C o al A ge
M c G r a w - H i l l D e v o t e d t o t h e O p e r a t i n g , T e c h n i c a l a n d
Pu b l i s h i n g Co m p a n y, In c. B u s i n e s s P r o b l e m s o f t h e
- M Carmody
J a m e s H . M c G r a w , P resident .
T .
J o h n M . u a r m o d yE . J . Me h r e n, V ice-P resident C o a l M i n i n g I n d u s t r y E d ito r
Volume 33
N e w Yo r k, M a r c h,1928 N u m b e r 3
S t a t e s m a n s h i p
E N L I G H T E N E D self-interest seems f o r the m o m e n t to be g uiding the plann in g of bituminous coal o p e ra to rs . Responsible leaders a re beginning to ta k e a lo ng-range view o f th e ir industry. Policies b a s e d on the fallacy t h a t the follies o f to d a y will leave to m o r ro w ’s actions u n s c a rre d a re giving w ay to the conviction t h a t the only solid fo u n d a tion f o r th e f u tu r e is intelligent b uilding now.
N o w h e re is th e r e a g r e a t e r need f o r this enlightened self-interest t h a n in m erc h a n d is ing. N o w h e re , p e rh a p s, h a s this new spirit been m o re strikingly illu s tr a te d th a n in the symposia on coal’s o u tsta n d in g problem s in the two prec e d in g issues o f Coal A g e . F O R long y e a rs bitum inous coal o p e ra to rs
have indulged an individualism in sell
ing th a t has led to ruinous com petition.
F e a rfu l t h a t a rival w ou ld get an o r d e r they sought, prices h a v e been slash ed w ith o u t re
gard to the b a r e costs o f p ro d u ctio n . Coal has been m ined b e fo r e it was sold a n d sold to save d e m u rra g e . A com m on p ractice in industry g e n e ra lly ? H o w m an y cars o f steel rails a re ro lled b e fo r e th e r e is a custom er for t h e m ? N o n e . H o w m any cars of cement lie on r a i l r o a d sidings a w a itin g a custom er? A g a in th e sam e an sw er— none.
T H E fact is m o d e rn indu stry is lea rn in g how to c ontro l p ro d u ctio n a n d how to co-ordinate t h a t c o n tro lle d p ro d u ctio n with consumer requ irem ents. T h e coal ind u stry is learning too, b u t so lo n g as th e r e a re thousands o f small units w o r k in g w ith in a narrow shell c o ntro l will be only a g e stu re — and th a t largely futile. W h e t h e r t h a t co
o r d in a tio n m a y be best ac ce lera te d in indi
v id u al cases th r o u g h consolidation o f physi
cal p ro p e rtie s , com m on financial c o n tro l o r district selling units a r e m a t te r s o f detail.
I n every case th e rea l te s t will be such t h o r ough-going efficiency in o p e ra tio n an d d is tr i
butio n t h a t no critic can find a void able waste.
B U T th e r e is still a n o th e r step necessary if the m o v em e n t is to a tt a in th e full m ea su re o f success. C o -o rd in a tio n o f p r o duction a n d consum ption d e m a n d s the co
o p e ra tio n o f the la r g e b uy er as completely as it d e m a n d s the u n r e s e rv e d s u p p o r t o f the la r g e seller. I t d e m a n d s a p a r tn e r s h ip in in te rest t h a t tran scen ds th e daily b a r t e r i n g because the interdep en d en ce o f coal a n d gen e ra l ind ustry is to o basic, to o vita l to be ig n o re d by e ith e r th e coal p ro d u c e r o r the coal consumer. T h e r e is to o much to be ga ine d by a com m on a tta c k on th e b r o a d e r pro ble m s to risk any o t h e r a p p ro a c h .
E X T E R N A L d e v e lo pm en ts in th e p a s t
decade have b re d m isu n d e rs ta n d in g upon
b o th sides. T h e r e is every rea so n to believe,
how ever, t h a t th e r e is a real willingness a n d
a readiness u p o n th e p a r t o f b o t h th e coal
p ro d u c e r a n d th e la r g e coal consum er to
e n d e a v o r p a tie n tly a n d sym pathetically to
pierce th e fo g which h a s enveloped “ th e coal
p r o b le m ” in an effort to reach comm on
g r o u n d and com m on u n d e rs ta n d in g . T h e
coal business to o lo n g has been considered a
th in g a p a r t f ro m business generally. T h e
time seems ripe to effect t h a t in te g r a tio n of
coal w ith in dustry a t la r g e which will m ake
f o r th e profit a n d security o f all.
A S tu d y in B la c k A r t
A I M E
Contributes Its A n n u a l H a rv e s t of Ideas T o the Extractive Industries
A V E N T IL A T IN G C O D E w ith teeth seems likely to be adopted
■ by the ventilation committee of the American In stitu te of M ining and Metallurgical E ngineers as a re sult of a decision to prepare a model code at the 136th m eeting of the Institute, held Feb. 20-23 in New York City. Some light was throw n on the barrier-pillar question reg ard ing which legislation in Pennsylvania doubtless will be passed before long.
Auxiliary fans w ere shown to give safe ventilation provided the air de
livered to the fan was pure, was ade
quate in quantity and if gas was not allowed to accumulate by the shutting down of the fan. W a r was declared by the paleobotanists on the chemists at the classification m eeting and both for a time seemed likely to fare badly
at the hands of the practical men—
all of which is not news. It is sure to be thus to the end of time.
So m any items w ere on the pro gram th at the excellent coal sessions could be discerned only by deliberate reading. Y et those who attended the coal meetings, of whom there were 100 to 150, found excellent m aterial for consideration.
Especially attractive w ere the gen
eral session on Coal and Coal P roducts, the session on the stabiliza
tion of the industry and th at on en
gineering education. B ut to all who attended, coal m en and others, the crowning feature was the address by the Secretary of Commerce, H e rb ert H oover, the recipient of the W illiam L aurence Saunders medal.
In all 1,445 registered and perhaps
2,000 attended. A t the dinner about 700 w ere expected and 1,200 came, straining the capacity of the banquet hall of the W ald o rf-A sto ria to p ro vide fo r so m any persons. In all there w ere 71 separate events, includ
ing the annual meeting, the Rocky M ountain Club meeting, th e smoker, the banquet, luncheons and dinners w ith or w ithout technical features, the excursion to P erth Am boy and other like events.
T here w ere 47 purely technical sessions. These features kept the visitors and staff abundantly busy from M onday, w hen the m eeting com
menced, till T hursday, w hen it closed.
T he institute harvests yearly some of the best ideas and m ethods of the ex tractive industries and this year it certainly can record a bum per crop.
Seeking Safety and Economy in Ventilation T H A T ventilation is one of the
big problems of the coal op- _ erator was the them e of the opening address of George S. Rice, chief mining engineer, U . S. B ureau of Mines, W ashington, D. C., at the ventilation sessions of the A .I.M .E . on Monday, Feb. 20, over which he Presided during the morning. Pie said that in Illinois it had been ascer
tained that five to ten times as much air as coal was removed from the mines and that in 40 m ines the power costs of ventilation w ere 22.45 per cent of all such costs.
was interesting, he said, to note at Prof. H enry Briggs, professor
°t mining, U niversity of Edinburgh, stated that in Great B ritain the aver
age ratio of air to coal on the weight asis was about 6 to 1. In some col- leries this ratio was 10 or even 12 0 ■ Some 80 million cu.ft. of air per minute was in continuous move
ment in British mines, and the annual
bill for ventilation was but little short of $10,000,000 per annum or 4c. per ton.
•Mr. Rice pointed out th at the power increased so rapidly w ith increased
w m m & m sH m szzzt'-'A ,; '
W . S . W e eks
volume of a ir w here the airw ay was not augm ented th at to p u t any m ore than a certain quantity of air in a mine m ight not be impossible but was clearly impracticable. T h e im por
tance of efficient ventilation in re
ducing mine costs w as but little appreciated by the mine operator.
Dan H a rrin g to n ’s repo rt on “ M etal M ine V entilation” followed. Only one other subcom m ittee chairm an had prepared a report. T his was Dr. R. R.
Sayers, chief surgeon, U . S. Bureau of M ines. T his was read in p art by M r. Plarrington. D r. Sayers de
clared th at some of the inert dust used fo r rock dusting was dangerous.
O xygen, 95 per cent pure, could be breathed by guinea pigs fo r 50 days, 16 hours a day, w ithout harm . O n the other hand, straight oxygen breathed steadily fo r fo u r or five days caused death.
The paper on “A ir-C u rren t R egu
lators,” prepared by W . S. W eeks,
March, 1928 — C O A L A G E
139
H . P. Greemvald
U niversity of 'California, Berkeley, Calif., was presented by A. C. Callen, head of the m ining departm ent, U n i
versity of Illinois, U rbana, 111. M r.
W eeks assumed that the drop in pres
sure through an orifice was with Kv- . v- .
—— where — is
9or ¿e
air as with water
the velocity head in the duct and K is a factor that depends only on the ratio of the area of the duct to the area of the orifice.
T A B L E I . — C O E F F I C I E N T S (K ) F O R G I V E N O R I F I C I A L R A T I O S
R a t io C o e ffic ie n t R a t io C o efficien t
10 0 .6 4 5 2 0 .6 9 4
5 0 .6 4 6 1 .7 5 0 .7 0 9
4 0 651 1 .5 0 .7 2 9
3 0 .6 6 3 1 .2 5 0 .7 7 4
W h e n d u c t a n d o rifice a r e e q u a l— t h a t is, if .th e r e g u l a to r is o m i tte d — th e r a t i o a n d th e c o e fficie n t a r e b o t h u n it y .
M r. Callen said that he had found that these results, so fa r as he had checked them in the laboratory, were correct, and H . P. Greemvald, super-
G. E. M cE lroy
vising engineer, Experim ental Mine, U . S. B ureau of Mines, Pittsburgh, Pa., said that the observations of G. E. M cElroy, m ining engineer, associated with him, also checked w ith those of M r. W eeks. A nsw er
ing Cadwallader Evans, general m an
ager, H udson Coal Co., Scranton, Pa., M r. Callen said th at the duct and the orifice w ere placed sym
metrically and were of the same shape.
T he paper by F . E. B rackett, m in
ing engineer, Cumberland, M d., on
“ Propeller F an Calculations,” was presented. In this paper M r.
B rackett uses results obtained by three m anufacturers of propeller- type fans, obtaining several empirical formulas and ascertaining formulas for the required size of fan under certain conditions.
In the afternoon, A. C. Callen oc
cupied the chair and H . P . Green- wald described his interesting work with H . C. H ow arth, superintendent.
Experim ental M ine, U . S. Bureau of Mines, P ittsburgh, Pa., in testing the recirculation of air and mine gas by auxiliary fans. H e showed that when a certain quantity of air per m inute is passed up a straight airw ay and an auxiliary fan is placed to divert all that air"into an entry at right angles to the first, recirculation is practically inevitable, no m atter how’ fa r the fan is from the side entry.
T hat is a most im portant observa
tion, even though one not entirely surprising. A lthough his fans were placed one at the m outh of the side entry and on the intake side, one 8 ft.
back on the flank of the main entry away from the side entry, one 8 ft.
back on the same side as the side entry and one 16 ft. back on the op
posing side, in all cases w here the auxiliary fan attem pted to absorb the w’hole main current it drew quite im portant percentages of gas into recirculation.
V itiated air w’as found going back near the roof along the main entry toward the intake fo r a distance of 50 to 75 ft. Somewhere it fell tow’ard the floor and was draw n into the fan for recirculation. T h at undesirable condition was corrected w’here the quantity of air supplied was 2.5 times the quantity of air circulated by the auxiliary fan, and that in every case regardless of the location of the fan.
Similar results were obtained when auxiliary fans w ere used to ventilate the dead-end extensions of the straight entry. Check brattices near the fan wrere not found helpful in reducing recirculation. I t appeared
F. E rnest Brackett
dangerous to use any m ore than 40 per cent of the main air current in places ventilated by an auxiliary fan.
M oreover, it wras proved that in all cases the gas percentage in the re
tu rn air w ith a given emission of gas reached a certain definite figure which was never exceeded, no m atter how long the test wras extended.
It m ust be recognized, R . D. Hall said, th at rarely indeed in any prop
erly conducted mine are the main cur
rents in any split as m eager as 1,000 cu.ft. per m inute or even 2,000 or 3,000, fo r in one w ith 75 men with an allowance of 200 cu.ft. per minute per man there would be 15,000.cu.ft.
provided. Somebody remarked that at the end of the split it would he different, but M r. H all declared that then the air used would, in a gassy section, be full of gas and the practice fraught with danger unless permis
sible m otors w ere used to drive the fan. A. W . H esse, chief coal min-
H . C. H ow arth
C O A L A G E —
Vol.33,TA B LE I I — RESULTS OF TESTS W IT H S IN G LE FAN AT A S ID E E N TR Y
A Canvas tu b in g
•— G a s in A ir, P e r C e n t 1--- * I n R e t u r n
A t F a n of S id e I n M a in I n l e t E n t r y R e t u r n
Side Entry
Fan (B’s) and Gas Pipe (G ) Locations
ing engineer, Buckeye Coal Co., Nemacolin, Pa., stated th at at the Nemacolin mine the splits usually carried 20,000 to 30,000 cu.ft. of air.
George S. Rice’s paper on “ Con
trolling Factors in F orm ulating a Coal-Mine V entilation Code’’ was then presented by the author. It con
tained 31 questions as to desirable practice, such as the degree of separa
tion of intake and retu rn , the fire- proofing of main intake, the location of the main fan, its reversibility,-the incombustibility of its housing and drift approaches, the use of booster and auxiliary fans, the chemical limits of air vitiation, the quantity of air
A ir D e liv e r e d C u r r e n t , M a in C u r r e n t , G a s B y F a n , C u .F t. C u . F t . L i b e r a te d
C u .F t. p e r M in . p e r M in . p e r M in . A t F a c e - ..
F a n in m a in e n t r y 16 f t. f ro m o u tb y e e d g e of s id e e n t r y o n o p p o s ite s id e of m a in e n t r y (B j)
1.020 1,020 1 .0 0 1 0 .6 0 . 2 1 .5
1.020 1,420 0 .7 2 9 . 2 0 . 0 .3
1.020 2 ,160 0 .4 7 1 0 .3 0 . 0 I . I
F a n in m a in e n t r y 8 f t. f ro m o u tb y e e d g e of s id e e n t r y o n o p p o s ite s id e of m a in e n t r y ( B2)
1.030 1,000 1 .0 3 9 . 8 0 . 8 1 .7
1.030 1,880 0 .5 5 1 0 .3 0 .1 1 .3
1.020 2 ,530 0 .4 0 9 . 0 0 .0 0 .9
1.030 3,020 0 .3 4 1 0 .0 0 . 0 .2
2.020 1,960 1 .0 3 1 7 .3 0 . 6 .3
2 .020 3 ,030 0 .6 7 1 8 .8 0 . 2 .0
2 .0 2 0 4 ,040 0 .5 0 1 9 .5 0 .1 1 .0
2,010 5 ,000 0 .4 0 2 3 .0 0 . 0 0 . 9
F a n in m a in e n t r y 8 f t . f ro m o u tb y e e d g e of s id e e n t r y o n Barne s id e of m a in e n t r y (Bs)
980 1,020 0 .9 6 9 . 9 0 . 8 1 .6
98 0 1,940 0 .5 0 9 .7 0 .1 -> .4
980 2 ,470 0 .4 0 1 0 .0 0 . 0 1 .2
1.050 1.050 1.050
F a n a t o u tb y e e n d of s id e e n t r y n e a r o u tb y e r ib o f t h a t e n t r y (B r)
1,020 1 .0 3 9 . 9 1 .2 2 .1
1,990 0 .5 3 1 0 .0 0 .1 .5
2 ,460 0 .4 3 1 0 .2 0 . 0 1 .4
0 .9 0 .7 0 .5
0 .7 0 .7 0 .4 0 .5
1.0
0 .5 0 .5 0 .5
0 . 8 0 . 6 0 . 6
1 .3 0 .7 0 .5
required per man, the air current in each non-w orking or unsealed place, where these quantities should be m easured, the num ber of men allowed in a split, the definitions fo r non- gassy, slightly gassy and gassy mines and similar questions.
H . N. Eavenson said auxiliary fans could hardly be dispensed with. In driving drainage tunnels advances of
1,400 ft. or more were m ade per m onth owing to the assistance rendered by auxiliary fans.
H . I. Sm ith proposed, and Eugene M cAuliffe seconded the proposal, th at a committee of nine be appointed by the chairm an of the ventilation committee fo r 1928 to w rite and sub
m it such a code. T h e m otion was carried.
Is Profit or Production Industry’s
A T T H E C O N F E R E N C E on /A problems of overproduction in
I X . industry m any w ere the opinions given as to m eans by which in
dustry’s great capacity m ight be adjusted to today’s limits of norm al trade. E. D e Golyer, outgoing presi
dent, presided.
Some urged th a t w orking time in plants be curtailed systematically to level off the peaks of production. T he case of the bituminous industry was presented by E. C. M ahan, president, National Coal Association, who said:
“When coal operators think and talk about overproduction w hat they really have in mind is day-by-day p e r
formance in the m ining of coal which has not been ordered and in the ship
ment of coal upon open consignm ent.
It is that continuing small per cent of production in excess of orders and the shipment of unconsigned coal which makes it possible fo r the buyer rather than the seller to name the price, and which results in the sellers actually buying the orders fo r their own products. T he decrease in the cost of production accruing from full-time operation provides a con
stant temptation to the coal operator to take chances on a portion of his unsold output.
March, 1928 — C O A L A G E
E. C. M ahan
“ T his brings us squarely up to the outstanding economic problem in the bitum inous m ining industry. T here has been altogether too much shadow boxing in forum s of discussions on this subject, w ith the result th a t the vital issue has been obscured. I am convinced th at the only sensible ap proach is by w ay of im proved m ar
keting m ethods. R um ors of m ergers are now thick and I am hopeful th at every prospective consolidation will
materialize. Control of capacity in few er hands should sim plify the task of introducing sound m arketing and distribution practices.
“ I am heartily in sym pathy with all m ovem ents which m ake fo r in
creased operating efficiency, but I stress the point th at intensified p ro duction, through m echanization and otherw ise, does not strike at the root of the problem. V olum e often is gained by price recession which usually m ore than offsets the savings effected through decrease in unit costs.”
S. A. T aylor, consulting engineer, P ittsbu rg h, Pa., gave the results of an investigation he m ade in 1926 as to the factors entering into the decline in the rate of increasing consumption.
F rom 1840 until 1910 consum ption increased 10 per cent annually, but from 1910 to 1925 the rate of in
crease was only about 2 per cent a year. H e found by using the effi
ciencies of 1910 as a base th at im proved m ethods o f generating power in central stations in 1926 dispensed w ith the need fo r 100,000,000 to n s;
use of byproduct gases displaced 35.000.000 to n s; burning of tars, 15.000.000 to n s; im proved combus
tion on railroads, 45,000,000 tons, and
141
oil, 200,000,000 tons of coal. T he en
ergy equivalent of the total of these figures check with the increase in the use of power.
A. C. Lane, speaking fo r New England, suggested that seasonal freight rates be made effective during a portion of each year, a fte r the storm s in w inter and before the move
m ent of crops in summer.
John Janney, of Nevada, declared th at accurate inform ation is needed fo r solution of the problems of over
production, for the study of which a com mittee from the institute should be named. H e does not feel that the governm ent would look with dis
favor upon reasonable m easures for correcting overproduction. H e also invited inquiry into the m atter o f' shortening the w orking hours as a corrective influence tow ard overpro
duction, which might at the same time effect a lower operating cost. M r.
Janney said that at one mine in the
W est laying off one of the working days in the week actually served to reduce costs. P . B. B utler, Joplin, Mo., added that reduction in the num ber of hours worked in the Joplin district has created a m ore healthy condition.
Stephen Tuthill, secretary of the Am erican Zinc Institute, said he would not be surprised if the present Congress reviewed the Sherm an Act and recommended its fu rth e r consid
eration in the next Congress. In this connection he suggested th at industry follow the example of labor. “W hen labor wants som ething,” he said, “it m akes up its mind w hat it wants, then gets it.”
H arring to n Em erson, of New Y ork, expressed the belief that if equipm ent w ere replaced every 10 years instead of every 20 years,
$150,000,000 w orth of it would pro
duce twice as m uch as $250,000,000 w orth of it; further, that if working
hours were cut in two and the rate of pay doubled, industry could produce four times as much. M aterials and supplies would be used up faster and the labor freed from the production of necessities could be diverted to the establishment of fu rth e r necessities and luxuries.
O. E. Kiessling, statistician, U. S.
B ureau of Mines, stated that the prin
ciple of supply and dem and is not a law and consequently cannot be ap
plied to the complex society of A m erica today, even though it might function in the sim pler society of England. E arly economists did not term this principle a law ; rather they looked upon it as a form ula not neces
sarily correct. It is an erro r in economic reasoning to think th at free competition sets production or that low costs in m ining will wipe out competition. M r. Kiessling declared that m uch of present-day economics is “bunk.”
Lump Coal—How to Get It
\ T the main session of the coal
and coal-products committee,
■I
over which H . N . Eavenson presided, a paper by L. E . Tiffany and S. S. Lubelsky, U. S. B ureau of M ines, P ittsburgh, Pa., was presented by George B. H arrington, a sum m ary o f which follows :
T o determ ine the effect of using explosives with varying rates of deto
nation, quantitative tests w ere made in a Pennsylvania mine where the Pittsburgh bed was being extracted.
In these tests five different permissible explosives w ere tried.
W h ere the coal was blasted w ith an explosive having an interm ediate rate o f detonation 4.7 per cent m ore lump w as obtained than when the explosive w as used that had the lowest rate.
A lthough sim ilar tests w ere not made in other mines, we are of the opinion th a t there is at every mine a rate o f detonation which will produce a m axim um quantity of lump. U nder a given condition, however, this criti
cal rate will vary w ith the coal.
In m any mines of southern Illinois which w ork the No. 6 bed the ap
proxim ate angle between the direc
tion of the w orking places and the face cleat planes is 45 deg., the w ork
ing places usually being driven either north and south or east and w est and thé direction of the face cleats in general running about N. 45 deg. W .
In such places the w orking faces tend to overhang, particularly if the holes are not drilled deep enough.
In a Pennsylvania mine additional tests, sim ilar to those already de
scribed for the same mine, were made to ascertain the relative effect of driving on face and butt, the coal being drilled and blasted in each in
stance in a sim ilar m anner. I t was found th at in a butt entry 10 ft. wide and w ith the coal slightly m ore than 7 ft. thick 54 per cent of the coal screened on the tipple was lj- in . lum p coal. T rials w ere then made in places 18 ft. wide driven on the butt. U nder this changed condition the lump-coal percentage was in
creased to 56.8.
O n the other hand, w hen the w ork
ing place was only 10 ft. wide and driven on the face, a 57.7 per cent yield of 1 J-in. lump coal was ob
tained. In rooms 18 ft. wide driven on the face the percentage of lump coal was 59.1.
W here the holes are drilled nearly flat, or almost parallel to the bedding planes, 5.1 per cent m ore lump is produced than w here the holes have a steep inclination. By flat holes 64.2 per cent of 1 J-in. lump coal was obtained.
T he im portance of loading out all coal loosened by a shot before firing the n ex t one was exemplified
by two tests. In the first all the coal brought down or loosened (about 30 to ns) by the rib shot, which was fired first, was loaded out before the second hole was fired. T his method resulted in the production, by actual screen test at the tipple, of 59.1' per cent of 14-in. lump coal from the entire cut.
In the second test the quantity of coal loaded out before firing the second shot was only 8 tons. This was the minimum quantity th at had to be removed in order that the miner could shear in along the rib to the back of the cut on the side w here the first shot was fired. By this latter m ethod there was only 56.5 per cent of 1-J-in. lump coal produced from the entire cut, o r 2.6 per cent less than by the first method.
T he shotholes should be drilled a fte r the w orking place has been cut, otherw ise their placement m ay not bear the proper relation to the cut.
T ests m ade in a m ine w orking the P ittsburgh bed showed th a t each rib- hole should be placed 12 in. from the rib and the same distance below the roof, also th at the hole should be alm ost flat and parallel to the line of sights. H ow ever, in the tougher coal beds of southern Illinois, as represented by the No. 6 bed of the series, it is found necessary to in
crease the distance between the rib
142
C O A L A G E — Vol.33, N o.3S. S . L ubelsky
and hole to as much as 2 or even 3 ft.
During a recent investigation in a southern Illinois mine a determ i
nation was m ade of the most desir
able location fo r placing the holes in both rooms and entries. F o r hand loading in rooms the placement of holes is as shown in Figs. 3 and 4.
Figs. 1 to 4, inclusive, re fer to methods employed in mines w orking the No. 6 bed of southern Illinois.
In these mines 14 to 24 in. of coal is left in place to support the roof, and there is a persistent mother-coal parting on the underside of the roof coal. In the upper third of the bed there are several other partings of mother coal. In Figs. 1 to 3, inclu
sive, the holes are placed 12 in. below the roof parting. T hey are nearly flat and ini their entire length do not rise more than 4 in.
There is a tendency to incline the holes so much th at they pass through the parting and into the roof coal, l’his practice is bad and increases the dangers of mining. W hen the roof coal of the No. 6 bed in southern Illinois is drilled, the explosives break it and allow the shale above the coal to fall in large quantities. T he operations involved in cleaning up a fall and timbering the broken roof make additional costs and hazard.
In some sections of a Pennsylvania mine where the coal would not sep
arate readily from a slate roof it was found advisable to incline the holes so that they would ju st touch the roof at the back of the hole.
Overhanging faces and ribs are caused principally by poorly placed or shallow holes. W hen holes are drilled only 6 ft. deep for a 7-ft. un
dercut the overhang tends to increase
about 1 ft. afte r each cut has been cleaned up. Only that portion of the hole which is vertically above the undercut can be considered effective
(see Fig. 5 ).
In one southern Illinois mine th ir
teen room s were visited at random and m easurem ents made of the three holes in each room. T he average depth of hole was 76 in. with an aver
age overhang of 25 in. Fig. 5 shows a section in one of these rooms where there was an overhang of 36 in. One of the holes was drilled to a depth of 78 in., as shown. T his would have been the proper depth fo r one drilled in a vertical face from b to d, but with the overhanging face the depth of the hole should be increased 36 in. or by as much as the coal overhangs at the m outh of the hole.
T H E F IR IN G of a charge of ex
plosive in a shallow hole abc will tend to shatter th at portion of the coal represented by cfgh, while that in the portion cgi is broken only to a slight extent and can be brought down only by an excessive am ount of
P e r c e n t a g e S a v i n g s in L u m p C o a l P r o d u c e d
By blasting w ith correct
explosive ... 4.7 By w idening place 80 per
cent 1-4 to 2.8
By driving tow ard cleats of
coal 2.3 to 3.7
By drilling horizontal shot-
holes ... 5.1 By completely loading out
coal fro m one shot before
firing another ... 2.6 B y air-spacing cartridges of
explosive ... 2.0
pick work. T he portion h ji is not affected by the blast. T he overhang at h has been increased by 6 in. F o r the m ost efficient blasting the quantity of coal in the portion efg h should be as large as possible and th at from
cji as small as possible.T he hole should be drilled so th at a vertical line w hen projected from the back end of a hole will intersect the undercut at a point 6 in. short of its end.
S horter holes than these cause the face to overhang. Faces out of plumb 3 o r 4 ft. frequently w ere observed.
T he excuse made fo r gripping a cut at the ribs has been that the face or ribs overhung so much that the un der
cutting machine could not be properly operated.
Explosive charges should never be reduced to such an extent as to make the bringing down of the coal uncer-
J. E. T iffa ny
tain. T he shattering effect of p er
missible explosives can be reduced by the use of air-spaced shots. T h ere are a num ber of ways of doing this, but the best results are obtained by reducing the diam eter of the explo
sive cartridge, the diam eter of the drillhole rem aining the same.
I N A N investigation in southern Illinois the size of cartridge was changed from I f x 6 f in. to I f x 8 in. By this and other changes the quantity of explosive used was re duced by 10 per cent and there was an increase of 2 per cent in the quantity of 6-in. lump coal produced.
H ow ever, in other mines where tests w ere made, air-spacing did not . always perm it the charges to be reduced. In these instances the ad vantages of the practice w ere con
fined to im provem ents in the firmness and size of lum p produced.
W illiam German, technical rep re
sentative, E . I. du P o n t de N em ours
& Co., Inc., suggested th a t m iners be equipped w ith suitable scraper rods for the removal of cuttings from drill
holes, if blownout shots are to be avoided. D rilling before cutting is a bad practice, as also is the charging of the second of two holes before the first is detonated. Both practices are likely to cause blownout shots.
No hard and fast rule can be es
tablished as to the effect of the rate of detonation of an explosive on the quantity of lump coal produced, de
clared M r. German. In a m ine in W est V irginia a permissible explo
sive w ith a detonating speed of 15,000 ft. per m inute was found to produce much better lum p coal than one w ith a speed approxim ately half as great. H e said the u se'of ordinary
March, 1928 — C O A L A G E
143
blasting cables-,was uncertain, that the Paragon Electric Co., of Chicago, offers a high-grade rubber-covered cable fo r this purpose.
H e asked if anyone in the audi
ence had good reasons why explosives other than those of the permissible type should not be excluded from coal mines. O ne operator replied that by experience he found the shatter
ing effect of permissible so great that tender roof was broken, resulting in increased danger from falls of roof.
T he difficulty was remedied by use of pellet powder, which he does not consider dangerous in non-gassy mines. T he change was not made w ith a view of increasing the lump coal produced, as the product is crushed anyway.
Josiah Keely, president, Cabin Creek Consolidated Coal Co., W est V irginia, said the substitution of pellet powder fo r permissible resulted in an increase of 9 per cent in lump coal. H e added that many m iners are
inclined to pulverize pellet powder in the hole in an attem pt to get a quicker acting explosive.
A paper on the valuation of coal properties was presented in brief by John B. Dilworth, of the E dw ard V.
d’lnvilliers E ngineering Co., P hila
delphia, Pa. In com m enting on this paper Eli Conner, consulting engi
neer, Scranton, Pa., took issue with M r. D ilw orth on the use of a base line of actual earnings in appraisal cal
culations. T he method, he said, is reasonably satisfactory, but it is not always equitable. H e said he knew of one enterprise appraised in this m anner on the basis of earnings in fo u r good years which today is in bankruptcy. M r. D ilw orth rem arked that no safer m easuring stick can be found th an th at of bargaining between owner and lessee. S. A. T aylor said that when a lessee desires to sublease a property, one-fifth of the value of th at property to him as an operator is an equitable appraisal.
---8 4 -... *•
Fig. 5— Illustrating Cause o f Overhang
T he coal - m ining industry and general conditions in R ussia were described in a travelog by John A.
Garcia and illustrated w ith motion pictures and accompanying comments by Charles E. S tu art, of Stuart, Jam es & Cook, engineers, New York City.
Figs. 1, 2, 3 and 4— M ethods o f Shooting A dopted in Sotithern Illinois
R o o f coot/
p r i
9'— s ' - U n c/ercu t■'F ig .l
*\t£'\<----s ’— Fig.2
X~
til
in*,ci «
<Ol ‘ il ->*K -6"
<o;
mi
oil
'«il
ii r — --- s r r c.
?
k~‘T I
yB/vebanc? V <q O --- * = = !
Unctercur ‘
Fig. 4
144
F irec/ay
C O A L A G E — Vol.33, No.3
W hat Size o f Pillar to Leave and W here T HAT it is a folly to leave pil
lars under roads and buildings, that it wrecks them m ore cer
tainly than if the coal w ere removed from under them in a methodical manner, was the contention of R. V.
Norris, consulting engineer, W ilkes- Barre, Pa., who presided at the m orn
ing meeting of the ground movement and subsidence committee of the A.I.M.E. on W ednesday, Feb. 22.
These pillars by holding up p art of the roof and letting down the rest prevent the healing of fractures and cause permanent breaks of the ground that do much m ore dam age than is caused when the coal is entirely extracted.
It is not necessary said M r. N orris, to fill all the spaces excavated. To protect the surface it will suffice to fill the extracted areas in the beds nearest the surface. In the anthracite region as many as fourteen beds may be mined, and the action of the m in
ing of one bed on that beneath is one of the most vital of problems.
IT. W. M ontz, chief m ining en
gineer, Lehigh Valley Coal Co., described a subsidence caused by pil
laring. Along one side was a rail
road and some houses. T o protect these a big block of coal was left, but the effect of the subsidence on the houses was nevertheless quite evident.
One monument in the unm ined area is slightly higher than w hen originally located. Over the solid m easures were about 90 ft. of unconsolidated glacial drift.
Eli. T. Conner, consulting engi
neer, Scranton, Pa., said that when blocks of coal w ere left to protect buildings more damage was done than if they had not been left.
R. D. H all said th a t consideration should be given the structural forces at work. The roof m ight break verti
cally if weak, especially in those parts of the anthracite region w here there were large deposits of unconsolidated sand. Collapses from shear, how ever, usually w ere limited to shallow workings or those heavily burdened by loose measures. Such collapses took place suddenly.
The roof in general m ight be re garded as a deep beam but more properly as a thick plate. I t was this consideration th at m ade M r. H all conclude in 1910 that the roof would break at the surface over the sup
porting pillar, and in this he was con
firmed in England by Dickinson,
March, 1928— C O A L A G Ewhose experience had been such as to afford proof of this fact.
H ow ever, when the roof has been torn over the pillar and in the ex cavated space, it tries to lower itself into the opening and, being thick, it finds, like a fat m an, th at though bending is in itself easy it brings discom forting compressions. These compressions stop the bending and cause arch stresses and these stresses horizontal stress, and this again tears p art of the roof loose from the rest.
T h e fat m an has lost a layer of flesh.
George H . A sh ley
T h erefo re he bends m ore easily. T he arch becomes a beam once m ore and so it continues. Now, this is a serious operation and it takes time. I t has often been noted that collapse is slow, and it is in this w ay that this fact can be explained.
A s fo r the lower m easures above the ' draw slate that are rent by the horizontal shear described, these be
come isolated beams th at m ight be term ed cantilevers w ere it not fo r the fact th at they are loaded over the pillar by a nipping w eight of some hundreds of feet of strata. T hey are, therefore, not cantilevers but encastré, or built-in beams freed by fractu re at one end and held tightly at the other.
T hese fractu re in a direction lean
ing back into the excavated area.
T hey do not necessarily have any linear connection w ith the funda
m ental fractures which m ay have barely form ed a t the tim e when these subsidiary fractures occur. T he fundam ental fractures over the coal m ay themselves be stepped.
A t the afternoon m eeting H . G.
M oulton, consulting engineer, New Y ork City, presided. George H . A sh
ley, state geologist of Pennsylvania, H arrisburg, Pa., addressed the com
m ittee on “ B arrier P illars” on behalf of a commission— of which he was secretary— appointed by the G overnor of Pennsylvania to determ ine w hat b arrier pillars should be left between properties and against flooding.
A pillar only 5 ft. thick, he said, would hold a considerable head of w ater, for its powers of resistance were based on the hold it had on the roof and floor and not on its weight.
T he method of basing the resistance of a dam on its weight m ight serve well on the surface w here there was nothing but friction to prevent move
m ent, but it was not satisfactory w here the stru ctu re was under v erti
cal pressure.
T h e problem, then, was to find a m inim um safe thickness th at would enable the pillar to retain its integrity under the superincum bent weight. T ests had been made on the 10,000,000-lb. testing machine, but it is not clear th at tests on cubes, however big, are expressive of mining conditions.
N aturally the shape of pillar frac
tu re is im portant. I f the unbroken roof stretches out over the pillar edge so th at the weight of roof on the pil
lar exceeds the weight of the rock w ithin the vertical projection of the pillar from its top to the surface of the ground, then the pillar left will have to be larger than it would be if the roof had a tru ly vertical fractu re and m ore th an would be necessary if the roof broke back over the pillar.
A. B. Jessup, vice-president and general m anager, Jeddo - H ighland Coal Co., Jeddo, Pa., said th a t the coal might hold w ater only to have it come through the roof, and added that, w ith a pillar 200 ft. w ide under a head of 125 ft. of w ater, leakage was considerable. M r. Ashley said that w ater would travel 1,000 to 2,000 ft.
in some seams. T h e fact th at where the seams dip, coal outcrops are wet, shows th at the w ater travels through the coal seam. M r. Rice said that possibly wide barriers would serve m erely to prevent big rushes of w ater and not percolations and seepages.
M r. Rice declared th a t small cubes give a false im pression, as clay bands tend to drag the coal off the sides.
F urtherm ore, the coal spalls but that
spalling on a big pillar may not be im portant, for the falls may prevent the extension of the spalling. T he Sankey commission of G reat B ritain said that in the B ritish coal fields 3,500 to 4,000 million tons was tied lip in barrier pillars to isolate w ork
ings against w ater, gas and under
gro u n d fires and to surround the properties. T hese pillars, S ir R ichard Redmayne said, ran from 22 to 60 yd.
thick.
Charles Enzian, m ining engineer,
B erw ind-W hite Coal M ining Co., W indber, Pa., said that in one place where a pillar was 1,000 ft. wide and the w ater head was 60 ft., so much w ater percolated through the coal that the w ater had to be drained by driving a place through the pillar.
T here are many subterranean chan
nels that m ake it impossible to entirely impound water. W hen grou t was in
jected at a pressure of 400 lb. per square inch the w ater in a spring was badly discolored though the spring
was 1,800 ft. away from the grouting operations.
Legislation should provide against only the catastrophic hazard. It should not attem pt to give protection against the gentle feeding of water through barriers. T o show how small a pillar will keep back w ater, in one instance a 6-ft. pillar withstood a pressure of 56 ft. of w ater. That the pillar was no larger was dis
covered only a fte r a squeeze had crushed the coal.
PVhat Industry Seeks in College Graduate
E d u c a t i o n a l institutions have done well, all things con
sidered, in the teaching of engineering stu d e n ts; yet it is felt there is room for much improvement, influenced by the national bodies of practicing engineers. W hatever in
adequacy exists is in large measure due to the failure of engineers’
societies to guide and prom ote the expansion of college training. Indus
try and society both demand of the engineer qualities which he does not possess or has failed in general to display. M uch of this is due to gaps in the program fo r the training of engineers.
Encouragem ent has not been given to the development of qualities of leadership; an appreciation of social responsibilities and an understanding of economic phases have not been im
pressed upon the younger engineers.
T he Society fo r the Prom otion of E ngineering Education is seeking a solution of the problem. A t the ses
sion of the institute on engineering education an analysis of the report on the problem by this society was presented by W . E . W ickenden, di
rector of investigation of that or
ganization. W . B. Plank, head of the departm ent of mining, L afayette
College, presided.
“W h a t In d u stry W an ts the G radu
ate to K now ” was discussed by C. R.
M ann. H e emphasized th at those in
trusted w ith the guidance of techni
cal education may profit from the changes in general education in the last ten years. A n analysis of the teaching of m odern foreign languages in some 600 schools showed that one group learned m ore of the vocabulary in two years than another group in fou r years. W hen w ords w ere a r
ranged in order o f frequency of use it was found th at a better command
of the language followed. Analysis of use is a principle which might be applied to advantage in engineer
ing education, he said.
Job specifications are grow ing in use. These specifications should not embrace qualifications fo r the job but
Cadwallader E vans
rather clearly define w hat are the duties. M en on the job may profit much by w riting and analyzing such specifications fo r their own activities.
Student-training courses in an th ra
cite m ining for the purpose of ap
pointing m en fo r responsible jobs in his company w ere outlined by Cad- wallader Evans, general m anager of the H udson Coal Co. As this com
pany operates 22 collieries and em
ploys some 18,000 men, a demand for engineering, operating and m anagerial talent constantly exists and is m et to an extent by graduates of these practical courses conducted by the company in its own plants. Two different courses are o ffered; one is a tw o-year course
for which only engineering graduates are eligible; the other is a 30-weeks course offered to men already in the employment of the company who have had no less than two years of experience as a m iner or a miner's laborer and who have demonstrated their energy and ambition.
F o r the selection of candidates for the tw o-year course various colleges are visited and graduating students interviewed. Those displaying possi
bilities of greatest development are invited to Scranton, at the expense of the company, w here a final selection is made. S ix to ten students are chosen from a group of about twenty- five. Each student is required to sub
m it a report covering each division of the course.
Experience in the training of these men has led the company to change the course considerably. T h e table below compares the initial with the latest schedule:
A ctiv ity 1915-1917 1925-1927
M ining E n g in e e rin g D e
p a r tm e n t ...6 m o n th s 4 months In sid e M ine W o r k ...6 m o n th s 6 months M echanical a n d E le c tri
cal D e p a r t m e n t s 4 m o n th s 3 months P re p a ra tio n ...5 m o n th s 2 months S ta tis tic s 2 m o n th s 1 month T ra n s p o rta tio n a n d
S a fe ty ...1 m o n th 1 month L o ad in g Coal ... N one 7 months
T he m ost notable change is that which - compels the student to spend seven m onths loading coal, whereas this experience was not required in the initial schedule. T h e students are in charge of a supervisor. They are assigned to various collieries and serve as helpers to m en on the job who are specially selected fo r their willingness and ability to act as leaders.
E ach student is required to submit a report covering each activity in the course. T hey are trained to observe,
146 C O A L A G E — Vol.S3, N oS
think and to report accurately and specifically only such inform ation as is vital to successful operation.
Students for the 30-\veeks course are chosen from the company’s forces only. Due to the fact th at the ex perience of these men varies in wide degree an individual schedule is pre
pared for each. Each prospect is required to w rite several pages on a mining subject fam iliar to him be
fore selection, so as to dem onstrate his ability to w rite the English language with reasonable clarity. F o l
lowing is a typical schedule: T ra n s portation (3 weeks) ; safety (2 ) ; engineering (2 )'; labor departm ent (1); robbing, tim bering and use of explosives (7 ) ;. preparation ( 1 ) ; ventilation (1 ) ; w ith section forem an (4); pumping ( 1 ) ; w ith yardage checkers ( 2 ) ; classroom w ork (6 ) . In the classroom they are taught the fundamentals of elem entary m athe
matics and m in in g ; they also are
given a course of drill in the use of statistics as to company operations.
A course in student training con
ducted by the Bethlehem Steel Co.
was described by H . T . M orris. I t is m oré strictly known as a probational observation circuit, of ten weeks’
duration, through which 60 to 70 col
lege men are put each year. T hey go through all plants, see all opera
tions and are closely interviewed.
T h e purpose of the circuit p ri
m arily is to enable the students to determ ine w hether they are satisfied to join the com pany as a life pursuit and w hat line they would like to fol
low. T h e circuit enables the com
pany to observe these men at close range. T hose who finish the circuit and express a desire to stay are asked to start at the bottom. I t is felt th at these men should know the workm en and operations, no m atter w hat posi
tion is their goal.
P ro fe sso r Plank stated th at L. E.
Young, operating vice-president of the P ittsb u rg h Coal Co., is planning a course of this kind. T h a t young engineers should not expect to enter industry on p re ferred term s was em phasized by M r. W ickenden. J. M.
Carm ody, editor of Coal A ge, said th a t technical schools have not sought the aid of the technical press in p u t
ting across to industry its responsi
bility fo r'a ssistin g in the trainin g of engineers. H e m ade particular re fe r
ence to those schools offering m ining courses.
W hen asked how m any men tak ing the training course of the B ethle
hem Steel Co. continued in its em
ploy, M r. M orris said 60 per cent of those trained in the last six years.
T he general opinion was th at this percentage is gratifyingly high. M r.
M orris offered the inform ation th at those graduated from the course five years ago are now earning an aver
age of $305 a month.
Classifying Coal by Its Nature and Uses T H E battle of coal classification
is still being waged w ithout any evidence whatsoever as to w hat the outcome will be, and the meeting on that subject held Feb. 23 under the auspices of the coal and coal- products committee of the A .I.M .E . was merely one of a series of such minor actions in the long struggle.
A. C. Fieldner, U. S. B ureau of Mines, stated the problem, declaring that two classifications w ere being prepared, one having to do w ith the true nature of the coal and the other with its uses.
Howard N. Eavenson read the Paper prepared by Clarence A. Sey- jor, of Swansea, W ales, who w ro te:
There can be little doubt that the ultimate or elem entary composition of the ‘pure coal’ is the best basis of classification. O ne still hears state
ments that the determ ination of this ultimate analysis is like crushing a work of art in a m ortar and analyzing the powder or like counting the num ber of times a given letter occurs in a sentence. Such com parisons are misleading, and the criticism might
^ aPphed to organic chem istry as a The graphic investigation of the composition and properties of coal showed already in 1900 that at least '? independent variables w ere re quired to define the position of a coal
A . C. Fieldner
in the natural series. T h is accounts fo r the failure of the older attem pts at classification. Coal differing as much as cannel and lignite may have the same volatile m atter, and cannel and anthracite may have the same calorific value.”
All this, however, leads M r.
Seyler into a complicated classifi
cation in which appear anthracite, carbonaceous, sem ibituminous, m eta- bituminous, orthobitum inous, parabi- tum inous, perbitum inous, m etaligni- tious and ortholignitious coal and lignite.
W . H . Thom , U. S. Geological Survey, said th a t the definitions of coal should show the interplay of two variables, composition and calorific value. M oisture m ust not be over
looked, because it is not extraneous but an essential of vegetable life.
B oth M r. T hom and W . F rancis, re search chemist, S afety in M ines R esearch B oard, G reat B ritain, agreed that the stage in its development at which the coal w as subjected to pres
sure had an im portant effect on the nature of its m etam orphic changes.
M arius R. Campbell, senior geolo
gist, U . S. Geological Survey, said that the chemical composition of vege
tation was much the same no m atter in w hat age it was form ed. T o this R einhardt Thiessen, U. S. B ureau of M ines, took much exception. Though the chemical composition of the various parts of a plant grow ing in one period m ight resemble the same parts in another plant grow ing in an other period, the relative proportions o f those parts would differ.
H . J. Rose, research chemist, K oppers Co., P ittsburgh, Pa., was not disposed to take an average cross- section of the coal but p referred rath er to pu t in separate classes the various parts of the coal bed, the anthraxylon, the fusain (m ineral charcoal) and the splint coal when the latter two appeared. Each had its
^arch, 1928 — C O A L A G E
