.
Lighting.
Ifaked LightB. — TLc origionl niid most successful method of lighting; thi minei' iit hid wurk wiis to employ the ordinary tallow niiidli', or HDiall oil-lamp. The illumination given ie far better than that of any enclosed lampa; indeed, naked lights are so superior in Ihix respect, that the inducement to use them sometitnes over8tps discretion. In some mines, tire-damp is found in mail titles, and through using miked light. accidents happen at raw inter%-alM. To secure the maximum safety the enclosed type of lamp should be adopted, but it is mi open questioa i whether. o-ing to the smaller amount of light yielded, tfaa 1 increase in the number of accidents from falls of roof and sideB will not mora than coiintertuUance those due to explosioDS, IM* CHitse even with safety lamps ab6olut security is not obtainable. Miners much prefer working at collieries where naked lights are
Ordinary tallow eandlee of i6 or tS to the lb., of the proper hufvliieiiis to withstand the heat of the mine, are the common I ilUimiuHnt iu non-fiery seams. They are usoally stuck in a ball I of day. which allows them to be attached to timber or coal in any i-equird position. In Scotland a small oil-lamp is very largely I >iMploy(<l. It giii'ett a good light and can be carried about e but cannot be attached to the timber or sides in the same ready I way that a candle can. i
AFXTT XiAJIFS.— Atthebenningctf thiscenturysoBBauy i accidents tiH,ik place through the employment of naked tita, tub j i) attempt vras maile to devise some anangement for insuIatiiiK J the (tauie a ani) for ptveDting it from prodocing tax J iu the surrounding atmcephere. I
DkTy'a InTMttioB.— Perhape what might be called thn finA ' aafirty lamp i'aa that invi*uted by Pr. Clanny. in which a e vt air wait lasted into a buup through a stralom of water below, while the prtxhtcis k4 coiub<>4i esotped thitiugh a "'"Vt byer " "' Humfihry T ' '
the lirst lamp in a |innriple wtuch is stiil
nrtKU fonnreUtined, and 'I
Lightinu.
which forms the rnain element of security in every modem safety
lamp. lie found that an exploeioQ would not pa.HS thi-ough amuU
apei-tures and tnbes, and before the close of the yeer 1815 gavfi
to the worlil a wire-gaiir.e lamp. The Davy lamp (Fig. 403*),
osorinully and still constructed, consists of a cylindrical gnuze, a,
screwed to a bra&t riug,
which, in its turn, is attitche*! V],iq am wn nA
to the oil vesBol, b. The
gHuze if. protected from accidenttkl
blows by three iron
pillai, e, |iasHing up ward is
from the brass base to tin
annular ring at the top, to
which is further attacheil u
metal cap or hootl, d, above
wbioh a loop ls placed to
enable the lamp tobecarrietl
about. Aa an ndditiunnl seounty
, u cylinder of
gauze is attached at the top
of the tirat one fomiiug 11
cap, e. To trim the wick
and to regulate its height
witbC'Ut opening the lamp,
a thin piece of wire,_/, called
a " pricker." puKsett up a
closely fitting tube through
the oil vessel. The gauze
sliouhl not contain lesH than 784 apertni'es to the Mjiiare inch.
Clanay. — In this lamp & portion of the gauze of the Uavy is replaced by a glasi cylinder, a, protected by metal bars, h (Fig, 404). The other an-angemeats are similar to the Davy. The feed-air which supplies the fljim has to enter the lamp above the glass, and lionce gets mixed with the products of combustion, the result being that the light afi'orded is very little superior to the Davy.
Stephenson. — The celebrated engineer, Ueorge Stephenson, then at Killingworth Colliery, was experimenting upon safety lamps simidtaneously with Sir Humphry Davy, and indeed constructed one where the ingoing current was ptuaed through small tubes. As soon as the wire gauze was proposed, he adopted it iu
his lamp, which then took the form shown in Fig. cylinder of glas!', a, is placetl inside the wire gauze, and
In all the lamp illuatralioos, the various psrU
TEXT-BOOK OP COAIMrNlNG.
Figs. 405 and 406.
over by a perfoi-ateil copper cap, h. The feed-nir is admitted 1 through a number uf small perforations, c, below the bottom <rf the wire gauze and glass cylinder. If the lamp is to bum well, it is vecy necessary that these small perforations should be kept free from dost, which is rather a difficult matter.
Mueseler. — This lamp resLmbtes the Clanny, as it consists of a glass cylinder at the bottom and ft wire gauze one above, but its main feature is the io* troduction of a central metl chimney, a, sapported by a horizontal gauafl ' diaphragm, b, placed at the top of the glas (Fig. 406), The products of combustion pass up the chimney ' and induce a strong . draught sothatthefeed-air is drawn smartly down on to the flame, and produces good combustion. This lamp, by a Boyal Edict in 1S76, 18 ilone permitted to be used in the fiery collieries of Belgium, and only three modihcatioDB of a typical form are allowed. The total height of tiie chimney must be 4.6 inches, it ha to have 3.55 inches of its height above the gauze diaphragm, and its base mu be 0.85 inch above the top of the wick tube.
Design of Lamps. — The modifications introduced into safety lamps have all been with a view of rendering them safer in currents travelling at higli velocities. Davy himself pointed otrt that his lamp should be guarded by a shield when exposed to a rapid current of explosive air, as if not, the flame would be forced through the gauze. Tlie safety is also due to the fact that the email holes offer such a lai'ge extent of cooling surface, that when the flame impinges on the gauze, the heat is conveyed away bo rapidly and the temperature so reduced, that flame cannot pass from one aide to the other. If the gauze becomes hot, it loses its power of isolating flame, and hence it is most important that gases should not be allowed to continue burning in the lamp, or they ' will inevitably ignite the external atmosphere.
Experiments made in this country and abroad, determined that the Davy lamp would pass flame if exposed to a current having I a velocity of 8 ft. a second, and that none of the other lamps just J described were safe if the velocity exceeded la ft. a second, with 1 the exception perhaps of the Mueseler, which Itaa a slightly higher I
limit, if tlie current tneetn the lamp horixontAlly, but it [la&ses flame far more reuilily the others, if the current strikefl it obliquely. Although this danger wiw ofteo pointed out, no of&diil action wn.s taken in the matter imtiJ the Roy&l Commission on Accidents in Mines reporteil that such wiut the case, iknd the result of wliich is that the OoflI Mines Regiilation Act, 1887, contains 11 clause (General Rule 9) which pmcticnlly proliibits the use of the lamps just described in the form illustmted. At the same time, such lamps form the basis of all the modern on&s, but the latter are safe'guarded by tlie addition of shields.
It should, however, be pointed out that something more is needed in a. safety lamp than the fact that it is safe in explosive curi-ents of high velocity. Experiments at the surface are cai-- ried out with lamps perfectly clean ; the experim enter's hands are in the same condition, the currents to which they are exposed are of high velocity and iire composed of fresh air mixed with gas, while coal-dust is conspicuous by its absence. Underground, the conditions are essentially different ; no matter how high the velocity is in the gate-roads, it in considerably reduced when it passes into the working place ; powder smoke hangs about, and small quantities of carbonic acid gas are mixed with the air current. From the nature of hisavocation,the miner's hands are by no means clean, he handles lamps in a rather rough-and-ready Style, with the result that dirt nnA greet* are ti'ADitfeiTeil to them. C'oal-duat also clogs the inlet holes and gauze. It therefore follows that the behaviour of some of the modem types of safety lamps after they have been some hours underground, and in the return ail-current, is not what one would desire. Thin, however, is exactly what might be expected from the nature of the conditions which the lamps are constructed to withstand. In order to be safe in the highest velocity of air current, they must lie encloaeil in one or two shields, and the inlet ai-ea for feed-air must be reduced to the smallest dimensions. So long as they are clean, and remain in a strong current, the reniiisite amount of air for proper combustion is ilelivered to the flame, but when the velocity is small and the lamp gets dirty, or is used in impure cun-ent, the light given is of a very inferior character.
Another jioint of coiisidprablc importance is that by Mr. Mnrsftut," and confirmed by several other observers, that every type of tamp facilitates more or less easily the passage of flame resulting from an internal explosion. It is neces;<ary that a certain relation should exist be* -"lume in .t
lamp and the surface open 'he products of
combustion resulting frou' experiment.
proved that exterior tur-
Textbook Of Coal-Mining.
oolaide the lamp were more rare as the open surface of the g me enlarged.
Mr. Marsaiit proved that — ( i ) A small diameter lamp (such w SKry) does not readily pass an esploaioo, as the volume sosceptiblo 1 to explosion is inagnihcant. {2) A lamp without ass is secure against tlie effects of internal explosions than a lamp witli a gla cylinder, as the glas in the lamp confines the games there at the time of an esploeion and acts like a tauioon ; it is tbeicfotv both advisable to reduce the height and diajBeter of the laaa. (3) A wire paige of conical shape of the mate atpaatj ia utv secure against the transmissioii of internal exploimi than is ons of cA'lindncal shape. (4) (iaaes leeultiDg boai eambiHtMO plaf a 'd part in preventing exto'iial explonoos, and it might tlte- ', be advisaUe to ffuide them by a chimne)-. (5) A t vamatt ot feed-air [we-ents tlie filling up nf giass B an explosive mixtnm, and oaaaons the fonnatioD ot
t tbe bottotn of the Utnp.
OSSHH XiAlUfi. — In describing aooM tTpiaftl
tpB, the marks oooeertuDg tbeaa mastfaetaiEenaaipljiBgto
"n practical wcridi and eigKwm d. OnlMicfa lamps
s have been prorad by nanaioas ezperimeDta to
W'hb safe in all vvloctties which ordinarily oceor in coal Mune&. Ab
F BVerioasly Btated. this is not the ooir point Tcqnired in a laap>.
Knowing then to be safe, the great is to select some form
of a shift, and which wiU abo dktoct gaa in
sooall quantities qaicklr and distinctly.
Bopplirtuto-Onj. — Tbe Bept of tfaa Royal lwiwiaiiai a— iA.t. in Hinea Gist drvwattentiuatatheonpBnl foraiof this type. Tbe hmf thiB w y ; ited to bTooiabty is so
FM. tpT.
H is iqKvdnced to of dearly showing the I wUch have taken pbee. Its pcewbiny (and ia which it diflets fion all nnakra afrty ha) is the adiaission of free air fnm the top fow tube and
iatofy BMT the eil waiL It is impOKiUe fat a cVTeM (onsh directly down the inlet thee, as (hey am MolacMd by the top of dMta Ihaanty g
Lighting.
The outlet aiTaogetnentji of most lampi are haphazard, and bear no relative proportion to the area of inlet. With the discharge i-egnlftted in suuli a manner the top of the gauze ia kept in a bath of carbonic acid gas, and should internal explosions occur, gaa will not continue burning in the lamp. Sliding shutters were also placed at the lower' end of two tubes, by which means the feedair could either be taken from the top or the base of the tnbea, an improvement properly appreciated by any one regularly testing
Id the foiTn now generally adopted, three inlet tubes instead of four are used (Fig, 408). The third tube is con.siderably broader than the others, and acts ns a reflector. The Rhield-plate, a, in the hood is matle of such a nixe aa to completely cover the inlet boles. Thifi ia an important point, as it waa found that if such was not done the lamps were often extinguished in an unaccountable manner. The height of the outlet cone must ' be such na to just reach the level of the shield -plate, when it then occupies a position intermediate between the two horizontal rings* of holes, li b, which are placed in the hood for the products of combustion to escape by. A row of circular holes is put in the top crown of the lamp, and 1;% covered by a thin sheet brass plate 1 1 in. diam. To stifle Fio. 409-crimped in thi-ee places, the C crimped partK touching the j M crown, as shown at c. These impivremeDts remove the defect of the light being suddenly extinguished from no appai-ent cause. The same result is obtuned with the form of hood shown in Fig, 409 ; here the outlet cone and inlet tubes are covered by a piece of brass bent into the shape illustrated. One hole, in. in diam., serves for the escape of the products of this being protected from direct currents a piece of sheet brass crimpeil as before mentioned. This shape of hood acai'cely appeal's of such a safe character as the former one, but a large number of lamps have been constructed to this design. Another impi'ovemeut which facilitates cleaning is that the ring securing the glass in position is screwed on to the vertical plate forming the air inlet chamber, d (Fig- 408). instead of the frame of the lamp.
It follows from this that when the lower gauze ring ia unscrewed all the inside parts of the lamp at once fall
In the lamp of latest design the portion of oilvesiiel supporting
35S Tkxt-Hook Of Coalmining.
wirk tuU has IvtMi lowereil, but the wiek tube itself has been KMithtMUHl. M) that tho dame is only lightly lower than in the ohl t YiH'>. The of the wick has inci'easeil. and now htaiuls at I iiu'h full.
uuiiiouuis small improvements, which may not sepaitely MH'iii if much iiuiHrtaniV. but which in conjunction materially atVcct the iu*:u*tical working, ivriainly make the present design Ml to the earlier ones. Taking tirst its lighting caps-ity ; untie r orilinaiv con vHt ions it t;ives more useful illuminAtiou than any ithev lamp. Photometric test* ivuiiucted at the surface are l\>rthe siinie ivaxm* as weiv refen-ed to when dealing with vcUviiy trial>. In additivni. one other fact must be pointeil out. With the plutonieier. either when against another lamp or a vnuidle. the two articles are pLiceii on the 4uue lex el. and it is the horiiontal rav>. or those that are utuly wliiv-i'. rMc:: the s'xveii an-l decide the result. I'oUieries itxiuiiv lii;iit to Iv thivwn in all dirvi-'tions, especially and liev.v r.akrvl lights an? ot:ei: under conditions which uiav at ;i!iv :ime Ivviue <.ui::::erous. Thev are niH
actualU u'.iNite. '..o oi-.e wl.other :hev mav l:come m>.
.Ml >l;icMo.i '..iiiivc- s-.:::Vr fr.in tl:e .:reat iLsadvantajze aiv luwjvv'iiiU o: l.iiiivv diAiiie'.cr :hA:: :Le ;c'.A5fr. axi'l nstillv act like a >i:.u!c. I':-.:'.:. .11: y "ijih: s:rik:i.g v.ywiri?.. The conical j; ! a t 1 1 '. c lit- y y l. i : - i I iay ye rt r!ii> j vc t he cont rary act ion, a'* it dc:Uv:> : -.e T'-.trU :l;e v.k::. ind :he shield above p u'\ c n '. N I i-j y s rea . ". : : j.e y . djv ". t rr : hey Are specially .1'.". J. I c.vjL'niva:: :: : :1>. r-.i.c cai. be rapidly taivy.x Ve :. :f.:. ai w-i-l — -hj.: ycsiriionthe
'iiikN ivv-:- '...' '. .L.-. r-s. A- \:d,sy z:c2i<, v.-h the inlet
i- : ; .:: "oie ui'iieru ':impfr
U!'
I : 'iT.
i-
'
,
r
-
ny
"till
f
't
'A
i:
...I--'" -i'-'iir'-uiy ▼orsnxir it
Lighting.
sliows u, cap on the flame where those lampK fail to whow the BliRhtest indication.
Ntimerous experiments have proved the safety of thiw type in (uri'entE of high velocity. The riitk of internal eifplosions outwards ie pmcicolly absent, owing to the tmiall quantity contained in the lamp, the regulation of the outlet of the products of combustion, and the conditions under which feed-air is introduced. Theoretically an internal explosion is impossible, as owing to th admission being below the flame, any fire-damp i£ burnt as it arrives, and the inside of the lamp is titled entirely with the products of combustion ; but this, however, is not absolutely the
A statement was once made to the uutfaor that thit. lump went out so soon when introduced into gas that it was impossible to dearly ascertain whether such gas was tire-damp or black-dump, if only smuU quantities were present. Ua the other hand, he hus been assured by an overman, who bus specially been working and e.\amining places with this lump for over twelve months, that not the sligbtfst difficulty has experienced in this respect. With black -damp the Same drops and fades away, but if any gas is present, a slight " spiring " of the flame is immediately noticed, and this takeii place once or twice before the light m lost. Of course it is possible to abuse anything. If the lamp be pushed bodily and suddenly into gas it certainly goes out before any definite mdication is obtained ; but if it be introduced slowly and steadily, and withdrawn as soon ns gtm is indicated, the light is not oftn lost.
Bonneted Uueseler. — This type of lump has deservedly been held in good repute for many yeiu-s, and the report of the Mines Accidents Commission on the ahieldeil variety was very favoui'able. As a detector of gns it ranks a very good second to the Gray ; it shows gns in a clejir delicate manner, the cap produced being very distinct.
Owing to the pre.sence of a chimney in thie lam]), when it in d the products of combustion pass outside the chimney and foul the inlet air, with the consequent result that the light is extinguished. This, in combination with the shield at.'ting as a shade, make the examination of the roof n matter of difficulty. Thi.'. disadvantage of the Mueseler lamp upitears to have lieen rather exnggemted, iif it stands u fair amount of tilting, especially if the time during which this is done be not of long duration.
Ashworth'a HueHeler, shown in -to. is one of the safest
of all lamps, us it lias been tr rreuts of loo ft.
Mueseler type in havingaj J one, nnd
the diaphragm is mninil i ty is due
to the double 8hi< provided
with a conical o ion is
36o TEXTBOOK OF OOAIrJUSIXG.
mrid: Uw upper put tbe axuae it kep in \mlhvttarbonic cid *nd in any iaunttl exploaon, tbe H g't iKmcaiaiar eitmgwbJied tnd the inlet mir fooM. The in fire sbo the diiwtiao br the ir mn dOia proton rf rotnlmiaoo, ami thai the inmM* are All TicJMii mrrwitf. ten in the inode ehwld ud Mv!L in ihe onwr <w. the hner hcinc mu-the . A fveiog shutter. fc jiawd abcT* the beriwnt*! inlet holes DMT ibe i. rf gW Dd this is doMd, the fced-*ir is npe-:iM TO witr the bcOa in the ooter shidd near the
Xotv* SV-oiiiwtti uwa:u.-a Tk> . Ir fc i. this kap
-o ;i. *'t.:'it ii* f. uu w li- >cniiu-> szanboi Wnh
lh* K-oi TVca.'VK oc I .'CJ
LKJHTINti.
3t'i
i'lO. 411.
cylindricivl one without ii top, a middle one of the Cliinny type, iiud an inner one, i-eally built up of two gauxea and u chimney.
This lamp detects glut readily, bums well in a good current of air, but biidly in a "dampy" one, does not get hot {probably owing to its large internal volume), and stands a fair amount of tilting without the light being extinguished. Aftr being in use several hours underground the light gets very defective. The author ia not aware that this type has been used extensively at any colliery. It is composml of six part, neglecting washers, and is of complicated construction. As there are many lamp perfectly safe under ordinary conditions it seems improbable that this form will come into general use.
Uarsaat. — The report of the Committee of the Ellis' tiever Prize, and uf the Accidents in Mines Commission brought this, then new, lamp very prominetitly befoi'e the mining public, and results obtained iii practical use increase the favourable opinion. It has, however, received a few small moil iti cations from the form in which it wius experimented upon by the two CommiHsionN referred to above. As originally constructed, tuso rows of inlet holes wei'e supplied, one at the bottom of the bonnet, a (Fig. 412), and the other in the horiajntal flange, b, forming the base of this part. The Accidents in Mines Commission recommended doing away with the holes in the base of the bonnet,* and in most of the InnipR now constructed in this country this is carried out. In the form illustrated, tlire slightly conical gauzes are employed, but often two only are used. They are protected by a sheet-iron shield. After considerable experience with this lamp, the author expressed an opinion that it appeared to be the moat suitable for the working miner ; its construction was simple and strong, and it gave a reliable indication of gits, and :i good light.
Further experience has not materially altered tliat opinion, as, although the tamp finding most favour does not go by Mr. saut's name, yet it is practically a lamp of his type, with an addi* lion which increases its efficiency and lighting power in the impure current* of return air-ways.
Deflector. — During an excursion in LancashirB ' nj'a
attention was called to this lamp, iind as compl'
jdM
niltyin getting some of the Dilr>
36
Text-Book Of Coal-Mixtng.
a few lamps of tlus type were obtained aod placed ia the hands ei' the miuerH at oue of the coUierieK under his charge.
Fig. 413 illusti-ates the lamp, aad it will be seeu that the Mar- Bftut is followed, so far as the airangement of gauzes, sltield, oil veasel, and glass are t'oncemed. The ilistiactive difference, however, consisCn in the guiding of the inlet Kki. 413. air; thia is admitted through a row of
holen in the horizontal dange. aupport-
%v i"g the shield, and is prevented from
I impinging on the gauze by a vertical
cylindei' of brass, a, inches high, which acts as a guide, and directs the in -going current vertically upwards. a point nbout 1 1 inch above the hi zontal flange supporting the shield, angle-ring,, is introduced, the horiionl part of winch completely fills up the space between the outside gauze and the inside of the shield. The other fliinge pi'objects downwards close ngaiiist the gauze, minating just before reaching the vertti cylinder which proceeds from the h( zontal Range forming the base of shield. It will be noticed that the vtrtical cylinder, a, is not placed ckee to [he gauze, but occupies an intermediate ])osition between that part and the shield. The inlet airafter being directed upwards meets this "deflector,' and is thus thrown on to the flume. As the lamp get* hot, ah-is Slicked in, and paiised on to supjKirt combustion. This fi the explanation why such good illumination is obtained, end of a shift the light given is nearly us good as it wi beginning. After burning a short time and getting hot, illuminating power sensibly increases, and no difficulty ' enced in lighting the lamp when all the pai'ts are cold.
In all ordinary lamps a rapid circulation is obtained as soon as the parts get hot, but no appliances are introduced to properly dii'ect the inlet cun'ent, and, as a result, the greater part passes away at once with tbe products of combustion, only a portion going downwards to supply the flame. In the Deflector," all the nir which enters reaches the flame, and beforo doing so is rented by contact with the warm deflecting ring and gauzes. To this heating. of inlet air and proper directing of current is due the fi that this lamp will bum in on air containing such a quantity carbonic acid gas that all ordinsiy forms, even unbouneted are extinguished.
The lamp is supplied with a solid top, e, and the shield secured by a lead rivet, d. This is an advantage, as the lockii
luga,
space ;l
DO tn
Liohtino.
3S3
of the bonnet cau be left to the lust minute, and until the miner has satisfied himself that all the parts are in their proper poBitioii. Tin Can Davy. — lu the North of England the ordinary Davyis endowed in a tin cnse, provided with r window (Fig, 414). If this case ejctends the
entire height of the fKi. 4r4, Kir;. 415,
laiiip, the Necurity afforded is greatly increased. the Royal Uommission on Accidents in Mines ' stated that the addition caused the himp to one of the safest tested, hot they also {mint out that at high velocities n very eniiill diHerence in the form of the case, or in the position of the lamp with respect to the current, greatly affects the behaviour of the lamp,
Thorneburry.— A lamp nhifh has attracted considerable attention lately is that invented by Ur. Thorne, in which a heavy petroleum oil, having a flitshing pouit of 250% is burnt in a cone aimihtr to those employed in paraffin lamps (Fig. 415). Two concentric glasses, a and 6, are employed, which ai-e not disturbed when the lamp h taken to pieces for cleaning. A metal chimney, d, which cnriies uway the products of combustion, leads directly from the inner glass, while the gauze, h, leads from the outer glass, and as a fiu-ther protection in currents of high velocity, a second piece of idiot gauze, e, is attached. The whole is enclosed in u metal shield. The feed-air enters at the point, c, passes down between the two glasses, and through tlie gauze,/, into the combustion chamber, y.
The light given is of a very character, and the height of the flame can be easily regulated by a pinion and milled disc. This is, however, a soui'ce of annoyance, ji.-. the ftaeW watch-key which tilh on Ui the sqniiTOsbaft *lic iiiiiii.n very easily wears round, and jiit at the -'sJied to be put into opemtiott,
the itev ttum" 'ment does not. Ro f ar as
safety is concerned this lamp gives excellent results, and in the hands of an official of the colliery may be used underground in strong currents of air, but it has a tendency to get very hot, especially if it stands anywhere. It is very complicated, and weighs more than any other lamp, and requires more delicate handling than an ordinary miner will give it.
Sight Lamp. — An improvement of considerable importance has recently been introduced by the Sight Lamp Company, who employ a shield, having a great number of perforated holes through it, but which has a glass lining especiaUy made for the purpose. In this way the shield does not obstruct the light to anything like the same amount as a solid one does. Breakages are not of frequent occurrence, as the glass is well protected by the perforated shield ; there is no space between the metal and glass shield.
Conoluaiona. — Owing to the large amount of useful light given by the Hepple white-Gray, the way this is directed on to the roof, and the delicate indication of gas given by this lamp, it is preferred to all others for use by deputies, firemen, and timberers. It requires, however, very careful handling ; and the light is easily extinguished even when gas is absent. Men are apt to get careless, and carry it about with the lower slide holes open, and when in that state, if the current impinges suddenly on the lamp, the light is lost. The distribution of light on the roof is due to the truncated cone form of glass, which is claimed to be stronger than a cylindrical one, and to automatically aooommodate itself to sudden changes of temperature. The ramdity with which gas is detected is a great point in its favour. Witi this lamp it is scarcely possible to miss the smallest quantity, even when passing huiriedly from one place to Miother, which can easily done with any other form, as, unless there is an appreciable quantity of gas present, they require to be held a definite time in it before any indication is given.
For the ordinary miner who requii*es something a little less delicate than the Gray, the Deflector lamp gives excellent results. The light given in impure air is superior to that obtained from any other form, and it will continue to bum even when the unbonneted varieties will not. It gives as good an indication of gas as any other lamp, with the exception of the Gray and Mueseler. The author obtained a number of different types of lamps for use at one of the collienes under his charge, and after an experience of two years there is not a miner at the pit who, if he had his choice, would not select a Deflector lamp in preference to any other, his reasons for this being that it bums brightly in slow and impiu*e currents, gives a good light for a long time, and will endure a great deal of rough usage.
Oil. — The i*eport of the Accidents in Mines Commission first drew attention to the fact that a mixture of one-third petroleum and two-thirds rape or seal oil was more suitable for safety lamps
Lighting.
i'S
tlmii refined colza. It ia necessary that tlie peti-olutim slioiild be of the bet qunlity, and that no more than the quantity given above should be used. The mixtui'e is considerably cheaper than bet I'ol/a, and gives equal illHininatiiig power, and tlie wick Iihs not such a tendency to form a hard cake on the top.
Mineral oils are but rarely employed for safety likuips, although attempts have been uiade from timeto time toutiliie them for this purpose. BenKoline is used in some of the made by the Protector Company and by Wolfi*, of Zwickau, Saxony. It is a volatile substance ajid requii'es the gi-latest cnt-e in its application. No free oil ia allowed to remain in the oil vessel, which is filled with a sponge, and as the nick itself does not bum an usbeirtoe one is provided. In filling the lamp a small quantity of benEoline is poured into the vessel and the sponge eatnmted, all exile is then emptied back again into the tAnks. It certainly gives a nice clenr light and produces no smoke, but requires so many precautions in the fillingroom that it has never been largely employed in this country. A special charging apparatus has to be providing. and no naked lights can be introduced into the room where the lamps are replenished. The employment of mineral oil ia not allowed in the fiery mines of
Wiolt. — In the lamps of recent introduction, flat wicks ai-e invariably employed. The illuminating power of the old fonns of safety lamps, when the wick was round, varied from 0.3 to 0,5 of a staDdnixt candle, but where tv Hut wick in employed it may rise as high as 0.7. With a view of further improvement Mr. A. H. SCoket) has introduced a wick tube which i.' guttered along one side and the wick is supplied rather wider than the tube, so that it takes a corrugated form. A longer surface of fiame is obtained and the supply of oil to the wick is Mr. Ashworth obtains a sinulnr result by making the wick wider than the wick tule and the tube broader than the wick.
A {>oint to which little attention has )>een drawn is the material of which the oil vessel is constructed. In England it isinvaiiably made of brass, while on the Continent it is just an regularly made of ii-on. Mr. Marsaut's expeiimenbi proveil that the lighting power is influenced by the material oE which the lamps are constructed, and that a hi-asa lamp only pave 70 per cent, of the luminous intensity of the same lamp in iron. The explanation of this seems to be found in the superior heat conibictivity of the former, na the lamp bottom gets very hot and the oil becomes viscous. Brass oil vessels seem to becheuiMthan if made of iron, owing tfl
the ease witli which they cs Mr. Asliworth ooatu thett of hat (tin),
fixtennivel' all gaps I
To r
le the objection
;i conductor
sportunt that wt be ground
TKXT-BOOK OF OtUL-MCCDEG. dM,CartftlMT
— 1W ii%iinl 4m tmfiajmi ik tkM of
[ 11 fill I J ihii iimil iiilii hiili il mmiiIiJ Hhi W caDed ft lo at D.M it tw nMSjr te cycneJ by aav 1
Mafmttie Laata. — In types of ) lock has I l ( w g ,iiiiil iWih itir juiliiiliiw of ytf w fu l HaeM L tfiL. The gonecBl rzHiigBMaA i fiiil i b iMfiiiji
"iltobev
t be <ntbo( saitafcfe ififiMwee, bat tiiey I a'te ftt amt of order and an enBbenoBe £u rtm- I Honnt, and indwd tlw ump k gL , awthod of eecaring mietj UmpA k is tfaat of eaqilajiiig a [an cf lead, wlni u lirated into pke and [ hM ft defioa ponded apai it. It is ingwiMe to the bmp
mganmi
I witboBt beakiBg tins pin, and altbvl of eone, anj o [ dariring can open the lanp, it cannot be done withaat detection. D lockiBr anmaennHit is iOaatnted in tif. 413, and
a bored for the reeeptton of a lead rivet.
I Hhe JMip, fitted to a hwe eollar, y, a m roo n di n g the ofl Teasel, I eaaly be toned mand, grring oonpauation for tho and the oil vesel, and owaMing the pmjeetifat, fat exactly toge&tt. „ „ Doeat of the Uvgan lamp poaaenea several
I foiaUof novM. ▼sel.tbeatlMr k the iper part of lamp, Willi <rertical boles, are ptovidnl, a and 6 f <Kg. 4ii),bttttbe passage in the upper projectioci does not go I CDnpleteJT thim it. A small epring ratcfa, t. is Ettuated in the lower projection and will allow a cylinder of eqiul diameter to the bde to pass by if the direajon of motioii be vertically upwards.
t
the internal have been fitted together, a sliding pillar is employed, which, when the oil vessel is screwed up, proji into the base of the shield and pi-eve&ts its being removed, but, ou the other baud, when the oil vessel is taken off, the pillar e&n he pulled dowD a short ilietanre, thiis releasing the sliield.
This hiia recently been improved ; it now locks both shield and oil vessel. In Figs, 416-18, a is the upper horizontal ling of the cage of a lamp on to which
the shield b wreweil, and Kh:b. 416, 417 and 41S,
b is the bottom one that i-eceives the oil vessel. The sliding-biip, c, occi, .. position shown in Fig, 416 while the sliield is being screwed on, and ns soon 113 this is done, the bar is pushed upwards and tkee the position illustrated in Fig. 4 1 7, locking the shield. The oil vessel is now screwed on nnd then the sliding- Imu" is imnered a little, its
bottom end going into a recess in the oil vessel. This motion la not sulticient to take the pin entirely out of the shield, and, as a result, both shield nod oil vessel are locked, nnd the slicUng-bar is then secured in this position by a lead rivet (Fig. 41S).
Casting Hivats-A machine largely employed for casting lead
rivets is that of Howat', which consists of a series Figs. 419 and 430) of the exact size of the rivet, arranged in a Cimilar manner around central spindles, d 4, which have a niuah- B-sbaped head. These spindles can be moved vertically upwards iWAns of the ci-oss-bar, e, and lever,/. The top is covered by a 1 1 having holes through it at A h. Molten leml is poured in ' eite holes, and fills up the recesses, c c, the lid is lifted ante,, and by depressing the handle,/, the bunches
Textbook Of Ooaimixisg.
itnl eora to wfaidi ue Mtwdicd, they an over a
die, and with one blow of paaA tlwcoitnl of Imd
detubed, ud the livtU m Mt mdy (or Me. EMh madiiM
three wts of twelve riret et a tine. Baligbtios Lamp—An tmoftmtaxt aoaetiiiw ptoridcd to pnt odt the flame if Uie tamp Flu. 411. he tiQBCTVwed, but this afl<)rds so
Eronfy, ae it tempts the miiMr to cam* matches aboot with him to relight the lamp, which may be done without detection. With the Protertor Ump, bowerer, hj tneMBB of a locking bolt, after bemg onoe aDscrewd the lamp tmxmat be rltgbted witbont onloaking. If the oil ves!l \e. Fig. 421) b withdrawn, the wic:k pa:&es down the ' sides of the tube, a, and the flame 1 k put out and cannot again be lighted and replaced in podtion until the tube, a, is taken from the lamp and put in its proper position in the oil Tesel. The tube, a, locked by the built, . which, when pushed home, is kept in position by a small spring.
The number of lamps which become extinguished from tUffetvnt caoiiea in the workings is very great, and amounts, according to Rtatifitics, at many collieries to as much as 20 per cent., which hare to either relighted, or other ones served out to the men. The gmeral practice is to provide special lighting stations, and to insist on men taking their Inmps to tliese places when tbey extinguished. Such a station must be situated at some point where a naked light is allowable, and as this li often onlr at or near the pit-bottom, men have to travel a considerable distance when Uieir lights become extinguished, which acts in ft very salutary way in causing them to take every precaution to prevent losing their lights. As in some mines naked lights are not allowed at nil, a cei-tain number of extra lamps are taken down, which replace those that become extinguished.
Where a volatile iUuminant like benioline is employed, a relighting arrangement can be applied. In the WolH' lamp a strip of pa})er is employed, provided with fulminating spots, each of which can be brought opposite the wick by a step movement, and at the Mime time be struck by a trigger released by a spring ; the fulminating compound explodes and ignites the benzoline vapour.
Man. Geo. Soc. xrii. 280.
Licihting.
Tlie proCHw con be repeated until the whole of the caps itie exhausted, when the paper containing tbeiu is reniDvcd aad n fruAh piece put in ite place.
A Bimilnr device is that of Mr. H. BIsom,* but is applicable to vegetable oil lamp. A small wire is fixed in the lamp on the oppoeite side of the wick trimmer, and carried one or more ordinary matches, which cud be lighted by frictioit. When tlie light is extinjfuished, one of theae matches is rubbed on a rougliened plate and iffuites, the lamp being tilted so as to bring the wick over the uiatch, A guard plate, or shield, is fixed against the adjacent match to prevent the flame of one accidentally igniting the other.
The objection to any such appliance is, that supposing any lamp has been extinguished through the presence of an explosive mixture, when one of the matches wiih struck, nn internal explosion would be produced which might result in the passage of dame to the external atmosphere.
Cleaning Lamps. — Where n Uirge uumberof safety lumps ore
Fia. 413.
employed they arc now genemlly cleaned by mncliineiy, which consists of a series of revolving brushes fitting the *evil parts. To remove the oil odheiing to the gauze, powdered magnesiun limestone is generally sprinkled on the brushes. In some cases to obtain a tiimilor result the gauzes are steeped at intervals in a solution of caustic potash.
For removing the internal fittings of lamps, a simple arrangement (Fig. 423) can be employed. It contiits of u nut, a, which fits into the projecting luga on the lamp-gloss ring, and on turning the handle this ring is unscrewed.
A more elaborate machine is that of Uowat's (Fig. 423), wliich both rivets the lead plugs and unscrews the various putts of lamps, it consists of a cup, A, containing a number of slots, whidi ro"
Text-Book Of Coai-Minino.
rotated by turning the handle, B, The lamp bottom nnscrewed by placing it in the cup, with the projection I one of the slots, and then turning the handle. In order to r the internal fitting, the cup A is taken off, and the lamp placed on a square nut thus exposed, which fits into the pi-ojecting togs on the ring securing the lamp glass, &c., in their proper positioD. A few turns of the handle removes everything, and after cleamng, a reversal of the above operations soon puts the parts together. To rivet, the lamp is placed on the platform, C, with one head of the rivet against the stop, D, when half a turn of the h&ndle brings the movable bar, E, forward, and locks the lamp. To aniock the lamp, it is placed on the platform, F, with the head of the rivet under the cutter, G, which on being depressed cuts off the rivet. The lamp is then i-emoved, placed at other end of the platform, F, and the handle, B, reversed when the eccentric block, H, pushes the rivet out.
Electrio Xiight TTnderground. — Many collieries are now provided with the electi'ic light underground, but the system extends only a short distance from the thrift. The ordinary iacandesoent light, if worked direct from the dynamo, requires two conducting wires to convey the current, and as illumination is specially required in the working places, it seems improbable that the direct system of lighting as is employed on the surface will ever be tised Tindergroimd. The working places are naturally moving day by day, falls of roof are common, and as the space is confined, conducting wired would He quite out of place there.
Secondary Ball-ertei. — By employing what are known as secondary batteries, or accumulators, a charge of electricity can he stored up to be given out as required. These secondary batteries consist of a series of lead plates covered with spongy lead, arranged in cells and surrounded by a soltition of dilute sulphuric acid. VariooH elements are employed, and the cells are arranged differently by several makers, all with a view of i-educiug weight and increasing efficiency and luminosity. With a lamp weighing about 4 Iba., a light equal to i or standard candles can be produced for about twelve hours. The lamps are charged by connecting them to a dynamo, and passing in a current for from eight to ten hours, or for such a length of time as is necessary. It generally takes as long to charge as to uncharge. The lamp itself is a smaJI incandescent one, and the light can he turned on and off by a switch.
Accumulatoi's require constant care, even when made of large size, andstillmoreisthisthecasewhen they are of small dimensions. During the progress of discharging and re-charging, gas is given ofT by the cells, and it is, theiore, impossible to hermetically seal them. A small hole has to left for the escape of this gas, and as the celts contain a liquid, this liquid also escapes, and being an add, attacks the connections and eats them awny ; sooner or later
LIGUTISt!.
Mhoct-oiivuiting I'esulte. Thei'e is ftlxo (vilisiilei'ablp dilSciilty iu tletermiuiug when the celU me charged ; tfaey oftn appear to be so, Hod yet after taking the lamp underground, the liftht goew out in a few hours.
Primary Batterlet — If some form of imttery can he designed at a low working cost, which will provide in iteelf electricity of sufficient concentration to work an incandescent lamp, it will, no doubt, meet with cnusiderable favour. The diidvantage of primary hattrieit, by which is meant a battery which ia I'eplenished by putting fresh plates and fresh chemicals into it, is that they are expensive to ke-p in aetiou, >ui they cODSume a, lot of materild and involve considerable trouble in emptying and charging tbem.
Prohftlily the most succeBsful up to the present is that of Mr. A, SchanechiefF,* wliich has for its elements carbon and rinc, the exciting fluid being a solutiou of basic sulphate of mercury in the acid sulphate, one pait of the salt being dissolved in three ports of water. In one form, the elemcuts occupy a little lees than one half of the cell (the top part) and the solution a little less than the other half. The top and Itottom of the lamp being hermetically sealed, on turning the battery upside down the solution fiowe on to the elements and the lamp begins to work. The great advantage is that no gas is given off. A second form is so arranged that the plates are electrically disconnected by lifting them out of the liquid. Lord Kelvin reports that the batty has a high E. M. F. (1.39 volts) nnd a very low resistance (0.15 ohm for 10 sq. inches of zine surface). Its disadvantages are, the cost of the exciting fluid (4s. a gallon, although it is stated that y. -jd. a gallon would be allowed for the spent litiuid with ita solid residue and frije mercury, but the loss at collieries would be considerable), and that the liquid is also exceedingly corrosive and attacks everything. Tlie consinnption of zinc is about lb. in fortyeight hours. As constructed at the present time, both forms of portflble electric lights are far too delicate* to be emplojed by the ordinary every-day uiinei'. They will not give good i-esult eveu in the hands of the oflicials.
Delioate Indioatora.— The ordinary safety lamp will not detect a smaller amount of gas than ij per cent., and in dry and (lusty mines it is desirable that a smaller amount than this should be discovered if present. To do this, what are known as delicate indicators are employed. Several forms are very ram plicated, but others exist which give good results in the hands of miners.
Pttter iMmp.i — The most successful is the Pieler lAmp. It consists of an ordinary oil vessel, but the illumiuaut is pure alcohol. The wick, which is composed of silk, can be raised or lathe wick tube in the oi'dinary manner. To prw'
Si'
Textbook Of C0A1,-M!S1Kg.
side,
lamp H
seeing tlie Bsune of the buruiag iilcohol, a conical afield is vided, covering the flame. The wire gauze is of the Davy type, but much larger, to allow for the increased height of the flaise pi-oddced. III the later lamps a shield, having a door on one side, has boea added as a protection, as in its original form the lamp was very uiisaife even in currents of the most oi-dinary velocdtyjT When moving about, the door in tlie shield is shut, but when a obHervation is being taken it is opened. With this lamp ! cent, of produces a cap of 1 inches long, witli i cent, the cup reaches a inches, and when i j per cent, is present the cap reaches the top of the lamp, and is of it deep blue colour. This lamp is only useful for detecting low jierceutages of ga, aiid must not be taken where fsfin might be present until a previot exiua illation has been mile with an ordinary E&Fety lamp. TImi> J FieUr lamp should only be used by pei'sons of cx|>6rieDce a discretion.
AthuKrlh's Lfimp.' — In this form, which is a modification ( the Hopple white-Gray lamp, ben/oline is used as the illuminon I which not out)' gives an excellent Ught, but when reduced and aJ special burner employed produces a very hot flame, which aids tlw 1 detection of tire-damp. The glass of the lamp is ground dead for over two-thii-ds of its inner surface, and completely deadens all reflection, ThismaterJAllyuBsists the detection of the cap. It is said to give an indication of per cent., and to detect gas better than nny other luuip, with the excepbiou of the Fieler. Its advantage ct sets in the fact that it gives a good light when not used for te iug purposes. The Pieler lamp is simply a gas-tester, and anotlM lamp has to be canied about to light the miner on
Coloured Glaus. — Mr. A. L. Stea'en3on t propose. to apply t law of the absorption of light, and employs n piece of ooloure glass, which shuts olf the tiame of the fufcty lain, and rendu evident the-pale blue cap in a more distinct wanner than is poa-fl Bible with the unassisted eye. Either a slip of blue pot opal i adjusted on a lamp whenever it is desired to moke an exuminatioa, or a jiair of spectacles may be fitted with gUi.ss of this <.'olom-. states that such addition is most beneficial, enabling an observeito detect the presence of gas when quite invisible to the unaided eye.
Lireiiiys IndieaUir.X — "When a coil of platinum is heated in contact with marsh gas, the combustion of the gas adds some beat to the platiniuu, which cunseiuenily glows more brightly than if it were in lur. This is the prineipltwhich Mr. E. H. Liveing Iuk lltilied iu his indicator. It consists of two coils of platinum wir throiigU whii'h au electric current is (losseil by turning tb handl of a small magneto uiacliine. Utie of tbeee spirals is
r-n closed ii
t tube made and filled with pure n
e end of each
s suriwunded h
spiral ia provided with a gliiSR cover, the two facing each other, while in between, a small screen, sach as in used in photometric experiments, is placed. When the air of the mine is quite free from fire-damp, both spimln glow (wjually, and the screen would be midway between them, but when tire-damp is present, one spiral glows more than the other, and the screen has to be moved farther from it to equalise the amount of light on the two faces. A graduated scale is provided which points out the percentage of gas present due to any position of the screen.
After one spiral has been heated more than the other on several occasions, its electncal conductivity becomes altered and the two will not glow to an extent, even when a trial is made in pure air. To allow the instrument to accommodate itself to this change, it is possible to move the lero point of the scale. After using the imitrumeut several times, before taking it into the mine the iiliding sci-een is moved until its two sides appear equally bright on turning the handle. The screen should then stand opposite Kcro on the seule of percentages, but if it does not the scale should be moved slightly until it is right, which is done by loosening a smalt thumb-screw that holds it. This instrument i-eadily detects J per cent, of gas, and with a little practice any intelligent person can operate it.
Biblifigfaphy.— The following is a list of the m6re imporUst
" dealing with the subject-matter of this cliapter:
WALKS. INST. : Thr Fifr-Jfimp Cap, Wm. GnllowaT, Schantdiirfi PhrtaUr Primaru , A. SphanBchieff, : Ijorge Jncandtteett Electric Lampi v. Are Lamp), S. F. ivl. 370.
i Oh Ike Pir'rr Snftty Lamp, C. Le Neve Foster, irii. 153 :
itix. 364. KED. INST. : Nolt* on Saftln lMiap>. H. W. HoghcB, i, 2Sj ; DfltdioH 0/
Fire-damp, J. Ashworth and K. Clowes, li. 352 ; Thi 7%ornhirrjr
.la/y Lamp, S. I). Wain, ill. 3z6. soa IND. MIN. : Eliult (ur III lam]>r de tireti ile ninnini, J. B. HnrsaDt
Serie), xii. jai ; XoU ur hi lainpt Pitlrr, A. Simon (j* Serie),
REV. I'Ntv. : Xote iHT la laiiiiif4 tlcrtryiuet portallrti povr nine, E. Mauoa
S. B. 1.! Oil an Improivd Mfthodi' DeUrtiug Small Quanlitim Iff Ij
Oai, A. L, BtOKVeniott, xxvi. 133; On a Xcr ilrtlioii 0/ iMtrvai oerytimailQiiaiiliHao/'ltijIoHiiuiible Oat,E. H. Liveiag.xxrii. 187 xxvDJ. 167 ; ftuleii on lie MaeneUr fm/i. A. R. Sawyr, xxix. T On tht FrintiplM 0/ Eledrir LighUnij and the Vonntraetion nud ../ Eltdric LUjhtimj ApparaliiM, S. F. WaUtot,
Mamaut Lamp M. Walton Brown, xxxiv. i6i ; The Pitler Lamp and Mode of Indtcatmg small QuantitieM of JWe-damp T. W. BunniDgrt xxxiv. 285 ; Testing of Safety : Account of Experiments made bt, Profs. Kreischer and Winkler P. Phillips Bedson, . 3 ; CuveUers Lock for Safety Lamps, B. L. Damas, xxxvi. 51 ; Aei-royd and Best's Safety Lamp Cleaning Machine, Wm. Ackroyd, xxxvii. 121.
ANN. DBS. MINES. : Sur Vempioi des lampes electrvjues. Report of a Commission (S Serie), xviiL 699.
BRIT. 80C. MIN. STUD. : Safety JjampM, A. H. Leech and W. H. Roatledge. vi. 1 19 ; Heath and Prosts Shot Firing Lamp, £. S. Hope, xi. 42 ; How to Light a Colliery with hlrctrirityl S. F. Walker, xiii. 147.
Cjapter Xiil
WORKS AT srUFACE.
Boilers. — TLe generation of steam til a collier'y u a point of considerable important.'e. Nob long ago the ai'guawiit wan often put fortli that coat ut a volliery cost nothing. Ceitaiuly, u quantity of unsaleable mUieral is prudut-ed, hut tliis beam a stall proportion to the total output. When labour was cheap, little machinery was employed, requiring ouly a limited quuniity of steam. The tendency, however, nt the present day iij to do nothing by hand that can be performetl by machinery, and, aa a result, greatly increased quantities of sLtam have to be lued ; the consumption of coal has cuiTespondiugly increased, and in tulditiuit to the portion of tmsiileable proiiace, tht) better quality of cool iitvB also to be ued. In consequence of this, fuel-saving appliances ore becoming quite common ; indeed, many of the more modern collieries are as well deugued in thin respect as any other branch of engineering.
Under the old regime, cylindrical externally llxeil boilers were invai'iably applied, and a great deal may still be suid in favouiof them. They certainly do not raise steam economically, but w a gr'eat extent this fuUing is counterbalanced by their low cost of I'epairs, and the facility with which they may be cleaned from inorusiation resulting from bad water. This is the chief recommendation of boilers of this type, and where the wuter ia vei'y bud they cannot be surpassed.
The tendency at the present day is to employ bigli pressure steam. Its advantages are numerom-, as superiority in economy is not its only recommendation. Its uso from the beginning materially affects the capita] outlay at any coUiery. If instead of uitiiig 50 llu. pressui'e, 150 lb(>. is employed, which is now becoming common, not only in the six of every engine on the place leas, and the cost also, but thn "m smaller, the size of
the steam-pipes is reduoi ' letalliitioii can be
made more compact -
The gnemtior boilers,
of which llierr form
Text-Book Of Coal-Mining.
called the Lancashire boiler, which consists of a cylindrical having two longitudinal tubes running the entire length, may be taken as the type upon which other designs are based. Two fires are employed, one in the front end of each flue, and the products of combustion, after pasaing through the boiler, are convey* along each side, and finally returned beneath the bottom to tf chimney.
In the Galloway boiler, the two main tubes in which the til are situated, merge into one of elliptical foi'm, in which ore placed' taper vertical tubes, the circulation of water and heating surface being thereby increased. This boiler is in extensive use, anil for 'he past fifteen years has stood in the foremost rank as an efficient and cheap steam -pi-oducer.
In the Arnold boiler, a longitudinal tube extends for soi distance along the flue behind the bridge, and connects the npi and lower pai'ts rf the boiler through the flue. The introduotu of thii tube is claimed to inci-ease the eflfective heating surface and to split up the flame of the heated gases, so that more of their heat is imparted to the water. Another patented feature of this boiler is the barrel shape of the rings forming the flues. This construction gives a greater area of heating Gui-face thiui tl cylindrical shape and more strength.
The final division under which boilers may be classed ia that the multitubular or locomotive type, in wluch a eerie of small tubes placetl longitudinally are arranged within the shell, but such class is capable of further subdivision. In one type, the hot gases pass through the tubes, which are surrounded by water ; while in the other, the tubes are full of water. the hot gases circulate on the outside. In the latter type, the tubes are placed, in an iucliued position and are connected with each other and with A horizontal cylinder by vertical passages at each end. The u cyUnder is kept half full of water, and steam forms in remaining portion. Multitubular boilers have not I'received mi favour at collieries.
All high pressure boilers should be provided with two valves, which are best of the dead-weight tj-pe,a common form shown in Fig. 424. The valve, a, which is ball-slmpetl, is by brackets to a cylinder, 6, upon whichanumber of weight*, thi-ended. The advantage of this construction is, that there fear of any of the parts rusting and sticking. Instead of ploying only one set of weights, sometimes the valvesare arrani in groups, the discharge apertui-c of each being made exactly square inch in area.
Kconomical and quick generation of steam is considerably by delivering teed-water into the boiler as hot us possible. general procedure is to employ the exhaust steam to supp necessary heat. At East Howie Colliery, Durham, the ezb steam is turned into an old boilei'. Cold water enters at the
lucas .
M
rface
J for
of
Works At Surface.
anil in alloweil to fait on to a series of horizontal trays one beloK HDiither in step foi-m. The feed-water lienteil to 200', and is then forced by n donkey pinup the boiler.
Exliannt injectorc are becoming largely employed, these, nn their nnme implies, neeexhaUHt not live steam, and as they automiitically wimmeiice working the)' can be usw! with intermittently rnnning engines. The practice of bringing the exhaust steam into contact with the feed-water ta open to the objeotioQ that the greater part of the oU and grease which is in the engines is cnn-ied baclc into the boilers.
s thiN, nt Ahram Colliery, Lancashire, the arrange-
Via. 435.
t sliowu in Fig. 425 ifi employed. Tlie exhaust steam is turneil into a vertical chamber which is iu free com mimical ion with the atmosphere through an opening at the top. Feed-water enters near the Itottom through a pipe and is forced to circulate through a spii'al ami ou reaching the extremity passes by another pipe into tlie boilers. The exhaust steam which is in contact with the outside of the tube heats the water to nearly boiling point, and ns the steam lias free paiisage through the appliance, no back pressure is put on the engine.
Meohanioal Stoking.* — Firing by hand lieing n very labor' Consult .Uoc*; ri.y, J. ¥. spencer, Imi. C.E
TEXT-BOOK OF COAL-MININt!.
operation, uiunerous attempts have been made to BUpecsede it by mecbaniciLl means, and at thepi-event time many ui devices are in operation. They may be divided into two types — (a) whei-e the fuel 16 fed from a hopir on to a plate, and then canied (oron to the bai-s ; (6) where the coal is thrown on to the fire in small quantities at a time, by either a email revolving fan or k .1 shovel iiioved by a spring. fl
It may now be regarded that the claim made for such macliiuee ' uF using an inferior class of coal and raining steam cheaper may be conceded. With theui the fiiv is added to by the smallest quantities at a time, and the operation is perfectly i-egular, which call never take place with hand firing, unlesK one man is kept to each boiler. A saving also results from the fact that the fire doors
ly does this prevent smoke, butl r, uB cold air is pi'evented froal
gM
K of the
are rarely if ever open. Not it reduces the wear of the bi getting on tn the hot plates.
The bars in both tj'pes of stoked to all move forward together, to to I'etum by ones and twos at a time, leaving the fire behind, bi at the same time breaking it up. In this way the fire is gradual' carried forward into the boiler, tiually dropping over the brid| nt the end with the coal wholly consumed.
A niechaniral stoker of the coking is shown in Figs. 4X1 and 427. A trough, A, runs across the front of the boiler, the slack for consumption ie placed there. The projecting of the movable luis form the bottom of the trough, and as the travel forward cany with them a certain proportion of fuel each stroke. The bars run on i-oUere, rr. and e forward some 5 in. at the same time by tappets, the thickni of the layer of slack carried onward being regidated by distance between the bottom of the trough and the plute, p, wl
Wokks At Surface.
can be either raised or lowered by revolving the wheel, c. The shick imiUier; underneath a fire-brJok arch, which red hot, and is ignited ; the bant return in twos, leaving the lire where it wan Ciikeu to by the forward motion.
This operation in repeated twice a inmate, or as often as is desired, the rate being so arrangeil that when the charge reaches the end of the bars complete combustion has taken place. The clinker drops off at the end of the Imi's, and when tit to be pulled out is removed througli the iloor, d.
Coal ConTeyors.Mechanitnl stoked reduce Ubour to certain extent. They take ofi* cleaning and feeding the fii-es, but "till i'e<]iiii uftnual labour to fill the hoppeiv, and as these are usually some distance above the ground level, their feeding requires conHiderable labour, as the coal has to be thrown upwards to a height of at least six feet. The advantages of mechanical stoking are, therefore, not fully realised unless some automatic means are provided for conveying the coal into the hoppers, and the economy is alill more marked if, at the same time, the ashes lire also conveyed away automatically. The latter is of consideriible importance, the coal employed with mechanical stokers is generally of n far inferior character to tliat used with band firing, and consequently makes a larger pro- Fio. 438. jiortion of ashes, this being the caste when verj' inferior qualities are burnt,
Anan'angementforautomatically conveying the coal and removing the ashes, as fidoptod at a large colliery, is shown in Fig. 418. The coal, after being freed from all large, is raised by a bucket elevator, or Jacob's ladder, and delivered on to a channel formed of iron phites, in the bottom of which, opposite each hopper of the mechanical stoker, are fixed sliding doors, which are under the control of the stoker, who can ojien and shut them by means of skiitably arranged levers. Below each hole is a reversible trap which either directs the coal into the shoot going to the hopjiers, or into a stur&ge bin. Ti-avelliog along the channel in an arrangement known as a " conveyor," which coiisista of a series of plates fastened at intervals to a chain (Fig. 429). As the chain moves along, the coal is carried forward in front of each K.THper, and passes down through any of the openings which are not closed by the sliding duoi-s, and thence by the shoot into the feed hoppers.
A culvert with a Kimilnr conveyor runniup in it
ri
Text-Book Of Coal-Imikixg.
along the front of the boilers. The ashea are i-nked into this 1 culvert, and are earned ajong by the creeper to the end, where theyfftll into a trough and are raised by a Jacob's ladder into a truck, then pans away to the refuse heap.
Another form of conveyor consists of a spiral i-evolving in a
Msmieircular trough. If the spirrkl is made stivug enough tbt appliance works very smoothly ituJ gives good results with sm particles, but unless the shuft of the spiral is well supported I beuriiigi, it has a tendency to "sag," and soon wears bottom of the trough.
Coating Steam Pipes.- To pi-event condensation and loss o heat by nidintion, Ixiiler houses are often I'oofed in, not perhaps MO often lit collieries iis iht'y should be. The pipes conveying steam to the different engines should bIso be protected by some extCMial covering. A very guod cheap kiud is to bind on a. series of rough wood bars all the way rimnd the pijies. At MaiiemontK the covering employed possess the advantage of being movabU A zinc or sheet-iron tube the steam pipe, and a li of ashes is ploceil between (K 430). These tubes are made i e side, and a clasp, b, a.t the other. A great many different kinds of non-conducting materials fi covering steam pipes are in existence. The subject has been n carefully gone into by the late Mr. W. J. Bird, who states ths.t im an actual case the loss of steam was reduced fron 12.16 per oeDf when the pipes were uncovered to 1.86 per cent, with 1 pipes. The saving is increased by increasing the thickness of lJ covering, but this thickness has an economical limit, broadly be stated that the great majority of the compoaitioi give very satisfiustory i-esults, and that the worst of them is b than nothing at all. They are liable to deterioi-atiou from datnjj and heat, and should protected by a covering of tai' ; in pla where the covering is liable to receive blows it is f urthei' protec by a layer' of felt, followed on the outside by a sheeting of zinc.
a with a hinge, c
Works At Surface.
Workebops. — As the great mnjoiity of collierief* uitnitiiftted away fixtui towns, it is verjneoessai-y that they should lie provided with mechanics' shops, either o( h simple or elaborate character, depending ou the sixu of the mine. At the largest collieries nearly everything is mile on the ground, indeed, iji many cause, new engines ai-e built there, and tlie shops rival those of engineering establishments. At all mines a certain staff of mechanics have to be retained to attend to breakages, and if good men nre fo be kept, they must have regular employment. It is far better tu do repairs on the spot than to send them away. Not only is time saved, but the cost is reduced, as urgency work has always to be paid for at increased nites. In all cases a small lathe and diiliing machine should he put down ; in the smith's tikop, the fires should be blown by fans, and a steam hammer erected, this tool being perhaps the most useful about any coUierj-.
The practice of building and repairing railway waggons at the mine is now becoming common, and elaborate wood-working machinery is put down for the purpose. Boring and morticing machines and band saws ai'e then required, but in all cases the introduction of wood-boring macliintis results iu economy. If performed by hand, the operation Is a most laborious one. while a Kmall machine with revolving auger cheaply.
For sawing timber, either ft circular saws are invariably put down. For cro.-vS cutting, these are either fixed to a swinging arm and drawn against the piece of timber placed in front, or, what is better still, the arrangement shown in Fig. 43 1 is adopted. Motion is given to the beltdriven pulley, a, fixed on the shaft, b, in which a long keyway is cut, and through bevel geai-ing a movement of ivtation is given to the oii-cular saw, e. By means of levers, the saw can be pulled forward by the ntteudont in the direction shown by the arrow, cutting through the timber placetl befoi-e it. The pulley, II, remains in its place, but tbe key in tbe long key-way, and the shaft, 6, continues revolving.
I be puithased ver;- deeper or for props aud Itars,
Chaptek Xiv.
PREPARATION OF COAL FOK MARKEf
Neral CoiiBideratioiis. — No operRtion connected with mini has piissed tliiough giv-ater changes dining the puKt few yei than that of cleaning and sorting the coal. In thiK country mi many good coals existed that a ready sale was found for them in the state they came from the mine. Naturally the bext seamH were worked first, but as they became exhausted, the iiiferira* qualities had to be mined. It, therefore, became necessary n only to adopt a more etpial division into sizes, but to employ soi means for removing the impuritieer, in order that the dirty coal i) its clean state may become equal, if possible, to the good coal lie dirty condition.
The trade of the present day requires a more careful diviHion into aiMs than, it did b, few years ago, and for such means employed to obtain such division have become much more elaborate and made to perform their work moi-e accurately. The j coal coming out of the mine has lirst to be emptied on to a screen, i an operation which is perfonned by various machines called "tipplers." After passing over imd through the screen, the mineral is revived on travelling bands or belts, and the dirt picked out of it by attendants. It passes from the belu into shoots and thence to waggons, in which it leaves the colliery.
Ho long as the coal is large, the stones and dirt mixed with it can? be picked out fairly easily, but in the smaller qualities where thwB refuse is tine, other means have to be adopted, either dry or wetfl cleaning, called " washing." Both methods depend on the differeafefl specific gravities of dirt and coal. In the former, a current of aiej is directetl on to the mised material, and blows the lighter farther ihau the heavier refuse. In the latter, moving water i employed, which has the same effect. The former haBnotreceireil a very extended application, but the latter is not only lar;gelyh employed, but is becoming more and more used every ilay.
Although it would be impossible to give hei-e anything like complete description of the many varied types of instulatii which are carried out iu different countries to suit diffrat
Preparation Of Coal For Market. 3S3
conditions, yet the main featui-e: of tUe various parts of the apparatus used for coal cleaning will becousidered under their respecdve heads, and an outline given of the way several plants are arranged.
One importajit point must be dwelt on at the outset — vis., that it ifl impossible to force the trade of any district to take a certaio cIhhs of coal, and that cleaning and sorting appliances must be put down at each colliery to suit the trade of that district. What is acting very well at one place with economical results might work just <l8 ecoDomically at another place, but if the sizes and qualitiee made are not suited to the trade of the eeooud district, the result of its application would be a failure. Before, therefore, adopting anytliing, it is essential that the oonditione under which it is working should be compared with the conditions under which it will have to work in its new situation.
Circulation of Tuba. — As soon as the tubtt leave the cage at the surface, they have to be conveyed to the tipplers, and, after emptying, returned again to the pit mouth. If ihe screens are near the shaft, the heapstead will be covered with iron platee called " flat sheets," upon which the tubu can be turueil about in any direction. A better plan is to luy line of raiU and ensure movement taking place in definite patlis. The tubs can then be pushed, or the mils placeil at such an inclination tliat the tubs gravitate towards the discharging place. As they are genei-ally taken off the cage on one aide, and put on it again from the other, if it is downhill to the tipplei-s, it must be uphill going back, and consequently a more or less greater expenditure of labour is refjuired to perform the haulage, the amount depending on the size and weight of the tubs.
No better appliance hue been introduced fur minimising the coat of conveying tubs about the heapstad than that known as the " finger" or "creeper" chain, which weim originally designed by a Belgian engineer. It conKiais uf tin endless chain travelling; under the tubs, provided at intei-vaLs with vertical projecting pieces of iron (a a, Fig. 432) fastened tn the link):. The entire length of the top lialf of the chain rents on a girder of wood, b, which actK both as a support and guide. It is driven by a sprocket.
Fig. 432. Fio. 433.
or cogwheel, the teeth of which have a pith pial to ttiat of the chain. When a tub is conducted to the commencement of this chain, the tii'st passing hook seizes the axle and drags on the tub, which is released at the other extremity.
Such apparatus ia generally arranged as in Fig. 433. The tubs
Text-Book Of Coal-Misisg.
Wve the cage at tli shaft, and after beinj; weighed machine bC a, graWtate to the tippler at 6, the road being st inclined. The tippler is horisontal, and so placed that the tubs s on arriving there. Ther are emptied, and then piislied on by tliAl next foUowing tub, and proceed, still by gi-arit&tion, to t c ; the roaii here ia, therefore, at it lower lerel than the pit tool fIVom c tod the tubs are carried along by a creeper c-haio, the iomL tiling in the direction they tra\'el, until at d the level of tlie rwK f ifl at such a height alive the pit's mouth that the tubs gravilAt there as soon an they are released from the chain. Adv deeiml variation in this amingement can be made, the commou one being that instead of the tulw gravitating to the tippler they are lift
Fic. 434.
wheel Ik also fixed (Fig. 434). of a rope, while the other end i
there by a creeper, and tben gravitate bock to the . TbLs is perliapa the preferable BiTangement, an more heit it% obtained from the screening level to the ground.
1 n some ouies t hescreening eetAbliMbment is not at the pit's mouth but farther away, and the banking level is at the surface of the ground. If the screens ure any diitntwv awiiv, the tubs can I vi.ye.l there, and lifted t retjiiired height by any 1 the foruih of haulage whid have Iteeu described, ImfcJ instead of doijig this, it itcommon to raise them dire by iin ordinary steam lift.
With a stm lift for height of, sny, 30 ft., t' piston would have to equally long, and would I come not uulj' costly bud expensive to work. To over come this dilHculty a short< piston Ls used, but the pis< rod is oounected througli rope to u small wheel keyM on a shaft, on which a lat To the latter is attached one t
nected to a cage in wliich tlMJf
a placed. The piston ti'avelling a short distance, but altacht to the smaller wheel, raises the cage a much gi-e.itei' distance, a this is connected the laier diameter wheel.
Preparation Of Goal For Market.
3&5
After the tubs have been i-used thi height they can gravitate Imck to the shaft, but if the horizontal distance small they attuiu too high a velocity, unless their progi-ees is checked by Komo means. Such is done by placing wooden planks between the rails, od showii ill Fig. 435, and as the tub inpasMog over has to depress the end, ((, its velocity is retarded. These planks may also be placed to engage the sides of the tub.
A creeper chain as ordiimnly constructed cannot work round n curve. At Clifton CoUieiy, instead of employing flat links as is usual, a creeper is constructed of ordinary round iron chuin and works in guides, which not only govern the direction but also keep the chain do'.Tn. A section throiigli the ide Ls given io Fig. 436, It will lie seen thut only enough space in left open at the
ichine a
Ki<;. 43S,
top for the projecting piece to work through. It whh found that something of thiM kind was necGHsary, as the chuin was continuiilly going out of an ortlinary guide open at the top.
TIPPLBBS.— Thi-ee classes of this thoe discharging the coal forwaril ; (Ir) where the tub is turned backwards ; nnil (c) where the dischiirge is side w ay E,
Front Tipplers. — The owl i nary construction is shown in Fig. 437. The tub runs on and is locked in position by the lioup part, which catches oveithe axles. The machine is pivoteil ikbout a centre, 6; when the tub is full, equilibrium is unstable, and the machine turns round the centre point in the direction / indicated by the an-ow, emptying out the coal, the rate of turning ; being regulated by a brake. Ah soon as the coal is discharged, the centre of gravity falls below the axis, and the tippler returns to its former position.
The disatdvantiigc of this class is the distance couk have to fall on to the screen, occasioning considerable breakage. Seveiul devices arc in use for minimising such objection. In Kiggs' (Fig. 438) the front is eneloaetl by an upright plate hi
Text-Book Of Coai.-Minino.
its upper side, and during the revolution the coal is not disuliarged'fl until thia pkte nearly rests on the screen barB,
At Cowpen Colliery, Northumberland,* a sliding door provided at the top of the end tipplers to prevent breakage o coal when emptying. Half the tippler is covei-ed in with a fiw plate (fl b, Fig, 439), the other portion, b r, sliding o When the tub ia pushed into the tippler, the whole revolves abc the bxIh, (/, and no coal in discharged until the ead, e, of t siding door drops on to the fixed projecting stop, e, which puslu it open in the direction indicated by the arrow. The opening so made is small at the commencement, when the coals have to be dropped furthest, and reaches its maximum when the tub is just above the screen bars.
Back Tipplers. — With the object of I'educing the dista through which the coals have to fall, back tipplers weiv designed In these, the tubs run on in the direction of the arrow, A 440), and are pi-evented going too far by the stop, B. By 1
movement of the lever, L', the oatcli keeping the tippler position is withdrawn, and revolution takes place in the du-ecti of the arrow D, the speed at which this is done is controlled by 1 strap brake, upon which pressure is exerted in the direction of tM arrow, E, and during the revolution the are kept in proper position by the stop, F G H, consisting of two linlq F G and G H, each pivoted near its centre, Aa soon afi th contentR are emptied, the tipplei' retums to its proper positioi the catch is put on by the lever, C, and the end, F, of the secon stop is depressed as indicateil by the atTOw, this raising the eni H, and allowing the tub to be removed.
Side TippleiB.— With the tipplei just Jesciibed, the coal onljl falls a short distance from the tub on to the screen, and break is small. The same result caii be obUined by sliding doors, apphed to forward tipplers, but both have two objections, wliid|| are serious ones — (1) the tub has to leave the tippler by t' '
Fed. Inst, i. 95.
Preparation Of Uoal For Market. 387
same path as it went in, whicli occasions coDsidemble wast of time; (2) the discharge oF coal takes place from the end of the tub, which is comparatively speaking of small dimensions, and the tendency ie to deposit the coal in heaps on the Ecreen, such action being unfavourable to perfect removal of the small.
To remove these disadvantages, xide tipplers have been dei'igned. They eonsiat of two circles of iron connected together, resting on grooved whel Fio. 441, bearings, two of which support each hoop (A A', Fig. 441). The tubs run in from one fide of the appliance, and are supported in their inverted position by two wide pieces, B B, which piwject over the wheels. The revolution tn either be completed or return in the same direction, and the tub can either lie pushed thiough the tippler or pulled book into the place it originally came fi-om.
The advantage ai-e, if the tub comee out at the oppnmte end to which it enteiv, loss of time in tnauieuvring is avoided, and as the tipping takes pliice sideways and throughout the entire length of the waggon, the coal distributes itself equally over the whole sui'face of the screen. Tipping is easy, because when the tippler is in its normal position, the centre of gravity is above the 4utre of rotation when the waggon is full ; whereas it is below after the tipping. Equilibrium is unswble when the tub is full, but stable when it is empty.
A circular plate, terminating in a uitivable platform resting ou the bars of the screen, prevents the coal from falling during the tipping, and conducts it without shock on to the screen.
When these tipplers are revolved by hand the operation is rather slow, and, in addition, the rough unregulated movements resulting from handwork are prejudicial to the preservation of the coal. To increase the efficiency, side tipplers revolved by machinery are now used in the majority of cases. If one of the rollers supporting the tippler be made to engage with another wheel keyed on to a shaft which is constantly revolving, its motion is communicated to the tippler, which commences to revolve and discharges its contents, not with a sudden rush, but with a. slow regulated movement.
The two wheel can be connected by an ordinary fiiction or cone clutch, which la thrown in and out of gear by an attendant. This meiins is iit Harton Colliery. An attendiint dpreesett 11 foot treadle and throws the clutch gear into action. When th tippler has made )l revolution, he moves his foot aiid diae' the apparatus. The disadvantage here is thai tb to remain at the ti|>plerall the while it ia revoh his foot, the motion stops.
a
3S8 Text-Book Of Coal-M.Ining.
At Bascoup Colliery, this incouveuiem* lias been avoided by adoption of a friction coupling arrangement, represented In Fig. 441, which makes the tipping automatic. On the shaft, a, caiTjing the bearing rollers of the tippler, is keyed a friction wheel, A, and a second friction wheel, d, is also keyed upon the shaft, c, this being constantly involving in the dii-ection indicated by the arrow. If a third parasite roller, e, is put into contact with the two first by a given movement, it is clear that the movement of the sliaft, c, will be transmitted to the hoop of the tippler, which will 11 in the direction shown bv the arrniv. Upon the shaft,/,
to one of the hoops of the tippler, is wedeil a lever, g, aurrjingM counterpoise, h, and a small roller, 1, the latter' being able to Iw itself in a mortise cut in the hoop, and preveut the tippler fn turing when in its normal position. The lever, j, is also key upon the axle,/. This is double, and includes the bent or 1 " lever, k, one of whose branches carries the counterpoise, p, Ifnrer can turn upon the axle, y, by slight friction, and cfui 1 tailed by the propping, supporting, screw of the le ' ' parasit roller, e, is Ixiund to the elbow, k, by means of the a I, which cannot fall, as it is propped at 111. This support ] necessary, as when the tippler is not turning, the roller, e, does n touch the wheel, a. The counterpoise, h, having a greater wei than the counterpoise, p, will maintain it {p) mised wfaea small wheel, 1, is in the notch of tlie hoop, and, therefore, roller, e, will not touch either of the wheels, b or d. But, on t contrary, if the counterpoise. A, is i-aised, the lever, k, 1 free, the counterpoise pushed the pai'asite roller upon tba ti
effort frees it, for if iit any part tlie V grooves of the wheel
Flos. 44 J
Pkepauation Of Coal For Market. 389
frictinii wheels, And the tippler revolves. 'I'be caiinteriJoiBe, A, is ot held by the wnrkuutn whu oonduc-ts the tipjijog during the whole time this tiikes plnie. He merely raises it to stidi an extent thut the little wbeel (.oinesoiitof the notch, and iiftei'U'birds letn ito. The stniill wheel then runs over tlie hoop until it iiji) falls into the notch, the having then nine an entire
The lever are placed at such nn angle in their normal position that the arm, k, is free, and at the same time sufficient friction can lie ohtAJned on the wheels without touching the regulating screw of the lever, J, so that wear is taken up. The fi-iction wheels are designed so that only the smallest pressure haa to be exercised I against the pHmsite roller to cause it to grip. An equally small
H effort frees it, for if iit any part the V groo'
(coincide, the points of contact change constantly, and separation is easily made. This rutviinbige doe not exist in other forms of disengnging apparatus.
Duplex Tippler. — Mr. Henry Finlier bits introduced a tippler at Clifton Colliery by means of which two tubs are emptied each revolution. It consists of two duplicate parts, a and b (Figs. 443 and 444), placed diametrically oppoHite each other, and both carried by the central shaft, c, joumallnti in bearings, The two partn, It and b, balance each other in all positions, hut wlien u loikded tub, sliown at d, is run on the upjter part the weight turns the tippleiover, empties the tub, and bi-ings the lower pirt and the empty tub, shown at f, into the upper position, so that the hitter may bo removed, and be replaced by a full one.
The shaft, c, is provided with a brake wheel,/, for locking the tippler in position while the empty tubs are being re)>laced by full ones. The brake band is actuated by the lever, g, pivoted at
which automatically applies the biiike b,v the action of the weight, 3'. The outer-end of the lever, g, is i-sided to i-please the brake by the lever, h, at its centre, connected at ooe of it eiids to the lever, ff, and at the other end to a lever.j. The latter turns about a centi'e at one end. while the other is connected to a foot treadle, /.-, which can be depi-es.sed by the attendant.
The chief ttdiantage claimed for the appliance is that the speed . of tipping is greater than with machines of ordinary constmction, as one tub is emptied for each half revolution. This advantage can he obtained with any side tippler by constructing it to hold two tubs, end to end ; appliances of this type are by no meant: nnmtnnioQ, indeed, at the No. j pit, Lens Colliery, a side tippler is in use holding four tubn, all of which are emptied by one revolution,
A disadvantage of the machine, as at present conKtrucbed, that Uie tuba have to be withdrawn by the same way as they go on to the tippler, occnsioning loss of time in niameuvring. In addition, the revolution is effected by the weight of the loaded tub, and is more or less u rapid, unregulated one, tending more to (Arow the coal out. of the tub thin to empty it. Much ine-driven tipplers are cei-tainly preferable with tender coal.
The latter diaatlvantage is. to a great extent, i-emoved by on excellent arrangement of a bahnce-shoot. The upper end of Urn shoot is formeil of transverse segments of convenient lengths, arranged so that their inner surfaces form a curve approximating to that described by tbe tippler. Tlie two segments, I nnd m, are carried by the sliafts.p ami r. The segment, /, is counterweighted by the weight, p', at the end of the lever, a, and m by a , n, connected 10 a chain passing over the pulley, By the action of these counterweights the segments, load tii, take the position shown by dotted hnes at f and in' when they cm-ry no load. When the tippler is overturned, the segmental, / and m, break tbe fall of the load until this overcomes the action of tbe cnutiterbalancing weights, p' and n ; the segments than recede from the tippler, and permit the mineral to pass down the shoot.
SCBEEHB.— The old type of screen consisted of a number of bars placed side by side, at equal apart, at such an inclination that the coal, if emptied on to the top portions, slides down the bars to the lower end, and during its passage the Cue is removed. The width between the bars de[>ends on the size of the coal to be made. The form of the screen bar is of importance. They are often made nf a simple rectangular section, but Iw.rs of this form possess no advantage. They soon become choked up, and do nothing todii-ectthecoal into the apertui-es. After considei-able experience the section shown in Fig. 445 lias lieen adopted at Hascoup. Tbe top of each bar is triangular-shaped ; the two sides are parallel for. a short distance, and then converge towards the centre. The triangular ridge on the top dii'ectA the piece of coal into the openings, and as soon as nny piece gets a short distance through
Preparation Of Coal For Market.
it i-endily falls awny, For the space between If large quantities itre to lie dealt with
the burs gradually gets
on ordinary fixed bar either have to be [ilaceil at u high inclination, or increased in iiiiuiher, and the slope made less. In the former case separation ia not only imperfect, but the uoal travels at a high velocity, eKpecially tou'iknls the bottom of the screen, with the
Fio, 446.
result that it is not only hi-oken on the green, thereby iiiu-easing small, but with a tender am], a furtlier breakup results in passing into the waggons, aometimes producing as much slack tts is taken out by the screen. The velocity may be either I'educod by decreasing the inclination, or by placing movable doors at certain points, an ordinary fonu of this being shown at Fig. 44O.
The elect of reducing the velocity ia to diminish the ijuantity {Htasiug over each screen, and to inci'ease the cobt of cleaning, itecause a largei' amount of labour is required to assist the iwreeniiig by i-aking the cout over the btirK, For such reasons screens worked by mecluuiical jiower have received extended application during recent years. Either the bars may he movable, or the entire sci'een may receive a reciprocating motion.
HoTftble Bar Soreena.— A simple hut eHective device for increasing the sorting capacity of bar screeoB iB that adapted at Brinsop Uall Colliery, where an up-and-down motion Js obtained from two eccentrics, liaving a throw of about H in., one being fixed on each side of the sci-eeu. The screen consists of two sets of bam arranged alternately, one being fixed, and the other movable. The movable barii are about 4 in. longer than the fixed ones, and while the top ends of the latter are bolted to the framework of the sci'een, the former are fastened to a crosspiece of iron, the of which are turned and rest on a lever. This lever turns about a centre at its lower end, but the top portion I'cets on the eccentric, no that during the revolution of
Text-Book 01' Coahhixikg.
thiH eccentric, tbe lever is alternately raised and lowered,! carrying with it the movable bars.
Fig. 447 xhowB tbe arrangeme&i. m Yia. 447- All tlie lower bai-a are threaded o
the spinilie. A, the fixed ones i secureil at B, while the movable
project above, and a to the bar, C, wliicli rests lever, D K, working nbont the fixed oenti-e, I). By the motion of the eccentnc, F, the movable are raised, but only to u proportionate extent, an tbe bar, C, i fixed nbont 15 in. I'rora the fulcrum of the level-.
The most successful wreeii of this elias is tbat (employed bo largely on the Continent, the desi of which is due to Mr. Briarl. In its original form it foneisted of alleruete rows of tixed and movable , which when at Kst lay in tbe same plane. All tbe movable were fixed in a framework, married at its lower end by two cranks, at its iipfer extremity by two eccentiics keyed on a shaft, to which a notary movement is given. The ai-mngement was 60 constructed thitt during tbe lii'St half of the revolution of the eccentric, the movable bars were can-ied foi-ward above the fixed Ixirs, while in the latter half of the revolution tliey returned beloic the tixed Iwre, the result being that the cxal when tipped on to the screen was by the movable bare and carried forward ft distance to tiie thivw of th eccentric, and then rested ea 1 tbe fixed bai-H while tbe latter half of the stroke was being made, I To increase the capacity of each screen, both sets of bars were I goon made movable, this being eS'ected by driving each aet bv m eccentrics keyed on shaft:! 180 degrees ajiart, with tbe restiltl that each set of barn not only moves backwards and forwards, bat. T one Ket is above tbe other when moving forwai-d, and below whea J moving back, while at the begiiinitig and end of each I motion they ore level.
The screen as at present constructeil is shown in Figs. 448, j and 450. which are respectively a aide elevation, plan, and c section on line a h (Fig. 448), It consists of two seta of bars, 4 mid B.thi'ended on shafts, D D. The driving shaft. C, is onnked at two points, and two links, G tJ, are provided, one bi nected to A, and the other to Iwifs, B. These links are e pended at the fw end, as shown in Fig, 448. Distance shafts, 1 are provided for the purpo.se of keeping the driving levers, Q, peily spaced, and, in addition, it is to one of these shafts th t central bar of the screen is wedged, when the constniction is B that tbe distance between the bars is capable of variation. J 45 1, which is a reproduction of a photograph of a model, dea shows the two sets of bai-s, and the way they ai-e connected to t driving levers.
The great advantages of the Briart sereeii nre : tbat it may fc
Preparation Uf Vom. For Maukkt. 393
placed horizOBtal, thus diminishing the Leight of the beapstead; by regulating the speed of the driving shaft the quautity paseing over thm can elno be varied within certain limits, as the coal is moved forwards double the throw of the eccentrics for each revolution ; manual labour ig diminished; in addition, as the bars on up-and-down motion, the coal is shaken throughout it8 and perfect removal of the small ia obtained.
Its only disadvantage in that common to all bar ticreensthat the longitudinal Hlits between the bars allow long thin pieces of coal to pass through, and Huch perfect sizing is not obtained as in given by a sieve made of wii-e netting. In the form constructed in Germany even this objection ha been removed, as the bars instead of being formed of stripe, are made of channel ii perforations in the aide. At Bascoup, the dri' eccentrics originally employed have heen replaced by elb which absorb less work. The two fiystems of bars are movabi and driven from the same bkIb, on which the elbows keyed diametrically opposite each other. This modification, previously employed in Germany, allows the sti'oke to be diminiect by one-half, and to balance one system of Imrs by the other.
Jigging Soreena.Recipi'ooiting screens are en-tily and cheap!; constructed, and size thecoal very completely. They consist gene*! rally of woven iron netting carried in a frame and suspended f stays, two on each side. A rocking motion is imparted to whole Gtructure by means of reentries keyed on shaft, which revolved by a small steam engine (see Fig. 478). In general tl direction of motion is the longway of the sci-eeu, but in others is sideways. As the travel of the cool is assisted by the Hhakin| a jigging screen can placed at a smaller inclination than a f liar screen, but the slope must be stee[>er than with the Bi screen. Instead of wire netting, plat having holes puneht through them are used, and if these holes be circular instead oCi the sizing is perfect.
Recently Mr. E. £. Cose* has designed a screen which receivflQ a gyratory motion siniilar to that of an ordinary hand sieve. Tl chief problem was to support the screen in such a manner that will gyrate easily and safely, and at the same time to balance the centnfugal force and prevent its shaking the building. This has been done successfully by a method which consists tially in supporting one horizontal ])late upon another by of three or more double cones (Fig. 452). while the motion of gyi tion is given to the upper plate by a crank, a, upon u shaft [ ing through and journulled in the lower plat-e. The clues freely in a prescribed path on the lower plate, while the upj plate moves upon the other end of the double cone.
Tliese cones are guided in various ways, but when the screen
Amer. Insr. M.E. xii. 39S.
rovo-
Preparation Of Uoal For Market. 395
e coQical, BO that the weight of the screen has u tendency, to force the cone towards the centre, thus counteracting the ceiitrifupxl force to a great extent.
Fig. 453 illustrateK the appearance of a single gyi-ating screen. The lower plute of Fig, 451 has here become a box and the upper plate a screen box, provided with n number of trays, one above the other and inclined a pulled. a. in fixed to the shaft, h, above which ia ) the Hcreeu Iras.
Revolving Screens. — Instend of giving the eating motion, cylinders revolving about an employed. If the openings betwi'en the bars, or the mesh, if the cyhnder is of -ii-e gauze, \-ary through different lengths of the cylinder, several Kizes can be made on one of these screens. They are nicely employed for lurge coal as their capacity is small, only u few inches of the circumference being at one time in action. If any quantity is passed tiu'ough, the screen heconies overcrowded and acts like an elevator, lifia the coal a part of the way up the sideH and throws it back into the screen, pi-oducing n considerable amount of small. For separating the smallest sizes, as required for coal washing, such screens are, however, largely employed.
Spiral Scraans. — In the coal districts of (lennany a spiral revolving screen is used with success.* It consists of a long strip of plate, perforated throughout its length with holes of different sizes. This strip is wound into a spiral, and the ends closed and mounted on a shift. Th(>ir diameter is greater than their length, in some cases nearly double, and screening is often assisted by blows from a wooden hammer, or jerks from springs. The oonstmctiOD will be iindetetood from Figs. 454 and 45:
N..I
S'ilJ
TEXTBOOK OK COAL-MINlXl!.
Tlie i-onl to be sepui'sletl U delivered into the centmi part whicli is a cone-slipped circle larger in diameter in its outi' end, to facilitate the ilelivery of the larger pieces of coal whicii do not puss through the first series of holes. The conl passing through the first holes falls into the second division, 2, and by the revolt- tJon of the >Li-een is sqiaifited, the pieces too large to pass throi the second series of holes being retained upon the plate until ' reach a point in the circumference where a channel receives tl down where they are discharged out of the side of the screen. The coals passing thiTiujih the holes in division 2 are further separated, a portion passing through plate 3. All, Jiowever, that remains on this plate is discharged whn the point 3 comes
ANn 455-
opposite the channel in the <ircutnfei'ence. The Kama pro goes on uutit finally all the remalmng coal is (lischnrged thro plate 4.
It is claimed for this <device that it is smaller than an ordini revolving screen, that the space occupieil is lesH, that the coal not broken nearly so much, a saving of from 6 to 7 per a being experienced as compared with old types, and that t screening into the T'etpiii-ed sizes is most effectively done. speed of rotation vaiies from 6 to 8 times a minute, and with green 7 ft. 6 in. diameter, by 4 ft. long, 50 tons an houv c treated.
OreenwelVa Screen.— This sci-een* consiets of a numl parallel endletis chains Khieh travel between angular bat's 1 VBiying sections suitable for the size of coal to be made, a diminishing from the top of the screen. The liars re fixed, I the chain travels at a speed of 70 feet per minute, a is carried forward it falls between the ohMins and fixed 1 The dirt is pickeil out as the coal travels along. The advantfl
Brit. Siic. Min. Slinl. liii. 95.
Of Coal For Market. 397
claimed are (i) small first cost anil the stnall cost of repairs; (2) the Bmoll height taken up : (3) as the chains are level thera is little breakage.
VaryiDg tbe Sizes made hy Screans.— lu cun sequence of th exigencies of tniile, ilifi'ererLt size of coals are often reiiuired, and nch change niiinot be made ciact bv Vfirying the spaces between the baia or altering the size of the mesb. With wire netting screens, the only wuy to make the change iw stop the screen, take out the one riddle and replace it by another.
Plating. — It aometimee happens that tmscreened coal is required--that is to say. in the s*tate it comes from the mine, with none of the fine removed. In such caaes a methoil of " plating " the screen is employed. At Hilda Colliery this is done by an arrangement of cranks, a b, c d
tres, a and c. These cranks support a plate which, when not in use, stands 6 or 7 in. above the screen grating. If these cranks ore turned, the plate Ls lowered on to the screen and cloeee up all the openingB. The guides for the plate are curved, as the ci falling necessarily describe the arc of a circle.
t'miiha. — With the oi-dinavy bur screen, If one size is beinj; made and another retjuired, the Screen liaK to be stopped, and the bare pulled out and replaced by othera. To render this opemtiou easy, the hai-s are usually threaded in a kind of comb which, in its turn, is dropped into and held iti position by a shoe on eiich end. To alter the sixe of conl being made, the bars are lifted out of the comb, which is then replaced by another one having openings of a different width, into which the bars are replaced,
A better plan than this is that cf employing a scjuure bar, ou each side of which in attached a comb having iliflerent sized slot. Here to make an alteration, the screen bars are lifted out, and the comb bars
I rising c
turned over until the pi-oper-sized openings are up-
In other places a circular piece is cut out of the end of each bai- wMch reat on a
droular shaft, fi (llg. 457). The ,-paces between the bars are kept by hoTOeshoe washers, a, whicli can be added to or removal quite easily. One of these waBliers is shown enlarged at A.
Variaile Crost-btira. — All the pi'eceding aiTUDgciuente posHec some objectionable points. Not only is there a. considei'able loe of time, but in putting up or pulling down, llie bei often] become altei-ed and get bent and strtiined. To avoid thea inconveniences, Mers. Guinotte and Hiiai-t have deigneil tlittJ arrangement I'epi't'sented in Figs. 458-460, by means of whiofal the spacer between the bivi-s can be instiintaiieuusly varied without J stopping work.
The screen bars, an (Figs. 458 and 459), nre carried by spindle 1 b b, threaded with light-and left-hand FcrewR, which carry thai eleevea or nut-s, c e, having thread cut in the opposite direftioa. W
KiGs. 45S
The direction is the same for all the screws and nutjf, and all the sleeves wre threaded on the shaft, rf, common to the whole ff (see Figs. 448-451), the two being connected together tboj key, e, fitteii into a key-way running iilong tbo whole length o£ the shaft. The sleeves, ec, ai-e other-wise free j they turn with the J shaft, but can glide longitudinally upon it. If the shaft, d, i tui'ned, the sleeves and spindles ivtate, and consequently the I
separation of two consecutive burs will augment and 1
according to the direction of rotation.
If one of these outs is bolted upon the shaft, the bai would ! be displaced on either side of it, in amounts pi-oportional to their 1 diatjince from the fixed jxiint, or the same lung may be done by fixing one bar. j
Fig. 460 shows how the bars are connected amongst themselves, I and renders clear how the same relative distance is retained aftar 1 varying the original opening. To prevent confusion, the two sete J of bars are di-awn one above the other. Taking the upper set J first : the middle bar, A, is icedged in the centre of the acreea as ttm is keyed to the shaft, E ; coiieequently, when the shaft, d (Pi 458), is rotated, thii bar does not move, and the nut, b (Fig. i remains at rest, but ax the shaft turns, it necessarily follows thi
Preparation Of Coal For Market.
the screw, e, eutera the nut, while at the same time, the other end of the screw, c, enters the nut, 458), of screen bars, 460). Ah a result, bai-s B move towartls A, a. distance doubU that due to the pitch of the crew. That is tu say, if the pitch is 1 inch, and the shaft, rj ('gi uiake on e- fo birth of a I'e volution, the hars, B (Eg. 460), will move a total distance of un inch.
These harn, however, are not the ones nearest tu the cuutral liar A, as those of the lower set, D D, uiljuin A. ]f this set be now considered, it will be noticed that, instead of a bar being dxed, the screw, c (Fig, 458), is wedged on the shaft by a bolt, G (Fig. 460), paf.sing through it. Consequently, when the shaft is rotated, the screw turns with it and travels into the nuts on bars, 1) D, dragging them towanls tlie centre. Here the shaft makes
one fourth of a revolution as with the first set, and as the crew only works into the nuts on each side, these will move of aa inch, and bars D are only disphiced of on inch.
ABsuming, therefore, that the original distance between the was 3 inches, the result of turning the shaft is that the centre bar of the screen, A, does not move, but that the bars, D, immediately adjoining close in I inch each, reducing the space between the beia to 2 j inches. The burs, B, which are the next adjoining ones to D, were originally 6 inches from A, but as they move J an inch, are now 5i inches away, D is ij inches away from A, and, consequently, ij inches away from B. Thus the distance between the bars has been sltered from 3 to I J inches.
The other bars of each set move towards the centre in amounts proportional to their distance from it. The fuither tbey are away, the greater is their motion, as they are dragged a distance
equal to the fcuui of the motiou of all the right-and lert-hitm
The iJistance between the bare is indicated at the extremity the shafts by a jiduated dial. With the Rid of these cross-b without stopping the workings, any variation in nize required fo| trade purposes can be readily obtained, within the limits allowed for in conBtructioD, this being determined beforehand, nod as thl movement is performed by simply pulling a lever and noting finger on a dial, any workman can do it.
The cost is high, owing to careful construction and fittii required, but theiv is little wear, and the results obtained com pensate for the additional outlay.
Belts. — After separation by the screen, the '' large coal are I'eeeived upon belts, by the side of which attendant are stationed to pick out dirt and htonea with which the cotd ifl associated. The length of lliese belts in dependent to a great extent on the nature of the coal and trade of the district, but in all cases is greater, the dirtier the coal. In the Midlands, where MBveral qualities of large coal ai*e made, all of which are loaded tcether down the mine, it was at one time the common practice to wheel each tub from railway waggon to waggon, picking out the various quahties. This practice has been superseded by the employment of travelling belt. All the coal from the mine is tipped on to one end and gradually passes in front of a row of attendants, who pick out the qualiticH requii-ed fcr the trucks they are lauding, and let the remainder pns by to be taken oH' further on by other attendants loading difierent qualities. To enable many waggons to be loaded at one time, the belts are made proportionately long, frequently from 200 to 300 ft.
These belts, however, are moi'e for sorting the coal than fop cleaning it. For the latter [mrpose, even with the dh'tiest they rarely exceed 60 or 70 ft. The widthof the lielt is govemedl by the length the attendants can easily reach. If they a stationed on both sides. 4 ft. 6 in. is a common width, but bettis results are perhaps obtained with only 4 ft.
Belts may be constructed in several dill'erent ways. The foi most generally in use consists uf steel phites attached to 1 emlless chain. These chains are usually made of alternate ain4 and double links, which are preferably connected to the plaNJ forming the belt by being bolted to angle-irons which are live ' to the plates. This construction allows a plate to be taken out a replaced without cutting any rivets, as would have to be done the links of the chain were riveted direct to the plates.
A construction largely employed in Idincashire is to rivet p of angle'iron (a, Pigs. 461 and 462) to each plate and to 1 link, b, to them. The links of one plate overlap those of the ol and a bolt, e, is passed from the links on one side of the plai those on the other, thereby forming the hinge around whicfrl
Preparation Of Coal For Market. 401
pints turn, when they arrive at the driving tumble-or sprocketwheel. Sometimeii the plates are secured to the driving chain by a hooked bott, which pAKsea through a hole in the links and is secured on the top of the plate by a nut.
These belt** are driven by tumblers whicli have their xnaA shaped to engage with the links. This system of driving, with any average load, has been found to give better results than on octagonal drum, which is sometimes employed. Belts may eitlier
be driven fi-om the " leading," or " following" end, both of which are equally efficient, unle the load carried is a very heavy one; as the " following " end is moi'e conveniently situated to the motive power they are usually drive from it. They are supported at intervftlM by rollers ¥ig. 463), which serve the double pui-pose of lessening the power retjuired to move theu and of preventing any sag, and, as an additional Fig. 464.
support, the edges ti-avel in an angle-iron elide, yto/*. —
To reduce friction, roUers are sometimes pH fm
provided at the sides of the plates (Fig. 464), those running in the angle-iron guide already i-eferred to.
To readily remo\'e the dirt picked out of the coal, many belts ire provided with a partition in the middle, consisting of two angle-irons riveted to the plate. The attendants pick out the dirt and deposit it in this trough. The dirt is then carried along with the coal, but separate from it, and discharged down a shoot at the end. Where this ifl employed, the shoot leading from the Km. 465.
Ben is provided with a V- guard, which prevents the coal passing into the central trough, and directs it to the two sides of the belt.
For delivering coal from belts at points along their length the arrangement shown in 465 18 applied at Aldwarke Main CoUiery. A roller, a, diagonally across the belt at any point where deliver*
Shoot I
Text-Book Of Coal-Mining.
and Bweepa off the por! into the shoot. Thw roller travels in guides, and can b6 raised and lower-ed to give intrmittHt Jeliveiy. Many materials, such as hemp, wire ropes, Jcc, have been used in the construction of picking belts, but have not received much favour. In Lancashire, belts constiticted of woven wire netting are Jarfrely employed and possess one marked advantage, as thev rid the coal from any fine which has not been removed during the passage over the screen. Some coals have small pieces of dirt adhering to them, and these have to be chipped off by the attendants. A quantity of smail is produced which, if solid belts are employed, is carried away with the large coal, but if wire gauze ones are in use, the small pieces fall tbraugh and a more efficient separation results. These lielts are built up in several ways; a common foi'm is sho'n in Fig. They are obviously luisuitable for carrying the smaller qualities, for which plate-belts can only be used.
Revolving Tablea. — To economise the large amount of space occupied by cleauiBg belts, circular picking-tables ai often employed. They generally consist of a horizontal circular plate revolving about a veilical axis. The centre part of the plate Ls made higher than the circumference where the coal is delivered. All the dirt picked out is thrown on to this shelf near the centi-e and removed from time to time, while the coal is (lisobnrged at any convenient point by a scraper.
An improved an-angement, designed by Mr. Wm. Haydock, is in
where a mixture of coal and cannel has to
be very carefully soiled. A circular
—f vertical shaft driven by bevelled gear-
"Tlj ing, and in the centre is a raised plat-
, j-ii J .- form, or boss, 0, upon which the picked
mftteiial is placed by hand. Curved
on hinges at the drcumference, are pro-
-ided, and these direct the ijualitiesmade
into their respective shoots ; D is a
the i-aised portion, and is used tt>
turn the material otl' this part on
to the table. The mixed coal and cannel is delivered on to
the edge of the table by the screen, B, and the material which
occur-s in the smallest quantity is picked out and deposited OQ the
raised platform, G, that is to say, if coal and cannel iu being
sorted and coal predominates, then the cannel will be picked out.
The table revolves and brings the material up against the scraper.
e at Abmm Colliery, 1 IKD 46S.
at
Preparation Of Coal For Market. 403
E, which sweeps it off into the shoot, ns shown by the aiTOW. The caunel on the raised platform is swept oft' by the semper, D, anil dii'ected into its proper shoot by the hinge, F, The tables are 12 ft. to 15 ft. in diametet', and make about li I'evolutions pef minute. If a cannel truck is not in position iintfevthe shoot, this mineral Kkn be allowed to accumulate on the platform, C, by raising the scraper. D.
Loading Sboota. — When the coal reached the end of the belt, it is directed down a sboot into a waggon. These shoot*, if fixed, have to be placed at such an inclination that the ooal readily slides down them, and towards the end it attains considerable velocity, dashing violently into the bottom of the truck and causing considewble breakage. With a tender coni this becomes
FiQ. 469.
rfw
a serious matter, attempts have been made to minimise the damage.
A common procedure on the Continent is to make the shoot a series of plates, which travel along as a belt; indeed, it may be considered a belt, but instead of the plates being flat, each one is of angle form. The vertical ridges effectually prevent the coal slipping (Fig. 469). Each lump is gradually taken down the slope and deposited in the truck. The leading end is carried by a movable jib, and can he raised or lowered to suit the height of coal in the waggon.
An ingenious coal-lowering apparatus luu bwa introduced by Mr. C. Soar.* It consists en & BiiM (a. dotted line, c, actuated flD
at such a. speed that, as the belt delivers the coal from its enil, i shelf is always in a propeiposition to receive it. The top shaft, e, workain two travel blocks, I/, which travel up and down between the fixed guide bai-s, h. The whole apparatus can be raised oi' lowered, and held in any position, hy a. rope attached to a winch. Tbi cool has no greater' distance to fall when the truck is empty tf when fidl, and is put down as if by hand.
An excellent loading shoot is employed at Boscoup, turned about its point of support and lengthened or shortened aC will by means of a suitable arrangement. The part a (Fip. 47 1 ), can slide in the part h. A counterpoise, e, whose chain is lised to the part a, balances the entire shoot when at its minimum length, The variation of the length is made by a small wind
Fig. 471
mounted at the extremity of the puit a, and whose chain ' fastened to the end of the part h. A second windlass fixed to it allows the hopper to be raised or lowered at will ; the chain of the windlass, which causes the part a to enter the part 6, stretches the chain of the windlaes, d, thus making the whole perfectly rigid. A movable nose/, also allows a discharge at two points of the axis of the hopper without displacing it ; this nose bos another rfi/e, playing the port of a stopper and regulating the discharge.
With the old of this telescopic shoot, the coal can be direct d to any part of a waggon's surface, practically without any dn: Not only does this save expense, one man doing the work, butt most tender coal can be loaded without breakage. It isn that the shoot should be kept full of matei-ial.
TYPICAIj ILLUSTBATIONB. — Having described different parts of a screening establishment, a description of eevet arrangements as applied at colheries is given to illustrate the m they are combined amongst themselves. To a certain extent, ai
Preparation Of Coal For Market.
desired arrangement am be made, the one adopted depending, as
has been before remai'ked, upon tlie (.-onditions locally existing at tlie colliery, the amount to be treated, and the quantity and nature of th* refuse.
Pembertoii Colliery, — The screens here have fixed bars. All the tubs are tip{)ed on to the first one, which removes the slack, this falling into a hopper. All that passes overthis Hrreeu is conveyed by a ahoot on to a travelling wire picking belt. During the passiige of the coal along the belt, any dirt in removed by hundpifldng, and any fine particles which have escaped falling through the first screen pass through the opening in this wire belt, and fall into a trough with sloping sides, in the bottom of which it an endless sci-ew, which by its revolutions carries the slack into its pi-opei
reaching the end of the picking belt,
cond screen, which sepai-nteM it into two qualities ; the
fic
bu'
drops at once into
a railway waggon, while the cobbles which ]iass through this screen fall on to a travelling belt made of iron plates, and are conveyed to another truck. The arrows indicate the direction which the coal takes.
Brinsop Hall Colliery. — At the Arley Mine Pit, the coal, after pa.ing over a aci'een, in carried along by a steel-wire picking belt, 16 ft. long by 4 ft. wide, and having a mesh in. by in. To do away with the disiidvantage of fixed screens, the lower portion of the bars ai'e made movable by the arrangement already described. The Eci-een is divided into two portions by a movable plate, alxjut 14 inches broad, working on a hinge at itf, upper end. By means of the hinged plate, the coal can be steadied on to the bars, and, in addition, a vertical rake-stop in prorided for the same purpose. The bars above this plate have an inclination of 14V in. to the yard, while that of the lower ones is lyl in.
Running the entire length of theinckiug beltuud on sedan,
ai-e fixed two planks on wliich the chip"' " ' all the slm-k
pisxluced by this operation fa"' "sUes and
INwses down a shoot into th he helt
a second screen is fixed wit) 'Akes out the cobbles, the ren
AU the dirt and inf id
4o6
Text-Book Of Coal-Mtning.
thrown on to another tmvellmg belt running by the eide of tM first one, about 20 ft. away, but placed at ft slightly higher inclination. Fig. 473 shows an elevation of the entire installation, while ig- 474 gives a eross-section of the arrangemeQt of the belts. These dirt belts are formed of old flat steel-wire ropes lying side by side, and are about ig in. brand and 37 ft, long. Any got
coal is chipped off aad thrown down a shoot on to the se<.-oad main screen, while the dirt and inferior coal on to the end where they are divided, the former being directed down a side shoot into tubs, while the latter paiiseB over the end into land sale carts.
Fju. 474.
Jjtzii
FiC!. 475.
Hilda Colliery. — This colliery is situated in the centre of town, and tlie ariBugement of the heapstead affords a fine illust tion of what can be done in a confined Kpiice if retjuired. On led ing the cage the tubs gravitate to a turntable (a. Fig. 475), ( can either be passed to two tipplers used for land sale ; to a thi road, if dirt or refuse ; or to a fourth road, if for the screens, wIm they are caught by a creeper and lifted up to such a height thi when released they run by gravity 011 to the weighing machi where they are automatically arrested by an arrangement show in Fig. 476. A rod, a 6 c, is slung from a convenient place, i the end,c, being kept in position by itfi own weight and prevent
Prepahation Op Coal For Market. 407
fftUing to the gi-ound by the coUar, d, on the vertical rod. A tub ii< tihown held in {uiaition on the weighing tiiHoliine. The next tub coming in the direction
indicateil by the arrow, v, ,,/,
striken the rod near the point, 6, and as it proceeds dovm the rails Uft up the end, c, and i-eleaees the tirst tub. As mon, however, as the back end of the tub passes the point, b, tlie link drops down and lockfl the tub, keeping
I the r
the succeeding tub releases it.
After the tubs ai-e weighed they run on to a machine-driven side tippler and are discharged, thence proceeding to a second turntable (i, Fig, 475), and being turned tlirough .a riglit angle ; thence to the haft. The whole area of the flat sheets is about 60 ft. by 45 ft., a being about iS ft. away from the pit, and li about 15 ft.
After being tipped, the coal i a received into a regulating hopper, and thence passes on to aware-gauzejigging-screen, in which three gHiuesaresuperimpoHeilone above the other (Fig. 477). The fimt takes out large coal and delivers it on to a picking belt ; the second, which bus a mesh inch square, separates nuts, which are delivered on to a small cross-belt, iind from thence to a picking-belt running parallel with the main belt; while the third gauze separates the remainder into peas and duff, or tine. By an arrangementof traps, the nuts and peas can be I'eniixed and loaded as one class of coal, and the peas and duff as another, or, if I'Ciiuired, all three can be combined ; in addition, the top screen L-an be plated and unscreened coal made and loaded at the far end of the main belt, a reversible trap being provided there for such purpose.
Placing the screens one below the other, without any shoots to conduct the material [lossing through one screen on to the head of the screen immediately below, saves an amount of vertical space ; but the sorting cannot bo so accurate es is desirable, as the coal which falls through utar the base of the top screen scarcely passes over the next screen at all, but at once goes to ittt Khoot. If all the coal has to be delivered to the top of each screen, it' level must be a considerable height above the gm come this disndf-antage a common practice
4o8 TEXT-BOOK OF COAL-MiyiNG.
tield is to convey the coal from the base of one screen to the top of the next one by means of conveyors emiilar to those olreftdy deBcribed.
Hewlett Pit. — At the No. 2 shaft two separate shaking ea-eens 111% fixed. The general an'sngement wi!l be seen fivm Fig. 47S. The coal is tipped on to the ttiftt screen, to which a racking motion is imparted by menna of an eccentric and rod, e, the screen being suspendeii by four hitch, two of which are shown at a & and a' b'. ThistirKt screen is fixed at an inclination of 14 in. to the yRrd, and the meshes ai-e i in. sijuare. The round coal passing o falk on to 11 wii-e picking belt fised in '
Fig. 478.
where the best (merchants') coal is picked ofl, the cobbles paHsiotfl over the end into a truck. All the material patting through the!] first screen is conveyed by a shoot to the head of a second sa'een, suspended by the arai.s, e d, c' d', wliich also receive a recipitjcating motion by an arm,/, and eccentric keyed on the s:inie shaft as the first one. The meshes here are j in. square, and the mineral is divided into nuts and stack.
Anicbe Colliery, Frftooa. — Only one tippler is used, tfai living a machine-driven side-tip one, and all the is tui on to a Briart screen, placed on a small inclination. The 1 coal passing over this screen is conveyed down a shoot on to tiiivelling hempen picking belt, No. I, which carries it to a way truck. Dining its passage there the coal is sorted by faaOi uito two sizw, part being placed on the No. 3 belt (Figs, 475! and 480).
All the passing through the sci-een with oscillating 1 falls on to a jigging-screen (No. i), worked fiwm an eccentric i
e ordinary manner; this sct-een is fixed at right angles to t
it one, and the motion is sideways. All the coal parsing over
Preparation Of Coal For Market.
is carried on to belt No. 3 ; all that falls through dtopH on to a second jigger fixed immediately below the fii'sf, aod exactly similar to it, except that the holes are Einaller. The small coal passes throiigh, fulls on to a, belt, and is at once conveyed to the trucks ; tlie larger coal passes over the soi-een and drops on ta a travelling belt, No. 4, which runs parallel to No. 3, and at right angle.' to the screen.
The coal from the first shaker-sci'een Is taken by the belt dii'ectly to a waggon, but that from the second screen after being carried along on its picking belt, falls on to another belt at right angles, and is conveyed to its proper waggon.
A noticeable feature about all the jigging-screens which the author bus Keen on the Continent, is the fact that they are made of perforated sheet iron with cii-cular holes, no wire netting,
Figs. 479 and 480.
T-f
either with square or ciiular boles, having been uiet with. Tiie advantage of circular holes seems to be that only the pi-oper sized }>ai-ticles can paae through ; with 8<|U&re holes, the diagonitl line is longer than the sides, and Inrger pieces than the square of the Diesb can fall through.
No. 6 Fit, Baaconp. — The collieries of Mariemont and Bascoup possess very complete screening-plants, which allow the different kinds of cil to be easily separated and cla&sified. That at No. 5 Pit, Bascoup, is the most recent and complete one. It is shown in plan and sectional elevation in Figs. 4S1 and 4S2. The former is to scale, while the latter, for the sake of clearnusK, is a diagrammatic representation. The siTeen, picking belt£, &q., are situated in a building, 142 feet in length, and 92 feet in width, placed in the axis of the pit frame. The building comprises three levels or stages. ( ist) The floor is used entirely for the haulage of full and empty tubs, and inclines towards
410 Text-Book Of Coal-Miiting.
winding sliaft, so 03 to allow the waggons to return there gnivity. (2nd) The intermediate stage is honEontal; it is at this level that the handling (sorting of the coal, &c.) is done and where the principal supervision ia required. The railway level or charging floor. The freight roads are not horizontal, being inclined in various ways in oi-der to facihtate the handlin[[; of the waggons.
Cireulation of Tuba on the Upper Floor, — As soon as the tub( come off the cage, they are pushed on to one of ttie four ways' {a, Pig. 4S1), and conducted by a ci'eeper chain to the top of an inclined plane whose summit is nt the commencement of the curve leading to the tippler. At this point the tubs disengago themselves from the chain and continue running, partly by tb acquired velocity, which is very feeble, however, and partly by thi
Fig. 4S1.
way
'tal, I
' an II
the
Bi'tiou of their own weight. The height of the incline ia detour mined expei-mentally, so that the waggon stops on arriving at the tippler, b. Each succeeding tub pushes away the one thiit bus just been emptied. The empty tubs gravitate down the roads, e to the rear of the shaft at d. The direction of motion ia showi
Soreeiis taking Tioo Si:M. — The two groups of apparatus, I and 4, make two nizes, large and " toiU-venanl." From ) tippler, i, the coal falls upon the Briart screens, e, inclined jit i the large coal remaining upon the sieve passes into the hoppei", inclined at 12°, from which it is conducted to the plA The coal passing through the screen is received upon a ahalci shoot, ff, which throws it upon two revolving picking tblea, I where the dirt is removed ; the coal falls into a loading hopper.
Scrgeiia makinii Five Classijicaliona. — The two groups i, apparatus, No'', i and 2, are much more complete than those yM described. They make five sizes: large, "f/ntVfcteriMi
tiletde moineaux,"' and fine. From the tippler, 6, the coal iit emptied on tu the first Briart screen, i, inclined at 10°; this retainci the large coal, which passes into tlie upper, f, whera it unites with that fumiished by Nos. 3 and 4. which posses through the screens is received upon a shaking shoot, k, inclined at 1 5 , which leads the coal to the commencement of a. second Rriarl horizontal screen, I. The " gai/ltUries" which pass over the screen are pushed on to the cleaning belt, j, and cai-ried into the loading hoppers, from which they are put into trucks. All the coal passing through the second sieve, I, falls donn a shoot and is lifted by a bucket elevator, m, and delivered on to the third screen, n. This is horizontal, and retains the " gnitielint," which then go to the belt, o, by means of which they are conducted into a. loading hopper in the name way as " gnUhUriea." The Mime hopper also receives the yaHkliitt furnished by the
Fig. 4Si-
other screen of this group. Finally, a fourth screen, fj, receives thiit which falls through the third, by the aid of a i%httkiug table, V- The " tettg de moineaux," which pss over screen 2', aw received on a cleaning belt, r, oud eoudueled to the centre of the work-Khed, where they can either be loaded iu a truck or sent back Qji'ain by a second belt towards the screen, and muted with the fine after it has Ijeen washed, the course adopted dejiending on the demands of trade.
The fine, which passe** the four screens, faiU into the hopper, a, from which it can either be loadetl directly into trucks by a shoot, or sent to the washer by means of the conveyor and bucket elevators, it and r, which deliver it on to n reciprocating table, where a further sizing takes place, to be desci-ibed later on. The fine, instead of being transported by belts, and loaded at a central spot, like the gaiiltltrie, gnUletim, and tfUt ile Tnoimaux, is either loaded into a wa(;gon at the place where it is sepai'ated, or if ilestiiied for tlin washers, b sent there dii-ect by belts, 4o., from group No. I. No, 2 group can also send its fine to the washers, but as it is rather removeil from them, the limtkll coal is taken by a liell to the bucket-elevator of the first group.
Text-Book Of Coal-Mining.
Wathery. — All the coal destined for the washery, ufter being lifted by the bucket-elevator, is dehvered upon a i-ecipi'ocatiiig table, formed of a series of pei-forated iron plates, nrmoged ona below the other', wliicli subdivide it into the following Kiies: dust, from o to 5 mm., and giuinn, from 5 to ii, from 11 to 16, and from 16 to 25 mm. Each of these four sizes is washed separately in a manner similar to that described subsequently. The two former in felspar washers of the Coppee system, and the two latter in the uut-wnsbers of the same Urm. The three sizes, 5 to II, II to 16, and 16 to 25 mm., are mixed together agmu after washing, and sold. Alxiut 40 tons per hour can be treated-
Croaa Greek Collieries, FennaylTftnia. — Anthracite coal cannot be sold in the state thut it comes from the mine. Owing to its compaii't nature, and the practical absence of volatile matters in its composition, it will not burn well unless the lumps are nearly of a uniform size, and are free from dust. The method of preparing anthracite coal for the market is therefore entirely diflerent from that adopted with bituminous varieties. LTniform and varied sizing is essential, in order that when the lumps are burnt the air may have a free passage between them. In addition, large amounts of slaty or argillaceous coal and carbonaceoiis shale are intimately induced with the pui'e coal, aud cannot be separated by hand-picking ; it is also generally impossible to sell all the large coal as it comus from the mine. Por these reasons, machinery has to lie employed to break up the larger
The more recent and elaborate machinery employed in Pennsyhanirt, has admirably described by Mr. E. D. Coxe,* but as hia memoir covers 77 pages ot printed matter and is illustrated by 43 plates, it is impossible to give anything but the briefest summary hti*.
The coal is first tipped on to a tinted bar screen, which allows most of the small coal to pass through. Tlie large coal passes by shoots on to a movable bar screen, and all the small that falls through is joined to that obtained from the fixed bar screen. XJp to this stage, practically only two sorts are made, each of which is treated The lump coal ia then divided into three sorts, the first being the shale and slate, which goes to the dirt heap ; the second is pure coal, which is sold as lump-coal, if there is any market for it ; the third product consists of pieces of cool and shale adhering to each other, and is too impui'e to go to market in its existing condition. Sometimes the shale can be chip{)ed off with a pick, but more geneitilly the mixture cannot be cleaned in this way, and has to be put thivugh a, set of crushing I'ulis, and then ti-eated in gyrating screens, aud the dirt picked out. The pure coal also passes through rolls, and is afterwards
Amer. Inst. M. E. sii. 39S.
Preparation Of Coal For Market. 413
ieiini-iiteil on. gyrating screens, into several sizes or qualities, similar to those mentioneil below.
All the coal that hou passed through the fixed and movable Utr screens is conveyed to two screens, each of whioli make three sizes, called steamboat," " broken," and " egg." The smaller coal passes to another pair of screens, known as the stove or wet screens (A), which are situated a little lower down. The steamboat coal from both screenct passes into a picking-shoot, and from thence to a loading-shoot, provided all the steamboat coal can be sold. If it cannot, a portion is passed through a set of rolls, and separated by screens into " broken." egg," stove," " chestnut," pea," buckwheat No. i. No. 2, and No. 3, and dust.
All the coal which goes to the stove or wet screens (A), ia divided there into stove, chestnut, pea, and No. 1, 2, and 3 buckwheat, and slime. These screens are worked wet — i.e., a large amount of water is put on them, ils the coal they treat contains mud and other impurities, and in oi'der to make a good separation it is necessary to wash it. In addition, alt the wet coal from this screen is cleaned in jigging coal-washers.
The movable bar screens are a modification of the Briart screen, arranged so that the bars only move up and down half as much as they move forward. With this construction the coal, although fed forward with rapidity, is not thrown up and down so much. The gTating screens were designed by Mr. Coxe, and have been previously described.
The rolls employed for breaking the coal dilfer in one point froui those generally adopted. The difiWrenc is in tlie form of the teeth. The rolls used are known as corrugated rolls, and the teeth are continuous from one end to the other. There are no points. The end of the tooth ia slightly rounded, and the doing the work is cast in chills, so as to give greater endurance. It is claimed that this type of roll breaks a lump of coal into two pieces of nearly the same raze, while with rolls of ordinary construction the pointed teeth brek the coal in much the same way as the stroke of a pick would do ; that is, the lines of fracture radiate approximately from the point where the tooth strikes the lump of cool. Experience has also shown that separate rolls should be employed to break the coal into difi'erent sizes, as although all sizes the size which is being broken are alwaj-s made, yet the most economical method is to break any size as nearly as possible into the size immediately lielow it. In other words.it is more economical to break "lump" into " steamer," then break "' steamer " as far as possible into " broken," the " broken " into " egg," and so on ; of course, at each time eliminating all the coal below the size that you wish to break, beforo passing that size through the rolls.
Automatic shale-pickers are used in some parts of the establishment. They dejtend for their action on the fact t'
the coal genemlly breaks into cubical masses, the pieces uE slme of the same length and width are of much less thickness. Henee, if a quantity of shide and coal which has been passed throujjb a screen and properly sized, the shale, if placed edgewise, would drop through a elit over which the oonl would ,
COAL WASHING.Below a certain aiie it is impossible to pick out the flirt mixeil with coal, and recourse has to be made to washing, for which a large variety of machines have been designed. Their principle and action are similar iii every respect to those employed for ope dressing. but here it is the lighter material that is valuable. The theory of the subject is that bodies of different specihc gravities fall through water at ditTerent velocities, the heavier more quickly than the lighter, that is to say, if both piecett are of approximately the same sise; because it is obvious that a larger piece of a lighter material meets with as much resistance in passing through water as a small piece of a heavier material. For such reaMcn a preliminary -siKing should alwaj-a take place before wasliing.
Sizing Apparatus.The small coal which passes through the last screen is generally further suldivideil, either by means of revolving sieves or trommels or reoiprotatuig tables. The latter, do the work better, but are not so convenient, as watr cannot be employed ; with trommels a stream of water is introduced and materially assists the operatjou. The disadvantage of a trommel having a mesh of varying size is that all the material has to pass over that part of the screen which has the finest mesh, and consequently the wear is considerable, but with such a aoft substance as coal this objection is not very serious. It has been found that revolving screens require patching in the small (fins) poi-tions about every'ye.ir; their general life is somewhere from five to seven years, except when there is much sulphur present.
Revolving screens are unsuited for separating sizes below J inch ; and an apparatus which retains its German name, 'ipiuJcatten" is employed. It conaistt; of a series of pyramidal boxe, upon whose sloping sides no umteriaJ otn settle. Each box is larger than the previous one. On entering the first trough, the speed of the water containing the material in suspension is the particles of larger size settle down a little, and escape the velocity of the current, so that they soon reach the bottom of the trough.
The number of boxes determines the number of sizes made. A stop-cock is provided at the bottom of each box, thi'ough which the deposit can he swept out at any time by opening the tap ; this device avoids any neceaaity for interrupting the main flow.
Trough Washers. — The first type of washer consisted of a trough, provided with a series of vertical stops, which prevent the coal and dirt passing on (Figa. 483 and 484). At the point whei the coal is washed the supplying channel is divided into two ; into each of these divisions the stream of unwashed coal can be
Preparation Of Coal For Market.
45
directed at pleasure. As soon us one tixjugli is full, the dirt coal aiiii water is directed into the other, and a ciin'ent of cleiiti water turned into the first trough, while at the name time the deporats of coil which have accumulated against the stops, a Viiis. 483 AM) 484. nre iigitated by the attendants with rakes, with the reMilt titan the lighter i-oal is carried over the obstruction, while the dirt (pyrites principally), being of luglier specific gravity, remains behind. The waidied coal passes on to an inclined sieve, where all the water is drained away, and thence by a shoot into trucks. As soot) 8H all the coal is removed from the wa.hing troughs, n hole in the bottom (shown at f>, in Fig. 484) is opened at the liiwer end, the vertical stops ai-e lifted out of position, and the aecumulatioDi of dirt are swept down and pass away through the hole, which ih then closed up again. The vertical stops ai-e returned, and as by tbia time the second trough contains a full charge of unwashed cool, the stream of dii'ty coal and water is diverted into the first trough, and a similar series of operations to those just carried on in the second channel.
It is obviaiiB that a krge amount of IhIkjiiiis required. To reduce this charge, mechanically moved rakes are employeil, the best form of which are those i-along backwards, not forwMils, or the unwashed material is likely to he pushed over the diim. The amount of water required is also very great, and the quantity of coal that can be treated is limited. Altliough the cost of working is large, yet np-keep and first cost are verj' low, and it appears that, under certain conditions, a trough washer gives us good results as any other form.
Robinson's WttBher.— This wellknown macliine consists of an inverted truncated cone, with a diameter at the top iihont four times that of its diameter at the bottom (Fig. At the Iwue of the cone is fitted a water-jacket, a h, into which water under pressui-e can be brought, and which jmsses into the machine through a series of perforations all round the cone, the diameter of these holes being generally about in. Still lower is a cylindrical chamber, c, conti'rolled by two slid
no. 4S5.
Text-Book Of Coal-Miking.
by the levers as shown. A strong shaft, /, is fixed vertically exactly in the centre of the cone, and to it, through the medium of iL cast-iron cros.heidi, are bolteit four arma, two of which are shown at g und h. Each of these arms carries three iron bars, t, projecting downwards and oiirveil round at their loweiextremity, in order to work close against the sides of the cone. The central vertical shaft terminntea in four arms, k. Rotation is effected by bevel gearing.
The principle of this machine is the one common to all current classifiers — vi., that if two equal -sized particles of different specific gravities are allowed to drop through a stream of water, by regulating the velocity of the water it can be ai-ranged that the particles of highest specific gravity shall continue to fall, the lighter ones are driven upwonls. Within certain limits, it not necessary that the particles treated should bo all of the size, but it is perfectly clear that, unices some preliminary aiii) takes place, there is a danger of either coal passing away witi the water, or diii) being carried up with the coal, both of which results ai'e unprofihible and undesirable.
The actual operation of washing m conducted in Uie following manner : Coal is introduced at the top of the cone and falls into tiie water, and is kept in a state of agitation by the revolving arms. Situated some distance above the machine is a cistern, from which water under pressure is brought and introduced into the base of the cone through the pipes, a and b. the reguli distribution being effected by the holes in the plates ab-ead] alluded to. The water-pi-essure is so regulated that it is sufficieaf to lift up all the particles of coal and carry them over the top the cone, while it is not strong enough to force up the dirt, whieb falls downwards and accumulates in the base of the cone. Itft removal is effected by the two sliding doors. As a rule, e is closed. When the space between and d is full, d is closed and e opened, and the dirt discharged. The wosheil coal, after passing away at the top, is received on a perfonited plate, and the greater part of the water drains away.
The success of this maclune depends to a very great measure on the carefulness and attention of the attendants. The chief pointe are the time given to flushuig, and the regulation of the discharge of the dirt. The machine is compact and occupies tittle space ; it is also sti'ongly constructed and is not liable to breaks down,
CoppSe Machine. — A great many of the very largest washingestablishments are fitted either with the Coppee or Liihrig machines, both of which are identical except in small details. Two different machines are used, one for washing the coal from |-inch upwards, called the " nuts washer," and the other caJled the "felspar machine" for washing coal of sees from f-inch down to powder.
by the -.
M
Preparation Of Coal For Market. 417
The nuts machine (Fig. 486) is of the ordinary contitiuoUH jig type, and consists of two compartmeDt, a and h, in one of which the piston works, while the other is provideil with ft perforated strainer, slightly inclined from front to bock. The piston, p, receives an up-nnd-down motion by being oonnected to cranks on a horizontal shaft, and the amount of this throw can be varied from ij to 4 in. An opening, w, runs along the front of the washing compartment, and through this clean coal continuously passes away. The shale is dischnrged through a small cy 1 i ndrical com partment,
d, connected to the side of the casing, but which starts above the level of the strainer, leaving a free space between the strainer and the lowest end of the compartment of about 3 in. It is open at both ends and communicates with the outside of the machine through the opening, r. It is provided with u sliding door which regulates the discharge of the shale.
When the unwashed coal is introduced into the machine and the piston descends, it drives water into the compartment, b, and lifts the bed of the material resting on the strainer. On the return stroke, the heavier dirt falls faster than the lighter coal, while in the upstroke the lighter coal is lifted farther than the
Fios, 487 And 488.
M
I+4H-1
remit U, that the two substances separate into
' of course, the highest.
r M nf ' "ilar construction, but differs mateii-
It consists of a box, divided into
linal partition, in one of which the
r
Textbook Of Coaiuisixg.
piAoii works u befora {Kgt- 47 and 48S). It is minded into two or wiaetiBMB three oomputoients in thedtractaon of its length, each wwimimirwring with tlw other bj opmapt, o, aioBg the eide, uul through these the washed oosl pMna unj. In t£e nuts washer, the holes throogh the neve *ie 'P'—miT than the size of the iuatrisl being trated, and ooDaequeiitljr no di>- cjtsrge taJcef plane thioogh them. In the vMchiDe, thej are hur than the material, and the dirt paM8 throw the neve into the lower part of the appaiatua. Three aevs aiw generally employL The dirty ooal is introduced at one end and gnwlnally paseee down over the remaining gratings, the dean material being tinally discharged at the opposite end.
The chief peculiarity is the introduction of a layer of fear, from tKO to three inches thick, on each sieve, whose specific gravity is greater than that of the material to be concentrated, and yet less than that of the gangue. The raxee of the pnrtids of this bed are largs-than the holes in the sieve. The whole framework of the machine ia tilled with water up to the level of each sieve, and as the pistons work up and down, a volume of watr is forced through tiie hole in the bottom of each deve, lifting the bed and the layer of material on it, and then allowing the whole to hll gun on the return stroke. The lighter coal rises to the sorfaoe, uid the heavier dirt gnuluoUy tiniLj its way through the bed or felspar, when it falls into the bottom of the compartment to be removed from time to time. It is essential for thorough cleaning that the size of the felspar should be as small as allowable, and that the particle>( of mineral forming the bed should be of convenient denicity, have well defined rectilinenr angles, and be of great darility to rexiot wear and teiir. A point of considerable tmportAnce is the proper regulation of the deliver)' of water, which is controlled by a tap ; upon thix depends the progress of the material and the time it operated upon.
For very dirty coal, perhaptt 00 machine does its work so efficiently ft* this ; indeed, every one gives it the character of removing dirt. It is, however, exno. 489. pensive in firet cost, but
-/- ' . percentage of dirt origin-
"'"y present in the comL,
( -USfA- s'Afir If it is small, and, say, <mejviiiimtr
coke from the resnltiif j
-1"/' .. the other hand, where the J dirt amounts to from to 30 per cent, and only 3 to 10 per cent, is taken away, the ool is very bad. With a dirty coal, probably it is beat to use mach' of this
Preparation Of Coal For Market. 419
Fig. 489 gives a. duigitimmatic representation of a woshety in South Wales treating about 100 tons per ilay. The fine cxmI from the screens (bitra I in. apart) is raised by a bucket-elevator and delivered into a revolving screen, and separated inhi three portions: (1) the large, which passes over and goes to a "nuts" washer ; (2) a sits between J and f io., also treated in & " nuts" washer; (3) the size below iu,, which is carried olf by a streain of water and delivered into a second revolving sci'eeu, having perforations in. diameter. Two sizes are made hereof i) f in. to I in. ; and (2) J in. to nothing. These are washed separately and then re-united.
The nuts washer are situated a floor the felspar machines, and all the coal from them after washing is delivei-ed on to a pair of rolls and crushed, and is afterwards mixed with the washed coal fiwm the felspar machine.s, the whole lieing raised by a bucketelevator, and then carried by a revolving screw and stored in four bunkers, each holding about 40 tons. Each one is filled consecutively, and the discharge is so arranged that the coal stands in each as long as possible in order that the water may drain
One small engine, about 15 in. cylinder by 3 ft. stroke, does all the work, and there are only two men employed in the building — viz., an engineman who looks after the machinery on the first floor (engine, felspar washers, and pump), and an attendant who looks after the " " machioM and regulates the diMharge into the bunkers. Is addition, one man is employed outside to see that the stack is being delivered all right from the screens. The cost of an entire installation for washing 200 tons per day woiild be from zooo to ;25oo. About 1000 gallons of water are loet per hour, this being, say, 10 per cent, of the total qtiantity used, and the life of a plant is variable, depending in a great measure in the way it is looked after. In bad cities it may be five years, in good fifteen years,
Conoluslona. — The relative advantages of coal wishing have been fully considered in a paper by Mr. R. de Soldenhoff* and in the discussion which followed. The interesting point is the absolute cost of washed coal, after charging the cost of the unwashed coal delivered to the machine. For example, a certain number of tons of coil are delivered to a washing machine, which if not washed would in the ordinary course of afTairs be sold for a certain sum per ton, the impurities contained in them being weighed with tbecoal. During the process of washing the greater part of these impurities is removed, and the resulting product weighs conaidetiibly lews (at Dowlais 4697 tons of unwashed produced 343J toos of clean ooal, the remainder was dirt and Iosh in
e 4697
Text-Book Of Coal-Mining.
lost which could h&ve been sold at a certain rate, and tbi reprefent a certain of money' which, being divided by number ol tons of vasAed coal recovered, gives a certain axao\ which must be added to the cout of waHhing.
As the value of the unwneheil coal increases, so does tl charge, nnd a point may easily be reached where it neuti the inoreused value of the washed product, especially if the is sold, not coked. In the latter case {coking) the a!advantages producing coke with little ash are great, less Sax is required the furnace, and less slag is produced, and also less coal has to be handled. Washing might easily make an uncokable coal into & cokable one ; as a very impure coal, although a caking one, vamy, owing to the large amount of ash in the coke, be unsaleable.
There is another point which must be specially noted same water must not be used over and over again for was without some efficient filtering arrangement, or the lustre of coke will be completely lost. At Earaock Colliery, IjiarkRhire, t;he water is pumped on to the top of the dirt-heap, and allowed to percolate through it before being used again. Settling tanks do not entirely remove the difficulty.
Dry Coal Cleaning, — Messrs Baiiaux and Ltonard" describe an apparatus for cleaning coal by means of an air blast at Rhein- Preussen Colliery, Germany. The coal is first separated by a. trommel into live sizes, the largest of which, i to 3 inches in diameter, goes direct to the coke ovens ; the others pass each to a. separate cleaner, where the coal is spread out in a trough about 6 feet 9 inches long by 2 feet broad, divided by a horizontal perforated plate into an upper and lower chamber. One end of the trough is in communication with the air blast, the other witli th cleaned coal dust-chamber, from which, however, it is separated by a sloping screen, the bottom end communicating with a hopper placed below the trough. In the lower comportment of 1' trough is an endletui belt, which carries the coilI to be cleaned an opposite direction to the air blast.
The air blast blows the pure coal-dust through the screen, the larger coal against the screen, down which it slides into hopper, while the stones, too heavy to be affected by the blast, carried forward by the endless band into another hopper.
The clean coal gave 7 per cent, of ash, and the stones (faij 45 per cent, of coal. The cost of cleaning (exclusive of iui and depreciation of capital) was given at 0.791/. per ton.
Briqufittes. — On the Continent, the manufacture of briqi as a means of utilising small coal is in great favour. English miningpractice is piubably fui'ther behind here than in any other operation. The great reason for this seems to have been the absence of a market, which was probably due to the uncompromising form of
A
Preparation Of Coal For Market. 421
the lulicle manufactured, <hoagh recently English firms liave tftkea out patnte for improved mode of traversing and locking step by step a revolving mouth-plate, which may be subdivided for interchanging moulds.
Briqiielts of the shape generally manufactured in England are iiiiBuitable for domestic use. On the Continent every shape is made, varying fiom an ordinary brick ovoidal perforated bullets about the size ot a goose's igg ; the former may be uaed for locomotive, and the latter for domestic purposes. Lai qu&ntitieB are made every year, and the demand is increasing. The only objection against theni is the rather dense and nasty smoke produced on burning.
80 much attention has been given to the subject, that the machines employed on the Continent seem to be a decided improvement on those used in this country. The one most in favour is that of Messrs. Bietrix & Co.,* who, after an experience of many yeara, have avoided the use of steam as a heating medium, finding tliat the presence of moisture sliould be avoided in the manufacture of homogeneous briquettes. In preparing the paste, the first procedure is to dry the coal in a small furnace, having a rotating plate for it bottom. The fire is placed on one side and petwes over the coal and returns underneath the plate. During its passage through the fui-nace, the coal in turned over by means of rakes and vanes, and on its discharge ie mixed with as small a <iuantity of pitch as poiisible, which has been brought there by an elevator.
The tno substances are intimately mixed by a sci-ew and conveyed on to the feeduig plate of the machine, the chief feature of which is a horitonltil mould-plate and double system of levers, by the aid of which the briquette is compressed on both sides. The rotating plate which contains the dies is provided with a series of short roller pegs projecting downwards, which engage at intervals with a M:rew-thread cut in a revolving shaft. In this way the plate ix turned, and at each turn locked in position while the presses enter the die, motion only taking place when the plungers are out of the dies. The dies are attached to a beam coniiectd at one end to geared cranks, while the other is attached to an hydraulic piston. Tlie paste receives double compi'ecision, fii-st by the top plunger iinil then by the bottom one. If any hard body gets into the press by accident, the hydniiilic piston rises and prevents damage.
As the coal is first dried in a furnace, the briquettes (untain a very small amount of moisture, and, in oddilion, less pitclk is i-ecjuiied, as the coal, to a certain extent, is softenetl. The machine is very simple and compact, one of the main fenturea also being the certaijity with which the coal and tar aT mixed, this being a
failing with toBiiy mtuiliineij, pitch being very expensive. As tl mould -plate is horizontAl and hiw three of its holes erpoeed to the feed acrupera at one time, it is always properly charged. Double compression is admittedly siicb an udvautage that every one at the present time uses it.
In the machines making ovoidal slmpea, two plates are employed,
the lower one fixed horiziutally and the upper one iucUned at an
angle. The horizontal revolving plate on
Fio. 490. which the \mste is fed is provided with two
fi-om the bottom of which project vertical
epiniile The upper plate b provided with
two rows of oval recesses which corrcepond
with the cups in the lower plate. The two
plates turn on shafts, h and c, and during the revolution approach
each other, and at this moment the lower cups are used ap
by a cam, which pushes up the Epiudles to which they are attached,
and by these means the briquettes are compreied. A little
further on iik the revolution the two plutea sepurat again, and
tlie cups being still further raised, the briquettes are discharged,
Bibliograpbr. — The following is a list of the more impoi' memoirs deiiiing with the subject-matter of this chaptei
CNIV. Du char/ftmeat et dii dichurffiartt ekemiiu defer el lur Its coia narlyabltii, G, Dngnet (l* SBl, Ir. et 549; Aole luc le ntttoyage ilu charhon par p(( toufii, ' Buianx et Leonard (2> Serie), i%. 135 ; La prfparalion da du 'e baum dc la JttJir. F. Pelera (2° &ede), xv. loi ; Salt
trial/f mrtxinl-nif du paili yo. 5 de la toailf dtarbonniirt de Bateotip, A. Strie), zviii. 531; KottfentT iet initaUatiom tfe ckargeiaeiU i/u vorl de Cardiff {AngUterre), 3. Alardic (j* Serie), xi. 233 ; FiJnrieatwn dfn offffiomir otviilei, }irOcfdi fuKrqiumhtrg, O. HoUer <3" Srio), xvi, 161.
N. BTAFF. INST. : The Taping and fkrecHing of J. Kigg, iv. 103.
INST. c. £. : Coul H'thing, T. F. Harvcj, Ixx 106.
M. K. I. : On an Ajpamltm far lariag tht Sreatage of Coal irhrn falli'Hff from CoSitry Serftat into Railirai/ Waggoni, A. M. Potter, xxv. 361 ; Cleaniiut of Coal at /i, A'o. S Pit, J. DaffliBh, xxvi. 161 ; JSchmidfrn Spiral Heroimng Scran, D. P. Morion, xxviii. 183 : LUhrtff'i JUtUiod of Coal Walking, E. P. Rathbone, xxix. 159 1 On lAe Dry, or . Jutthoil of Cleaning Coal, £. P. Ratlibane, . 245,
XIX. INBT. SCOT. : Detcrt'ption of a Self-tippinji Cage and " Otmboat,
ix. iSj; N., lievoTt of IJommit of Patent Fue), J. Clark, liii. 236.
a T. Moore, iv. 250 ; On tU Oeneral Prmtlpla of Coal Wat, " J. Kowan, ix. igj ; Notet on Coal-Cleaning Maehinet. D. Cowan, 229 ; Jieport of fJammillee on Coal Cleanmg, xi. 145 ; iloMufacttire
: Coal Wa4hi,vi, J. BrodeD, i. I19 ; .in iimrored Ooal- Wailiiag ilarhi*e. A. Hivitre, x. 294 ; Improrementt in Gxd Wathiug, R de Soldenhof, 88, : SOC. MIN. STl'D. : Metkodi of Banking and iiereeing, E. F. Melly and J. Stevens, Iv, 67 ; Coal Cleaning. A. T. CroDBhaw', y, 61 ; Cold- H'a/hing Plant. H. Palmer and J. H, Ward, vili, i ; VUitt ic lome LancathiTt Collkriee. H. W. Uaghes, zU, S3; The Nca Coat
PREPARATION OF COAL FOR MARKET. 4aj iieparaloT ami Wiifher at Ikr ZalUrn Hi, Mar DorlmuHd, W. Bell.
AHEB. IKST. M. E. : ImjTorttnenti in Coal Waihixg, ElcraHaa, and (imrrj/lng MarKihery, S, StulK, xli. 497 ; An Erperiment in Coal Walking, t. H. Drowii. xiii. ui ; The Iron Brtaktr at Drifim and tka 3laekiitery aaeil for Jiandting and Preparing Coal at the Crott Caltitriei, B. B. Ooxe, xlx. 39S.
cifES. CIST. ; fiiit and Praent Method* of Jtanlang Coai al Annctiey Colii/ry, J. Timms, ivL 157.
MAK. GEO. aoc. : Streetiing Arrantfemtati al Briniop Ball fMlirriet, A. H. Leech, iviii. 373; Dacription of a Paltnt bcreca, G, C. Gteenwell, Jnn., XI. 440.
FBO. IN8T. : Serttmng Plant at KoMt Bettoa CoUiery, S. Tate, l. 3i Im- pTortd Ceal aertening and Clennimg, T. B. Foater and U. Ajton, i. S3 1 Sottr't Coal-Lotcering Appariatu, C. Sokt. i. tSj.
SOC. IXD. MIS. : Lacagtdet charbont, Uax. Evrard (1° Si-rie).ii.iSl ; Etads tur la large de la kouille aux minei de Batige*. J. B. MaTuat (i" Sprie}, viii. 3S7 ; Lnroirt aufddipath : Jletier de taragt da Martinet, M. Luidrivon (z> Seiie), lii. 303 ; Etude tur Vagglomiration de* comliattibUi particvUirtTnent inr UiproeMt rmploift par Biij! et Cie, L. BftUult (z* 8Me), zii. 4G1 ; Mackina a oggUmirer Rout, H. VeilloD (3° Srie), xiii. 575 : Preparation memniqut dtn diorhant aiu: de Dteite, H. Biunuet (i* SHe), xiv. 363 ; Prfparatitm micamqttt da kouiUt* dam te Sard de la /Vittire, L. Parent (3* SKrie), XV. 33 ; Xole lur laroiV il eAurboN, dit " Laevir ii paUllet." Max. Bvrard (3" Sirie), ia 317.
Coat-Handling Machinrrg at Oi* Bondoiit I'ard of Ike Dtltnrure and Hudion Canal Canipany, HcientiHo Americao, Jaue 1S90, p. 360.
MaUiiard-Tata Tipping Cage vted in French ColUtriet, Engineering and Ulning Journal, 1. 119.
Prai-KohUninduitrit, E. Freiaslg, Freibe:, 1S87.
Kohienaftfbereitvng, B. Lomprecht, Leipiig, 188S.
Soles on Coaifireiiing Brovn Conl info Driqwtttt, die., B. SUubel, Colliery Guardian, Augait 189J, Ixiv. aSo.
Index.
ABBh, Sir F. A., on coal duat, 316,321 Abram Collier;. La.Dcasblre, 377, 401 Accidents from blasting, 90
in boring, 3 1 Acid water, effect of, 305 Adams and Forster-Brown on cost of
sinking, 125 Adelaide rock drill, 6z Atter-damp, 315 Age of coal. 7
con5Qits. si
crossings. 343
current, distribntiOQ of, 341 measarement of, 345 prodDctioD of, 327
friction of, 3rj, 324
quantity required, 313
vessels, 303 Aix-la-Cbapelle, 121 Aldwarke Main Collicir, Yorkshire,
Alternating currotits, 56 Amsrioan Bjstem of boring, 26, 35 Ammonite, 79 AropAre, 37 Anemometers, 345 Angling of winding ropes, 251 Aniche Colliery, France, 408 Anthracite, 12
mining, 168
preparation of, 412 Anticlinal, j
Anzin Colliery, France, 246, 160, 279 Aqoeons rocka. 1
Areher k Robson'a watering-can, 323 Ardeer powder, 79
Arley Mine, BrinsopHall Collier;-, 405 Arnold boiler, 376 Aab in coal, 14
conveyors, for boilers, 379 Aahworth's lamps, 365, 372
Uueieler lamp, 359
wick tube, 365
Atkinson, J. J., on air fri . ,
on fans and furnaces, 340 and W. Coulson on tubliing, tt6 and Daglisb on anemometers, 346 on water-gauEesldR
Atkinson, L. B. &: C. W. cutting, 72
AtkinsoD'H conductors, 59 electro motors, 5S
Atkinson. Messri>., on coal dust, 3.
Aobin Colliery, France, 82
Axles and wheels, 1S4
Bagnall's sleeper. iSo
Bailey & Co.'i pumps. 301
Bainbridge, K., on eage bearers, on lubricalion. 1S6
Haird's coal -catting machine, 69
Balance bobs, 291
Balance platforms for cages, 37S,
Barometer, 347
Barraclough's pulley, 205
Barriers. 154
Barrow, J., on boring, 30, 33
Basconp Colliery. Belgiam, J48, 272, 278. 388, 390. 394, 404, 409
Basianz and Iouard on coal cleaning, 420
Baskets, 39
Batteries for blasting, S3
Baore on boring. 30
on steam condensation,
Bedson. Dr. V. P., on gases 'in ookl dust. 319
Beihilfo Mine, near Freiberg, 63
BeU End Pit, South SraffordahinL 183, 209, 210, 242, 277, -"-
Belling out shafts, 14;
Helta for cleaning coal, 40a
Benzoline for lamps, 165
Bestwood Colliery, llottingtuuiii 264,26s
Bessemer steel ropes, 237
uwl I
Sever & Dorlitig'* clutch, iij
Brakes for branches, Z14
Bewiolc, J. T., oa boring, 34
bttulBgo, 194. ai4
Baet Collier?, Krance, 196
Koepe winding, a64
J37. 84,3ia, 349, 373. 43a
winding, 151. 364
Bickerahaw Colliery, Lancaalilre, 253,
Bnncepecb Colliery, Durham, 318
Braucbes. haulage on, 101, 204.311,
Eioktord'B fuse. 80. 85
voUev fuse, 85
Biram'B anemometer, 345
Breaking ground, 38
aird,W. J., on coating Btoam-pipes,
Briart's pulleys, 203
Bits, boring, 19
screens, 39a, 398
rook drUl. 66
Bituminoui coal, to
Bridle chains, 240, 341
Block damp, 114
Brinsop Hall Colliery, I.lancashire,
BlackweU CoUierj-, Derbyshire, 190
Blanchet pQeomatic system of winding
, z6i
Broomhill Colliery, Northumberland,
Blasting. So
by electricity, 8j
Brough. B. H-, on surveying, 35
gelatine, 77
Brown, M. W., on explosives, 79
in dry and dnaty mines, 77
on fans, 332
pOHition of holes for, 85
prohibited, 89
Budille, introducer of panel working,
Mubitilates for, 87
Block* or stops. 193, aas
Bull engine, 396
Blowers, 14, 31S
Bulling iron. 44
Blown-out allots, 86
BdIoulo, H. K, 00 cost of horse
Boilers, 195. 375
Boilers, andcrrouod, 195
on method of working, 155
Bams' brake, 351
Burnet's roller wedge. SS
Bord and pillar. 15a
Borehole M Spcrenberg;, 34
CA.QK, attaching rope to, 339
Cage chains. 340. 341
Bordioles, casing. 33
Cages. 234, 374
snr-eying. 35
tnangnlar, 43
uses of. 36
widening. 33
Camphausen Colliery, Prussia, 371
Candles, 353
Boring, methods of, 18
accidents in, 31
(':.nkl.>w it.kinD-. Yorkshire, 295
cost of, 34. 67
cross cuts, 75
frame for sinking. 99
hole, wet, 66
ri-cord of, 34
sinking by, 1 18
Borings in coal, itas from, 16
Boraet's drill, 46
CasinK boreboli-B, 33
Cocker sprags, 1 34
Casting lend rivetK. 367
Cockson, C, oil fans and famaMH
Catclies at pit lop, 170, 173 Calynen Colliery. 8. Wales, 336
Chance, H. M., on borinR, 35
Coffering, III
on working Mammoth bed, 168
Cogs or chocks, 135
Changing tubs, xn
Chandron method of sinking, 1 18
Collieries referTed to ;
Abram. Lancashire, 377, 403
ChoctB or cogf, 13s
Ain-la-Chapelle, lai
Choke damp, 314
Aldwarke Main, Yorkshire,
Circulation of tubs, 145, 271, 176, aSat,
Aniin, Frunoe, 246, 260, 279 '
Aubin. France, 83
Clanny lamp, 352, 353
BBBCOUp. 148, 37a, 278, 388, 390.
Clark, R. W., on coal ontting. 74
Clay Cross Colliery, Derbyshire. 190
Bell End. 1H3, 209, 210, 14a. 177,
ClayioB iron. 44
28a
cottT.39S
safety lamps. 369
Bfzenet, France, 196
Blaokweil, 190
Clenring borehole, ar Cleat, 6. 152, 158
Brancepeth, Dnrham, 318
Brinsop Hall, 391, 405 Broombiii, Northnmberland, 196
Cleavage, 6
Clifton Colliery, Nottingham. 374, 276,
Clips for haulage. 217
Canklow sinking, Yorkshire, 295
Celynen, South Wales, 336
detaching, 220
Clutches, 100, III
Clear Spring, 37
Clifton, 274, 376, 35, 3S9
oleamng, 395
commercial value of, 13
Dairy pit, Wipan. 341
composition of, 10, 11, 13
Denaby Main, Yorkshire, 276,
definition of, 9
dust, 316
Dowlais, 323, 419
dust, action of moisture on, 333
Eamock, Lanarkshire, 430
conveyors tor boilers. 379
East Franklin. 37
Kast Howie, Durham, 376
Elemore, Durham, 196, aoo
electric, 71
Gillot and Copley, 68
Epinac, France, 263
Higg and Meiklejohn, 68
Eppleton, 154. 190, 328
' BBird, 69
Hanover, Westphalia, 264 1
Harrison, 69
HiirriB Navigation, 16, 100, 104,
Li%g, 70
Harton. 387
Goolden, 72
Has well, 316
Jeffrey, 73
Hutton. Durham, 307, 34a
Van-Depoele, 7a
Hewlett, 40S
Stanley, 74
Hilda. South Shields, 233, 273, 406 .
formation uf, 9
Hohenzollem, Pmssio, 227
lowering apparatus. 403
Homer Hill, 2S0
preparing for market, 383
Hottingner shaft, Epinac, 36xH
siring, 414
washing. 414
CoatinE sleam-pipes. 380
Cochrane, W., on ventilators, 330
Llwynypia, 333
INDEX. 4n
Lye Cross. i8i, 190, wS. J14, 141,
Cost of blasting it. hand getting, 89
a8:. 344
boring. 34. 16. 7S
coal CDtting, 73, 74
drilling, 48, 63, 67
Marihaje, 89
Menhyr Vale, 16
electric pumping, 309 feeding; horses, 1S9
Honnkirchen, Prussia, Jl6, 3o New battle, Edinburgluliire, 116
haulage, 224
Nunnery, 145. 186, 320
I'embertoD, z3o, 405
Plymouth, 59
lubricuLion of tubs, iS?
Poohin, South Walts, 323
metal supports, 138
Podmora Hall, 89
Konirod Hall, Staffordshire, 125
Rheln-I'renssen, Gonnany, 410
Roche la Moli-Sre, 108
St. Adolphe, Halne St. Pierre,
timbering. 13S. 140
Sandwell Park. I36, 231. 233
waehirg cool, 419, 420
Covering pit top, loz
CouUon. W., and J. J. Atkinson on
Shipley, 88 '
tubbing, 116
Shireoaks, 1 18
Counterbalancing in winding. 251,
SkeltoQ Part, 222
Sneyd, K. Staffordahire, 165
pump rodx, 291
WbarnclilTe aillutone, 16. 127
CoxG, K. B.,011 anthradte oleuing,
Ynishir, 323
Cose's gyratory screens, 394
Colliery Owners' Association on Hubsi-
Cradock on strains during windlog,
denoe, 150
Cradock's ropes, 238
Combe for screens, 397
Craig, W. Y., on blasting, 89
Composition of oosl, 10, 1 1. 13
Compressed air, 48, I97
motors, 55
Condensers, steam, 260
Curbs, garland, 106
Conductors between cages, 246
puti'ing in, for tabbing. 1:3
electrio, 58, 59
Conduits, air, 55
Contormablo atrnta. S
Conical drums, 251, 256
Continuous electric currents, 56
DAaLiBii, J., on boring, 27
Contracts, 38
Dagllsh and Atkinson on anemowater
gauges, 348
Cooling coropreBsed air, 49
Dairy Fit, Wigan, 341
Coppee washers, 416
Cores, extracting, 34, 3$, 30
Dancing " of valves, 54 Davey, H., on pomping-englne gear,
Cornish pumping engine, 295, 299, 300
valve, agi
42S
Index.
Dare differential engine, 296 Davis and Stokes* commotaton, 58 Dam* sdf -timing anemometer, 545 DaT7, Sir H., on lamps, 354 Davy lamp 352, 363 Deep workings, draining. 305 Deflector lamp, 361 Delicate indintois, 371 Demanei, C, on rail guides, 243 Denabj Main, Yorkshire, 276, 294, 301 Detachers, automatic, for dips, 220 Detonatois, So Diamond boring, 27 Diamond boring reamer, Diamond Boring Co., 33, 34 Differential engine, 296 pnllej, 209
Direct-acting steam pomps, 298 Disposable hydrogen, 14 Doors, 342
Doable-beat valre, 292 Donble-stall method of work, 161 Douglas, M. H., on laying out kips,
Dowlais Colliery, South Wales, 323,
Draining deep workings, 305
tfhaft daring sinking, no, 3cx>, Drawbars, 185 DresKcrs, 41 Drills, hand, 42
machine, 60
supports for, 99 Driving fans, 336
pmleys, 203
roads, 48, 129, 136 Drums and valleys, 193, 203, 205, 207,
Drams, throwing in and oat of gear,
winding, 250
winding, diameter of, 238
for lining shafts, 97 Dry coal cleaning, 420 Dudley, P. H.. on rails, 177 Damont on sabsidence, 150 Dynamite, 76
Eabkock Colliery, Lanarkshire, 420 East Frasklin Colliery, Pennsylvania,
East Howie Colliery, Darham, 376 Edmeston's catch, 213 Efficiency of electric transmission, 59
fans, 337 EHers, K., on electric locomotives,
Electric batteries, 370 Uasting, 80, 82 coal-cutting machinery, 71 conductors, 58, 59 drills, 65 haulage, 226 horse-power, %7 lighting, 370
signals, 283
transmission, 56, 19S, 309 Electricity, 56 Electro motive force, 57 Electro motors, 58, 71 Elemore Colliery, Durham, 196 200 Elliott's multiple wedge, 87
drill, 46 Elsom, H., re-lighting lamps, 369 Emilia Colliery, Germany, 122 Endless chain haulage, 202, 383
rope haulage, 198, 205, 214 Engine-house, 250 Engines for fans, 336
for haulage, 198
for winding, 248 English Fan Coioamission, 349 Epinac Colliery, France, 262 Epfdeton Colliery, Durham. 154, 190,
Equivalent orifice, 33S
Evans &, 8on*s pumps, 299, 300
valves, 292 Expansion joints, 196 Expansion of steam, 257 Explosives, 75
firing of, 80 Eyre's steel wheels, 184
Faiblet, W., 00 air friction, 324 Fan brake for haulage, 194
Capell, 333, 339
Cockson, 333
compared with furnaces, 340
efficiency of, 337
engines, 336
forms of, 330 335
Guibal, 330. 339
Schiele, 333, 389
Waddle, 331. 339
Walker, 334. 339 Faraday lines of force, 56 Faraday and Lyell on explodoD, 316 Faults, 4
proving, 36 Favier*s erosive, 79 Fayol on subsidence, 150 Feed-water, heating, 376
Feeding hones, 1S7
Felspar washer. 416
Gray lamp, 356
Fencing pit tops, 179
Greasing ropes. 137
Ferguson, D., on puUojs, io6
Orenwell. G. C, on tubbing, 117
Finger ohun, 3S3
on working, iss
Greenwell's screen. 39S
indicators. 371. tdio Safety
Orimmitt's overwinding apparatus,
stink, 170
Grlsoutite, 79
Fires in mines, 37, 170
Guibal fan. 330, 339
FiHne explosives, So
Guide troaghs. 247
Firtha props. 137
Fish plating, 178,243
for winding, 234, 243
tippler, 389
Flat ropes, 356
greet>, 383
Forater-BrowQ and Adams on coat of
Gunpowder, 75
Fosaiu! 3, 7°'
Gumey, Sir G., on ventilation, 319
Frankfort, electric transmission at, 60
Hall, H.. on ooal dost. 311
Franti's catches, 271
Hand-machine drills, 45
Friction of air, 324
Hand-tool.i. 39
Hanover Colliery, Westphalia, 264
Hardy Pick Co.'s appliances, 40,45,
Furnace ventilation, 327
HtrfU Navigation Colliery. South
Fuses, So
Wales, ,6, 100, 104, 1*6. 248,
Galloway boiler, 376
HarrisoD's coal-cutting machine, 69
GaUoway, W., on coal dust, 316, 318
Harton Coltiory, Durham. 387
Haswell Colliery. Durham, 316
Hoswell coal-gettor, 88
guides for sinking. 103
shaft top doors, 102
brakes. 194, 114
sinking at Llanbrudueb. 107
clips. 117
Garland curbs, 106
clip detachers, 220
Gas indicators, 371
ditches. 212
pressure of, in borings, 16
comparison of systems, 124
releasing, 36
dLrectacting, 19S
Gases occluded in coal, 15
drums and pulleys, 193, 30o, zoj,
in mineH, 314
Gauge of rails, 177
electric looomotlvcs 216
Ganges, water, 348
endless chain. 201
Gelatine dynamite, 77
endless rope. 205, 214, 124
Gelignite, 77
engines For, 19$
Geology, 1
Germans, 80
Budn and UJl rope, loo. 125
chine. 68
Glasses for lampa. 36s. 37.. .
Gournay. de, on Koope wtadlBI
Headwaji, 151
II&lcb of miners, effect of explosives on, 78
Helve
tump, 3;6
Hewlett Colliery. Limciuhire. 40S
HUdn foUiery, South Shields, iJJ, 73. 406
Hilt on coal diut, 317
Hipkin's sleeper, :So
HohenioUern Collierj, Prussia, 227 '
Hoista, 275, 277, 384
Holing in road, 131 I
Holm&n's condenser, 303
Homer Hill Collierj, South Staffordshire, 3S0
Hood, A., on watering dusty mines,
Hoppita. lot
Horloi Colliery, Li6ge, 143 Horse haulage. 187 Horse power for , 337 HorHea feeding. 1S7
for haulage, 198
for , 304
life of, 181. 191 HoUinguer Shaft, Pinac, i6z HowHt's Ump-c leaning machine, 369
rivet nachlne, 367 Howell drill, 46 Hudson's turntable, iSi Hnnting, C, on horses. tSiJ Hussmann. coal-boring machine, 75 Hydraulic mortar, 10;
power for pumping. 307
rock-drill, 63
traDsmissioa of power. 63, 307
wedges, SS
Igheocs rocks, I Inolicos, self-acting, 19a Indies torn, fire-damp. 371 Indaration of rock, 3 Ingersoll'a rock drill, 61 IngcrsoU-Sergeant's coal-cutting ma-
Injec
'.377
Jenkins, 154 I Jig-brows, 192 ! Joints, eipaniuon. 196
for limber tela, 135
for pipe?, 196. 288
for spear rods, 390
in ruck, 5 , Jones, J. , on cost of tublnng, 1 1 8 I Jumpers, 42 I Junctions, iSa, 195, 316
Kiiselguhr, 76 Kibbles, 101 ' Kiud-Oiaudron method of sinking, 1
I Kind's free-fiUling cutter, aj
P'og. 33 I King's hook, 367
! Koepe system of winding, 363
LABnim. arrangement of, 151 I..aminatloa, 2 Lamps. 352 Lancashire boiler, 376
method of working, 156 Lang's wire ropes, 238 Lay of ropes, 238 Laying dust in mines, 332
rails, 177 Lead rivets, 366 Le Chatelier and Mallard on ocmI'J
, 317, 319 Lee, J. F., automatic detached, 23i I'g's cool-outttng machine, 7a Lens Colliery, Franco, 54, 139, 390 Lfionard and Basfaux on cwl okaaing
, 420 Levels, 129
Lifte 27s. 177, 384 Lighting, 109, 35J
Lime cartridges, 8S
Lincoln Colliery, Penniylvani*, 37
Lining boreholes, 33
shafts, 93 Lippmann's method of sinking, lao Liveing's indicator, 373 Llaobradach Colliery, South
I.lwynjpia Colliery. Sonth Wales, jij 1 Loading shoots, 403 '
Locked coil ropes, 238 Lucking safety lamps, 366 I/ocomotivea, 226 Longdcn, J. A., on shoeing, 189 shaft pillars, 149, 151
Longwoll methfx, ijd
Needles, 45
Ncunkirchen, Prussia. 3r6, 320
Lubrication, iS6
Lahrift wubcn, 416
Lje Cross Fit. Houth Staffordfbire,
Nitro-glycerine, 76
:8a, 190, 20S, in. 241, iSi,
NunneiT Colliery, ShelSeld, 145, 1S6,
Ljell and Faraday oo explodoiu, 316
washer. 416
MiCOBoBGE, E. F., 3S
Machine drills, liand, 45
(Etnii4'b free-falling catter, 14
powor. 60
A., on griaoutil, 79
Magnutio loclts, j66
Oil vessels of safety lamps. 365
Oiting ropes. 237
Mahlet on Koepe winding. 364
tub axles. 1S6
Main and toil rope hanlage, 19S, aoc
Orifice of passage. 338
lis
Ormerod's hook, 167
Mallard and Le ChaWliac on coal
Oatburstsof gas, 315
OTur-rope haulage. 114
Mariemont Colliery, Delgium, a4i, 141,
144,380,09 Marihaye Colliery, Belgiam, 89
Overwinding, preventing, 166
Palmbh, H., on loss in ventilation, 344
PasReld's brake, 153
Marsaot. J. B., on lamps, 355
Pedestals for tub axles, 185
Martin, W. H., on watetiag dnatj
mines, 323
Marvin aleottio rock drill, 65
Pennsylvania anthracite cleaning, 411
Masonry, 104. 140
method of working, 168
Mather and Flatt's system of boring.
Percussive drills, 41, 60, 6$
Picks. 39
Mucbanical stoking, 377
Picking belts. 400
Ueinicke's system of ooonterbalanc-
Pieler tamp. 371
Pile driving, 95
Melly, E. F.. on the Warwickshire
Pillar and stall. 151
coolfieid, 170
Pipes, arrangement of pump, 301 supporting in shafts, aSg, 294
Metthvr Vale Coiiiery, South Wales.
Pit frames. 329
Metamorphie roclca, i
Pit-top covering. io>
Plating for screens, 397
Mine fires, 37. i?"
Plates and turntables, 181
Moorp, J,, on pumping, 308
putt. F.. on working Mammoth bed,
Moore's hydraulic pumping plant, 308
Morgan lamp, 360, 366
Plough steel ropes, 237
Mortar, 105
Plunger pumps, 1S7 Plymouth Colliery. South Wales, 59
Mossboi, 118
Motors, air, j5
Poeuojatic hoisting. 261
electric, 58
Fochin Colliery, Sooth Wales, 323
MoL-seler lamp, 354. 3S9
Miiltltuhular boiliTS, 376
shire. Sg
Munsobeid cottl-boring; ooohiai 75
PoeUohmethod of sinking. :2i
MurguB, D.. OB ventiUlion.338, 347
MusgravB expansion gear, 158
t3' I"J
PrepuratioQ of coal for market, 3S2
Pricker, 45
Primary batteries, 371
Props, timber, 133
or Iteps, 270 Prospecting, 18 Protector limp, 368 Proving fntilts, 36
FniBsiaii Fire-damp CommissiOD, 316 Pullevs and , 193, toi. ao5, 207,
Pulle;B, tDBioii. ill
winding, 133
diameter of, 338 Pulaometer, 295, 310 "-, 286 mpB, Buley I
Bull 296
connecting to rods, 191
Cornisli, 395
direct-acting. 298
Evans liSorta, 299, 300
sinking. 293, 300
Tangjes, 303
Worthington, 300
Quadrants, 293
Quartering, 96
Quicksand, sinking througti, 94, 1
Quincy Qnanies, U.S.A-, 66
Rackabock, 77
Bails, arrangenient of, 192
aa guides, 343
at junction, ai6
gangeof, 177
laying, 177
length of, 177
aectioDB for, 176
apeoificationa for, 177 Raminelsberg Mine, drills at, 67 Rammlog, 44 Ramrod Hall Pit, South StaffordBbire,
Kaodllrill Co., 65
Reamer, 33
Redmayne, R.A.S-, on boring, 35
on working, ISS Regulating doors, 343 Relighting safely lamps, 36S Repairs, 381 Reservoirs, air, 55 Reversed faults, 4 Revolving screens, 395
tables. 402 Rhein.Preussen Colliery, Germany,
Richter on spontuii
Riding column, 296
Rigg and Meiklejobn's coal-cotting
machine. 6S Ripping, 158 Rixing main. i88 Biviiaint, 40 Roads, 129
KobinsoD's waaber. 414 Robnrite. 78
Roche la Motlre. France, loS Rock drlllB, Adelaide, 62
electric, 65
Marvin. 65
supports r, 64, 99
tripod, 55 Rods, boring. 19. 22 Rollers for bandage, 194 " f, ripping, 158
Bopporting. 132 Rope, 236
boring, 24
capping*. 239
greasing apparatus, 238
over and under tubs, 314
threading, 224
winding, couQtrbal&iiciDg, M Rope-ways, boreholes as, 36 r Rosenberg, L., on blasting, 86
on tunnels. 67 Rotary drills, 42 Royal Commission on Aocidentd i Mines, 318. 319, 3S5. 356
on coal-dust. 331 Rutherford and Thompson's clip, ZJ
Ryder's lock, 366
Safety cnes, 268
cartridges, 77
hooks. 267
valves. 376 Safety latnps, 352
Ashworth's, 365, 373
Asbwortb's Maeseler, 359 ,
bonneted Mnsseler. 3J9
Clanny, 352, 353
cleaning, 369
Davy, 352, 363
deflector, 361
design of, 354
pause, 3S3
4.U
im.:-? - r";l wifx"
scciiis:.c 'r
—
-j: r - rt
Kir*. yA It-; Til:.-* :iLr ii;
rj :x-
?->i fir ".-r-Lr :ii:.:> :1 :,i
zL-i-iT i iir cc-ci|.iiHUi,49
fori, '-2
one
ISjicar rods, iSg
Sperenberg, boring iit, 34
Spiral dmmB, 251,256
SpontftDeoos corauii-non, 170
Spmy producers, 513
Spring pole, 2 1
Spaddiog. 27
Square work, 105
Squibs, 80
Utablea, 19a
Stages tor waUing, 107
Stall aod pillar, 1 52
Stall roads, 156
Stanley'H heading mactioc. 74
Htauss' props, 271. 277-
Steam coal, 1 1
condensing, 260, 303
engines, 19S. 248, 336
expansion. 257
jet ventilation, 329
lifts, 384
pipes, 37i 196, 380 piimpB, 298 traps, 196 Sleam-wayg, borehoiea as, 30 StoavensoD, A. Ii,, on tans, 338
on (ire-damp indicators, 373 atoel pit flames, 233 ropes, 237 sleepers, 179 supports, 137 Stepbenson lamp, 353 Stemming, 44 Stocks or trees, 288 fimkes, A. H.. on coal-dust, 321
wiolc tube, 365 Stoking, mechanicHl, 377 Stone head, 93 Stoop and room, 151 Stoppings. 342 Stops or blocks, 193, aos Strata, order of, 6 Stratification, 1 Stretcher bare, 64, 65 Htrikfi. 3 Stats, 134 Sturgeon b valves, 53 Btjthe, 314 Sabsidenoe, 149 Hiuisse on Koepe winding. 264 Sulphuretted hydrogen, 314 Ballivan Prospecting Oo.'s lijdraulic toed 39
Suiter cipansiou gear, aoc SupportiQK pipes in slit-rook
dnllB, £14
roof, 132 Surveying, 35 Suspended littf, 293 Swages, 66 Switches, 180 Syphons, 306 Synulisal. 3
Tables, revolving, 403 TaiUet cAfMiiinlef, 164
Tail-rope, torwinding. 3j6
haolftge, 198,20-. 33S Tamping, 44, 87
plugs, 87 Tangyes' sleBin putaps. 303 Taper ropes, 256 Tapping water, 36 Taia-Malissard tan brake, 194 Tempering tools, 43 Temper screw tor bonng, 36 Ten-yard seam, S. Stitffordahlre. Tenders for baring, 34 Tension pulleys, 311 Testing safety lamjia. 355 Thick coal working, 1I18 Thennomater, 347 Thomas, J. W., on gas
Thompson's calorimeter, 1 Thomebnrry lamp. 363 Threading the rope for haulage, : Throw of faults. 36 ThurUng, 131, 166 Tiller, horiug, 2o Timber, kinds of, 133
preparation oE, 381 Timbering, 93. '3* Tin-can Davy lamp, 363 Tipping kibble. 101
waggon, 103 Tipplers, 385 Tonitc, 79
Tonkin's valve, 399. 3°° Tools, hand, 39
for rock drills, 66 sharpening. 40. 43, 47 tempering, 43 Trafalgar Colliery. Glouceslc
Transformers, 57 Transmission of power, 36, 48, $
Trasenbter, L., on Koepe wlndii Trees or stocks, 2."''
f TrencJia compound, 79
Waggon, Ilroung, 103 Waltcer. 0. B., on cost otrual-oiitiinK.
Triger's method of siuldiig, lai
Trip eapanBion gear, 258
Tripod for drill, 65
on olectrio loconmlives, J17
Trommels, 395
Walker's brake. 214
Trough faolta, $
diaereiitial pnl!;, 209
tan- J34. 339
Trows, 132
hook. 26S
Tubbing, Ml
shatter, 331, 335
corrosion of. I17. 339
valve.-, 52, 54
coflof, 117
Walling stagBFi, 107
strength of. 116
Walls or bonds, 15!
Tnb controllers, aSi
Tubs, iSj
Warwii'kbire roetliod ot working,
Washing ooal, 414
changing. 2J3. 274
Water oartridgea, 77
supply, 37
keeping on oage. 236
k'ping back by tubbing, 1 1 1
Turntables, 181
rings, 106
tapping, 36
Watfriug diistv luineii, 323
Watt, 57
Ukconpobmablb strati, 5 UndercDtting, Me coal-cutting ms-
Weilges. 41
for getting coal — BumelT's, SS
ohincs. in roads. 131 Under and over rope haulage. 214
Elliot'!'. 87 Hiu-vvell, Si
Useful effect of faBs, 337
WhamcUlif Silkslone Colliery, York-
Wheeler, ProC. on cual-cuttJng, 69
Valves, dancing of, 54
for uir compressor,
Wick, 36s
Widening bore holes, 33
pump. 29a
safely. 376 Sturgeon's, 53
WUliami. joint for pipes, S89 Wills. W. R. tnb-releasiDK geAr. 277
IValkcr's. 5a
Wilion. K., on siio of cnginei, 249
Van-Dioele'B coalciilUng maohine,
Wind bore, 286, 395 Winding, 229
Ventilation, 313
distribution of, 341
in doTi-cast stutft, 2S0, 2S1
during flinlting, 109
in sinking, 101
driving, i3t
Wire bells, 402
fans, 330
rope-, 237, 'fi
furnace, 317
rope guides, 145
Wotn lam,.. 368
Woodwortb, B., tab controller, 2S2
Working branches and ciirvea. jot,
still jet,3J9
Volt, S7
Vosbwg lunnal. difflc u, 6j
double stall. 161 homewards. 161
in the broken. 154
T in tbewholr. 154
longwall, 156, 1 66 I two main systems, 149
methods of, 149 Warwickshire, 170
Pennsylvania, 168 j Workshops, 81.
seams near together, 169 i WorthingtoA s pumps, 300 South Staffordshire, 164
South Wales, 161 VkisHiB CoUiery, South Wades, 323
steep seams, 162, 169
thick seams, 164 1 Zauoksbode Colliery, Saxony, 226
Printed By Rai.Lan'Tynb, Hanson And Co London And Edinburgh