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.Dkpartment Op The Interior V Bureau Of Mines
" JOSEHII A. HOLMES. Director
A Primer On Explosives For Coal Miners
By
Charles E. Munroe
And
Clarence Hall
[ Repimt of United States Geological Survey Bulletin 423 ]
Washington
Government Printing Office
% 4
Bulletin 17
HEPARTMICNT ol' 'IMIi: hVTKRioK BUREAU OF MINES
J()SI':i'H A. llOLMI'iS. DiHiA i(K
A Primer On Explosives Eor Coal Miners
By
Charles E. Mijnroe
And
Clarence Hall
[Reprint of United States Geological Survey Bulletin 423]
Washington Government Printing Office
Internet Archive
in 2011 with funding from
University of Toronto
://www.archive.org/details/bulletinu17unit
Contents.
Piilje.
Inlnxliu'tion
CombuHtioii and explosion II
Kiro N
(/ombustiblo suhHtances 11
Explosion 11
Dust ex plosions 11
Air necessary to ordinary conbustion 12
Oxygen of the air necessary for combustion 12
Oxygen from saltpeter 12
Saltpeter supports combustion 12
Charcoal with saltpeter produces heat and gas . 12
Sulphur is added to make the mixture ignite easily 13
Chile saltpeter contains oxygen 13
Oxygen in other bodies 13
Nitric acid from saltpeter . 13
Putting oxygen into cotton, glycerin, etc 14
Sensitiveness and violence of fulminate of mercury 14
Low explosives 14
High explosives 14
Confinement essential to use of explosives 15
Folly of attempting to make explosi ves 15
Explosives 16
(lunpowJer 16
Black blasting powder 16
Danger from dampness 16
Keep powder dry 16
Granulating powder 17
Size of powder grains 17
Danger in using a mixture of different-sized grains 18
Potassium chlorate 18
Nitrocellulose 18
Nitroglycerin 19
Nitroglycerin freezes 19
Liquid nitroglycerin is especially dangerous 19
Dynamite 20
Explosive gelatin and gelatin dynamite 20
All explosives containing nitroglycerin freeze 20
Dynamite cartridges 20
Packing dynamite 21
Nitrostarch 21
Ammonium nitrate 21
Nitro-substitution compounds 22
Why nitro-substitution compounds are so called 22
Fulminates 22
Danger with furminates 23
Warning against manufacturing explosives 23
4 Contents.
Page.
Explosives for use in coal mines 24
Niinil>er of explosives 24
Explosives in open work 24
Kxplosives in inclosed work 24
Dan<jer from flames in coal mines 24
Noxious pases 2.7
Investiiration by Bureau of Klines 2o
Testin*; station at I'ittsburg 2i>
Explosives gallery No. 1 25
Permissible exjdosives 26
Classilication of permissible explosives 27
Advantages of permissible explosives 27
Danger from permissible explosives 27
Freezing of permissible explosives . . 28
Danger from exposure to high temperatures 28
Do not expose to sunlight 28
Keep explosives dry 28
Do not dry explosives too much 28
Use explosives promptly 28
Injury to cartridges from rough handling 29
Care in handling cartridges 29
Shipment of explosives 29
Storage of explosives - 29
Magazines 29
Detonators never to be stored with other explosives - 29
Opening boxes of explosives 30
Thawing frozen explosives 30
Thawers for explosives 30
Complete thawing necessary 30
Thaw houses 31
Thaw" houses not to be used for storage 32
Squibs, fuse, and detonators 33
Means of exploding explosives 33
Miner's squibs 33
How squibs work 33
Squibs should not be used in fiery mines 33
Fuse 33
A ction of fuse 34
Testing fuse 34
Fuse injured by bad handling 34
Care in cutting fuse 34
Detonators 34
Advantage in use of detonators 34
Grades of detonators 35
Attaching detonators to fuse 35
Fuse not to be used in fiery mines 35
Fuse and detonators must be of standard size 35
Electric detonators 36
Grades of electric detonators 36
Firing electric detonators 36
Delay-action electric detonators 37
Danger in use of detonators 37
(loN'l'KN'l'H. 0
Mining (oal with cxploHiviH 38
(/onditioiiH in coal iiiinoH 38
SI looting' tfl" tlu Holid -'{H
Need of llio Biow-acliiiK cxploHivcs 'M
Dependent, nliots 39
Overcluirdng 3'.J
Undereiittinjj; und slwurin 39
Sheurinji' 40
Cluire of explosive in sliearinj 40
Undeivutting 41
Cliarge in nnderentt in 41
IMjieini; of the shots 41
Advantage of small charges 42
Dei)tii of undercutting 42
Care in using permissible explosives 43
Dust must be wet down and removed 43
Humidifying mines 43
Shot iirea 43
] ioading and tiring charges of explosives 45
Loading bore holes 45
Primer 45
Densify of charge 45
Loading black blasting powder 45
Tamping stick 45
Placing fuse and tamjiing 46
Danger of tiring untamped holes 46
Fitting fuse in detonator 46
Fitting fuse and detonator in primer 46
Be careful not to pull detonator out of primer 46
Detonator not be completely buried 47
Dirt between cartridges 47
Fastening electric detonators 47
Some explosives, if split and tightly packed, may not explode 48
Instructions for tamping 48
Air spacing of charge to reduce shattering effect 48
Electric igniter 48
Instantaneous fuse , 48
Delay-action detonators 49
Safety in single shots — time between them 49
Danger from flame and sparks 49
Failure of formulas for size of charges 49
Comparison of effects of different explosives 49
Size of charge of permissible explosives for coal mines 50
Objections to overloading 50
Objections to underloading 50
Premature explosions, misfires, and hangfires 51
Keep away from a hangfire for half an hour 51
Partial explosions 51
Firing blasts by electricity 52
Danger of firing by flame 52
Connecting legs to leading wires 52
Splices should not be opposite — wrapping sj)lices 52
6 Contents.
Firing blasts by electricity — Continued. Page.
Connecting leading wires to firing machine 52
All connections to be made from bore hole to firing machine 52
Connecting detonators in series 53
Connecting holes 53
Danger from a break or short cinniit 53
Sources of current 53
Dry cells 53
Portable devices 54
Testing strength of batteries 54
Firing from electric-lighting circuit 54
Connecting up in parallel 54
Premature electric firing 54
Dynamo-electric machines 54
Rating of dynamo-electric machines 55
Magnetos 55
Leading wires 55
Insulation of leading wires 55
Inspection and repair of leading wires after firing 55
Testing the line 56
Use of galvanometer 56
Safety precautions to be taken 56
Explosives in sinking shafts and blastmg rock and dirt 57
Difference in conditions 57
Loading, tamping, and firing 57
Tamping high explosives 57
Proper strength of detonators 57
Firing shots in groups 58
Firing simultaneously , 58
Various explosives for use in sinking shafts and driving entries 58
Ammonia dynamites 59
Caution in use of ammonia dynamites 59
Gelatin dynamites 59
Safe shipment and storage of explosives 61
Responsibility to public 61
Federal law and Interstate Commerce Commission regulations 61
Explosives in baggage or household goods 61
Magazine buildings 61
Isolation of magazines 64
Care of magazines 65
Appendix 67
United States Geological Survey test requirements for explosives 68
Publications on mine accidents and explosives 61
Illustrations.
Platk I. (JjiH and (lust 'ulUiy Xo. I, rittshiir'r testing ntation FroritiHjiiert;.
II. Explosion at u coal mine near Newcastle, New South Wales 12
III. Explosion from coal dust in as and dust gallery No. 1, I'ittsburg
testin;:: station II
IV. A, Explosion of hi.<j:h explosive in bomb filled with water; B, Screens
for separatinjj: different-sized powder {irains 10
V. Ay Grains of black blasting powder; mixture of different-sized
grains of black blasting powder 18
VI. A, Flames from explosion of equal weights of black blasting powder and of a permissible explosive; B, boxes of dynamite, showing
method of packing it; C, thawer for frozen explosives 24
VII. Ay Miner's squib; B, miner's squib and fuse 32
VIII. u4, X-ray print of defective fuse; /?, side spitting of a fuse .34
IX. A, Crimping detonator on fuse; B, detonators and electric deto- nators 36
X. Ay Fuse and detonator fitted into primer; B, secondary battery, firing machine, and dry cell; C, testing firing machines and bat- teries 54
FiGUEE 1. Thaw house for frozen explosives; elevation 30
2. Thaw house for frozen explosives; section 31
3. Electric detonator; showing its component parts 36
4. Shooting off the solid 39
5. Shearing 40
6. Snubbing shot 41
7. First or "buster" shot 42
8. Bore hole fot permissible explosives 43
9. Bore hole ready for firing 45
10. Loaded bore hole, showing air space about the charge 48
11. Foundation plan, front elevation, and plan of ventilator hole of
brick magazine 62
12. Sections of magazine 63
Note.
This bulletin is issued and distributed in the hope that it may lessen the accidents caused by the improper use of explosives in mining operations. The Bureau of Mines will be glad to receive any suggestions as to additions or other changes which, in the opinion of readers, would increase the usefulness of this primer in accomphshing this purpose.
Int1{()I)U(Ti0N.
Uv J. A. Iiolmks.
Of Iho coiuiuon c.juisos of tho lai|,(W mine, nc-c.idontH, such us falls of roof and coal, and dust explosions, mine iircs, and tho niisTisc of explosives, all of which are often closely related, each must bo studied and fought in a manner ])eculiar to itself. The last mentioned, the misuse of black })owder and other explosives, is sometimes considered the least important of these causes of mine accidents; but its impor- tance is much <ireater than the statistics indicate, for the reason that the misuse of explosives is the true (ause of many of the fatal mine fires, gas or dust explosions, and falls of roof that are credited to other causes.
Both the quantity of explosives used and the number of purposes to which they are applied are increasing. They aie now made at about 150 plants, in different parts of the United States, and the product of a single year is estimated at nearly 500,000,000 pounds. Nothing in all this material is a safe or "safety" explosive when in the hands of a careless or ignorant person; and this is true whether considered in connection with the shipment or the use of these explosives. In addition to the large losses of life and property resulting from an improper use of explosives in mining, the recent statistics of the railway bureau for the safe transportation of explo- sives have shown more than 400 persons killed or injured and over S3, 000, 000 worth of property destroyed by explosives in transit by rail. The fact that three years of cooperative effort under the wise supervision of this bureau has reduced these losses to almost nothing encourages the hope that similar cooperative effort likewise greatly lessen losses of life and property from the use of explosives in mining.
The additions to the large death roll of our mines make a recurring appeal to the public for fair treatment of the coal-mining industry, and to the miner and the manager that they join in every possible effort for greater safety. It may never be possible imder conditions such as exist to-day to prevent mine accidents entirely. Little can be accomplished in that direction by either the operators or the miners working alone, but experience in all countries shows that
10 Introduction.
througli the hearty determined cooperation of both the accidents niay bo greatly reduced. This will require wise laws and regulations based on fact and experience, and the strictest possible discipline.
The accidents resulting from the improper use of explosives in mining can be most certainly prevented (1) through the use of the best and safest explosives; (2) through the handling and firing of these explosives in the safest manner by carefully selected and trained men; and (3) through the strict and competent oversight of these men.
This little book on explosives is published in the hope that it may aid in preventing such accidents. The aim has been to tell what explosives are and how should be handled, w4th a view to greater safety; and to do this in language free of unnecessary technicalities. It has been prepared by Charles E. Munroe, con- sulting chemist, and Clarence Hall, explosives engineer of the Bureau of Mines. It has been revised in the light of suggestions made by the mining engineers associated with the bureau, by several mine managers, by experts associated with the manufacture of explosives, and by Col. B. W. Dunn, chief of the bureau for the safe transporta- tion of explosives, who has also kindly added a brief chapter on the transportation of explosives.
Much of the information in this primer has been obtained from experiments conducted by the technologic branch of the United States Geological Survey at the mining experiment station at Pitts- burg, Pa. This station, wdiich is now part of the Bureau of Mines, was authorized for conducting investigations as to the ''causes of mine explosions." These investigations have shown the recent development of a new type of short-flame explosives, which can be used with greater safety than black powder in mines where there is dangerous gas or inflammable dust, because the flame from the explosion of black powder lasts from 2,500 to 3,500 times as long as does the flame from these newer explosives, and is therefore more likely to ignite the gas or dust in such mines.
A rUIMER ON KXI'lOSIVKS TOI! (!()AL MINKIIS.
By C. E. MiiNKoi-: and (i.auenck IIai.l.
( Ombustion And Explosion.
There is probably no activity of nature with which man is better
acquainted or has been l()n<ijer acquainted than with
fire, oi' whicli he has mack use from the earhest (hiys
lor warming his body, cooking his food, giving hhn light, and in more
recent times for breaking down rock, for making steam, and.for other
purposes. He has observed that a great number of substances can be
burned, such as wood, charcoal, coal, suli)hur, phos-
combustibie sub- pijorus, nnigncsium, zinc, oil and gas in their many
varieties, and many others, and he has made use of
them to produce heat and light. He has noticed that when wood is
burned in large sticks it is difficult to start the fire, and that where
there are but a few hirge sticks the fire burns but slowly. Wlien the
wood is cut into kindlings and these are heaped together, they burn
more rapidly. When the kindlings are cut into shavings and these
are piled together, they burn still more rapidly; and when the wood
is cut into dust by means of a saw and this dust is suspended in the
air and set on fire, it burns with explosive rapidity.
The same thing is found to be true of the other substances that burn under ordinary circumstances and are therefore called com- bustible. That is, the more finely divided they are and the more intimately this finely divided material is mixed with the air, the more rapid is the burning or combustion. This intimate mixture with the air is best attained with gases such as marsh gas (the fire damp found in mines), coal gas such as is used for lighting, and acetylene, or with vapors such as those from gasoline; and when these are thus inti- mately mixed with the air the combustion goes on so rapidly that it takes the form of an explosion. Although an explo- sion is easily produced by mixing combustible gas or vapor and air in the right proportions, explosions may also be obtained by mixing combustible dusts with the air in the right proportions and igniting them; and therefore we are
Dust explosions. o o ;
not surprised to hear that explosions have been occa- sioned by mixtures of sawdust or flour dust or starch or sugar or soap
12 A Primer On Explosives For Coal Miners.
or coal dust with tlie air. Many ex|)losions thus j)ro(Juced are very violent, and destroy life and property. (See Pis. 11 and III.)
In each of the kinds of combustion or explosion that have been
spoken of the combustible substance is mixed with
Air necessary to .qj- hc presence of air is necessary for the
ordinary combus- , . ,. . ,
tion. combustion or burning is proved by the lact that
when we cut off the air from contact with a burning
body the lire goes out, or, as we say, we have smothered the fire. Tlie reason for this has been found in the nature of one of the sev- eral different substances that the air is composed of.
Oxygen of the air This is the 2:as named oxygen, which is about one- necessary for com- , /.111 1 T Ml
bustion. mtii 01 the whole volume of the air. It is possible
to separate this oxygen from the air, and when this has been done and burning bodies are brought into contact with this separated oxygen it is found that they burn much more rapidly than in air, and that the combustion is much more brilliant. By repeated experiment it has been proved that all ordinary combus- tion is caused by the combination of the combustible substance with tliis oxygen of the atmosphere. Air deprived of its oxygen will not support combustion or life.
In view of these facts, and in view, further, of the fact that there are other substances in nature besides air that con- bustible substances, it Avould seem probable that com- bustion could be brought about through the aid of such oxygen- containing bodies; and this was long ago proved to be true. One of the first, if not the first, of such bodies that became known to man is saltpeter, also cjdled niter, or potassium nitrate, wdiich, because it occurs as a white efflorescence, like frost, on the surface of the soil in India, has been called India saltpeter, although it has been found to some extent in many parts of the world.
If solid saltpeter in the dry condition is mixed quite thoroughly a solid combustible substance, such as charcoal, comblTtion.'''''''*' the mixture burns easily when once it is ignited. The advantage of such a mixture is that the oxygen which is to support the combustion is in close contact with the char- coal which is to be burned, and that, therefore, this substance or mixture can be set afire and will burn vithout contact with the air, and will so continue to burn until the charcoal is completely con- sumed. As a result of the burning of the charcoal or carbon with the oxygen of the saltpeter a gas is formed. As Charcoal with another result of the burning of this mixture of char- heat and gas. coal and saltpeter heat is produced, and this heat warms up the gas, so that if it is unconfined its vol- ume becomes greatly expanded, and if it is confined it exerts pressure
A ON KXri-OSIVI'.S l"()U COAI, M I N KHS. 1 .*i
Mild <l<)('.s work. llciH'c, il" such ji mixliiir Ix' l)iim.'(| in Hk- Ijoic of a rock, it iiuiy bronk down IIk rock, or in I lie l)nrr<',lof a, Min, it will di'ivc Old. IIk .
It is found, hovvov<M-, that it is not oasy to ignit( such a inixtnrt* of
cimicoal and sallpctcr, <v(MI wIhmi niix<Ml in tiic Ixst
Sulphur Is added possible Way, and to ovcMConu (his diflicidty use is
to make the mixture , , ' , , , i , , i
Ignite easily. iiuuM ol aiiol luM' sin)stancc tluit ijMutcs oasily, one
luixturo ol' charcoal and salt[). This substance is sidphur, or l)rimstono, such as has boon used in th( |)ast, for I ho tips of sulj)liur or brinistono niatchos, for which (ho saiuo object of easy i<nition was sou<jht. So eventually the luixture has been made of charcoal and salt|)eter and sulphur, which are iinely <:Ci'Oun(l and closely mixed and then formed into grains, and such a mixture is called (gunpowder. As has been pointed out, it is simple combustion that takes place when such mixtures are set afire, but on account of the thoroughness of the mixing, the ])roportions in which the different substances are mixed, and the way in which the material is finally made into grains, this combustion may proceed so rapidly that there is an explosion, which is powerful because the solid mixture, occupying a very small space, gives on combustion a large volume of highly heated gases. About 1821 there was discovered in the desert regions of Peru and Chile another saltpeter, sodium nitrate, which has come to be known by the name of Chile saltpeter. Like the India saltpeter, potassiimi nitrate, it con- tains oxygen, and it give up its oxygen to combustible substances with ease at a relatively low temperature. Hence a mixture of it with charcoal (known also as carbon) and sulphur makes a body similar to that produced with the India saltpeter, and since 1857 such a mixture has been extensively used, especially in this country, for blasting in rock and in mines. Besides the India and the Chile saltpeters, many other solid sub- stances that contain oxygen and will give up their bodr oxygen easily, on heating, to combustible substances have become known, and many of them have been tried in the formation of explosive mixtures. Though one or two of them are used to some extent, as will be shown further on, none are used so largely as the saltpeters.
It has also been found that we can get the oxygen out of the salt- peters in other ways than by firing an explosive saitpeter. mixturo, as, for instance, by heating either the India or the Chile saltpeter in a proper manner with sul- phuric acid, when we obtain from them nitric acid, which contains all of the oxygen originally in the saltpeters. It has further been
14 A PRIMKli ON KXPl.OSIVKS FOR (OAh MTNKRS.
learned that when substances like cotton or starch or fjlycerin are treated \vitl\ nitric acid in the proper way there are Putting oxygen formed, froni tlie cotton, guncotton, or nitrocellulose, from tlie ijlycerin, nitroglycerin; and through this moans the cotton, the starch, and the glycerin, which are all com- bustible substances, are converted into substances much more higldy explosive and more ])owerful than mixtures made with the saltpeter and sul])]iur and combustible substances. In fact, such bodies can be made to explode by a shock such as is produced by a detonator or blasting cap when fired in contact mth them, and the explosion is extremely rapid and very much more powerful than that of the salt- peter mixtures.
It has also been found that by the action of alcohol upon nitric- acid solutions of metals, such as copper or silver or mercury, under proper precautions, substances may be formed which are still more sensitive and still more violent in their explosive effects than gun- cotton or nitroglycerin. The best known and the Sensitiveness and most widely uscd of tlicsc substauccs is fulminate
violence of fulminate n ttt-i i j i i i
of mercury. mcrcury. When dry, this substance is so sensi-
tive that a very slight blow, Yery little friction, or a slight rise in temperature will cause it to explode, and on explosion it produces a shattering effect upon any substance with which it is in contact. Moreover, the character of its explosion is such that if but a small mass of it is exploded in proper contact with guncotton or nitroglycerin or dynamite or other similar explosive, it will cause each of them to undergo a very violent explosion, which also will produce a shattering effect on the bodies with which they are in contact.
From what has been said it will be seen that there are at least two classes of explosives. One class is the saltpeter mixtures, in which an explosion is brought about by simple combustion that proceeds rapidly and gives rise to a large volume of highly heated gases, though almost one-half of the mass remains as a solid residue. Explosives of this class exert a relatively slow pushing effect
Lew explosives. i i i i
upon the substances with which they are m contact when they explode, and are called '4ow" explosives. In the other class are explosives of the character of guncotton and nitroglycerin, which undergo explosion by being suddenly and wholly resolved into a large volume of highly heated gases, the change proceeding many times faster than the combustion that takes place in the salt- peter class of explosives. Because of their speed and power these
explosives have a shattering effect upon the sub-
HgtIi 6XDlOSiV6S* cT* i
stances with which they are in contact, and are known as ''high" explosives, and also sometimes as detonating explosives.
A IMUMKi: ON KXIM.OSIVKS I'Olt COAL MINKRK. 15
Im'civ <'\|)I(>si\'(', when exploded, exeils pi'essiire in every diree- lioii. When Inid on loj) of n mck nnd exploded, iin-
Couflnoment os- |),,\\,1,.|- j,,,,] (.(Imm- cX p|( (si \C.S do Mot nirecl, llie entlal to use of ox- , i i i i
plosives. rock, l)eeaiis( u\oy (xpl()(lo so slowly inat. tlio asos
formed cnn lifl llie nir a])()ve tlieni and os(;ap(; hut dynamite, fulniinnte of nieicury, and othcM* lu<li explosives, if laid upon ])ritt.le or soft rock and detonated, may shatter it., heeausc they ox])l()(l{ so quickly that, tlu jases forir.ed can not lift, the laro voIuiik; of air wliicli confines them without pressin*:; ])ack forcihiy ajainst. the rock. (Sec PI. IV, A.) Tliis confinement air is not, however, close enough to *:;i\(' th( hest result, with any explosive. By l)orin< a liolc in rock and tampinj the explosive firmly in it, gunpowder and other low explosives may he made to break the rock, or a much l(;.s.s quantity of liiuli explosive will break tlic rock than is requinul to break it when laid u])on it. Coiilming an explosive is the ch(;aj)est and best way to use it.
It is foolish and dangerous for an inexperienced person to attempt
to manufacture any kind of an explosive except
Fouy of attempt- udcr tlic supcrvisioii and direction of a trustworthy
Ing: to make explo- i i -n i i at
sives. person who is skilled in the art. Many serious acci-
dents, which liave destroyed lives or inflicted injury on persons and property, have been caused by such attempts.
Explosives,
As may be inferred from what lias already been said, a large num- ber of substances are known and used as explosives.
Gunpowder. .
The one longest known and used is gunpowder, which has certainly been used since early in the fourteenth century. This is made by intimately mixing 75 parts of India saltpeter (potas- sium nitrate) with 15 parts of charcoal and 10 parts of sulphur. Each of these ingredients is ground to a fine powder, and then they are ground together w'hile moistened water, in the proportions given, until the mixing is complete. The material is pressed into cakes, which are then broken up into grains, which are dried, glazed by rubbing, and sorted by the aid of sieves into the various desired sizes.
Formerl} this India saltpeter powder was used both in guns and
in blasting, and while to-day some of it is used powder. in blasting, the larger part of what is used in this
country under the name of black blasting powder is composed of 73 parts of Chile saltpeter (sodium nitrate or nitrate of soda), 16 parts of charcoal, and 11 parts of sulphur. This black blast- ing powder is made in a manner similar to that described for gunpow- der, but less time is spent in making the mixture, and the charcoal is usually obtained from coarser-grained woods. The Chile saltpeter will supply more oxygen, and supply it more easily, than the India saltpeter, and therefore is a better and cheaper oxidizing agent; but the Chile saltpeter is not used in the manufacture of gunpowder because when it is exposed to moist air it takes up water by absorption
from the air and becomes wet. So powder or other dampness '°™ explosives in wliich this Chile saltpeter (nitrate
of soda) is used likewise take up moisture when exposed to the air and become damp, so that it is difficult, and sometimes impossible, to set fire to them. As gunpowder for use in guns and firearms must often be kept for a great many years, and yet always be in such condition that it can be fired at any moment with certainty, this property of absorbing moisture from the air makes the nitrate of soda unfit for use in gunpowder;
but blasting powder is not expected to be stored for
Keep powder dry. , , ... . ., ,
years, and m magazmes at mmes it is quite possible to store it for a wliile so as to protect it from exposure to damp air. Besides, by proper management it is possible to obtain this blastmg powder fresh from the manufacturer and use it promptly while in
flllH! All f)l MINTM
KULLfTIN PLAT! IV
.1. Explosion Of High Explosive In Bomb Filled With Water.
B. Screens For Separating Different-Sized Powder Grains.
A I'HIMKU ON KXI'LOSIVKS I'di; ((i\L MINKHS.
j,lnif. condil ion ; Ikmicc jkIn iiiilnc imiy hikcn, fnf (Monoinir iisr, of lll( sii|)(Mi(H" ('diciciicv and (Ii('h|)IM'ss of llic nili'nlr ol sodn in llic inninirnc(iiii-( of blasting powders if w( ) iJiciii dry.
lilack hlnstin |)o\vd<'r comrs into the iiuirkct. in tli<'- form of ;rjiiijs \vhos( (mI;('s luiv( been ronudccl oil' hy rid)l>in
OrauulatliiK (,, wrttluM' in H IVVol\in<' lnuivl alld wllicll HIV llsllully
cojit'Cd on 11h' siirfMcc, or , ns il. is ti'inu'd, will) i'a|)hi(.(', or MmcU lend. ohjccl, in ronndin; nnd <la/,in; llio jji'jiiiis is to rcMidcr iIhmu fr('< running, and I.Im also serves to d(Iay somewhat the takini,' up of moisture from th( air by Uio jjjraiiis.
The powder is divided into grades according to the size of jrains, as separated and eolleeted by sieves of differeiit sizes of openinjjs. (See PI. IV, B.) Tlio sizes most usu- ally offered for sale are eallcMl CCi\ iV, C, F, FF, FFF, and FFFF. Of tliese, CCV re|)resents the lar<i:est <i:raiiis, about five- ei.<j: iiH'li in diameter, and FFFF represents the smallest rairrs, about one-sixteenth inch in diameter. (See Vl. Y, A.) TJie rela- tion between the hitters desijnatinj the sizes of the |)()W(ler <rains and the sieves by which the different sizes are separated is shown ui the f ollowinsr table :
Sle of powder grains.
Relation between sizes of black blasting powder and separating sieve.
Diameter of
round holes
round holes
Size of
in screens
in screens
grains.
through
on which
which grains
grains.
pass.
collect.
i; inch
if inch
II inch
M inch
U inch
F
it inch
Ff
il inch
S7 inch
Fff
A inch
A inch
Ffff
?jinch
(a) inch
a Or 28-niesh bolting cloth.
To get the best results in the use of this powder in ordinary blast- ing, the grains should be of uniform size, so that Danger in using a the miner, having determined the best size of charge,
sized grains. ma}" liave no diHiculty in repeatmg it. Unlortunately not enough care is taken in separating the grains mto tlie different sizes, and powders have appeared in the market in which a considerable number of different sizes of grains were mixed together, so that the miner has obtained quite different re- sults from his different shots in the same mine of coal the same grade of powder. (See PL V, B.) Moreover, where large and small grains of powder are mixed in a charge, the fine grains, which 99160°— Bull. 17—11 2
Potassium chlo- rate.
18 A Primer On Explosives For (Oai. Miners.
burn freely, may ])n)(hi('(, in l)urning enough pressure to throw the large grains out into the mine where they can set the gas and dust afire. This makes such a mixture of grains a dangerous one in use. Tt lias already been said that man}- other substances besides India saltpeter (potassium nitrate) and Chile saltpeter (sodium nitrate) are known which contain ox3gen in such quantity and in such manner that they may be used as the oxidizing agents in forming explosives. Among these is tlie substance known as potassium chlorate. More than 100 years ago an eminent French chemist showed that when it was mixed witli ('()ml)ustible substances a most powerful explosive was produced; ])ut, unfortunately, this mixture was found to be so sensitive to friction, blows, and heat as to endanger the lives of those who sought to handle and use it. Many of the mixtures produced with potassium chlorate are so easy to prepare and explode with such violence that a great many persons have been tempted to make them, but until recently all those that have been devised have been rejected as unfit for use because they were liable to destroy those who attempted to make or use them. It is found, however, that when dry and finely ground potassium chlorate is mixed with a body like starch, and with oil and other substances, an explosive is produced that is fairly safe to handle. Mixtures of this nature have met with some use in Europe.
Attention has also been called (p. 14) to the fact that when puri- fied drv cotton is immersed in nitric acid in the
Nitrocellulose, '' ... , . , . ,
proper manner it is changed mto an explosive sub- stance through reaction with the nitric acid. When we withdraw the fibrous cotton from the nitric acid, wash it thoroughly to remove any acid that sticks to it, and then carefully dry it at a low temperature, the cotton appears unchanged to the eye, even when examined most carefully. It has, however, become a little harsh to the touch. When rubbed, it becomes electrified so that it sticks to the fingers, and when a flame is applied to it, flashes ofl with great rapidit} In practice, a mixture of sulphuric acid is used with the nitric acid in nitrating the cotton. By varying the strength and the proportions of the nitric and sulphuric acids, their temperature when the cotton is dipped in them, and the length of time that the cotton is in them, we can get a number of different products varying in the rate at which they will burn and in the degree to which they are soluble in various solvents; but every such product results from the replace- ment of more or less of the element known as hydrogen, which was present in the cotton, by nitrogen and oxygen (indicated by the formula NOj), which came from the nitric acid. Such a product, obtained by the action of the nitric acid on the cotton, will take
2q
A l'IMMi;i! ON i:.\IM.OSIVKS I'OU ("OAI. MINKHS. M)
life, niid Imiii llic more cnsiK llic n'oilcr Hie iiiiiiihcr ol ;r()ijj>.s (hill liavc rcpliiccd li\ (lr<);j;('ii in llir col Ion. We nmy, loi- <-oi)- V(MU(Mi('<\ (li\i(l(' llicsc \iiiions proJiicls inlo I wo cIhsmos. 'J'lioHii whicli conlniii I lie fewer ol" llicsr r(Hi|)s nr<' cmINmI pyroxylin, <n' soliihU iii(i'()('('lliil<>s(>. oi- collodion collon. nnd (hose wliicli conlain IIk <jjr(n((M" inimlxM- of I lie SO., rouj>s me known as ;nn collon. In I lic mninil'.'icl ui-( ol" mm col Ion 1 lie vci'v si I'oncsl nil ric and snlpliuric acids arc . After (lie |)I"(kIiic1 has washed so iis lo rcniovo most (d' the acid sli(d\in lo it , it is j)ul|)e(l w hile wet inlo a line powder in a. machine as is used in pulpini!; paper slock, and when the iun cotton has heen washed in this powdei'cd condition so as lo i-einovc the last li-ac(s of acid, it, is molded into l)l()cks and is used as ail explosive in that form.
Nilr()<:;lyc(M-in is pr(pare(l by slowly runnin< glycerin into a mixture of llu sti"on<z;esl nitric and sulj)lnn'ic acids,
Nitroglycerin. i i i r i I i 4 I I n
the whole l)em<]j stirred and kept cool during the process of mixinj. The reaction which takes place between the glycerin and the nitric acid is similar to that which takes place with the cotton. As a result of the reaction, NO. groups from the nitric acid replace hydrogen in the glycerin, and the mild, sweet, harmhvss glycerin is thereby changed into the powerful and dangerous explo- sive nitroglycerin. Nitroglycerin is a rather dense oil-like liquid. When pure it is colorless, but as it appea.rs in the market it is usually })ale yellow. It is somewhat poisonous, and one can be poisoned by it not only through the mouth but also by breathing its vapors or by allowing the liquid to touch the skm. A drop of it touching the tip of the finger will usually soon produce a violent headache. Fortu- nately, most persons lose their sensitiveness to poisoning after repeated contact, so that they cease to have the headache, but it
would still be dangerous for these persons to get any
may freeze after some exposure to a temperature of 52° F. (see p. 27) and it must be thawed before it can be properly used as an explosive.
Being a liquid, nitroglycerin is especially dangerous for ordmary
use, because it may escape from the cans or other Liquid nitro- yessels in wliicli it is carried or stored and run off
glycerin is especially . , , .
dangerous. to Considerable distances, so as to increase the chances
of accidental explosion by a blow, or friction, or heat; and also because it may, when placed in a bore hole, leak out into crevices or seams in the rock, and when fired give most undesirable results. In fact, during the middle of the last century, when it was offered for use, so many accidents occurred that many countries, by- law, forbade its use or manufacture. We can, however, prevent a
20 A PltlMKK EXPLOSIVES EOli COAL MINERS.
liquid Irom Mowing Mboiit by absort)ing it in a poious body, like a
s|)ong(\ This has been done with nitroglycerin, and the product is
called dynamite. Dynamite consists of nitrofflvcerin
Dynamite. , i i i- i i i ii i i i
absorbed m a solid body called the dope. There are many dynamites. One of the earliest known and used was made by absorbing the nitroglycerin in powdered ''rotten stone." As the ''rotten stone" coukl neither burn nor explode, it was called an in- active dope, and there are several varieties of dynamites with in- active dopes. On the other hand, nitroglycerin maybe absorbed in gun])owder. As the gunpowder explodes, as well as the nitroglycerin, when the dynamite is fiied, the gunpowder is called an active dope. There are a large number of dynamites made with active dopes, and with varying percentages of nitroglycerin. The standard straight dynamite used at the Pittsburg testing station may be taken as an exam])le of a d}Tiamite an active dope. It consists of the following:
CoinpoifUiun of standard straight dynamite.
Per cent.
Nitroglycerin 40
Nitrate of soda (sodium nitrate ) 44
Wood pulp L5
Carbonat e of lime calcium carbonate ) 1
Since it is a liquid, nitroglycerin, like other liquids, acts as a sol- vent, and it has been found that under certain con- Expiosive gelatin Jitjons it can dissolvc solublc nitrocellulose, and that mite. the mixture thus formed will set to a jelly-like
mass. In this way, or sometimes by the use of other solvents also, the substance known as explosive gelatin is formed, a substance that in some respects is regarded as the most nearly "ideal" explosive. However, it is too powerful for ordinary use in blasting, and it is therefore diluted by mixing it with a dope, such as the nitrate of soda and wood pulp used in straight dyna- mite. The mixture so formed is known as gelatin dynamite.
It has already been said that nitroglycerin when exposed to ordinary winter temperatures will freeze. Dynamite All explosives con- explosivc sclatin, and gelatin dynamite will also
taining nitroglycerin iii.i --x i i
freeze. ireezc, bccausc all oi them contain mtroglycerm, and,
like nitroglycerin, all of these substances should be properly thawed before any attempt is made to use them.
Each of these substances is put upon the market in the form of sticks or cartridges, which are made by wrapping tridgc"™ cylinders of the material m paper. The wrap- pers for djmamite and gelatin dynamite are paraf- fined to protect them from the action of water and the moisture ia
A I'Kimij: on i;\im.()si\'i:s kok cdAi, minkhs.
tho air, bocaiisc (li('\ coiilniii nil rale of soda ami liriicc may ahsorl*
moistlirci nixl Ixmoihc spoiled, and dcvdoj) new soinccs of duncf
in hniidlin and us(\ Tlicsc slicks usually vary in size from kovcu-
oihlhs inch to 'J I inches in dianiclcr, and llicy aic usuall}' S inches
loni;. 'rhe\ are usnall\' packecl in cuses conlainini* Packing dynamite. ..r,,, ,,
;)() pounds each. I he nniik I his side up, or ai
(lesi<in on the lop ol" Ihe case, shows Ihe posilioii in which llu cai-
tridjios aro j)n.cke(l. 'Tlie cases should always he placed so IJuil iIm
cartridjijos lie on their sides, and (h) lie so when iIk cases arci
storcHl with their toj) sides up.
For use ui coal mines it is su*:;<i:este(| that the explosive* he packed in cases or cartons <'ontainintj: the wcitht which the law of the <listrict peLiuits beiug taken into tho mine. (See PI. \'I, B.)
Besides cotton and jijlycerin, there are a larce number of substances,
such as suoar and starcli, that are chemically related to cotton and
ij;lycerin and throu<i;h the action of nitric acid, particularly in the
presence of sul])huiic acid, give rise to ex])losive substances, .\biny
of these have been produced, ])Ut so-called nitrostarch
Nltrostarch. -i i xi .1 I
IS the only one that seems to have any commercial importance. During the hist 10 years this has attracted some attention, and it has been ofl'ered for use both in this country and in Europe. It is a finely powdered substance like starch itself, but it does not need, as starch does, to be suspended in the air in order to explode on ignition, because even when in a pile it will burn with great rapidity if set afii-e, and tlirough the action of a detonator it explodes with great violence. It is not yet used by itself, but is used as a component in various explosive mixtures, particularly dynamites. Attention has been called to the use of potassium nitrate and so- dium nitrate in the manufacture of explosives. In Ammonium ni- 3ears another nitrate, formed by the union of ammonia with nitric acid and known as ammo- nium nitrate, has come to be somewhat largely used. It has been used in this country for more than a quarter of a century in the man- ufacture of some dynamites, taking the place of sodium nitrate and having the advantage over it that on explosion it goes completely into gases; but it has come to be used in Europe in the manufacture of special explosives for use in coal mines, for the reason that on ex- plosion it forms a large amount of water, and this lowers the tem- perature of all the products of the explosion. In the making of sev- eral of these ammonium-nitrate powders, various substances ob- tained from coal tar, which generally have been acted upon by nitric acid, are mixed with the ammonium nitrate.
22 A Primer On Explosives For Coal Miners.
The sii})st-anres derived from the coal tar, after having been acted
u[)OTi })y tlie nitric acid, are known as nitrosnbstitn-
Nitrosubstitution compounds. One of the best and longest known
of the substances obtained from coal tar is car- boHc acid, and wIhmi tliis acid reacts with strong nitric acid it gives us the nitrosubstitution compound known as picric acid. Other substances obtained from coal tar tliat are pretty well known are benzene, toluene, and naphthalene. When these are acted upon by nitric acid we obtain from them the nitrosubstitution compounds known as nitrobenzene, nitro toluene, and nitronaphthalene. These are but a few of the many substances that may be obtained from (;oal tar and furnish, through the action of nitric acid upon them, nitrosubstitution compounds. All the nitrosubstitution compounds will form explosives when mixed with oxidizing agents such as ammonium nitrate, or other nitrates, or chlorates, and many ex- plosives have l)een made from such mixtures. Moreover, these nitrosubstitution compounds have been used as components of dynamites, particularly because they lower the freezing point of the nitroglycerin in the dynamites.
The nitrosubstitution compounds are so called because the NOg
groups in them, obtained from the nitric acid, are Why nitrosubsti- Jiectlv Connected to the carbon atoms in the original
tution compounds i i i i
aresocaued. material, replacmg hydrogen atoms; whereas m gun
cotton, nitroglycerin, and bodies of that sort, the NO2 groups are linked to the carbon atoms of the original substance by means of atoms of oxygen. The nitrosubstitution compounds are usually ellowish to red crystalline solids, but as most of these solids are easily melted, they are often sent out in compact masses. A few of them are liquids at ordinary temperatures, and they have a marked aromatic odor. Some of these substances are poisonous. Great care should be taken in handling all of them, and one should especially avoid breathing their vapors.
As has been stated above, the most common fulminates are pro- duced by dissolving a metal, such as mercury, in a strong nitric acid, and pouring the solution into common alcohol. When the proportions used are correct and the operation is carried out in a proper manner, after an apparently vio- lent reaction there be produced a mass of fine, gray crystals that look quite alike. These crystals are fulminate of mercury, or mer- cury fulminate. The crystalline powder thus produced is washed with water to free it from acids and because of its extreme sensitiveness it is kept soaked with water until desired for use. It is principally used in loading blasting caps or detonators, and for this purpose the water may be removed from it by alcohol and it may be loaded into
A l'l{IMi:i{ ON KXTLOSIVKS KOH COAL MINKftS. 23
t\w ('o\)\wv capsules wliich w(l, vvil.li alcoliol, hiil i( should he jilways
honu ill mind (hnl, iJiis mercury fnlmimilc, cv<mi wImmi llioroiilily
soaki'd with or simk iiiidci' wal.cr or alcohol, will
DauKer with fui- LnMiiciidoiis vioh'Mc*' if oidy a .small
amoniil. ol" llic dry I'ldminat.c \n' exploded while toiic]iin<jj it, or very near il. Ileiicc extreme precautions should always bo taken wilh mercury fulmimite, whether the sul)st.anc<5 Ix wet or dry.
Tlio manufacture of explosives is by no means simj)le. I'rdess all
th( nuit(M'ials are of tlie proper kind and in ihe j)roper
Warning against condition aiid tlioy are used in tli( proper onhr, in
manufacturing ex- i i i i
plosives. tlie j)roper nuumer, w itii th( |)r()per tools and vessels,
and with all the [)r()per precautions at eacJi staje of the operation, the manufacture is a very dan<erous thinj to under- take and it is very foolish for anyone to undertake it by Jiimself.
Explosives For Use In Coal Mines.
It is evident that a large number of different explosives can be formed by mixing various combustible substances Number of expio- various oxidizing agents, or by using such mix- tures as dopes for dynamite, or by using them together with the different nitrosubstitution compounds. In fact, the num- ber is so great that a book published in 1895 gave the names of more than 1,000 different explosives, and many have been added to the list since that date. As the number of those in actual use is much smaller, it is clear that most of the explosives known are, for various reasons, unsuitable for use; indeed, no one of those more generally known is suitable for use under all circumstances. For instance, some of them on explosion give off a considerable volume of flame; some of them on explosion give off considerable volumes of poisonous or noxious gases; some of them explode so quickh as to shatter the rock or other material in which they are fired and break it down into fine pieces; some of them are too bulky; and so on.
It is evident that if we are seeking to break down the rock in an open quarry for the purpose of making use of that that produces a long flame, or gives off poisonous gases, or shatters the material, because the work is done in the open air, and because the rock has to be broken up into small pieces any- way, so that it is well for the explosive to do it. If, however, we sought to get out from that quarry blocks of stone such as marble or granite, which were to be used in building or for monuments, we should avoid using the shattering explosive and choose one that slowly, and without a shock, separates the rock mass from the deposit. Yet for this purpose also, as the work is in the open air, it might matter little if the explosive gave rise to a large flame or gave off poisonous gases, provided the quantit} of explosiA'e used was small. But the conditions in a coal mine are cidwork very different from those in a quarry. The mine is inclosed and not out in the open air, and, moreover, it is liable at any time to contain inflammable gases or coal dust, or both, which may form explosive mixtures with the air. If under these circumstances an explosive were used which gave off Dangerfrom j flame Oil firing, this flame, darting out from
flames in coal mines. . .
the bore hole, might set fire to the explosive mixture in the mine and produce a mine explosion. (See PI. VI, A.)
nuMrAii
( ii Mini '.
im
Hi
m
HiHHHI
K.P. R.P. M
M, J7.5
. Duration of flame, 1539 mill i&ec; height of flame, 50, 21 in. A BLACK BLASTING POWDER
O
Duration of flame, .342 millisec.-, height of flame, 19.79 in A PERMISSIBLE EXPLOSIVE
A. FLAMES FROM EXPLOSION OF EQUAL WEIGHTS OF BLACK BLASTING POWDER AND OF A
Permissible Explosive.
B. Boxes Of Dynamite, Showing Method Of Packing It.
C. TnA/.cR rOR rROZEN EXPLOSIVES.
(
A IMdlVII'lIt ON IIXIM.OSIVKS l'()|{ COAl, M I NKHH. 2f)
MornovcM", as tlx mine is mi iiicloscci space and as llic w liolrsoiiic ucss of I he air williiii il (Icjx'iids ii|)(ii ailificial vcn-
(llalioii, Il IS also ohjccl loiiahlc in siicli a iiiiiic lo make iiso of an explosive ;iviii; oil" any coiisidcraMc (|iianlily noxious iTJisos, which nuisl he removed ihe mine af'lei- the, explosion Ixoi'c* (h( minei* can safely I'eturn to his work.
Considonitions such as (liese have led lo an invest ial ion hy the
Bureau of Mines of the explosives olfered in the mar-
investiBatiou by ,.j. pm-posc of (let (Mil 1 i 11 iiir, ill the interest of
Bureau of Mines. ' ' . i i
the coal miner, which of such explosives nvo suitable for us( in coal mines and will do the work with the <n-eiitest dejroe of safety for the miner usinj them. Of course it is impossil)le to insure eomplete safety, for no explosive can he perfectly safe and every explosive should be treated with the <reatest care and con- sideration.
With this object in view tlie lureau of Mines lias a testing station
established at Pittsburg, Pa. (see PI. I, frontispiece),
Testing station at , , , , , i i i 1 1 i r
Pittsburg. where there has been erected a large gallery made or
Explosives gauery , 100 feet loug by 6 4 iuclics in diameter, and so made that it can be filled with fire damp, or with coal dust and air mixed, or with gas, dust, and air jnixed in any desired proportion, so as to reproduce the dangerous conditions that may occur in coal mmes. Attached to one end of the gallery is a very strong ''gun" with a chamber representing the bore hole in a mine. From this ''gun'' various exactl} determined quantities of the explo- sive to be tested may be fired, either untamped or tamped, into the mixture in the gallery, and thereby it can be learned whether or not the definitely known quantity of explosive used as described will cause the ignition and explosion of the mixture in the gallery\ Besides this gas and dust gallery there is at the testing station a collection of other apparatus and appliances by which to test the various proper- ties of explosives, and so to find their relative value and their relative safety for use in coal mines. This investigation has been going on since September, 1908, and there have already been pubhshed four lists of explosives that have passed all test requirements in a satisfac- tory manner and are considered to be suitable for use in coal mines, provided they are used under the prescribed conditions."
See p. 08 for prescribed conditions under which each of these explosives is to l)e used.
A Primer On Explosives For Coai. Miners.
These explosives are, therefore, called by the Bureau of Mines ''permissible explosives." The name of each brand Permissible expio- passcd the tests up to January 1, 1911,
together with the name of the manufacturer, is given in the following list:
sives
Permissible explosives tested prior to Jan. 1, 1911.
Brand.
Manufacturer.
Aetna coal powder A
Aetna coal powder A A
Aetna coal powder B
Aetna coal powder C
Aetna coal powder D
Bental coal powder No. 2
Bituminite No. 1
Bituminite No. 3
Bituminite No. 4
Bituminite No. 5
Bituminite No. 7
Black Diamond No. 3
Black Diamond No. 4
Carbonite No. 1
Carbonite No. 2
Carbonite No. 3
Carbonite No. 4
Carbonite No. 1-L. F
Carbonite No. 2-L. F
Coalite No. 1
Coalite No. 2-D
Coalite No. 2-D. L
Coalite No. 3-X
Coal special No. 1
Coal special No. 2
Coal special No. 3-C
Coal special No. 2-W
Coal special No. 3- W
Coal special No. 4
Coal special No. 5-L. F
Collier powder No. 2
Collier powder No. 4
Collier powder No. 5
Collier powder No. 5 special.. Collier powder No. 5-L. F
Collier powder No. X
Collier powder No. 2-L. F...
Collier powder No. 3
Collier powder No. 6-L. F. . . Collier powder No. 8-L. F...
Detonite special
Eureka No. 2-L. F
Giant A low-flame djTvaraite Giant B low-flame dynamite Giant C low-flame dynamite.
HeclaNo. 2 '
Kanite A
Masurite M. L. F
Meteor AXXO
Mine-ite A
Mine-ite B
Monobel No. 1
Monobel No. 2
Monobel No. 3
Nitro low-flame No. 1
Nitro low-flame No. 2
Titanite No. 3-P
Titanite No. 7-P
Titanite No. 8-P
Trojan coal powder A
Trojan coal powder B
Trojan coal powder C
Trojan coal powder D
Trojan coal powder E
Trojan coal powder F
Tunnelite No. 5
Tunnelite No. 6
Timnelite No. 7
Tunnelite No. 8
Timnelite No. 6-L. F
Tunnelite No. 8-L. F
Aetna Powder Co., Chicago, 111.
Do.
Do.
Do.
Do. Independent Powder Co. of Missouri, Joplin, Mo. Jefferson Powder Co., Birmingham, Ala.
Do.
Do.
Do.
Do. Illinois Powder Manufacturing Co., St. Louis, Mo.
Do. E. I. du Pont de Nemours Powder Co., Wilmington, Del.
Do.,
Do.
Do.
Do.
Do. Potts Powder Co., New York City.
Do.
Do.
Do. Keystone National Powder Co., Emporium, Pa.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do. The Detonite Co., Cincmnati, Ohio. G. R. McAbee Powder & Oil Co., Pittsburg, Pa. Giant Powder Co. (Consohdated), Giant, Cal.
Do.
Do. E. I. du Pont de Nemoiirs Powder Co., Wilmington, Del. W. H. Blumenstein Chemical Works, Pottsville, Pa. Masurite Explosives Co., Sharon, Pa. E. I. du Pont de Nemours Powder Co., Wilmington, Del. Bvuton Powder Co., Pittsburg, Pa.
Do. E. I. du Pont de Nemours Powder Co., Wilmington. Del.
Do.
Do. Nitro Powder Co., Kingston, N. Y
Do. Waclark Titanite Explosive Co., Corry, Pa.
Do.
Do. Pennsylvania Trojan Powder Co., Allentown, Pa,
d6.
Do. Do. Do.
Do. G. R. McAbee Powder &. Oil Co., Pittsburg, Pa. Do. Do. Do. Do. Do.
A iMMiMi.i; ON i;\n.(si\'i;s I'nis coal minkks. 27
Will) icIViriicc (() (he clnirnclci'ist ic coinpoiK'Hl of racli of tlioso
|)(Mniissil)l(' ('\|)l()siv('s, llicy may |)la<'('(l in lour
ciassiflcatiou of dasscs — jiinmoiiiu 111 iiitralo powders, i('j)r<'H(MiUMl hy
permissible explo- , , . i i I v
giygg Achilla, coal powder AA, nefilal coal j)oW(lcr iNo. 1,
Biliimiiiilc No. T), Bil iimiiiitc. No. 7, Coalite No. 3-X, Coal special No. CoHier powder No. 5, Collier powder No. .*i, Collier powder No. 5 special, Coiliei- j)owder No. 5 L. F., Collier powd(r No. X, Detonite spcM'ial, llecia No. 2, Kaiiili A, Alasiirilc M. L. F., Monobel No. I, Monobel No. 2, Moiiobel No. 3, Titaiiite No. 8-P, Titanito No. 7-P, and Titanite No. S-1; hydrated })oW(lerH, repre- sented by Meteor AXXO, and Ciant low-llanie dyiianiile A, li, and nitrostarcli powdeis, i-epresented by Trojan coal powders A, B, V, n, F, and F; and nil rotijlycerin powders, represented by all the others on the list.
The explosives on the list wliich are marked Tj. F. contain nitro- substitution compounds or other materials which have been added to lower their fi-eezing points.
With the exception of Detonite special, Hecla No. 2, Kanite A, Masurite M. L. F., Titanite No. 3-P, Titanite No. 7-P, Titanite No. 8-P, and the Trojan coal powders A, B, C, D, E, and ¥, all of the powders mentioned in the list contain nitro<2;lycerin, and they are all of the general nature of dynamite; but the components and propor- tions of the dopes have been so chosen and the mixtures so made as to modify greatly the shattering effect upon explosion and to yield a relativel} cool flame. As a result, the flames produced are short and not lasting, and coal is thrown out without being Advantages of powdered , when the proper charge of such an explosive
permissible explo-! , i,i. i i i i n-M
sives. IS used and this charge is properly placed, these
explosives are designed to take the place of black blasting powder, wliich has been found to be unsuited for use in coal mines where dangerous gas or inflammable dust is present, because of the great mass of flame which it produces and the long time that this flame lasts, and because of the quantity of poisonous smoke and nox- ious gases wiiich it gies out when exploded. Although explosives of the kind represented in the list of permissible explosives have been introduced into this country only during the last few years, yet their consumption now amounts to several million pounds annually and is rapidly growing.
Unfortunately, though the permissible explosives are good coal getters and yield short flames that do not last and miribfe''ioleT" of low temperature, so that there is Uttle dan- ger of igniting the explosive gases and dusts in mines when they are used, still the gases they yield on explosion may be noxious and inflammable; and miners are warned, when using per- missible explosives, not to return to the breast after firing them any
28 A PRIMER ON EXrLOttlVKS I'OR COaL MINERS.
sooner than they would if they had fired a charge of black blasting powder.
From what has been said regarding nitroglycerin, it follows that
all these permissible explosives, except Detonite spe- mi!s7bTe%i:Lr Hecla No. 2, Kanite A, Masurite M. L. F.,
Titanite No. 3-P, Titanite No. 7-P, Titanite No. 8-P, and Trojan coal powder. A, B, C, D, E, and F will freeze when exposed long enough to low temperatures, and then they must be thawed before they can be properly used. It is true that in making several of them, especially those marked L. F., materials have been added that prevent their freezing so readily, but the manufacturers do not claim that such explosives will remain unfrozen when the tempera- ture falls below 35° F. To keep any of the nitroglycerin' explosives permanently thawed, they should be stored where the temperature does not go below 52° F. On the other hand, care should be taken
that none of these explosives is subjected to liigh Danger from ex- temperatures, for this will render all of them more
posure to high tem- ,, . i-tii
peratures. sensitive to Explosion and is likely to cause the de-
composition of some of them. It is best that the temperature of magazines in which they are stored should not rise above 90° F.
Explosives should not be exposed for any length of time to direct sunlight, because this may lead to decomposition in sunught* those containing nitroglycerin, nitrocellulose, nitro- starch, or substances of that kind. Explosives should be stored in a dry place, for many of them contain considerable quantities of ammonium nitrate or of sodium nitrate and so will take up moisture from damp air and become damp. Too great dampness makes the explosive not only harder to Keep explosives weaker when fired. Besides, if the explo- sive is damp the nature of the gases produced will be different. Moreover, as bodies hke dynamite become moist, the nitroglycerin contained in them tends to run out; that is, what is called exudation takes place, and all the dangers follow that belong to liquid nitroglycerin.
On the other hand, explosives should not be kept in an extremely
place, for all of them, as made, contain some
sivstoo*muTh°" moisture, and if the place of storage is very dry the
explosive may lose this moisture. Such a change in composition will affect the explosive so as to change the speed with wliich the explosive reaction takes place within it, and therefore the character of the work which it does when exploded.
Naturally, the longer an explosive is kept in storage M place in it, and therefore the explosive should be obtained in as fresh a condition as possible and should be used as
A riilMK-lt ON KXIM.OSIVKS I'Olt (UAIi MINKHH. 20
Sixrn MS possihir nllri- il is icccivrd. Also, it slxnild hr k<'|)t stored in its or'iiind pacUiics in llic iini;i;)i/iin' outside iIk iiiiiic until wjmtcMl for inniKMlialo iiso, and I lien used prompt ly.
Dynaniito is |)iit up in sticks, which me \vrMpp('(l in and tlio
cni't I'idLTs so lornicd ni( nsindly dippccl in paradin to
Injury to car- the wi'appin watcM'pfool". As rou[li jian-
trldges from rough i r i i i i i i i i i
handling. (Iliii tJic joldcd (Ml<;es nniv he broken open and tju5
contents of t h<' cait ritl<e lliei'ehy exposed to t)je nioist- nro of tlie air, tlies( cait i'id<j:es slionid he hjindh'd witli 'icni cure, and they are host carried to t]e phico wliere tliey ai-e to he usecl in th(i cartons in w]iicli they are boujlit.
In ]iandlin<j; cxpIosiv(*s tlic <ireatost care must f)e taken to prevent their rallin< or <j;ettin<j sjiocks. TJiev must not he cartoidges. throvvn or (h-opped, and |)orti()ns of tlie j)ow(hT fall- ing]; from the cartridges must be carefully ji;uarde(l against friction, blows, or fire.
Explosives should never be carried by raihoil except in conformity
with the rules of the Interstate Commerce Commis-
shipmentofexpio- DubUslied bv the American Uailwav Asso-
elation. These rules make it unlawful to carry any explosives, except small-arms ammunition, on any public vessel or vehicle carrying passengers.
Explosives should be stored in properly placed, built, and aired
magazines. Such a magazine should be far enough storage of expio- £j,qjj Other buildiugs or works so that if an accidental
explosion occurred when the magazine was full it would do the least possible damage, and it should be so placed as not to be in danger from forest, brush, or other accidental fires. Magazines
are best built of cement mortar, but they are more
If 3.srd.ziii6s
frequently built of brick or of wood covered with corru- gated iron. In any case they should be provided with v/ooden floors, which should be kept free from grit and dirt. It is best that only one kind of explosive should be kept in any one magazine. If more than one kind of explosive (other than permissible explosives) must be kept in the same magazine, the magazine should be divided into
rooms, by partitions, and the different explosives kept Detonators never different rooms. On no account should detona-
to )d6 stored vth
other explosives. tors, or blasting caps, or any device containing ful- minating composition, be kept in the same magazine with any other explosive. These firing devices should be kept in a dry place by themselves.
Plans and specifications for magazines will be furnished by manu- facturers of permissible explosives. (See also pp. 61-63, and figs. 11 and 12.)
A Primer On Explosives For Coaj. Miners.
Thawing explosives.
The greatest care must be taken to prevent packages of explosives
from falling or getting shocks. They must not be thrown, dropped,
nor rolled. Wooden boxes containing explosives
expiostvtf. should be opened with extreme care, so as to avoid
friction and blows as much as possible. Tliey should
never be opened within the magazine, but in a properly sheltered
place outside of the magazine and at a distance from it. They should
be opened only by tlie use of a wooden mallet and a hardwood wedge.
The thawing of frozen explosives requires extreme care, and doing
it improperly has frequcntl} led to most serious accidents. No
attempt should ever
frozen made to thaw a
frozen explosive by placing the cartridge before a fire, or near a boiler, or on steam pipes, or by putting it in hot water, or by placing it in the sun. -While being thawed, nitroglycerin explosives are extremely sensitive and should be handled with great care. During the thawing the nitroglycerin tends to separate from the dope and run out from the cartridge (that is, to exude), and this is a source of danger.
When but a small amount of the explosive is required, it may be thawed in a thawer such as is fur- nished by all the inanufacturers of
explosives and has
been found safe for
use as directed. (See PL VI, C.) The thawer con- sists of a water-jacketed tin vessel, in which the cartridges are placed and which is closed with a tin
cover. Before the water is placed in the vessel it is warmed up to a temperature not uncomfortable to the hand put into it, and the cartridges are allowed to remain in the thawer until it is found, by gently pressing them, that they are completely thawed throughout. Wlien thawed, the material will feel plastic, or like flour, between the fingers. When frozen, or partly frozen, the stick
will feel more or less rigid and hard. It is neces-
because dynamite when frozen can be detonated only with great difficulty, and any part that is frozen will be but
Thawers plosives.
for ex-
tfEn
fr
anc
D
Window for thermometer
0 1 a 3 4- FEET
Figure L— Thaw house for frozen explosives: elevation.
A I'lniVIKM ON KXIM.OSFVFS F(H{ COAI, MIM.I5S.
irnpnrfccl l\' (Icl-oruilod in Mm lioKi; lirn(( no! only iiijin ->ii(Ii partly IVo/oii |)()\\(l(w fail l(> ivn i(s full rllVcl jis Mil nxplosi \n, hill lluro is a. s(Mi()iis nccidriil, in a, cnal iniiio Imro such j)ovv<liir is us(i(|, Ixicaiiso if a hlowri-oiit shot rosiiHs I h(i hiiriiin; sohd pari, may Ht firo to th(i (hist or l\H) (himp in thn air of niiiw
hoiis( should h( provi(hMl for I hci purpose of thawinj out lh(5 fi-oZ(n (explosive,. (S(u fi<(s. 1 and '2.) Ilaiis and spcM'ilications, lo<i:(tij(u* with a hill of nialcM-ial for such a ihaw
Thaw houses.
it:
,, .if
Ki o c o o o .'; C'l
Ic; c c o o o o o'
=§H
lO o o o o c o! o o o o o o c]
O O O O O O d
.;i
*4:
Section E-F
5 Feet
SECTION C-0 Figure 2.— Thaw house for frozen explosives? section. The cement mortar in the walls is made of 1 part
cement and 6 parts sand.
house, will be furnished, on application, by the manufacturers of permissible explosives. The thaw house should be large enough to hold all the explosives used in one day's work. It should be heated by a small hot-water heater, placed at least 4 yards from the house,
32 A Primer On Kxplosives For Coal Miners.
the hot wator boin pHssed into th( lioiise throiili iron j)ipes, at sucli a rate that the tenijxjratiire in tlie house will not at any time be above 90° F.
Thaw houses are intended only for the treatment of explosives for
immediate use, and not for the storage of explosives,
Thaw houses not f,)j. jf powders or dynamites are left in this high tem-
age. perature and dry air ror a considerable time, the
moisture that is a proper part of them will be driven oil', and, as stated l)efore, this will markedly alter the character of the powder or dynamite and may lead to accidents in its use.
d
ntiiir AW oi MINI s
OtIfTIN 17 PLATf VII
A. Miner S Squib.
B. Miner'S Squib And Fuse.
'rt
SQTTTHS, 1 rsK, AND DKTONATOIf S.
It, liMH 1)0011 inndci clcuir in llu discussion of conihiisl ion mid n.\j)lo- sioFi Jind ( lio d<s('ri|)(ion of \Hr'ioiis oxplosivcs that i\\(iy
Means of exploding: i i i III 1 1 c
explosives ' caiisMl lo o.\|)lod<i hv Jirioiis mojins. All ol
tluun can, iind(U" soino circninsiancos, 1x5 nindc lo oxplodo by i\n). Soiik of tluin can ])o caiisod to undoro a d(it()natin< ex|)losionl)y sotiinjjofr a dctouator in contact with t h(5in. In hlastin uso is iiiado of both thos( moans for scttinii; ofl* oxplosivos, tho nHius used boinsi: (Utorniinod by circunistancos.
In settiiiii oil' by moans of firo, iiso is ma(l(i of miner's scjiiibs, or of fuse. Miner's squibs (PI. VII, A) consist of tar)orin*'
Miner's squibs. , r-n -ir.
])aj)er tubes about 7 mches lonii:, iilled with fine gun- powder, one end of each i)aper tube boini treated with chemicals so as to form a slow-biirnin<j match, which, when inited, burns so slowly as to jive tlie miner time to reach a place of safety Ixifore the explosion. When used the squib is jlaced in the needle hole, or blastin<2: barrel, througli the tamping, with the match end of the squib outward. When the match is i<]nited the fire burns slowly
aloni: the tube until it reaches the powder core.
j£0 SQUibs vsork.
Then the squib darts forward like a rocket, leaving
a trail of flame behind which spurts out from the needle hole, and
the lire continues burning along the ])owder core of the squib until it
bursts out of the other end of the tube and so io:nites the charsre.
In experiments made at the Pittsburg testing station it has been
found tliat, though the burning match on the end of
Squibs should not he tubo of the squib does not inflame a mixture of
be used in fiery . .
mines. mnio gas and air, as soon as the powder core is
ignited tlie flame that then flashes out from the end of the squib wall explode the mixture. Hence squibs should not be used in any gaseous mine.
Fuse, as used in coal mines, is sent out into the market in coils 50 feet long, and in several varieties, but all consist
Fuse. '
of a core of mealed gunpowder inclosed in two or more layers of yarn and generally surrounded by tape that has been dipped in a waterproofing composition. (See PI. VII, B.) Some varieties are then dusted Avith substances like powdered soap- stone, to prevent the sticky surfaces from sticking to one another. The kinds of fuse most commonly used are hemp fuse, cotton fuse, single- tape fuse, double- tape fuse, triple- tape fuse.
99160°— Bull. 17—11 3 33
34 A PRIMER OX FA'PLORTVES FOR COATv MINERS.
Wlien one end of u I'lise of any variety is lighted the powder core
burns slowh' along the fuse till at last the flame
rushes out at the farther end and, if it touches a
charge of powder, sets it off. Like squibs, fuse throws off flame
when lighted, and hence the use of fuse in a gaseous mine can not
be recommended.
Fuse should be so made and should be in such a condition when used that any part of any coil will burn at a rate
that does not vary more than 10 per cent above or below the standard rate. This is of the greatest importance, because in setting a charge the blaster or shot firer cuts a piece of fuse to reach from the charge to the opening and long enough to give him ample time, after the end has been set on fire, to reach a place of safety before the flame fires the charge. In order that a fuse may burn at a regular rate, the powder core of the fuse should be uniform in character and should extend continuously through the fuse. Examinations of fuses by the X ray have shown that some- times the powder does not extend continuously through the fuse, but that there are spaces between the portions of the core (PI. YIII, Therefore, careful tests should be made of the rate of burning of pieces of the fuse whenever there is any doubt whatever as to its
soundness. Although the manufacturers may pro- Fuse injured by fse witli a rcp-ular rate of burning, the rate
bad handling. . °'.
may be changed by bad handling, as, for instance, by squeezing the fuse in handling or tamping so as to disturb the powder core, or by suddenly and roughl} opening the ceil when it is stiff from cold, so as to crack the fuse; or the fuse may be injured
by rubbing against the rough surfaces of the rock. Care in cutting jj cutting the fusc and in fitting it into place, care
must be taken that the powder core does not run out from the fuse, for that might cause a misfire.
Detonators (which are also called blasting caps, and sometimes are
called exploders, though the last term applies to any
Detonators. „ , . . . i ii
means oi producing an explosion, and tliereiore is not commended here) consist of copper capsules about as thick as an ordinary lead pencil, which are commonly charged with dry mercury fulminate or with a mixture of dry mercury fulminate and potassium chlorate that is compressed in the bottom of the capsule, filling it to about one- third of its length.
Dynamite and other detonating explosives are in practice fired by
means of detonators, for though they may be exploded
Advantage in use ]-j. ,-j squibs or fusc, or bv mcans of gun-
powder primers, yet the explosion so produced is not a complete one ; the explosives are not used to their best advantage ; all of the work thatthey can do is not done; and, moreover, the
¥
A I'ltlMKU ON I'.Xfl.OHIVI'.K I'oll CdM, MINKIIS.
pasos tliat MIC |)r<Kln(<'(l mv iisimllv (limnons. Wlicic liijli sivos aro cmploycil, it ia salVr to lire wilh (Iclonnlois shourr ciionili to caiiso their most/ complete ('xplosioii. I'crmissihlc cxploHivoH should IxWired by (UMomitois, and aic Ix'stlircd l)y clccliic ciclomitors of th(* st i*(Mi<th ])i-('S('ril)('(l for one. (S(m p. (>7.)
Sev(M'al <i;ra(l('s of theses detonators or blast cajjs arc to he found in the nnuket, and tli(v aro didVrently dcsitFnited by
Grades of detona- ,.,,. , r i ' riM ha.' m r
Qj.g (lillerent. jnannhHl . IJio strontlis of tiir
detonators most eommoidy used, as measured by the weipjhts of the fuhninatinj: ('om])osition eontaincMJ in tlicm, ai-e as follows:
Grtidrs of ilctouatora and iiu'i</hf of their /cs.
Testlng-staUon prados.
Conunorflal prade.s.
Weight of
charge in
grams.
Wi' of
charge in
grains.
No. 3
;1X, or triplo
0./)4
No, 4
4X, or (niadniplr
."jX, or quint uplo
OX, or sextuplo
7X, or No. 20
No. 5
No. (1
No. 7
No. 8
8X,or No. 30
Detonators are iiied by the aid of a ])ieee of fuse. Tlie end of the
fuse is inserted in tlie mouth of the blasting caj) and
Attaching detona- (.apefuUv pushed dowu until it gently touches the
tors to fuse. . i o ./
surface of the detonating comi)osition, and then the cap is crimped onto the fuse. (See PL IX, A.) The cap, with the attached fuse, is inserted in the charge to be fired, which, when placed in the bore hole and tamped, is r?ady for firing. The end of the fuse is lighted, and the lire burns do\\Ti the powder core until it streams against the detonating com])osition, W'hich then detonates and causes the detonation of the explosive with wdiich it is in contact. It has been found at the Pittsburg testing station that the flame
wiicli rushes out from a fuse W'hen it is ignited at Fuse not to be used moutli of a bore liolc will ignite an explosive
In fiery mines. . . .
mixtine of mine gas and air. Even though a safety device is used to prevent spitting from the end of the fuse, flame may burst from the side (PL YIII, B) . Therefore fuse should not be used, either alone or with detonators, in fier}" mines.
The practice of fitting the fuse to the detonator is common in
quarries, timnels, and mines that are not gaseous.
Fuse and detona- Accordingly, it is customary to make both detonators
standard size. nd fuscs in standard sizes, so that the fuse may
easily slip downi within the mouth of the detonator and yet make a neat fit wdtliin it.
k
A PHIMKR ON KXPT.OHIVKS FOR COATv MINKRS.
Electric tors.
V>y t'.io iis(' of (Icctric detonators (also callcMl olectiic fuses), the dangers tliat are common in tlie use of squibs or fuse in oaseous coal mines aie avoided. (See PI. IX, B, and fij]. 3.) These electric detonators are simply ordinary detonators that have been fitted with a means of firing them by the electric cu.rrent. Tliis is done by inserting within them two c()])])er wires, joined at the inner ends by an extremely fine platinum or other liigli- resistance wdre, which, like tlie carbon filament in the ordinary incandescent lamp, becomes heated till it glows when an electric current is })assed through it. This wire, known as the bridge, is placed above tlie detonating comj)osition, and is surrounded, by gun cotton or loose fulminate. The space above it and the mouth of the capsule are then filled and closed by means of a plug of sulphur or other waterproof com])ositi()n, wiiicli is poured in while soft. The copper wares pass through the ])lug and are long enough to extend out- side the ca])sule. TJiese outer ends are called the legs or wires of the electric detonator. Although the copper wares are bare within the electric detonator, the legs outside are covered with an insulating wra])})ing. These legs are made of different lengths in order to suit different depths of bore lioles. The charge of detonating composition differs in the dif- ferent grades of electric detonators so as to give different strengths.
The following table gives the grade and weight of charge for tlie more common electric detonators:
Grades of electric detonators.
Grades and weights of charge of electric dffomitors.
Sulphur filling
Te'tiiig-sta.tion grades.
CoiniTiercial grades.
Weight of charge in grams.
Weight of charge ingrains.
No 0
Single strength
Double strength
Triple strength
Quadruple strength.
No. 0
No. 7
No. 8
Gun cotton or
mercury fulminate (loose)
In loading bore holes electric *deto-
Sulphur plug
Platinum bridge
Mercury fulminaxe (packed)
nators are placed in the
tonators. c? j
nators with fuse are, and the bore holes are tamped in a similar manner. To fire the charge, the legs of the detonator are connected by leading wares to an electric device at a safe distance, and from it the current is sent to fire the blast. No flame can escape from the bore hole during the firing, for the tamping fills the hole completely, and hence blasting in gaseous mines is made much safer.
FiGCRE 3.— Electric detonator, showing its component parts.
IIIIKI All I II MINI S
IHM I I Il. 1 ; I: A r f
.1. Crimping Detonator On Fuse.
B. Detonators And Electric Detonators.
A I'ltlMI i; ON i:XIM,()SI\'i:s I'oK COAL M I N KHS.
Only clccliii- (Icloimlois nic used mI IIm' Til 1 .Inn fin;'- sfufio!) in the tosts ol explosives lor use in mines.
I Wluil nre called dehi -nclion ejcclric, *'exj)l()(lers " or <lelonalois are iiou heiiij ollered for use wlieic n niMnUer of
trie detonators.
niMV explode one jd'lei- nnotliei. This is done hy placing a pi(*ee of fuse or othei* device in th<' electric detoinitor bel\v(MMi the (let()natin< composition and the hride and inclosintr the wliolo so that th( flame may not escapes from the hiast Jiole. In the present state of knowledge this j)raetie( is not, commended lor use in coal mines.
In the description of mercury fulminate attention was called to
its extreme sensitiveiKss to heat, friction, or blows
detonators '
undergoes. All these properties therefore belong to detonators and electric detonators, and these httle devices should be treated with the utmost respect. Never attempt to pick out any of the composition. Do not drop them or strike them violently against any hard body. Do not lay them on the ground where they may be stepped on. Do not step on them, in crimping, take the gi'eatest care not to scjueeze the composition, and never crimp with the teeth, for there is enough composition in one of these small cap- sules to blow" a man's head open. Tlu\v should be stored in a dry place and in a building apart from any other explosives. They should never be carried into a mine with other explosives, and they should never be placed in a mine near other explosives except in bore holes. When carried or shipped, they should be packed firmly with a quantity of elastic material, such as felt or the coiled legs of the electric detonators, about them, and they should not be exposed to heat, blows, or shocks of any kind.
MININO COAT. WITir EXPT.OSIVES.
Xo niiivcrsnl nilo can he made for blasting coal, for the local
conditions, the character of the bed, and the method
Conditions In coal working make necessary the use of different means
in different mines and sometimes even in different parts of the same mine. Tlie best metliod of blasting in any given mine or part of a mine is determined by practical experience and observation.
The placing of bore lioles, as well as the size of the charge, is of vital importance. In placing them special attention and due corw- sideration should be given to the bedding and cleavage planes of the coal; also to slate and bone parting, horsebacks, clay slips, and other local irregularities.
In this country, apart from the not widely used long-wall system
and from the pillar pulling or withdrawing, in both of
Shooting off the little Or no explosive is used, there are two
solid. y ' .
general methods of bringing down coal in entry driv- ing or room work, namely, "shooting oif the solid" and undercutting or shearing before shooting.
In the coal mines of the middle mterior fields, where shooting off the solid is largely practiced and where there are no marked faces or butts, the following method is used : A hole is bored or drilled in the face at or near the middle of the seam, at such a slant as to make a small angle with the face. If an imaginary hne (AB in fig. 4) drawn from the back of the drill hole at right angles to the hole passes out of the open face, and if that distance is not too great, the hole is rated as ''safe" by those who use the method. If, however, the hole extends beyond A to X (fig. 4), the extended part is said to be ''dead"' and the hole is considered "unsafe." A hole is also con- sidered ''unsafe ' if the angle ACB is greater than 35°. In the softer coals and where the joints or cleavage planes (cleat) are favorable a greater angle is used, but no drill hole, even under such favorable conditions, is bored at an angle greater than 45°.
A l'IUJVIi;i{ ON i;.\l*L(>SlVKS I'oi: chal aiinkks.
'M)
Dependent shots.
Ill shootinjif oil ihc solid one lace of llic lo lie (lirnwn oil' is cxposrd. I I jiiiisl he loi'li oil' aloii"- I he line luff explosives. '
nioiif th( Ix'ddiii; planrs at (op and hollojii. Wiiric siicli IxMldiiijj; j)lan('s aro smooth (his is not, difliciiH, but generally (hoy aro iiTo<iihir, and a strong shoarin; force must ho o.\or(('d par- aHol (.() (ho IxMhhll philios, ho(h a( llir (op ntid holloni. 'i'his mothod to 1)0 oH'octivo rocpiiros a slow-actin;; explosive, and hlack hiastinj:; powdoi* has boon much used in I ho work.
A second hole and (von a thii'd one is sojnolijnos drillod and
charged before tlu* (irst one is fired, and these ar( callod
"dependent" shots. The fuses are sometimes niad( of diiroront lengths and lighted at the same time, with (ho expec- tation that the shots will go oil' in the proper order. Siioh j)ractice is now generally hold to be very wrong even in ''solid shooting" dis- tricts. The second and (bird lioles should not be drilled until after the first shot has been made, so that the loca-
tion of each shot can be properly judged.
The size or weigh ( of the charge in shoot- ing off the solid Aaries
m u c h
Overcharging. .
m dif- ferent coals. In fact, it is extremely difficult , p even in the same coal, to judge the amount figure 4.-shooting oflp the solid.
correctly each time.
If undercharged, the hole is likely to ''blow out;" hence it follows that holes are almost invariably overcharged, and in some districts all sense of right proportion has been lost by the miners.
Aside from the dangers in the use of black powder, the uncertainties in proportioning the charge to the work are such that the method of shooting off the solid can not be approved as either precise or safe. Many of the great mine disasters of this country have undoubtedly started from misjudged or overcharged shots off the solid.
The other method of bringing dowm the coal in which the explosive
is assisted by undercutting or shearing beforehand
readopted in most parts of the country. The object of undercutting or shearing is to expose two faces of the mass of the
A Primek On Explosives For Coal Miners.
Shearing.
coal to be brought down, and, as coal trenerally tends to break along vertical planes, to perniit the explosive to exert a wedging effect, rather than to shear or tear off the mass as it must in shoot- ing off the solid.
There are two ways of applying this method — shearing and under- cutting. Occasional!}', where the coal is hard to shoot down, both shearing and undercutting are done, so that a less amount of explo- sive is needed; in fact, in some places none is required, as the coal can be wedged down.
Where the cutting is by hand and the top and bottom part freely," shearing is the easier, and is usualty employed in entry or narrow work. In some cases the shear or vertical cut is made on but one rib, but generally it is made in the center of the narrow face and the shot is so placed as to throw the coal toward the shear. Where the coal is all alike in character and parts equally well at top and bot- tom, the hole is started at or near the middle of the seam and drilled nearly parallel with the shearing, slanting a little upward to cross the bedding planes, and also to clear itself of dust as it is being drilled. The hole should never go deeper than the cutting, and it is better for it not to go as deep by at least 6 inches as the cutting. In figure 5 the back of the bore hole is shown as reaching the projected line of the rib, but in softer coals the backs of the bore holes are usually at least 6 inches from the projected line of the rib.
In districts where black powder is still used it is conceded that a shot hole of this character should never be charged with more than 2 pounds of black powder, and better with much less. It is difficult to make rules for an exact amount, because the proper amount differs with the length of the hole and cutting, the strength of the coal, and the way that it parts from top and bottom. However, the work should never be so laid out that it will require more than 2 pounds of black powder. If one of the permissible explosives is used, the charge should be, in general, only about one-half (by weight) what would be required if black powder were used; but no work should be so laid out — that is.
Figure 5.— Shearing.
Charge of explo- sive in shearing.
A iinivii;K ON i;.\iM.()Si\'i;s kok coal minkhs.
Undercutting:.
Roof
no drill JioN sJioiiM 1ki so locaUul wilh r(for<in(n lo ijio sJumrin — as to re(jnir( moi( ijniii u. pound and a, Imlf of t 1m) (xj)losiv(
Wli(r llu j)la,('o is so tJnit anolJuw Jiolo is riHjiiind juiar tjin liist, wjicin iju lii'st. Jnis dofui its woilc pr-opcrIy a siinilni* silnnlion Icfl'l, for ilu) socond Jiol(
Whom i\w coal is nndri-ciil, ciljirr hy Ji.md oi- niadiiiM), iJu jun- j)os( of l]u siot is (o hrin* down luiiss of cojil l)y wodj;in<i; fioin abovci. In sudi a place tho i"(at(5r ])arl of Ijui force of tjic (v\plosiv( iis(ul in iJk first kIioL will to slioar oil' tlic coal on both sides of tlu sliot, tJui (ixpandin; <as(;s from tho c\j)losivo woi'kin< alon<j; tho Ijoddinj; ])lnno at tlio lino of tjio drill holo and tho mass ])iv- oting at tho back of the un- " dercuttiiiijj. Tlio stronger the bedding of the coal — that is, the loss mai-kod tho vortical pianos — the more dillicult is this shearing, whicli then bo- comes a tearing, rending ef- fect at tlie sides of tho mass, so that the shape of the mass is somewhat conical, the toj) being at the line of the drill liole and tho base at the under- cutting. Under the circimi- stances the coal above the drill hole generally does not come down, but it is usually so shattered that it may be pulled more explosive than later shots, but the amount should never be more than that already stated for the shearing method.
To help the first or 'buster" shot, if the undercutting has been done by macliine, it is advisable, and in some cases necessary, that the coal at the front edge of the under- cutting be ''snubbed" off either by the pick or by a small '*pop" or ' 'snubbing" shot (fig. 6). In narrow work, if the ''buster" shot has done its work properly at one rib, the second shot is placed at the other rib. In wider work the "buster" shot is usu- ally placed near the center of the room face and the second and tliird shots are placed on either side (fig. 7). Each of these is so placed as to throw down a mass of coal which practically has three faces free — the front, the bottom, and one end. The chief work of the shot is to wedge off the rib end and push away from the back. Such a shot usually only requires from one-half to three-quarters of a pound of one of the permissible explosives. The work should be adjusted to
Floor Figure G.— Snubbing shot.
Placing shots.
A Phi.Mkh On Rxplosivks For Coal Miners.
these charges, so tliat if three shots besides the snubbin< sliot (if one
is needed) are not enouijh, four or even five shots small Ihargel ° shouid be used. It is far safer to use a number of
shots witli a small amount of explosives in each than
to use a few shots with a large amount.; and on the whole less ex-
l)losive will be needed in all the small shots than in the few large shots.
The depth of the undercutting varies with the character of the coal
and with the thickness of the seam, but in han(l-])ick cutting! ° under- dcptli is not commouly greater than the
thickness of the seam. Where machines are used to undercut, the depth is from 6 to 7 feet, depending on the maclune. With machines the cutting is usually done at the bottom of the seam; if the seam is thin (less than 3 feet) the cutting is done in the under- lying clay, if there is any. Where tlie undercutting is done by hand pick, it is sometimes done in a soft layer near the middle of the seam.
Roof
Floor Figure 7.— First or " buster shot.
or in a parting of soft clay, but so far as the placing of the shots is concerned, the part above such an undercutting may be regarded as a thin seam, the coal below the cutting being lifted afterward by ' heaving shots. Generally the cutting is in the bottom, and where it is the shots are usually placed above the middle of the coal and sometimes near the top. "Wliere the coal is undercut and black blasting powder is used, owing to the powder's slow wedging action, the exact position of the shot is not of such special importance as it is where permissible explosives are used. As already explained, these are quicker in action than black blasting powder, and unless they dis- lodge the coal instantly their force is spent in shattering the coal near the drill hole. Therefore with permissible explosives the mouth and back of the drill hole should be nearer the roof and the hole should slant upward in order that the back of the drill hole may reach the top bedding plane (fig. 8). The break \'ill then be clean and a wedging action will be exerted along the top bedding plane.
A I'I(imi-;h on i;\n,()Si\'i;s loi; i'w minkks.
'Qoro
111 the use ol" pcriiiissihlc ex |)|<)sives, .sju'cial caro mIimiiM l>r InkiMi
(lull incli l))i(' hole lins I lie siiiic widlli tliiuulinijl
milllblo oxplosivos. . . rn
I liroiijjli it willioiil 1K) linrd i niiiinin;/. loo siinill ii Jiolc miiv cimsi cardidc to slick, and nil ro<dv(<'iin ex plosivrs or ('V(Mi black powder may ho exploded hy the Iriclioii of I lie lainpiii;' bar against, (lie sides of I he hole. Dnily allenlion should he ;_N\(n lo the (hills (hat are used in drillin}, iJie hore jioles, and I he points of the hits when heini; shnrpeniMl should he nnide to astnndjiid si/e. Jk'l'ore a shot is lired in n workin* place "hu;" dust and all other coal dust sliould he ( hoioujddy wet and sent out of
Dust must be wet workin*' phice. ca use of explosions lias heen
more common than the presence of coal dust when shots are heini: iii-ed. If the working place is natui-ally dvy, it should be tiiorouglily si)rinkled, and all the ribs, roof, and props witliin 40 feet of the shot washed down by liose before shots are fired.
Good results have beeji obtamed in bituiiiinous coal mines during Uie winter months by warming and
moistening
mines.
tering the mine by means of exhaust steam and spraying devices. In experiments made in De- cember, 1908, at the Pitts- burg testing station the out- side air entering the galler}" was warmed up to a mine temperature and moistened by drawing it through humidifiers. It was found that if the air is kept at a relative, humidity of 90 per cent and a temperature of 60° F. for 48 hours, thus giving conditions like those of summer in a mine, the taking up of moisture by the dust and the blanketing effect of the moist air prevent a general ignition of the dust by a blown-out shot of black powder.
Since the new permissible explosives began to be used it has been found that more satisfactory results are obtained in mines where the loading and tamping of all shots are done by a few competent men known as 'shot firers."
For the greatest safety the loading and firing of all shots should be done by shot firers after all other men have left the mine. The
Goal
Vy
Ftgure 8. — Bore hole for permissible explosives.
Shot flrers.
44 A Pkimick On Kxim.Osivks Foh Coal Miners.
pi-actice of havin<i; all shots loaded and fired by shot firers during the shift, wliicli lias lately been introduced in some of the mines of the Pittsburg district, is certainly a step in the right direction.
It is plain that the greatest safety and best work can not be ob- tained when the miners are allowed to load and fire their shots, because the new permissible explosives must be properly handled to get the desired results. The shot firers should be selected from the more intelligent miners, and they should be thoroughly instructed in the great dangers that arise when the permissible explosives are used in any other manner than that specified by the Pittsburg test- ing station.
Ii()AI>IN(i AND I ilMNCi ( IIAIMiKS Ol' KX IM><)SI KS.
In l)las(iM;j;, anv ('.\j)l<)si\ <iv(vs (he {rcalcst (lisiuplh
wluMi I lu* (har;i;(' most (()mj)I('!l(>ly fills flic horchoh
lioin sKJo to skU. il the explosives aic suppjjed
ill call i"i(l<( form (his condition can often he ohtained
in the bore hole hy splitting (he wrapper, <ifently pushin< a cartridc
down into place in (he bore hole with a (anipin stick, gently sc|ueez-
iw it so that it spreads out to iill the entire width of ihc hole, and
repeatini this wi(h (ach cartrid<z;c until the char<e has all been
put in. Filially, (he (h'(()nator is plac(Ml in (he last cartride put
in, and this cartri(l<je is known as the piinicu". Tlui
primer is <jjently pushed down into jnace m iirm con- tact wi(h th( rtMuainder of the char<i;e, and the hole is tamped (fi<. 9).
hargeis
5 ft
5 Inches
Fku'RE 9. —Bore holo rcafly fr>r firing.
Density of charge.
If the same weights of diii'erent explosives are of equal strength, the one that takes up least space — that is, the densest — will have the greatest effect in breaking coal or rock. Of two cartridges of equal size containing difTerent explo- sives the heavier cartridge is said to have the greater density.
Black blasting powder to be used in blasting is made up into a cartridge by means of a paper wrapper which has blasting powder. been formed about the handle of a pick. Ylien this cartridge has been charged with powder, the electric igniter or fuse is placed and well fastened, and the cartridge should then be gently pushed down into the bore hole by means of a wooden tamping stick, which is safer tlian any metal bar. An iron tamping bar should never be used. Wlien squibs are used, the cartridge of powder is placed in the bore hole and then the stemming " is put in about a copper or brass needle
a In this bulletin and in other publications of the Bureau of Mines, the material packed on a charge in a bore hole is termed "stemming"; the act of packing or ramming the material is termed '"tamping."
Tamping stick.
4() A JMilMKU ON EXPLOSIVES EOK COAE MINERS.
rod until tho hole is filled. Then the copper needle is withdrawn and the s(juil) is put through the opening.
When only fuse is used, it should be long enough to reach beyond
the mouth of the bore hole. The stemming should tamX/ ])acked in about the fuse quite to the mouth of the
bore hole, and the fuse should be completely sur- rounded by tamping.
It is observed that in some mines the practice has been to use
but a short length of fuse and to let the charge undamped hJies'!"'' explode untamped, or simply secured by running
the tamping bar into the hole. Tliis is a very bad and dangerous practice and should be forbidden.
When detonators are used together with a fuse, the fuse should
be cut off squarely at the end, gently inserted within nating composition, and then, with the Tuse held in the left hand, the detonator should be crimped onto the fuse with crimpers close to the open end of the cap, so as to make a perfectly tight and secure joint, care being taken in crimping that no pressure is brought to bear upon the detonating composition.
Two ways are in use of inserting the detonator and attached fuse
into the stick of explosive that goes on top of the
approved way is to open the top of the cartridge or
stick of explosive by unfolding the paper at the end; then to make
a hole by means of a wooden skewer or lead pencil in the top of the
cartridge, deep enough to let the detonator be pushed into it up to
the line of crimping; then to gather the end of the paper jacket or
envelope together about the fuse, the whole being bound vith twine,
so as to fasten the detonator and fuse firmly in place.
Another way that is sometimes used is to insert the wooden skewer into the side near the upper end of the priming cartridge so as to make a slanting hole in the charge deep enough to take the detonator up to the crimping mark, then to insert the detonator and bind it and the fuse close to the cartridge twine. (See PI. IX, A.)
The first way is perhaps more generally used, and it is better where the cartridge fits neatl} into the bore hole. Be careful not to "VVlien the sccond way is used, the bore hole must be of primer. larger, as there should be some leeway between the car-
tridge and the side of the hole. In either way, when the primer, \nth the detonator and fuse, is put into the bore hole, extreme care should be taken that they do not come apart, for if there is any space between the cartridges in a charge, or particularly
J
A n{iMi;i{ i;\i'i.nsi\'i;s I'on coai minkkk. 41
botw(Mi tlio (Nloimloi- 1111(1 (Iio (vxplosJNo in lim |)riiiiiii rMrtTi(l<o,
liH (V\()l()siili lii:i\' l)(i |)I(i\('.IiI(m1 }illn<(W ImM', Of iiiny
Dfttonator must ,, ('r\' j)()oro||(V LikfUvisCi, uImUI U fllSJi nild not bo coniploffly ' i i i- i i i i i i it i
burled. milor JH'ci III IojhIiiil:', . slimild Iki Iiikjui fliai
IIh (l((()iinl(>r is iiol, coinijlnhl y l)iiri<u| in (,lu5 (vxj)l()- siv(>, for as (lu I'lisc l)Uins nnd (ii() iusIks from ils <nul sonu? of il, may blow out over lop of llui (bloiialor and s(l- (ini to flu (xplo- sivo a!)out it bofon dclonator is s(t off. This has b(;(5ii a comiiuHi caus( of inferior and (h'lncM'oiis (v\|)l()sions.
The sanu sort of (rough hnpjxMis if cojd dust or any oth(5r dirt
Dirt between car- . priminr cartrid'o and iUn char-e.
In loaihnii:, extremtvcan shouhl \h) takciii to mak(5 siin that tiio cartridcs all (ouch one another closely.
Wlion electric detonators are used they are fastened in (h( j)riniin;' cartri(l<2:( in ways like those described above for det-
detonators.
tor is inserted in a hole in the side of the priminj cartridge, the ])ractice has sometimes ])een to fasten it firmly l)y taking a lialf liitch around tlie priming cartridge with the legs of the detonator, the loading and tam})ing being then done as alnady described. This last means of attaching the electric detonator to the priming cartridge is not a good one, because the legs are likely to become kinked, and also because there is a chance that when the priming cartridge is pushed into place the insulation may he rubbed off from the legs and the wires may be short-circuited.
Although it has been stated that with certain explosive, which
are somewhat largely used, the cartridge case may
Some explosives, if, ,. liii a n i i
split and tightly be split and the charge rammed nrmly into place, packed, may not ex- jg Universal practice arid should not be
done with all the ammonium-mtrate class of explo- sives (p. 21), nor with some of the nitro-substitution explosives, for if they are tightly rammed in the bore hole it is difficult or even almost impossible to explode them.
After the priming cliarge with its fuse and detonator or its electric detonator has been inserted in the bore hole, the hole should be tamped with clay or with other material that can not burn. It
should never be tamped with coal dust (either wet or
The tamping should be done by means of a wooden tamping stick. The pressure in tamping should be very gentle on the first tamping material put in, particularly if detonators are used in the primers, and great care should be taken at this time not to
A Primer On Explosives For Coal Miners.
disturb tlie position of tlie detonator in the primer. Special care should be taken not to draw the detonator out from tlie primer or tlic fuse out from the detonator. Wlien fuse is used, care should also be taken not to rub its surface off.
After tlie first 0 inches of the stemming material has been pressed down, greater force m.ay be used in ramming the rest, because the firmer the stemming is the l)cttor is the woik of the explosive and the less is the chance of a blown-out shot. The stemming should be continued quite up to the mouth of the ])ore hole. I£ fuse has been used, the upper side of it near the end may now be cut into on a slant, with a sharp knife, and the outer part bent away so as to form a notch in which the powder from the core gathers and to which the igniter is applied. This cutting prevents the loss of powder from the fuse and makes it easier to light.
The shattering effect of high explosives may be lessened in loading
simply by pushing the cartridges into place without
Air spacing of splitting or aftcFsvard squeezing them, so that an air
shattering effect. spacc Will DC Icit aoout the Cartridges m the bore hole, and til en proceeding with the priming and tamping. This air space notably lessens the shattering effect of the explosive (fig. 10).
Electric igniter.
Figure 10. -Loaded hore hole showing air space about the charge.
Where it is desired to use black blasting powder, electric black- powder igniters, sometimes called electric safety fuses or squibs, are recommended for setting off shots. They are made in a general way like electric detonators, but gun- powder or other slow-burning composition is used in them instead of detonating composition. They are much safer for use in C( 1 mines than ordinary squibs or fuse, both because they do not throw fire into the mine air and because they permit better tamping of the bore holes.
It sometimes happens that it is desired to fire a number of charges at the same instant. Tliis is readily done with electric detonators by coupling them up in series from hole to hole and firing by one discharge from the machine. This method endangers the roof and may cause falls. In mines other than coal mines it be done by instantaneous fuse running from a central fuse to the several charges, but this practice is not a good one in coal mines, because the fuse may set fire to any dust or gas that is present.
Instantaneous fuse.
A I'UIMKK ON i;XIM>()SIVKS l(K ((lAL M I N KHK. 40
In coal mines it is in()i'( coininoiilv lo (ir<' one or uhhc of llic clmri's bcrorc llii oilier cluircs, mikI (lii nuiy
Delay -action dot- i i I r . - i n r .1
onators (loilC 111 H Siri<,'l( llCt ot lirillj l)V tll( llsC
delay-Ji<l ion <'l('(iiic dcionjilors jilrejidy (icscrilxMl .')7). An oi'diinii'v ('leclric dchtiinldi' is placed in llie cliar<3 for tho central hreaUin; dow n siiol, and delay-aclion elect ric <leto- nators arc |)la('(Ml in (lie for tlu riidil and lefl ril> sliols. 'I'liis niclliod of lirin; has many nd V}inla(es over lii<' nielliods of lirin< successive shots by means of diirerenf Icnjlhs of rnnnin/ fuse, hut tioithor inclhod is rcc-ommended for use in assy oi- dnsly coal mines. Tho safest way is to lir( l)iit one shot at a time, and to .dlow linui
cnoiih l)ct\vc(Mi shots for the A'entilatin< current
shots- Time between , . . . , ,
thm. coml)ustion Irom the previous siiot and to carry
oir any coal dust that may have been thrown into the air by the shock of the previous shot. The interval of tim( that should elapse between shots did'ers with local conditions and the amount of ventilation, but in ordinary mininf practice the interval should never be less than live minutes for shots made in the same working place.
In the making up of charges for loading bore holes and during
the loading, extreme care should be taken that the AndspATiIr explosives are not exposed to the flames from naked
lamps or to sparks from the striking of metals upon each other or upon rocks, or from any source, since any of these may cause serious accidents.
As already suggested, the right size for a charge of explosive for
blasting in a coal mine can be found better by practice
Fauure of formu- bv tlieorv. Several formulas have been devised
charges. by wliicli to determine the right charge beforehand,
but unfortunately they have not given satisfactory results in practice. If the material or mass to be blasted were always alike throughout and of equal hardness, theoretical rules could be made to apply, but such is not the fact. Differences in the resist- ance of the material to be blasted and in the rate of burning or detonation and the breaking force of the different explosives all affect the results of a blast.
Thus, for instance, in soft bituminous coal a permissible explosive
containing only 20 per cent of nitroglycerin has Comparison of ef- \)qqii fouud to bring dowm more coal, and better
f ects of different ex- , , . , i c i i j.
plosives. coal, than one made under a similar rormuia but
containing 25 per cent of nitroglycerin. A very
quick explosive should not be used in bituminous coal mines where
lump coal is sought. For instance, 40 per cent dynamite, which
99160°— Bull. 17—11 4
50 A Primer On Explosives For Coal Miners.
Juis Ix'cii found 1)}' ex])c;rimeiit at the Pittsburg testing station to liave a rate of detonation of 4,688 meters (15,380 feet) per second, is unsuitable for producing lump coal; but the permissible explosives that have rates of detonation between 1,866 and 3,617 meters (6,122 and 11,867 feet) per second are found to be well adapted for this work. Ex])losives that develop very high pressures are also unsuited for this work. Thus the 40 per cent dynamite referred to above lias been found to produce a pressure of 8,308 kilograms per square centimeter (118,165 pounds per square inch), but the permissible explosives show pressures as low as 4,833 kilograms per square centimeter (68,740 pounds per square inch).
In deciding on the charge of a permissible explosive for use in
a coal mine it is safe practice to use about one-half
Size of charge of hq weight of black blasting powder that would be
sives for coal mines, needed to do the work; but no charge of permissible
explosives should be more than 1 J pounds. As stated before (p. 42), bore holes for permissible explosives are placed by a different rule for depth and direction than that which is followed when black powder is used. No permissible explosives nor any high explosive should ever be used in the same bore hole with black blasting ])Owder.
The most obvious objections to overloading are that it crushes
and wastes the coal, and that it throws fire and flame ovrioadinV ° out into the air of the mine. Another objection
is that the surplus force of the shot may so weaken the roof and surroundings as to cause falls, which may not occur, however, for some time after the shot has been fired.
Underloading, on the other hand, not only causes loss and waste,
but it may so fissure the coal near by as to make it underloading daugcrous to fire another shot near the place. At
the same time it may happen that the underloaded charge, though not strong enough to bring down the coal, may spring the bore hole, throw out the tamping, and give a blown-out shot; that is, a charge that is not heavy enough to make a blast may be heavy enough to act in a bore hole as it would in the barrel of a gun; and this may happen particularly if the tamping is not well secured and firm. Blown-out shots are especially to be feared in dusty and gassy mines, because it has been found that explosive mixtures, such as are present in such mines, are most sure to catch fire and burn most completely when a mass of flame, and more particularly a mass of glowing solid particles, is thrown into their midst. Investigation has shown that the larger number of the recent disasters in coal mines have been due to blown-out shots.
A l'l(IMi;i{ ON KXri.OSIVKS I'HK ('(i\h MINKIW. 51
Promatiiro explosions, inisfin\s, ami liaiiCiiw's arc iiiosi lik(*iy to lni,|)|)(Mi wluMi s(Hiil)s and fuses aic used lo Ht
Premature explo- (|i,tiu;(.s, ONvillfX (o (l('f<'('ts (liat may \)V in tlM\S( slons, mlsllres, and . , i i i aI
haugflres. (IcVICCS il'Oni i\H) lirsl, Ol' IliaV l)( caused HI tho
handling, cjU'iTinj;, oi* loa<lin of iIm-iii. Miners nvc.
(\s|)(M'Jally warned in cas(M)f alnin'firo to avoid rcluiriin to th( breast
until Indf nii liour Inis |)asse(l. Ilunfires ranly
Keep away from a ]i.u)I)(mi \\i(li ('l(ctric dcloruitors, l)ut it Is possible
hanpflro for half an , , , -ii i i i-
hour. t.nat ln(\y niny hii,p|)cn more oltcn with delay-action
detonators. Incomplete ex|)losions may result from several causes. They nniy
bo due to failure to pusli in all tlie cartri(l<es of a
air sj)ac( between them, or else a mass of coal dust or dirt, which breaks the ])ath of the detonation from cartrid<(; to cartrid<]:e. They may be due to the pulHn< out, even but a little way, of the detonator from the primer or of the fuse from the det- onator. In the use of nitrate of ammonia or nitro-substitution powders incomplete explosions may be due to too tight packing and compressing in the bore hole. In any case, a partial explosion is a marked source of danger; first, because it may have the efTects of an underloaded charge; second, because the unexploded part of tlie charge may burn and throw out flame and sparks into the mine, and also give out poisonous gases and fumes; third, because the unexploded part of the charge, if it is not burned up, may be brought down with the coal and give rise to an accident in the breaker, or, if it passes the breaker, to an accident in the transporta- tion or the use of the coal, lienever there is a partial explosion, if coal has been brought down, careful search should be made in the coal for the remainder of the charge.
In case of a misfire no attempt should be made to draw the charge, but a new bore hole should be placed at least 2 feet away from the first one and fired, and after the coal has been brought down it should be carefully looked over to find any unexploded material that may have come from the hole that misfired. ATien a hole charged with black blasting powder has misfired, the stemming and charge may be withdrawn, drenching them with water while withdrawing them. After the hole has been dried out it may be reloaded.
Firing Blasts By Electricity.
Tho methods used in causing the explosion of charges in blasting depend on the nature of the explosive. To cause the bflamr explosion of an explosive of the black-powder class, it is only necessary to put a flame to it, but a violent shock is necessary to cause the detonation of high explosives so that they will have their greatest breaking effect. As already stated, black-powder charges are set off by means of squibs, fuse, or electric igniters. Squibs and fuse are set on fire by means of the flame of the miner's lamp, or sometimes by heating a wire to the glowing point in the miner's lamp and applying it to the match of the squib or the cut end of the running fuse; but evidently these methods would be dangerous in fiery coal mines, and hence they should never be used in such mines.
An electric igniter or an electric detonator should be so loaded
into a bore hole that while it is in perfect contact with the charge the
legs of it reach at least 6 inches out of the completely tamped hole.
Both legs should be bared of their insulation for about 2 inches from
their ends, and the wires scraped bright so that a good
connecting legs to lepTical contact Can be made with them. Each leg
leading wires. , .
is then firmly connected with one of the leading wires by about five turns. It is bad practice to have the two spHces directly
opposite each other, because when the leading wires
Splices should not pulled the spliccs may touch one another and
ping'spiices. thus make a short circuit, which will prevent the
electric igniter or electric detonator from being ex- ploded . A better plan is to wrap the bare wire splices with tape made for the purpose, which will completely insulate them.
After the legs are spliced to the leading wares (and only after), the
wires are connected to the firing macliine from which Connecting lead- elcctric Current is to be obtained. This last con- machine, nection should never be made until all the men are
at a safe distance from the place where the blast is to be fired. The rule should be made and never broken that when bore
holes are charged the connecting up shall move from
All connections to , , i i r i x . i i rr<u 1
be made from bore the borc holc back to the tiring machme. Ine work hole to firing ma- jj mine should SO organized that it can never be possible for the leading wires to be coupled up to the firing machine while anyone is about the place where the holes are being charged and where the blast is to be fired. In heavy blasts
A PiniVlKH ON i;.\IM,()SI\ KS i'ihW. MINKKS. 53
in (]ov(l<)|)lii(int. Work, iikhc clcriiic (IctoiinloiN iiuiy iis(mI to jood M<l\niil u;n in ijid sjiiin- hoKi Jiolc. Vm liiis
Oonnectlue deto- . i , i i l
, |)iir|)()S( IJH'v nr(M'()im('.cl<'<| IN) in s(M'i(s, wliK'h nuMins,
uators tu aorlos. II'.' i '
for (vvo (Idloinilois, ijinl a Ic of <Mi('h is I)hi(mI and ijm two lo<]:s twistod t(>!j:((li(M- niid wiuppcMl willi insulating tujx, und llnit, then tlio two IVcM I('<j:s ai'(i jil Inched to (Ju Icjidiii} wires, just us whei(5 hut. a sin<jl( detonatoi* is used. I w coal niininj ehar<(i \is(mI slionld novor l)(i so as to re(juir( (Ik use ol" iiiorc tJian ono detonator in tio ,samo liole.
Wlion itr is desired to iirc two oi' moii Jioles at samc tinier the
detonators foi* tJusc jioles sjiould also he (;()nn(Ml(;d up
Connecting holes. i i i i i i i i
111 series, and to hiid<2e th( space h(tw'e(;n tiie Jiouis a cheap insuhited wire, known as connectini wire, wliicli is not as iieavy as the knidinji; wares, may he used. In eouphnu up a series of holes for this purpose, one le<]; of the detonator is connected to one lej of the detonator in the next liole, and so on to tlie lust liole. Tliere is then left one free k\2: in the first Jiole and one free in tJie last hole, and these are spliced to the leading: wires. The usual precautions should he taken to wrap all the splices insulating tape, so as to completely insulate them, and therehy insure a circuit through which the current may pass. It should be borne in mind that the greater the number of holes to be fired in a single blast the greater is the necessity for making sure that the circuit is Danger from a oomi)lete throughout, bccause if there is a break or
break or short cir- . . . i i i n i i i
cult. a short circuit at any point, the blast wall probably
fail to fire. The delay, expense, and danger caused
by such a failure can be prevented by giving careful attention in the
first place to the charging and the waring.
The electric current for use in firing electric igniters or electric detonators may be obtained either from primary bat-
Sources of current. . .
teries, such as dry-cell batteries, or trom secondary batteries, such as storage batteries, or from electric-lighting circuits, or from generators known as electric firing machines. (See PL IX, B.) Firing charges of explosives by means of ordinary dry cells has been prohibited in foreign countries, because prema- ture firing of detonators, and sometimes of the charge, has been caused by the wares coming into contact with the poles of the batteries. Safety-contact dry-cell batteries have lately been introduced abroad and in this country. These are made with a spring-key contact, or with two safety-spring contact buttons, wdiich are the poles of the battery. The two leading wires are laid on the buttons, which are at the same time pushed dowaiward. When the pressure of the thumbs is released the contact is broken. If the wires of a detonator accidentally come into contact with the poles of the battery, the current can not be discharged unless both poles are pushed downward.
54 A PRIMKK ON EXPLOSIVES FOR COAL MlNEKlS.
Dry colls, siiuill batteiies, and some firing macliines can be carried
about by the miner who is to a(;t as shot iirer, and this is an advantaire
that insures him against ))remature lirhig by any other person.
Such small devices can at best be used with ordv a few
Portable devices. , . . .
shots in one circuit. 1 ho number of shots to be fired and the length of leading wires and other conductors through which the liring is to be done must be known beforehand, so that a battery of sudicient capacity can be selected. Batteries often fail to fire blasts because they can not send such a current as will lire through the great length of leading wires, connectors, and detonator legs that is used for the blast. A simple way to test the strength electric lamp of known capacity and note the bright- ness of the light given by the lamp. Another way is to pass the cur- rent from the battery through a testing circuit whose resistance is equal to that of the circuit of a blast and wdiich has in it one electric detonator. If the battery fires this detonator (which should be put in a safe place) it is strong enough and is in good condition. (See PI. IX, C.)
Wlien the electric current for firing is obtained from an electric- lighting circuit the connections are usually made in tri-ughtilg°drcufr parallel; that is, one leg of every detonator is con- nected to one of the leading wires and all the other legs to the other leading wire. Care must be taken, by the use of insulating tape, that there shall be no short-circuiting Connecting up m tlicse conuections. This method has the advantage
that if there is a defective electric igniter or electric detonator in the circuit its failure will not prevent the rest of the blast from being fired; bat, on the other hand, this method is objectionable because at any time after the explosion of the good igniters or detona- tors the unexploded charge with the defective igniter or detonator may be blown out and scattered in the coal, or it may even be set afire or perhaps exploded in the air of the mine by shock or friction. Further- more, in this and other methods of electric firing an jpremature electric (.idental premature blast may possibly be caused by leakage from the electric main to the earth and through the leading wires or connections, which may have become bared by rough handling or may not have been properly covered by the insulating tape. Premature explosions have been known to occur that were caused by leakage due to defective insulation.
Firing machines, sometimes called blasting machmes, generate
the electric current to be used in firing by median-
mfchtaes™ mcans. A variety of such machines have been
invented, but the two best-known classes are the
dynamo-electric machines and the magnetos. The dynamo-electric
DUnrAlJ OF MINTH
BULltTIN 17 PLAT! X
WIMMMMlliriliiHaMtflMkMMiHaHIMlMHMHyMM
A. Fuse And Detonator Fitted Into Primer.
B. Secondary Battery, Firing Machine, And Dry Cell.
C. Testing Firing Machines And Batteries.
A IM(IMi:i{ ON KM'LOSIVKS lOlf ('n.\l. MIM.IS.S. f)f)
luacliilios aici inad* lil\( oidimii v iiamos used l'(tr itihthI iii}/ 'lMt ric curroiits, diircriiiL!; only in (linl tli<\V him uoiIumI hy liniid. TlMiy vim- lain a coil-woimd niinaluiii wliicli is lolalcil Ix'Iwimmi poirs of an oloct.i'(Uua<j::iH'( . Tliis aiina(iir( can be made lo irvolvn hy means of a ('.raid< or a viMlical lalchrl. ;j;(Mn(Ml diirct lo llic spindjr of iIh- arinatiiiHV 'Plui luaciiiiu's willi lalciu'l bars mr inadr so as to sloir llj) IIk"! cni-i-cMit dniin a sl.i()k(\ iinld jiisl as llicr si loko is ended ontirci ciin'oiit llial lias inH licicd is dis('hai';.!;('d llnoiiidi llic l(Midiri<r wii'os.
'I'lH>s< n\a(i)iiH*s aid built in dilbMcnl sizes and ai"e latod ac(!ordiii;_' to tlu ninulx'i' of ol(M',tri('. detonatois tluv ean fire.
.,X"'L°°">'''i' " "r."-!'"!"" n,n.:lm,.. will, wlun'. prop.Mly woi'kod, 1ii-e 50 dotonatois at one. diseiiarjje. The,
machines iisiially hnilt foi- use. in coal mines ai(*, r-at(*d as "4-hole."
luaeliines, and such a machine can ho conveniently carried ahont by
the minor or shot firer.
Tlie ma<j:neto macbinos consist mainly of an armatur( ievolvin<'' between the poles of a set of ])ermanent mai'nets.
Magnetos. , . i ii i i i i .
Lliey look much like the dynamo-electric machmes that are worked by cranks, and they are Tised in much the same way. These ma<>jieto machines are used to a considerable extent in for<'ion countries, but the 'piish down'' dynamo-elect lic machine is the one most commonly used in the United States.
The leadinji: wires that carry the current from the blastin machine to the blast hole are of insulated copper wire, copper
Leading wires. . . i i i
bemij: used because it is one oi the best conductors of electricity known and has the further advantap:e of bein<i: but little corroded in damp mines. These leading wires or firing lines
are insulated with a braided covering, whicli is better ingwU'ef rnade waterproof. In some instances the two wires
are twisted together and v/rapped with an additional coating of braid, making them into one cable, which has the advan- tage of being more easily handled than two separate leading wires, and has also the advantage of the added protection given by the additional braiding.
After the blast has been fired, the ends of the leading wires should
be immediately disconnected from the posts of the Inspection and ra- fii-ing machine, and the lines should be examined
pair of leading wires . n . i i , , , ,
after firing. lor their wliolo length m order to see that the insu-
lation has not been broken by coal or rock thrown against it, nor been stripped by the force of the blast. AYliere such defects or injuries are found, they should at once be repaired vrith. insulating tape, and then the leading wires should be placed where they are not liable to injurv until they are again needed.
Use of galvanom-
eter.
66 A 1R1MEI{ ON EXPLOSIVES FOR COATv MINERS.
For tostin tho lino nftor it is connected uj), and befoio the firing, in order to show that the circuit is complete and
Testing the line. , , . , . . . , .
tliat there is no leakajre in. tlie wires, a special gal- vanometer may be used, together with a battery such as many of the manufacturers of explosives now sell. This galvanometer, like others, bears upon its face a needle, wliich is turned or deflected if an electric current is present. By noting whether this needle is deflected or not one can tell whether the circuit is closed or open, and the extent of the deflection shows just how little resistance there is in the circuit. To use the galvanometer, the wires leading from it are connected to the two binding posts of the firing machine, to which the wires leading to the charge have already been connected. Tlie deflection may then be noted. The current generated by the very weak battery cell attached to the galvanometer should not be strong enough to fire the electpic detonators used in the bore holes, but is enough to deflect the galvanometer needle. This testing galvanometer, to\?t?ker''*'''°' its attached battery, should never be applied directly to the face to be blasted, even wdien it is being used to fmd out, wdien the test has no current, which of the electric igniters or electric detonators are defective. The tests for the separate detonators or igniters should always be made through leading wires long enough to let the person making the test stand where he would be perfectly safe if the blast should be fired; and on no account should this testing of the igniters or detonators be made while any person is so near that he may be in danger from the blast.
lOCPT.OSlVKS IN S1NK1NC3 SUM PS AND ULASTl\c; IM)C K
AM) Diirr.
i-(M'()inm(Mi(l(Ml ill aiiv coal iniiu' or \uiil of a coal niino
diticms""*'* t'Hily (Icvclopniciit work, hucIi as shaft sink-
iiiji; or (Mitiy driving" (lii-oujjjh rock strata, in such
Nvoik all should bo out of tlio shaft or working piaci; when sliots
aro iiiTd.
After the coal has been reached and it lias become necessary that shots shall be fired while nuMv are in the mine, permissil)le explosives only should be used. After a niiiH Jias been o|)ene(l up, if rock or dirt is encountered, whicli may Juippen because of a fault or some; other cause, it is quite necessary that })ermissil)le explosives be used, for it is Iviiowii that hiflammable gas is likely to be found in such places.
In the sinking of shafts or in the removal of rock or dirt by means
of explosives, the methods to be followed in loading,
and°flrin/' tamping, and firing the cliarges of ex})losives are
similar to those described for use in blasting coal.
In this, as in other work, electric firing will be found to be the safest
means of shot firing, and in the long run the cheapest.
It is not uncommon to liear the statement that high explosives, because they are quicker in action than low explo- piosves" sives, need not be tamped. This is a serious error. The fallacy of it has been repeatedly proved in the tests of many different explosives made at the Pittsburg testing station. It has there been clearly shown that the highest pressure an explosive can give, and therefore the greatest amount of energy it can set free, will be developed only when the explosive is confined m the smallest possible space. Hence after the charges have been loaded into the bore holes they should be tamped with such materials (the best being damp clay) as confine the charges most closely, and this material should be rammed m firmly, with the precautions ah-eady set forth, quite to the mouth of the bore hole.
In the appendix setting forth the test requirements for permissible explosives (p. 68) it is stated that electric or other detonators contauiiug not less than 1 gram of the fulminating composition should be used in fuing the charges. For use with high explosives in rock blasting, detonators of that strength are also best. Under no circumstances sliould an electric or other detonator be used of less strength than Xo. 5, con-
68 A I'Kimkk On Kxplosives For Coal Miners.
taining 0.8 gniiu of the fiiliTiinaling composition. The greater effi- ciency and certainty of tlic stronger detonator more tlian make up for its sligiitly greater cost.
In the sinking of shafts, after the soil has been removed and the overlying layers of shale and rock are uncovered, it becomes necessary to use explosives; and because in such a place tlie ventilation is always poor and the miner must wait for the fumes and smoke to clear away after each blast before he can safely return to his work, time can usually be saved by firing shots in groups Firing shots in of siuglv. Dynamite, or, when the shaft is
groups. . .
wet, gelatin dynamite, may be used for these shots, whicli should always be fired after the men are out of the shaft. The most economical and safest way of firing a number of shots at one time is by means of the electric current, with electric detonators. The older metliod of firing by fuse is dangerous and wasteful. Where fuse is used, there is always danger that a seeming misfire may prove to be a hang fire — that is, the smoldering fuse may cause the charge to explode unexpectedly. Also, if by any chance there is irregu- larity in the burning of the fuse, the miner can not properly judge the time necessary to get out of the shaft and out of danger after having lighted the fuse.
In shafts that run through rock, as most shafts do, there is no
objection to the shattering effect of firing several
Firing simuitane- same iustaut, and this method is
recommended; but when it happens that in shaft sinking the shattering effect would be harmful, and successive shots are therefore to be used, it is still advised that they be fired by electricity. For such shots, however, a less violent explosive may be employed, and the delay-action electric detonator already described (p. 33) may be used to good advantage.
The follomng explosives may be recommended, in a general way, for use when the size and condition of the material resulting from the blast is not important, for example, in the sinking of shafts or the driving of entries through rock :
For use where the texture of the material is very tough and hard as in tough granite, hard bowlders, and the Hke, 60
Various explosives i,-Ti-j i i -j.*
for use in sinking per ceut straight nitroglycerm dynamite is recom- shafts and driving mended. Where the material is of moderate tough- ness and somewhat brittle, 50 per cent straight nitro- glycerin djmamite is recommended. In material such as limestone and sandstone, 40 per cent straight nitroglycerin dynamite is recom- mended. In hard earth or compact sand, a 30 to 20 per cent straight nitroglycerin dynamite is recommended. In material such as a soft crumbly or seamy rock that requires a stronger explosive than black blasting powder but a slower explosive than dynamite, a granulated
A I'Kimkk On Kxim.Osivk.S Toh Coal M I N Khh. 59
|)()vv(l<'r ('(Hitaiiiiii}:; prr cnil iiilro'lycnin is r'coinimMKlrd, Tliis should iilwHys IhmI willi a priiuinjj!: slick of (l\ nniiiih'. Willi this oxc('|)li<m, (lillVr4'iil kinds of explosives slioiiM n<'\rr hr iim-.I in
V\)V V(ry soi'l work in cuts jukI tills, oi- for (juuriy work whon (limeusioii slouch is sought, hlack hlasliuj powder is r4'coinnuMid<M|. in n-iidinj work ihc blast Jiok may Ix' hollonied out willi dynainile Ix'foro (liar:;inji; wilh j:niiniliil<'<l powdi'i- or with hlark hhistin; powder, hut. l)efor<' it is chnried care shoid<l he tnken to see tjnit IIk' dynaiuito elinrirei has not left any tii<' in tlu' hole. In plasU'rinj,' or adoho work on howlders and s|)awls, or in hlock holing, a strong' dynaniito should ho used. Block holin<]: is the more i'tVeetivi and economical jnethod for iisi with howlders.
If the straight nitro}j:lycerin dymunites, as reeonnuended al)ov<,
are found to he too (luick or too violent for use, and
Ammonia dyna- results ()l)taino(l arc not as desired umhr the given
mites. . . , . 1 1
cireumstances, ammonui dynamites, winch give a more heaving and rending action, are recommended. They are made in several grades and are rated as of a certain percentage of strengtli, but this rating is not always made in a scientific way. The following composition is an example of that wliich is generally offered ill this country as a 40 per cent strength ammonia dynamite:
Vomposition of 40 per cent strength ammonia dynamite.
Per cent.
Nitroglycerin 22
Ainnionium nitrate 20
Dope 58
This composition does not contain so large a percentage of nitro- glycerin as the straight 40 per cent dynamite (see p. 19), and as tested at the Pittsburg testing station it is not found to produce the same results as the latter. Nevertheless the ammonia dynamites are often found to be more economical and more efficient for certain classes of work than the straight dynamites of the same commercial rating. The ammonia dynamites are less readily set off and are safer to handle, transport, and store than the straight
Caution in use of , ., i , ,i n , i i.
ammonia dynamites. <tynamites are, but they all reqmre stronger deto- nators than the straight dynamites to insure a com- plete and rapid detonation. They haAe the disadvantage, compared with the straight dynamites, of taking up moisture Aery readily, and great care should be used in storing them or ha using them in wet holes.
For use in very wet blasting and in places where there is poor Aentilation the gelatin dynamites are recommended.
explosion they yield only a small quantity of fumes and bad gases.
(>0 A PKIMKK ON KXl'LOSIVKS FOK ('()AJ> MINERS.
Like ammoTiia (lyiianiitos, gelatin dynamites are less sensitive than straight nitroglycerin dynamites, and they therefore require stronger detonators to caiisi their complete exj)losion. They become less sen- sitive during long storage, and tliey liave been known after long stor- age in tropical countries to become so insensitive that they could not be detonated by means of the devices ordinarily used in firing them. Gelatin dynamite is likely to decompose during storage in very liot places.
Like the ammonia dynamites, the gelatin dynamites are sold in several grades and are given a somewhat unscientific rating in com- merce. The grade known as 40 per cent strength gelatin dynamite, as generally oifered in this country, has the following composition :
Composition of 40 per cent strength gelatin dynamite.
Per cent.
Nitroglycerin 32
Soluble nitrocellulose 1
Dope 67
As tested at the Pittsburg testing station, gelatin dynamites have not been fomid to be equivalent in every respect to straight nitro- gl3cerin dynamites of the same commercial rating, and as regards economy they should seldom be used as equivalent; but they are superior for some uses, as mentioned above.
J
SAFK SHIPMENT AM) STOH A(i OT KX IM.OSI V KS.
Hy H. W . Ii NN.
A iTspoiisihilil v 1) lli(' i)nl)lic rests mnmiriicl iircM'.s and cominoii carriors (o secure the sale (leli\('ry at- desti- puirr"'*'""'' nation of exi)l()sives, and it is tlie duty cf the owners of explosives to store them safely.
Under authority <i;ranted by Con<ijross the Interstate Coninieiccr Commission has made reuhitions, bindin< upon shii)-
Federal law and , - r i c
Interstate Com- ptMS and commoR camors, lor tlie transportation ol merce Commission oxplosives ill interstate Commerce, and the ix'nalty
ol a ])()ssil)le nnc ol $2, ()()() and IS months imprison- ment is prescribed by law for a violation of any of these retulations.
The shipper must know and certify on his shipi)in< order that the explosive offered by him is in a })roper condition for safe transpor- tation and that it is packed and marked, as required by the regulations. To perform this duty the shipper should be thoroughly familiar with all requirements pertaining to his shipment. A copy of the regula- tions can be obtained by ap])lication to the railway agent, whose duty it is to furnish them to slii})pers.
The follo\ing paragraphs in these regulations are of special inter- est to the shippers of explosives for use in mines: General Rule A. — Paragraphs 1501, 1502, 1503, 1509, 1510, 1531, 1533, 1541 to 1556, 1558 to 1560, 1611 to 1614, 1648, 1661, 1665, 1666, 1668, 1674 to 1683.
Miners and other persons are sometimes tempted to pack explosives
for shipment with their baggage on ])assenger cars, or
Explosives in bag- ti\eir household goods for shipment by freight.
goods. To do this IS a criminal act tliat endangers the lives
of the innocent and unsuspecting persons who have to handle these packages, and that subjects the guilty shipper, when detected, to arrest and prosecution. The Federal law (section 236) prescribes an imprisonment of 10 years for anyone convicted of this crime when death or bodily injury residts from the illegal transportation of explosives. When no injury results the maxi- mum penalty is 18 months' imprisonment and a fine of S2,000. There is no standard type of storage magazine in use in this country, and the laws and regulations in foreign countries " ' governing the construction of magazines differ materially. In Austria, for example, magazines are required to be of light construction, whereas in England they must have walls at least 18 inches thick.
A Prtmek Ox Explosives Fok Toat Miners.
8"x 8" brick pier
6"x 8"si//
6'0'
8 brick wall
6'0"-
H
Ground
13 0' A
H
9'0'
-2'I0'
9'Q'
Ventilator holes spaced 5 ' centers
2y/x4y/'
B
l/ne
Front \4'4,"-*
Ins'ide
ji'/ii
face
Figure 11.— Foundation plan (A), front elevation (B), and plan "f ventilator hole ( C) of brick magazine.
A
A iM{iMi;i: ON i;\i'i,()SiVKs i-'ou com IMINKHH.
No. 24 corrugated
alvonlted iron roof
2" 4''purHni spaced to securr iron roof to
I board
2 X3 rafters spaced 3 centers intervening spaces fil/ed with asbestos fiber
2 X 12 joists
brick pier
A
brick
6'0'
Figure 12.— Sections of magazin:: A. section at linp pd in fiR. Li. B; B, section at line AB in fig. 1,2, A.
64 A Pbtmer On Explosives For Coal Miners.
Explosives should be protected as far as practicable during storage Against heat, moisture, iiiv, lightning, projectiles, and theft. The buildings shoidd therefore be weatherproof, covered by fireproof and bullet-proof material, well ventilated, in secluded locations, and not exposed to fire risk from grass or underbrush. T.ightning pro- tectors are best placed on a line of supports encircling the building and 20 to 30 feet distant from it. Figures 11 and 12 show plans of an approved type of magazine.
In June, 1909, the chief inspector of the bureau of explosives of the American Railway Association brought to the attention of the man- ufacturers of explosives in the United States the
soiation of maga- (|jjj(rers that attend the location of storage maoa- zines too near railway property and invited a con- ference to discuss the steps that should be taken to remove these dangers*
A committee was appointed by the manufacturers to make an exhavistive study of all the data that could bs collected the world over to show the damaire that had resulted from explosions. As had been anticipated, a great deal of difficulty was experienced in getting reliable information in regard to this damage. The com- mittee finally succeeded, however, in collecting more or less reliable information relating to over 130 explosions. From the data curves were platted on a large scale to show for the quantity of explosives involved the maximum distances at which structural damage to buildings had resulted from the explosions. The term structural damage covers injury to foundations, supporting walls (exterior or interior), or to roof or floor members. It does not include the break- ing of glass or the shaking down of plaster.
Erom experience gained principally at manufacturing plants, it was concluded that an effective artificial barricade sarroimdino* a magazine, or the intervention of a natural obstacle screening the property to be protected, would result in reducing the maximum distance observed in the case of unprotected magazines by 50 per cent. In studying the data collected, therefore, the curves were platted on the assumption that the magazine was thus barricaded or pro- tected. With the exception of two or three instances, concerning which there was reasonable doubt of the reliability of tlie data col- lected, the curves were drawn to pass outside of all the platted points showing structural damage. From these curves the following table was prepared to show the distances that, according to the quantity of explosives involved, should separate storage magazines from inhabited dwellings and railways. For any such magazine not pro- tected by an efficient barricade, or by natural protection, the dis- tance shoujirl be doiibled.
A ritiMi'iit ON i;xiM/)sivi;s kok coai. minkhh. 05
Minimuiri. distarurn hctum'ti haniciitlid nnujaziniH and idilnuifi or ni/idhihtl tin lUiiitjg.
|)l()siv('S nIohmI
(Tim
ricuii (tl.stiiiio'M
(iiiirillly off'X- liloslvi'S HlonMl
(fui
rli'iiii <IInIuii(*m
(poiiiKls).
Ilili:il)il(M| l)iiil(lin.s.
I'lihlicmihviiy.
(|)()(ls).
1tiliiil)lli-(l bulldiiiH.
I'(;rullwuy.
10,000
8!K)
Iso
30, 000
40, 000
1 . :'.40
50, 000
'100
()(), 000
70, 000
1,055
80, 000
1, 730
1,040
'190
90, 000
1,075
100, 000
1,100
1,000
200. 000
2, 095
1, 255
1,500
(500
300, 000
2, 335
1,400
2, 000
400. 000
2,555
1,535
3, 000
500, 000
2, 755
1, 055
4, 000
()0(), 000
2, 935
1, 700
5, 000
700, 000
3,095
1, 855
(;, 000
800, 000
3, 235
1, 940
7,000
900. 000
3, 355
2,015
8, 000
1, 000, 000
3,455
2, 075 '
It should be nndorstood tliat the proposed distances iven in the above table have not yet been sanctioned by law. Whenever it becomes necessary, however, for a court to decide what would be a reasonable distance in a locality where such a distance is not speci- fied by law, common practice would require resort to the testimony of experts. The above table represents the combined judgment of the best experts available, after an honest and prolonged study of all available data. It is probable, therefore, that the table will be accepted as a guide and that any person maintaining a storage maga- zine at distances less than those prescribed by it will be subject to successful prosecution before the courts for the maintenance of a public nuisance.
It will be advisable, therefore, for all interested parties to see at the earliest possible moment that their magazines are located in accordance with the above table. It is understood, of course, that, in any locality where the law on this subject is now specific, the law must be the guide.
Magazines should be kept clean and in thorough repair. Grounds around them should be kept clear of leaves, grass, or other materials that might feed a fire. These words should be conspicuously posted on them: ''Explosives — dan- gerous. No shooting allowed." The floors must be swept regu- larly and kept clean. The sweepings should be thrown in water or taken to a safe distance and destroyed.
99160°— Bull. 17—11 5
Care of magazines.
66 A Primer On Explosives For Coal Miners.
In case floors become stained with nitro<lycerin, cover the stains with dry sawdust, sweep up, and remove tlie sawdust. Then scrub the stains thoroughly with a hard brush and a solution of one-half pound of sulphide of sodium or sulphide of potassium in one-half gallon of wood alcohol.
Do not allow in the magazine any tools other than a wooden mallet and wooden wedge, or a phosphor-bronze chisel, and a screw driver to be used only for removing screws.
Do not open dynamite boxes with a nail imller or powder cans with pickaxes.
Remove all explosives from a magazine before repairing it.
Do not store detonators mth explosives.
Do not open packages of explosives in a magazine.
Issue first the oldest explosives on hand.
Do not store dynamite boxes on end, as this increases the danger of nitroglycerin leaking from the cartridges.
Persons receiving packages of explosives sent by rail should ex- amine them carefully to discover ruptures or other serious damage received during transit. Any information regarding such matters will be welcomed by the chief inspector. Bureau for the Safe Trans- portation of Explosives, 24 Park Place, New York City.
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roN in'i'ioNs rM)i:i: wiik ii i;\i'i,().si\ i;.s aick i j.m kd.
The coii(li(,i(>i\s imder uliicli (he lliitfaii ol" MiiicH IchIh cxploHiViiH to doU'Tinlim wlu'duT llu'v shall Ixf placrd on iLs list, ol" j)('nnis.sil)ro cxploHivcH arc uh foIlowH:
1. The nuiiiuracturt'r in to di'liver to the buuiiAU ok Minkh, Koutiktii and Bijtlkk Streets, Prrrsnuud, Pa., three weeks j)ri()r to the cliito Het for tostn, 100 ])()un(lH of each explosiv( that he deHiroa to have tested, lie is to be respoii.sible for the care, haii- dliiiy;, and (Unlivery of this material to tiie testing ntation and h( in (o have a repre.senta- tive ])rtvsent duriii}:; tlie test.s. In order to avoid dui)li('ation of work, it is nupnHted ihat tlie {iituillesl size of cartridge that the manufacturer intends to place on th(} market be sent for thewe tests.
2. No one is to be present at or participate in these tests except the neccjssary CJoNirnment olHcers at the experiment station, their assistants, and the representa- tive of the manufacturer of the explosives to be tested.
3. The tests Avill be made in the order of the receipt of the applications for them, lrovided the necessiiry quantity of the explosive is delivered at the testing station
4. A list of the explosives which pass certain requirements satisfactorily will 1)6 lurnished to State mine inspectors and will be made public in such other manner as may be considered desirable.
5. The details of results of tests are to be considered confidential by the manufac- turer and are not to be made public prior to official publication by the Bureau of Mines.
G. From time to time field samples of permissible explosives will be collected, and tests will be made of these explosives as they are supplied for use in coal mines in the various States.
Test Requirements For Explosives.
The tests will be made by the engineers of the United States mining experiment station at Pittsburg, Pa., in gas and dust gallery No. 1. The charge of explosives to be fired in tests 1, 2, and 3 shall be equal in deflective power, as determined by the ballistic pendulum, to one-half pound (227 grams) of 40 per cent nitroglycerin dynamite in its original wrapper, of the following formula:
Per cent.
Nitroglycerin 40
Nitrate of soda (sodium nitrate) 44
Wood pulp 15
Carbonate of lime (calcium carbonate) 1
Each charge shall be fired with an electric detonator (exploder or cap) strong enough to completely detonate or explode the charge, as recommended by the manufacturer. The explosive must be in such condition that the chemical and physical tests do not shov/ any unfavorable results.
In order that the dust used in tests 2, 3, and 4 may be of the same quality, it ifl always taken from the same mine, ground to the same fineness, and used while still fresh.
68 A Primer On Explosives For Coal Miners.
The following are the tests to which are subjected the explosives that the Bureau of Mines is asked to place in the list of permissible explosives:
Test 1. Ten shots each with the charge as described above, in its original wrap- per, shall be fu-ed, each tamped with 1 pound of clay stemming, at a gallery tem- perature of 77° F., into a mixture of gas and air containing 8 per cent of gas (methane and ethane). An explosive is considered to have passed the test if no one of the 10 successive shots ignites this mixture.
Test 2. Ten shots each with the charge as described above, in its original wrap- per, shall be fired, each tamped with 1 pound" of clay stemming, at a gallery tem- perature of 77° F., into a mixture of gas and air containing 4 per cent of gas (methane and ethane) and 20 pounds of bituminous coal dust, 18 pounds of which is to be placed on shelves along the sides of the first 20 feet of the gallery, and 2 pounds to be 80 placed that it will be stirred up by an air current in such manner that all or part of it will be suspended in the first division of the gallery. An explosive is considered to have passed the tet if no one of the 10 successive shots ignites this mixture.
Test 3. Ten shots each with the charge as described above, in its original wrap- per, shall be fired, each tamped with 1 pound of clay stemming, at a gallery tem- perature of 77° F., into 40 pounds of bituminous coal dust, 20 pounds of which is to be distributed uniformly on a steel trestle placed in front of the cannon and 20 pounds placed on side shelves in sections 4, 5, and 6. An explosive is considered to have passed the test if no one of the 10 successive shots ignites this mixture.
Test 4. A limit charge will be determined within 50 grams by firing charges in their original wrappers, without stemming, at a gallery temperature of 77° F., into a mixture of gas and air containing 4 per cent of gas (methane and ethane) and 20 pounds of bituminous coal dust, to be arranged in the same manner as in test 2. This limit-charge test is to be repeated five times under the same conditions before being established.
The tests now prescribed as those a permissible explosive must have passed ara those given above. But even the explosives that have passed those tests and are published as permissible explosives are to be considered as permissible explosives only when used under the following conditions:
1. That the explosive is in all respects similar to the sample submitted by the manufacturer for test.
2. That No. 6 detonators — preferably No. 6 electric detonators (double strength) — are used of not less strength than 1 gram charge, consisting by weight of 90 parts of mercury fulminate and 10 parts of potassium chlorate (or their equivalents), except for the explosives ''Bental coal powder No. 2," "Detonite special," *'Hecla No. 2," ''Kanite A," "Masurite M. L. F.," "Titanite No. 7-P,"and "Titanite No. 8-P," for which the detonator shall be of not less strength than the No. 7 (IJ grams charge of the same mixture).
3. That the explosive, if frozen, shall be thoroughly thawed in a safe and suitable manner before use.
4. That the quantity used for a shot does not exceed pounds (680 grams), properly tamped.
It must not be supposed that an explosive that has once passed the above- mentioned tests and has been published in lists of permissible explosives is there- after to be considered a permissible explosive, regardless of its condition or the way in which it is used. Thus, for example, an explosive named in the permissible list, if kept in a moist place until it undergoes a change in character, is no longer to be considered a permissible explosive. If used in a frozen or half-frozen condition, it is not when so used a permissible explosive. If used in excess of the quantity speci- fied (1| pounds), it is not when so used a permissible explosive. And when the other conditions have been met, it is not a permissible explosive if fired with a detonator of less than the prescribed strength.
oTwo pounds of clay stemming are used with slow-burning explosives.
A IMtlMKU ON i;.\I'lA)SIVl-:S I'OH COAI, MINKIlH. (/.)
Moreover, wrw wlui nil llio pn-ncrihed coikHi ioiiH liiiv5 Ixh-ii met, no |MTiriiHHill' 6X|)loHive hIuhiM iM'<<'HHiirily lo roiiHidrri'cl aiH |)criii:itM!iitly lM*iii|/:i iMTmiHMiljJr explo- l)iit Jiiiy |M'rniiH,sihlo rxplonivr wlini iiHcd iMKlrr the ])reH(rilM'(l coiHJilionM iiiiiy pr()|K)rly conliniM' lo hr r(>iiHi(l<'r<<l :t pcrmiHHiMo rxploHiv** iinlil iiotietJ of ilH with- drawn! or n>inti\id I'mm llic lint h;iH hern olhcinily pMhlinln'd, or iiiiti! itn iiiiiin- in oiniltcd from a lalrr list |id)liMh('d ly tin* iWin-iui of MinoH.
l'urtliermorr, I lie innmilncl iirciH of ;i |)('rminHil)l(i exploHJve may wilhdniw it at any lime wIhmi iMtroducinii; a iirw 'xploHiv(i of Hiipcrior (pialitioH. And aft<'r fiirlli<r expcriincntH and conftircnct'H, th<5 liiireau of M inert may find it adviHahle to ndopt a(hlitional and more Hevere tents to wliicli all permiMHihlo exploniveH may he Hiihjoctefl, in the hope that the lives of minern may ho HafejMiarded Ixjtter through the uhc of only those oxploHivcH that may j)aHs the more wwere teHtH.
Publications On Mine Accidents And Explosives.
The following publications, except those to which a price is attached, can be had free by appl3ring to the Director, Bureau of Mines, Wash- ington, D. C. The priced pubhcations can be had by sending the price, in cash, to the Superintendent of Documents, Government Printing Office, Wasliington, D. C.
Publications Of The United States Geological Survey.
Bulletin 333. Coal-mine accidents; their causes and prevention; a preliminary sta- tistical report, by Clarence Hall and W. O. Snelling, with introduction by J. A. Holmes. 1907. 21 pp. 5 cents.
Bulletin 369. The prevention of mine explosions. Report and recommendations, by Victor Watteyne, Carl Meissner, and Arthur Desborough. 1908. 11 pp. 5 cents.
Bulletin 383. Notes on explosive mine gases and dusts, with special reference to the explosions in the Monongah, Darr, and Naomi coal mines, by R. T. Chamberlin. 1909. 67 pp.
Bulletin 425. The explosibility of coal dust, by George S. Rice, with chapters by J. C. Frazer, Alex Larsen, Frank Haas, and Carl Scholz. 1910. 186 pp., 14 pis.
Publications Of The Bureau Of Mines.
Bulletin 15. Tests of explosives used in coal mines, by Clarence Hall, W. O. Snell- ing, and S. P. Howell, with a chapter on the natural gas used at Pittsburg, by G. A. Burrell, and a preface by C. E. Munroe. (In press.)
Miners' Circular 2. Permissible explosives tested prior to January 1, 1911, and pre- cautions to be observed in their use, by Clarence Hall. 1911. 12 pp.
Miners' Circular 3. Coal-dust explosions, by George S. Rice. 1911. 22 pp.
Miners' Circular 4. The use and care of mine-rescue breathing appratus, by J. W. Paul. 1911. 24 pp.
o