The preservation of mine timbers
27 p., 4 leaves of plates : 23 cm
Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.
Historic, archived document
Do not assume content reflects current scientific knowledge, policies, or practices
Issued May 31, 1912.
U. S. Department Of Agriculture,
Forest Seryice — Bulletin 107.
HENRY S. GRAVES, Forester.
Forest Products Laboratory Series.
The Preservation Of Mine Timbers.
By
E. W. Peters,
Engineer in Wood Preservation.
Washington:
Government Printing Office.
Bui. 107, Forest Service, U. S. Dept. of Agricultuie.
Plate
Issued May 81, 1912.
U. S. Department Of Agriculture,
Forest Service— Bulletin 107.
HENRY S. GRAVES, Forester.
Forest Products Laboratory Series.
The Pkeseryation Oe Mine Timbers.
By
E. W. Peters,
Engineer in Wood Preservation.
Washington:
Government Printing Office.
Letter Of Transmittal.
United States Department of Agriculture,
Forest Service. WasJiington, D. C, February 6, 1912. Sir: I have the honor to transmit herewith a manuscript entitled 'The Preservation of Mne Timbers," by E. W. Peters, Engineer in Wood Preservation, and to recommend its pubHcation as Bulletin 107 of the Forest Service.
Respectfully,. Henry S. Graves,
Forester, Hon. James Wilson,
Secretary of Agriculture.
Contents.
Page.
Object of the study 5
Agencies destructive to mine timbers 6
Practical methods of increasing the durability of timber 6
Peeling 6
Seasoning 7
Preservative treatment 8
Brush treatments 8
Open-tank treatments 9
Pressure treatments 9
Results of experimental treatments 10
Cost of treatment 12
Open-tank plants 12
Pressure plants 12
Application and preservative . 14
Durability of treated timbers 16
Description of experiments 16
Life of treated and untreated timbers 17
Economy in the use of treated timber 18
Saving in money 18
Saving in timber 22
Avoidance of waste 23
Summary 23
Appendix.
Analysis of preservatives 24
Coal-tar creosote 24
Water-gas- tar creosote 25
Illustrations.
Plates.
Pag:e.
Plate I. General view of gangway, Philadelphia & Reading Coal & Iron
Co Frontispiece.
II. Fig. 1. — Fungous growth on untreated mine timbers. Fig. 2. — Fungous gi'owth on imtreated portion of mine timbers 8
III. Fig. 1. — Wood preserving plant and framing mill erected by Ana-
conda Copper Mining Co., in cooperation with Forest Service. Fig. 2. — Wood preserving plant erected by Tennessee Coal, Iron & Railroad Co., in cooperation with Forest Service 12
IV. Fig. 1. — Failure from crush of an untreated loblolly pine collar after
18 months' service. Fig. 2. — Failure from squeeze of an untreated loblolly pine leg after 18 months' service 16
Text Figures.
Fig. 1. Relative importance of agencies destructive to mine timbers 6
2. Percentage of green weight lost in seasoning mine timbers 7
3. General arrangement of small pressure plant for treating timbers 13
4. Comparative life of brush treated and untreated gangway sets 14
5. Comparative condition of treated and untreated loblolly pine gangway
sets 19
6. Comparative life of treated and untreated loblolly pine gangway sets . . 20
7. Compai-ative cost of brush treated and untreated loblolly pine gangway
sets 21
The Preservation Of Mine Timbers.
Object Of The Study.
In mining operations the cost of timber is a factor of much importance. In 1907, $10,000,000 was spent for round mine props alone, while additional expenditures were necessary for lagging, planking, and other forms of lumber extensively used in mines. The life of mine timbers is in many cases very short, and as the supply of the better grades becomes depleted less durable kinds must be used. This, of course, tends to shorten still further the period of serviceability.
While it is possible that concrete and steel may to some extent take the place of timber in mines, their high cost and the difficulty of installing them will restrict their use to work that is permanent. Moreover, wood, besides being comparatively cheap to handle, possesses so many other desirable qualities that for many purposes a satisfactory substitute is hard to find. Yet the decreasing supply of timber and increasing price make its more efficient utilization imperative.
To secure authentic data on the efficiency of various methods of preserving mine timbers from decay, the Forest Service has carried on a number of investigations in cooperation with various mining companies throughout the United States. These companies are: The Philadelphia & Reading Coal & Iron Co.; the coal mining department of the Delaware, Lackawanna & Western Railroad Co.; the Tennessee Coal, Iron & Railroad Co.; the Bunker Hill & Sullivan Mining & Concentrating Co. ; the Hercules Mining Co. ; the Homes take Mining Co.; and the Anaconda Copper Mining Co.
These investigations have been conducted along two general lines:
(1) Tests to determine suitable methods of treating timber used in mines.
(2) Tests to determine the durability of treated and untreated timber in actual service.
Some of these tests have already been discussed in Forest Service Circular 111, Prolonging the Life of Mine Timbers, by John M. Nelson, jr. Since its publication, however, additional results of much interest have been secured.
1 Torest Products of the United States, 1907, Bureau of the Census.
6 The Pkesekvation- Of Mine Timbees.
Agencies Destructive To Mine Timbers.
Timber used in mines is exposed to destruction from many sources. Wear, breakage, fire, and waste are responsible for much loss. Wooden rollers and drum laggings must be frequently replaced on account of the constant wear by ropes and cables. Unprotected timber used in chutes and mills is also rapidly worn by abrasion, while crossties in main haulage ways are often badly worn by the feet of mules and cut by the rails. Large amounts of timber are broken by crush'' and 'squeeze," or by swelling ground," and much temporary timber is buried beyond recovery in workings which are filled with waste rock or slush" after the coal or ore has been mined.
Decay and insects, however, cause the greatest damage. If not totally destroyed by one or both of these, the timbers frequently become so weakened that they break under the pressure upon them.
60%
Wear
BRE'AKAGEa' FIRE
Waste From All Causes
Decav 6- Insect Attack
Fig. 1.— The relative importance of agencies destructive to mine timbers imder average conditions.
The relative importance of the different destructive agencies varies greatly with conditions within the mines. Figure 1 shows this relative importance as observed in mines of the various cooperating companies.
Practical Methods Of Increasing The Durability Of
Timber.
To protect mine timber from destruction by mechanical wear, or by forces of nature beyond human control, is usually impracticable, and preservative treatment of timber exposed to these agencies of destruction, or of that buried in old workings, would be unwarranted. On the other hand, a large amount of timber is destroyed by decay and insects long before it has given its desired service, and if this can be protected at a reasonable cost a considerable saving may be realized.
Peeling.
Peeling timber is a simple and inexpensive method of increasing its durabihty, and under some conditions is fairly effective. Bark retards the loss of moisture from timber, and unbarked wood therefore offers more favorable conditions for fungus growth than wood from which the bark has been removed. Moreover, the space
Inckeasing The Durability Of Timbee. 7
between the bark and the wood is an excellent breeding place for many forms of wood-destroying insects. In dry workings the life of timber may be increased from 10 to 15 per cent by peeling, although in wet situations peeling seems to have little effect.
Besides increased durability, there are other advantages to be derived from the use of peeled timber. The bark of unpeeled timber often flakes off soon after placement, causing an accumulation of inflammable rubbish in the workings, which must be removed at some expense. To peel timber in the woods or at the shipping point effects a saving in freight and in cost of handling. With loblolly and shortleaf pine the weight of bark usually amounts to from 8 to 10 per cent of the original green weight.
o
Description Of Material
Curve
SPECIES or
Timber
Form
Dimensions
s
N
A O B O
Loblolly Pine
Loblolly Pine
Red Oak
Mine Props
MINE Ties
MINE TfES
llDIA.XIOLONCi 5X5'x5'-4
sxs'xd— 4
o
oC.
Is
N
,-c
ao
A
/
s
&
B
r-
"
-o
lO B 20 25 30
Days Seasoned
Fig. 2.— Percentage of green weight lost by seasoning mine timbers.
Seasoning.
The durability of timber may in some cases be increased by seasoning. In dry, well-ventilated workings the life of seasoned timber is sometimes 25 per cent greater than that of green timber. In wet locations, however, the effects of seasoning are counteracted by the reabsorption of moisture.
Whenever practicable, timber should be seasoned in the woods or at the shipping point, in order to realize, through loss of weight, a substantial saving in the cost of freight and handling.
Figure 2 shows the rate of seasoning of experimental timbers. Curve A shows the percentage of green weight lost in the seasoning of round mine props at Pottsville, Pa. The timbers were first peeled 32112°— Bull. 107—12 2
8 The Pkeseevatiox Of Mixe Timbers.
and then piled on skids. Curves B and C show the rate of seasoning of square-sawed mine ties at Birmingham, Ala. These were placed in open piles immediately after sawing.
The curves indicate that from 15 to 35 per cent of the original green weight was lost in a period of 8 weeks. These tests were carried on during the summer months, and the timbers were piled so as to permit a free circulation of air, conditions favorable to very rapid seasoning.
The diagram indicates that the loss of moisture from loblolly pine is greater than from red oak, and that large timbers season somewhat more slowly than smaU ones.
To insure thorough seasoning the timbers should be piled sufficient space between them to permit a free circulation of air throughout the pile. Too rapid seasoning, however, may result in checking, and so weaken the timber. Moreover, if timber is held too long, decay is hkely to develop. This is especially tiTie in warm, humid chmates, and under such conditions the material should be seasoned as rapidly as possible. Summer-cut timber is also likely to deteriorate while seasoning, and. if possible, cutting should be done at some other time of the year.
Preservative Treatment.
While, under certain conditions, peeling and seasoning often increase the durabihty of timber, chemical preservatives give the best results. Before timber is treated preservatives, however, it should fust be peeled, and, as a rule, thoroughly seasoned. All timbers should be cut and framed to their final dimensions and form before treatment, since the sawing and cuttmg of treated timber frequently exposes untreated surfaces to attack by wood-destroying organisms. A description of the preservatives and of the methods of wood preservation commonly used in this country is given in Forest Service Bulletin 78, Wood Preservation in the United States, by W. F. Sherfesee. A brief description of the several classes of treatments referred to in this bulletin will, however, be given here.
Brush Treatments.
A fairly effective and cheap treatment is to paint timber \'ith two or three coats of hot creosote or some similar preservative. It is important that the wood be seasoned before treatment, for otherwise checkuig may later expose untreated portions of the timber to fungus attack. Care should, moreover, be taken to get the preservative well into all checks, knot holes, and surface inequalities: otherwise decay is likely to develop at these points.
The amount of preservative required for treatments of this character is relatively small, and no special equipment is needed. Brush
Bui. 107, Forest Service, U, S. Dept. of Agriculture.
Plate II.
m
r iM
w
B"
Fig. 1 .—Fungous Growth on Untreated Mine Timbers. Timber Third from Left was Treated.
Fig. 2.
Fungous Growth on Untreated Portion of Mine Timbers. Portion of Timber Treated, Lower Portion Untreated.
Upper
Increasing The Durability Of Timber. 9
treatments are therefore advisable when the amount of timber to be treated is too small to warrant the erection of even a small plant, or when it is necessary to restrict the initial cost of treatment to the lowest possible figure. The main disadvantage of brush treatments is that the slight penetration secured is not enough to insure the protection of the interior of the timber for any considerable period. The thin coating of treated wood may be broken or split, or fungus spores may enter through nail holes, checks, or splits, causing decay in the interior of the timber, while the outside appears sound.
Open-Tank Treatments.
A more effective method of treatment is the open tank. In this the timber is first immersed in a tank of suitable capacity containing the preservative, and the charge is then heated to a sufficiently high temperature to drive off a portion of the air and moisture contained in the wood. Since excessive heating is likely to result in checks which will weaken the timber, and since large quantities of preservative may be lost by volatilization, the maximum temperature of the hot bath should not, in the case of creosote oils, exceed 220° F. and, if an aqueous salt solution is used, should be kept slightly below the boiling point of the solution.
Following the hot bath the timber is immersed in preservative at d lower temperature, or it may be left in the hot liquid, which is allowed to cool.
The treatment of timber by the open-tank process insures a greater penetration of the wood by the preservative than does the brush method, and for this reason has proved more effective. In general, it is well adapted for the treatment of species which are easily impregnated.
Pressure Treatments.
With many species a satisfactory treatment can be secured only by the use of pressure. The essential difference between the opentank process and the pressure processes is that in the former atmospheric pressure is relied upon to secure the penetration of the wood, while in the latter the preservative is forced into the timber by artificial means. Owing chiefly to the difficulty of impregnating many species of wood by the open-tank process, the pressure treatments are the most widely used.
Pressure processes may be employed for either full cell or empty cell treatment. The object of the former is to leave the treated portion of the wood completely filled with the preservative, while the latter aims to inject the preservative as deep into the timber but leave no free oil in the wood cells. The oldest process of full-
The Pkeseevation Of Mine Timbers.
cell pressure treatment with creosote is as 'Bethellizing." A siniilar treatment with zinc chloride solution is called 'Burnettizing.'
Results Of Experimental Treatments.
Tables 1 and 2 show the average absorptions and penetrations secured in representative open-tank and pressure treatments of different species of timber. These results indicate that —
(1) Thoroughly seasoned loblolly and Pennsylvania pitch pme round mine timbers may be satisfactoril} impregnated by the opentank process.
(2) Green timber of these species is much more difficult to treat than seasoned timber.
(3) Satisfactory results may be secured in the treatment of seasoned western yellow pine by the open-tank process, the sapwood of this species being impregnated mthout difficulty.
(4) In general, pressure treatments are more satisfactory than open-tank treatments. By the former the time of treatment is reduced considerably, and the preservative is more generall}" diffused through the timber.
(5) Heart Douglas fir is impregnated with difficulty.
Table 1. — Results of representative open-tanh creosote treatments of various species.
Description of material.
Record of treatment.
Result of treatment.
Number of treat-
Hot bath.
Species.
Form.
Condition before
Cool-
ing bath,
Absorption
averaged.
Maxi-
Aver-
Average
treatment.
Duration.
mum tempera-
age tempera-
duration.
per cubic foot.
penetration.
ture.
ture.
Hours.
"F.
° F.
Hours.
Pounds.
Inches.
Loblolly pine, largely sapwood.
Round mine props, 10 mches in diameter, 7 to 10 feet long.
Green
hi
do
do
Partly seasoned, about 2 months.
do
do
Well seasoned.
Pennsylvania pitch pine.
We stern
Round mine props, 7 to 10 feet long.
do
Round mine
do
h- 1
hi
yellow
timbers ,
pme.
mine ties.
Complete sap-brood.
Besults Op Expekimental Teeatments. 11
Table 2. — Results of representative creosote pressure treatments of various species.
Number
Description of material.
Results of treatment.
of treatments
Condition
Description of treatment.
Absorption per cubic foot.
Average
averaged.
Species.
Form.
before treatment.
penetration.
Pounds.
Inches.
Loblolly
Mine ties, 5
Partly sea-
(1) Bath in hot creosote.
pine.
by 5 inches by 5 feet 4 inches.
soned.
Average duration of hot bath, hours; average maximum temperature, 200° to 220" F. (2) Entire charge cooled and
pressure applied while cool-
ing. Average duration of
cooling bath, 2 to hours;
average pressure, 14 pounds
per square inch; average
temperature, 190" F.
do
Mine ties, 5 by 5 inches by 5 feet 4 inches.
do
(1) Bath in hot creosote. Average duration of hot bath, 2i hours; average maximum temperature, 200° to 220° F.
(2) Cylinder refilled with cool
l-lj
oil and pressure applied.
Average duration of cool
bath, IJ hours; average
pressure, 12 pounds per
square inch; average tem-
perature, 173° F.
do
Mine ties, 5 by 5 inches by 5 feet 4
Well seasoned.
Cylinder filled with creosote and pressure applied. Average duration of pres-
inches.
sure, 19 minutes; average pressure, 55 pounds per square inch; average temperature of creosote, 185° F.
Douglas fir..
3-inch planking.
Green
(1) Bath in hot creosote. Average duration of hot
bath, 4i hours; average
'
maximum temperature,
215° F.
(2) Entire charge cooled and
pressure applied while cool-
ing. Average duration of
cooling bath, hours;
average pressure applied, 100 pounds per square inch;
average temperature.
198° F.
do
10 by 10 inches and 10 to 14- inch shaft timbers.
do
(1) Saturate steam bath. Average duration of steam bath, 3 hours; average pressure, 16 to 20 pounds per square inch.
applied. Aver-
age duration of vacuum.
1.9 hours; average vacuum,
16 to 20 inches.
(3) Cylinder filled with creo-
sote and pressure applied.
Average duration of pres-
sure, 4f hours; average
pressure, 100 pounds per
square inch; average tem-
perature of creosote, 190°
to 215° F.
t
12 The Presekvation Of Mine Timbers.
Cost Of Treatment.
The cost of preservative treatment may be considered under two heads: (1) Cost of treating plants; (2) cost of application and the preservative.
Open-Tank Plants.
The open tank is the simplest type of apparatus used for the impregnation of timber. The necessary equipment consists mainly of an uncovered tank provided with a device for submerging the timber. The tank may be so arranged that a fire can be built under it, but if a supply of steam is available it should be equipped with coils for heating purposes. If large timbers are to be treated, a derrick or gin pole is necessary for their convenient handling, A plant of this character, with an annual capacity of 100,000 cubic feet, may be erected at a cost of from $1,500 to $2,500. The low cost of an open-tank plant places it well within the reach of most mine operators, and this, perhaps, is its main advantage.
Pressure Plants.
The cost of pressure plants depends chiefly upon their capacity. Figure 3 shows the general arrangement of a small pressure plant, having a capacity of approximately 1,000 cubic feet per run, or 750,000 cubic feet per year. The total cost of such a plant will amount to from $12,000 to $20,000. The foUomng is a list of the main items of equipment:
One horizontal treating cylinder, 65 feet long, with inside diameter of 6 feet 2 inches, capable of withstanding an internal pressure of 175 pounds per square inch.
Two vertical measuring tanks, each of 15,000 gallons capacity.
One storage tank of 50,000 gallons capacity.
One hoist engine.
One pressure pump, capacity 150 G. P. M. at 175 pounds pressure per square inch.
One air compressor, capacity 460 cubic feet of free air per minute at 20 pounds pressure per square inch.
Sixteen cylinder cars.
One zinc chloride mixing tank of 2,000 gallons capacity.
Special attention should be given to the design and construction of a storage yard of adequate capacity for both treated and untreated material, since handling the timber before and after treatment is an important factor in the cost of operation. It is also important to locate the plant at a convenient point in the mining district, so that treated timber may be readily distributed to points where it is to be used.
1 Annual capacity based on two runs per day for 250 days.
2 Annual capacity based on three runs per day for 250 days.
Bui. 107, Forest Service, U. S. Dept. of Agriculture.
Plate III.
Fig. 1 .—Wood-Preserving Plant and Framing Mill Erected by the Anaconda Copper Mining Co., at Rocker, Mont., in Cooperation with the Forest Service.
FiQ. 2.— Wood-Preserving Plant Erected by the Tennessee Coal, Iron & Railroad Co., AT McAdory, Ala., in Cooperation with the Forest Service.
Cost Of Teeatment.
14 The Peeservation Of Mine Timbees.
The pressure plant shown in Plate III, figure 1, was designed by the Forest Service and erected by the Anaconda Copper Mining Co. at Eocker, Mont. Its capacity is about 570 cubic feet of timber per run. The equipment is as follows :
One treating cylinder 43 feet long and 6 feet in diameter, working pressure 100 pounds per square inch.
One receiving tank, 47 feet long and 5 feet in diameter.
Two measuring tanks, 12 feet in diameter and 17 feet high.
One general service pump, 360 G. P. M. at 125 pounds per square inch.
One pressure pump, 60 G. P. M. at 125 pounds per square inch.
One vacuum pump 7 by 10 by 6 inches, and jet condenser.
Eighteen cylinder cars.
One hoist engine.
The total cost of the plant, erected, was approximately $15,000.
Plate III, figure 2, shows a plant designed by the Forest Service for the Tennessee Coal, Iron & Railroad Co., and erected at McAdory, Ala. Its capacity is about 830 cubic feet of timber per run. The main equipment is as follows :
One treating cylinder, 6 feet in diameter and 65 feet long, working pressure 100 pounds per square inch. Two measuring tanks, 12 feet in diameter and 18 feet high. Two storage tanks, 11 feet in diameter and 36 feet long. One settling tank, 16 feet by 6 by 4 feet deep.
One pressure pump, capacity 150 G. P. M. at 100 lbs. per square inch. One air compressor, capacity 108 cubic feet free air at 50 pounds per square inch. One air reservoir 3 feet in diameter and 15 feet long. One surface condenser, 230 square feet of condensing surface. Twenty cylinder cars. One derrick and hoist engine.
The total cost of tliis plant, erected, including the necessary yard construction, amounted to approximately $12,000.
Application And Pkeseevative.
The unit cost of handhng timber at open-tank plants is higher than at pressure plants, usually amounting to from 3 to 4 cents per cubic foot at the former and from 2 to 3 cents per cubic foot at the latter. These figures include interest, depreciation, and operating charges, but not the cost of the preservative, which is by far the most important item. Table 3 shows the approximate costs of the untreated and treated loblolly pine gangway and entry sets used in the Forest Service experiments in the mines of the Philadelphia & Reading Coal & Iron Co.
Cost Of Teeatment.
Table 3. — Cost of untreated and treated loblolly pine gangway and entry sets placed by the Philadelphia & Reading Coal & Iron Co., in cooperation with the Forest Service.
[One set consists of one 7-foot collar, one 9-foot leg, and one 10-foot leg; average diameter of timbei 13 inches; approximately 26 cubic feet in one set.]
Condition of
material before
treatment.
Method of treatment.
Preservatives used, sold as—
Unit cost of preservative.
Amount of preservative used per set.
Cost per preservative.
Cost per
set of peeling, seasoning, and treating timber.i
Total cost of set in workings.
Green unpeeled.
Untreated...
$8. 50
do
$0.28
Seasoned peeled
Do
Do
Brush-treated, two coats. do
Impregnated
do
do
Coal-tar creosote.
Avenarius carbolineum.
Water-gas-tar creosote.
Coal-tar creosote. Zinc chloride..
8 cents per gallon.2
70 cents per gallon.3
7 cents per gallon.2
8 cents per gallon.2
4 cents per pound dry
salt.
li gallons per
per cubic foot.
do
10 potmds per cubic foot or 30 gallons per set.
do
I pound dry salt per cubic foot or 13 potmds per set.
$0.12
Do
Do
1 Cost of treating includes cost of labor, fuel, and interest and depreciation on plant.
2 Unit cost of creosote based on price of tank ear lots of from 8,000 to 10,000 gallons.
3 Unit cost of carbolineum based on price of barrel lots.
Below is given in detail the cost of untreated and creosoted 16 feet by 8 inches Douglas fir shaft sets placed in the mines of the Anaconda Copper Mining Co. These sets contain 1,127 feet b. m. of Douglas fir squared timbers from the Pacific coast, and 393 feet b. m. of lagging. The average absorption secured in the treatment of these timbers amounted to 4.5 pounds of creosote per cubic foot.
Cost of untreated sets :
1,127 feet b. m. squared timbers, at $20.50 per M b. m $25. 36
Framing timbers 13. 50
Cost of lagging, at $15 per M b. m 5. 90
Switching and unloading charges 85
Cost of placing set 18. 00
Total cost of untreated set in place 63. 61
Cost of treatment:
Cost of treating, including interest, depreciation, fuel, and labor charges. . 3. 34 Cost of creosote," at 15.6 cents per gallon; absorption 4.5 pounds per cubic
foot 8. 03
Loading and unloading charges 1. 23
Total cost of treatment 12. 60
Total cost of treated set in place 76. 21
16 Thb Peeseetatxon Op Mine Timbees.
lie co.t 0/ lh limb.r .n,l i.7 ° '" ""J""*!, with
DTTEABIllTY OF TEEATED TIMBERS DESCBIPTION OP EXPERIMENTS.
The experimental timbers were standard round "sanswav" nr leTYoT: -treated, each set consisting ofaifoo
T.B.B 4.-Untreate, e.j,erierUm,er. ,lace, in tke mines of t,e PMal.Uia &
Reading Coal & Iron Co.
Condition when placed.
Loblolly and shortleaf pines Do
Pennsylvania pitch pine
-Longleaf pine
Red and black oaks
Green, unpeeled . Green, peeled . . . Seasoned, peeled. Green, unpeeled. Green, peeled... Green, unpeeled.
Number ofpieces.i
'On.,p,eeeswMch are included ,n the rep;r;7;,,o„s in theAppendi. are counted;r~
Tv 1i I carbolineum, by the ooen tank method with various preservatives, and by the wesLre method
treated timbera. An analysis of the coal-tar and water-gas tar creosotes used m the experiments is given in the AppeiX
Bui. 107, Forest Service, U. S. Dept. of Agriculture.
Plate IV.
Fig. 1 .—Failure from Crush of a Decayed Untreated Collar After 1 8 MONTHS' Service, Silver Creek Colliery, Philadelphia & Reading Coal & Iron Co. The Timber to the Right, Placed at Same Time, WAS Burnettized.
Ww
f
r
'flP'H
r
Pi
m) i
Fig. 2.— Failure from Squeeze of a Decayed Untreated Loblolly Pine Leg. The Timber Directly to the Right of the Broken Leg, Placed AT the Same Time, was Bethellized.
Dueability Of Treated Timbers.
Table 5. — Peeled and treated loblolly and shortleaf pine gangway sets placed in the mines of the Philadelphia & Reading Coal & Iron Co.
Condition
before treatment.
Method of treatment.
Preservatives used, sold as—
Amount used.
Number of pieces.
Brush treated, two coats, do
11 gallons per set (J pound per cubic foot), do
Do
Avenarius carbolineum
Green
Open-tank process. .
do
do
Coal-tar creosote i
4 to 6 pounds per cubic foot . . .do.
Do
Water-gas-tar creosote. . .
Do
J pound dry salt per cubic
1 pound per cubic foot mixture of dry salts. 10 to 12 pounds per cubic foot do
Do
do .
Sodium and magnesium
chlorides.3 Coal-tar creosote i
Seasoned.
.do
Do
do
do
Bethell process
(pressure). Burnett process
(pressure).
Do
Zinc chloride 2
J pound dry salt per cubic
foot. 10 pounds per cubic foot. —
0.3 pound dry salt per cubic foot.
Green
Coal-tar creosote
Do.
Zinc chloride .
1 Analyses of these preservatives are given in the Appendix.
2 Injected in a 6 per cent aqueous solution.
3 Injected in a 15 per cent aqueous solution of a mixture consisting of 1 part magnesium chloride to 7 parts of sodium chloride by weight.
Injected in a 2 per cent aqueous solution.
DESCRIPTION or MATERIAL.
Average Life—
— Years
Condition
Material When Placed
Species
or WOOD
Preservative Used
Method Treatment
Solo As
Amount Per.Cu.Fx
" ' I
I
Green Unpeeleo
Loblolly &
SHORTLEAr
Pine
Untreated
wm
Green Peeled
Loblolly &
SHORTLEAr
Pine
Untreated
Green Unreeled
Pennsylvania Pitch Pine
Untreated
GREEN UNPfCLED
Black Oak
Untreated
Seasoned
Peeled
LOBLOLLY a
Shortleaf
Pine
Untreated
GREEN PEELeO
Southern
Longleaf
Pine
Untreated
.
Seasoned
Peeleo
Loblolly &
Shortleaf
Coal Tar- Creosote
,S Lb. I5 Gals Per Set
BRUSH TREATED e. COATS
Seasoned
LOBLOLLY a
Shortleaf
Pine
Avenarius Car0Olineum
,-S Lb. Peir Set
Brush Treated £ Coats
1I'"Iii'™"J1'T'Ii
Fig. 4.— Comparative life of untreated and brush treated gangway sets placed in No. 3 plane, Silver Creek colliery of the Philadelphia & Reading Coal & Iron Co., in cooperation with the Forest Service.
Life Of Treated And Untreated Timbers.
Most of the timber was placed during 1906, 1907, and 1908; and inspections were made in December, 1907; March, 1909; and July, 1910. The results so far secured are shown graphically in figures 4 and 5.' A detailed summary of the inspections is given in Tables 6 and 7.
Owing to the conditions in the various collieries, it was not always possible to make a complete inspection of all of the experimental timbers, nor was it possible in all cases to procure complete data on the cause of failure of individual pieces; but the condition of the timber as found in the various inspections offers sufficiently accurate data to warrant the following conclusions :
(1) All of the untreated material failed within from one to three years, while brush-treated timber remained serviceable for from three to four years.
18 The Preseevatiox Op Mine Timbers.
(2) The life of untreated peeled loblolly and shortleaf pine was from 10 to 15 per cent greater tlian that of similar unpeeled material.
(3) In dry, well- ventilated workings the average life of untreated seasoned loblolly pine was approximately 25 per cent greater than that of similar green material. In wet locations seasoned timber did not appear to outlast unseasoned material.
(4) Loblolly and shortleaf pine, brush-treated with coal-tar creosote and Avenarius carbolineum, proved to be from 50 to 100 per cent more durable than similar untreated material. Moreover, brushtreated loblolly and shortleaf pine proved more serviceable than untreated longleaf pine, pitch pine, and red and black oak. Brush treatment with Avenarius carbolineum was somewhat more effective than similar treatment with coal-tar creosote.
(5) The condition of timber treated by the open-tank process with sodium and magnesium chloride, although not comparing favorably with that of timber similarly treated with other preservatives, was better than that of the brush-treated timbers.
(6) Open-tank treatments of green timber with zinc chloride proved fairly effective, but the tests indicate that better results will be secured with seasoned material. Figure 5 shows that about 13 per cent of the green timber treated with zinc chloride by the open-tank process showed marked signs of decay after four years, while no decay was found after the same period of service in seasoned material similarly treated.
(7) With the exceptions noted, none of the impregnated timbers showed signs of decay after from three to four years' service, although some of them had failed from crush and squeeze. Plate TV shows to some extent the difference in the condition of treated and untreated material after eighteen months' service.
(8) In some instances impregnated timber, reframed after treatment, showed signs of decay. This was probably due to the cutting away of treated material and the consequent exposure of untreated portions of the timber.
Economy In The Use Of Treated Timbers. Saving In Money.
It is not only essential that treated timbers should last longer than untreated ones, but also that this increased life should be sufficient to make their ultimate cost less than for similar untreated material. In other words, an appreciable amount of money must be saved in a reasonable length of time. How much money is actually saved by the use of treated timbers can best be determined by a comparison of the annual charges for the treated and untreated
1 Most of the timbers were placed in fairly dry situations.
Economy In The Use Of Treated Timbers.
materia,]. By annual charge" is meant that amount of money which it would be necessary to place aside each year, at compound interest, to amount at the end of the timber's period of service to a sum sufficient to cover the initial cost of the timber in place plus compound interest on the investment.
Description Of Material
Condition Of Material
Condition
Of
Timber
Green Unpeeued
Seasoned Peeled
Seasoned Peeled
Green Peeled
Green Peeled
Seasoned Peeled
Green Peeled
Seasoned Peeled
Green Peeled
Seasoned Peeled
Green Peeled
Green Peeled
Perservative Used
Sold As
Coal Tar Creosote
AVENARIUS /uVlf',:
Amount Per Cu.Pt
.5 LB. fih GALS. PER set)
Sodium & magnesium
is% solution)
ZIfSC , CHLORIDE , (S SOLUTIOrnl
Zinc , Chloride . (6 Solution)
Water Gas
Tar Creosote
Water Gas
Tar Creosote
Coal Tar Creosote
Coal Tar Creosote
Goal Tar Creosote
Zinc Chloride (2% Solution)
Ilb. Dry Salt
4 Lb. Dry Salt
iLB. DRY ALT
4-eL8S.
4-6 Lbs.
lO-ISLBS.
.3 Lb.
Dry Salt
Method
Of
Application
Untreated
Brush
Treatment
2 Coats
Brush
Treatment
e COATS
Open Tank Process
Open Tank Process
Open Tank Process
Open Tank Process
Open Tank Process
Open Tank Process
Open Tank Process
Bethel Process
Burnett Process
SERVICEb% EO%
Legend
Sound
Partly DecayecStill SERvtCEABLE
Entirely DecayecToBe RemoveNot Serviceable
Removals Due To ALL Causes
Fig. 5.— Comparative condition of treated and untreated loblolly pine gangway sets placed in the mines of the Philadelphia & Reading Coal & Iron Company.
Figure 6 shows graphically the actual length of service secured from both the treated and untreated timbers set in the mines of the Philadelphia & Reading Coal & Iron Co. as observed at the time of the last inspection. It also shows the length of life necessary for treated timbers to make the annual charges equal to those for similar
The Pkeseevation Of Mine. Timbers.
untreated material. For example/ if the annual charge on peeled timber is to equal that on unpeeled timber the life of the former must be about one year and six months. The average life of peeled timber was found to be slightly higher than this. Timbers impregnated with zinc chloride should have a life of one year and eight months to make the treatment economical. At the date of the last inspection these timbers had already been in service for a period of three years and seven months, and 78 per cent of them were still sound. Figure 7 shows in fact that the increased service obtained by the use of a preservative treatment was in all cases sufficient to bring about a saving in money. It indicates further that in these experiments impregnated timbers have proved more economical than brushtreated ones. Moreover, for the period smce placement, the zinc chloride treatments show the greatest efficiency. Enough time has
DESCRIPTION or MATEIRIAL
life:
When Placed
Preservative Used
LIFE NECESSARY TO MAKfT ANNUAL EQUIVALENT TO ANNUAL CHARGES
Condition Of- Material At Last Inspection
Sold As
Amount Per.Cu.Ft
PERIOD or ACTUAL SERV.CE YEARS
PERCENt SOUND
Creen
Unpeeled
O O
Creen Peeled
Seasoned Peeled
Coal Tar Creosote
1.5 gals:
Per Set
Seasoned Peeled
Avenarius Car80L1Neum
.5 Lb. 1.5 Gals.
Seasoned Peeled
Zinc Chloride
.5 Lb. Dry Salt
EEAEONtD PEELED.
Water Gas Tar Creosote
10 Lbs.
Seasoned Peeled
Creosote
10 Les.
Fig. 6.— Comparative life of treated and untreated loblolly pine gangway sets.
not elapsed, however, to warrant a definite statement concerning the comparative efficiency of timbers impregnated with zinc chloride, with coal-tar creosote, and with water-gas-tar creosote.
Figure 6 shows graphically the comparative cost of untreated and of brush-treated loblolly pine gangway sets after various periods of service. The charge includes the cost of installation and maintenance, plus simple interest at 5 per cent on the investment, and was derived from the cost data given in Table 3 and the figures for average life secured from the experimental sets placed in the mines of the Philadelphia & Reading Coal & Iron Co., as shown in figure 4. The broken lines show the actual expenditures for a gangway set of average life.
Thus the original cost of a green unpeeled and untreated loblolly pine gangway set, including removal of old timber and placement of
1 Annual charges computed from the following formula:
in which yl annual charge;
amount of initial investment;
w=nmnber of years in recurring period;
r=rate of interest expressed decimally (in this case taken as 5 per ceni).
Economy In The Use Of Treated Timbers.
new ones, amounts to about $8.50. The average life of such a set is about one year and four months., At the end of this period the simple interest charges on the expenditure amount to $0.57, making the total cost up to that time $9.07, as indicated on line A. To this must be added a replacement charge of $8.50, which is represented by the vertical rise in this line ; the total charges for the two installations and the maintenance and simple interest on the first installation up to this time amounting to $17.57. After a period of two years and eight months the interest charges on the cost of the first
fEftlOD OF service:— YEAR5
Fig. 7.— Comparative cost of crush treated and of untreated loblolly pine gangway sets.
installation amount to $1.14, and on the first replacement to $0.57, making the total cost up to this time $18.71. A second replacement is then necessary, the cost of which is again shown by the second vertical rise in' the line. Thus the increased interest charges are represented by the increase in the slope of the lines connecting the vertical rises in the broken line, while the vertical rises represent the successive replacement charges. Lines B and C, showing the cost of brush-treated sets, are derived in a similar manner.
If a number of sets are considered it is unlikely that all of them will fail at the same time, and for this reason the average expenditures are better represented by the smooth curves shown in the diagram.
22 The Peeseevatiox Of Mixe Timbees.
These also show better the saTing which may be realized by the use of brush-treated timber. Thus in two years the average total charges agamst the untreated set, as read from the curve, amount to about S18.10. With a set brush-treated with creosote, on the other hand, the charges amount to Si 1.60, a saving of $6.50 due to the treatment. In four years this saving amounts to SI 3. 80, which represents the difference between S33, the total cost of the untreated sets, and S19.20, the total cost of the brush-treated sets for that period. The curves further indicate that brush treatment with carbolineum proved more economical than brush treatment with creosote. The fact that the initial cost of the timber at different periods is considered to be the same makes the curves veiy conservative, juice the price of mine timbers wiU unquestionably continue to rise. On the other hand, a certain salvage might have been allowed for removed props, which may be utilized for fuel or sawed iato lagging. Siace, under the conditions of the experiment, failure fiom mechanical causes, such as crush and squeeze, was more common in treated than untreated props, the former would have a greater salvage value, and the relative saving resulting from their use would be greater than that shown ia the diagram.
Siace the impregnated timbei have not been ia service long enough to enable their average life to be determined, most of them beiQg stiQ sound when last inspected, it is impossible to show the ultimate savitig in money resulting from their use. Even for the period siace their installation, however, they have proved more economical than untreated or brush-treated material.
Saving Ix Timber.
Not only vill proper preservative treatment result ia a direct saving ia money, but it make less timber necessary' for any given working. Furthermore, the use of treated timber makes it possible to utihze many of the inferior and more rapid species, which, though possessmg most of the requirements of high-gTade structural timber, lack durabihty. Treated timber of these species has ia many cases proved more serviceable than high-grade untreated material. Thus, in the eastern and southern States, treated loblolly and shortleaf pines may take the place of untreated longleaf pine, while treated red and black oaks may be substituted for untreated white oak. Douglas fir, which is now extensively used ia the West, may in turn be replaced by treated hemlock, larch, or western yellow piae. Inferior grades of timber can usually be bought for less than higher grades, and an additional saving thus reahzed.
Summahy. 23
Avoidance Of Waste.
Timber which is to be treated should, whenever possible, be round instead of square, since the sapwood of most species is more easily impregnated than the heartwood. Moreover, the use of round timbers will do away with the cost of sawing and the consequent waste.
A further economy of waste may be effected by careful inspection, and a rigid condemnation of all unsound material. This is especially important where the timber is to be treated, for it is poor economy to apply an expensive preservative treatment to defective material.
The utilization of waste mine timbers has sometimes proved profitable. Sound sections of broken or partly decayed props have been sawed or split into laggings, planking, etc., and in some cases it has been found profitable to use this material for fuel or to sell it for pulp wood. In many cases such methods afford a considerable saving and also provide a means of disposal for waste.
Summary.
The results of the investigations discussed in this bulletin may be summarized as follows:
(1) Decay is, in general, the agency most destructive to timber used in mines.
(2) Although decay may often be retarded by peeling and seasoning, treatment with a suitable preservative is more effective.
(3) The average life of green, unpeeled, and untreated loblolly-pine gangway sets, under the conditions of the experiments discussed, was less than one and one-half years. Brush treatments with creosote and carbolineum increased this to three and four years, while impregnation treatments with zinc chloride and creosote left from 70 to 90 per cent of the timbers sound at the end of four years.
(4) The use of treated timber results in a saving in the cost of maintenance of workings and a reduction in the amount of timber required and makes possible the utilization of inferior species of wood.
(5) Brush treatments are economical when the amount of timber to be treated will not warrant the erection of a small open-tank or pressure plant, or when only a short increase in service is required.
(6) The open-tank process is adapted to the treatment of small quantities of easily impregnated timber. When a large amount of material is to be treated, a pressure process should be used.
(7) Mine timbers impregnated with zinc chloride and creosote oils have shown the best results. Up to the present, no difference in their durability has been noted.
(8) An efficient system of inspection and careful supervision in the use of timber will reduce waste and result in considerable economy. Necessary waste can in many cases be utilized.
Appendix.
Analysis Of Preservatives.
Samples of the preservatives sold as coal-tar creosote and water-gas-tar creosote, and used in the experiments described in this bulletin, were analyzed in accordance with the method described in Forest Service Circular 112, "The Analysis and Grading of Creosote," by Arthur L. Dean and Ernest Bateman.
Analysis of Coal-Tar Creosote.
Original oil. — Green color, almost solid at ordinary temperature, specific gravity at 50° C.= 1.0330. Fractional distillation.
Fraction.
Temperature.
Distillate.
Index of refraction.
Character of fraction.
No.l
No. 2
No. 3
No. 4
No. 5
No.6
No. 7
No.8
No. 9
No. 10
No. 11 ..
No. 12
No. 13
No.14
Residue
Per cent.
Milky liquid, floating soUd, 12.9 per cent water. White, crystalline, solid. Nearly white, crystalline, solid. Pale yellow, crystalline, solid.
Do. Yellow clear, liquid. Brownish, yellow, clear, liquid. Yellow, clear, liquid.
Do.
Do. Bright yellow, solid.
Do.
Do. Dark yellow, solid. Red-brovTi paste, soft at 60° C.
The sulphonation test was applied to the fractions distilling between 285° C. and 295° C. A residue of 2.9 per cent was obtained from the former, and of 2.5 per cent from the latter.
Appendix.
Analysis of Water-Gas Tar Creosote.
Original oil. — Reddish brown, no crystalline solids, green fluorescence, specific gravity at 50° C. =1.0641. Fractional distillation.
Fraction.
Temperature.
Distillate.
Index of refraction.
Character of fraction.
No.l
Per cent.
Faint pink, clear oil. Scarlet, clear oil. Claret, clear oil.
No. 2
No. 3
No. 4
Deep brownish-red, clear oil. Very deep red oil.
No.5
No. 6
No. 7
Gray black, not clear oil.
No. 8
No. 9
Brown black, not clear, water.
No. 10
1.6K6
No. 11. .
Deep brown red, clear oil. Deep claret, clear oil.
No. 12
No. 13
No. 14 . .
Yellow brown, clear oil.
No. 15
No. 16
Do.
No. 17
Orange red, clear liquid.
No. 18
No. 19
Do.
No. 20 . .
Yellow crystalline, solid. Red-brown pitch, burnt odor.
Residue
The sulphonation test was not applied.
THE PEESEEyATION- OF MINE TIMBERS.
is
o
-o
o
raojj siBAomaa
oo
coo
oo o
o
o
o
ipjt;u9 jaqnmsr
pal-Boop
o
o
lOO o
Co
Allied jeqirm
Co
o
O CO O lO 00
Ooo
ss
pimos jaqnmsi
Tt
p9jo9dsin
oocOjHco 03QOCO co
,2ociico5:iooo":)<N
O-O"* OOOO iMiO 00510000
9Dtaj9S Jo
pOIJ9d 82BI9AV
Coccoimco
s9snBo WB
t- 00 rf iC IC IM 00 05 CO O CO O Oi-H
-*05 Cosoio
M
Tnojj
p9lB09p
ocoocoioocoootr-oco
Im
I9JT1U9 jaqumK
p9i£B09p
tOOCOOCOCOiOOQ-COOOO r-t
OOt-hC
ocqcooocoo-tc
ICOCOCO 05COCO lOCO (MO00t>
o
p9j09dgni
. M'O
S9D9TdjOJ9qiimN:"
oooo-* oo.-h ooic-hoc
loo 1-1 03
90Taj9S Jo
pOU9d 9§BJ9AV
(Ni-<<MC i-ii-H
sasriBO HB
Co
oo
o i
tnojj siBAOina'a;
p9lBD9p
22 00 Co Co
Cc Occ:
o
Co
coco
o
.lajpna jgqumM
Ooco'S'O
o
Co
Ooo
o
o
AiiiBd jaqran.si
05 00 Co
COCO --oo
o
t-H !
iiO
'o
p9j09dsnT
Jo
?a
"lO
?5
jo
S909ldj0J9qumj\[
tQ.-iOO
lO
i-OiO
o
io
!iO
S
90Uvj9S Jo
p0IJ9d 9SBJ9AY
.T-Hoo
O ;
o
;0
„
t
§
o
Si ftl
§1
4 it
T3 C
B
a
q
D
a
§
ft
§
"3
ft "Si
: i§
C3 g
if
lit
' If s 11
l|;
11 ;
Hi
It
ft
o
"o 'cso S'o'cs'o S'o § ©5
ft o fS
o a so
h:i
h-l
h5
t-
h
Appendix.
50 CD OJ CD CO t-- kO
Cocdmoco
O 03
r-lrHO
oo
o
!3 ft
1l
2 ft § C3
03 &ft
II til
?S
to
coco IC
coco --H
|il
It
-*Co Co
.o
d
o
o
'S
a
H
Tj
CO O r-l
Cc Co Cci
o
tf
'd
S
o
Ip
c&
a
g
(M (M
m
|ii
?8
g
-d ft
o
a o
ft
een, unpeeled, untr peeled, untreated... seasoned, peeled.
r„ft
P
Uypine, Uy pine, Uy pine ted with Uy pine, -tar crews
o o o-' o o
H?
SCO g o
gfto.g fia®03-