Coal Age : devoted to the operating, technical and business problems of the coal-mining industry, Vol. 40, No. 11

C ^{o a l} A ^ge

Established

1911

DEVOTED TO THE OPERATING, TECHNICAL A N D BUSINESS PROBLEMS OF THE COAL-M INING INDUSTRY S Y D N E Y A. H A L E . E d ito r

N e w Y o r k , N o v e m b e r , 1 9 3 5

D r e a m s C o m e T r u e

A

organization of soft- ,coal producers into a commercial research agency was only a dream. T o day, thanks to the enthusiasm and h a rd w ork of the adven­

turous spirits who could envisage its possibili­

ties, the dream has become Bituminous Coal Research, Inc.; the first research project ac­

tually is under way and others are in the making. T hese projects embrace studies in more effective utilization of coal as a raw fuel and in new uses. Both types of studies are es­

sential to a sound program , but the potentiali­

ties o f scientific exploration into the still uncharted area of new uses excite fresh dreams of future expansion of production.

R i v e r s o f R o c k

I n M A N Y p a r t s

of the coal field, large prehistoric rivers have removed extensive areas of the coal seam, wholly or in part, and re­

placed them with sandstone and sometimes shale. T his is characteristic of large parts of central Pennsylvania and even of p arts of the Low er Productive M easures in the western end of the State. In other places, especially in southern W e s t Virginia, the coal seam comes to an end, no t because of eroding rivers but because the p e at bogs had a limited area.

Faults also cut out seams; rarely, however, in the U n ite d States.

D rilling h ith erto has been used to find these seam defects which interfere with operation.

But drilling is expensive and may reveal a full- size m easure which when reached by mining may be found to be only a foot or so from a fully developed “ coal w a n t.” M any compa­

nies have exhausted their resources by driving rock tunnels in the hope o f penetrating these

♦

bodies of sandstone and arriving at coal seams beyond.

For these companies geophysical researches promise a means of accurately determining the edges of the coal deposit— if not of its thick­

ness also— at much less expense than by drill­

ing and tunnel driving, and doing it so early that the mine can be laid out and its tonnage forecast with accuracy. In O ntario geophysical surveys to delimit a lignite deposit have been made by the Provincial D ep artm en t of Mines, and in France the edges of a lignite deposit be­

low a hundred feet or more of loose sand was similarly surveyed.

J o i n t R e s p o n s i b i l i t y

W i t h t h e s i g n i n g

of the new A p p a ­

lachian wage agreement, the th re a t o f any m ajor interruption in bituminous-coal produc­

tion for many months has been definitely re­

moved. This is a distinct public gain— and both operators and union officials are to be con­

g ratulated for making it possible. W h e th e r the new agreement of Sept. 27 and contracts granting similar increases in oth er bituminous fields will prove advantageous or a handicap to the industry itself, however, will depend largely on how wisely this new instrument fo r peace is used.

T h e past record of the industry is persuasive evidence th a t progressive coal-mine m anage­

ment is as firmly committed to the theory of high wages as the w orkers themselves. But successful translation o f th a t theory into actual practice involves application of anoth er phase of the mass-production principle which has m ade increasing wage rates both supportable and profitable. T h a t phase contemplates con­

tinuous reduction in to tal and unit costs of

production while wage rates remain constant

or advance. And the secret of this departuie from the older relationships between produc­

tion costs and wage rates is to be found in mechanization.

Restatement of principles so axiomatic in the newer and more enlightened machine-age philosophy seems w arranted at this time be­

cause wage-negotiation discussions placed so much inferential emphasis on price maintenance as a prerequisite to wage stability. Price con­

trol is unquestionably desirable and necessary as a check on ruinous internal competition. T h e greatest danger, however, is external, and the coal industry cannot afford to be at a price disadvantage in the battle of competitive fuels.

It must be prepared to meet competition with­

out sacrificing either its profits or the living standards of the mine workers.

Responsibility for lower production costs rests jointly on management and on men. M a n ­ agement must be ready and willing to make in­

vestments in equipment and modernization methods which will reduce costs without de­

pressing basic rates of pay. Labor must be ready and willing to cooperate with manage­

ment in making such investments profitable even if such cooperation means the temporary displacement of some men. In no other way can the industry hope to expand its markets permanently and so increase the opportunities for employment in the mining districts.

M i l e a M i n u t e

M a n y m i n e s

pass air in the main returns at a speed of a mile a minute and many more have speeds as great or greater than th a t in their shafts. Air traveling at that speed has a resistance as great as that experienced by a fast train traveling in still air. Ribs, roof, floor and timbers are moving in such mines at a relative speed to the air equal to th a t of crack expresses. N o wonder the problem of streamlining mine roadways furnishes a prob­

lem as vital as that confronted by railroads, street cars, buses and automobiles.

But the speeds mentioned are not as large as actually exist. Behind an obstruction the air is traveling slowly, not traveling at all, or traveling backward. Some of the airway is not partaking at all in the forward movement. So actual speeds must be greater— sometimes far more than mean speeds— thus increasing resist­

ance. Care in heading alignment is absolutely

essential. A t one mine all deviations from sights are repo rted to the chief engineer, who makes it m a tte r for diligent inquiry and dis­

cipline. But roughness is as fatal as irregu­

larity. R oof falls and crosscuts are as harm ful as other roughnesses. Projected concrete should be used w herever ro o f falls are to be expected, to prevent irregularities in the roof, w hether natural or the result of timbering, especially where express speeds are involved.

Increased pressure involves leaks, and, if air quantities are to be m easured at the face— as they should be— leaks make it necessary to de­

liver more air at the fan and to o p erate it at higher pressure if the required volume is to be.

delivered. A time comes when g reater pressure will not increase volume, for leaks will bleed it off and prevent it having the desired effect.

Streamlining, therefore, reduces resistance in­

directly as well as directly.

W h y S t o p P l o w i n g ?

S t o c k h o l d e r s a * n d d i r e c t o r s

of A ppa­

lachian Coals, Inc., have been busy in recent months debating the future of th a t pioneering organization in district and regional sales agencies. T h e argum ent, h e ard faintly during the heydey of N R A , th a t the province of such agencies was being p reem pted by government bureaus has acquired g re a te r volume since the enactment of the Guffey bill. If price fixing is to be a governm ent function and its benefits are to be conferred on all mines, why, it is asked, should any group of producers con­

tribute to the support of a cooperative sales agency which can offer no g re a ter protection than Uncle Sam gives to non-contributors?

W e r e price fixing the only service private agencies such as A ppalachian Coals had to offer, the question might be difficult to answer.

But, when m easured against the w ork already done in m ark et research, fuel engineering and sales p rom otion and the still untapped possi­

bilities in those fields, price-control activities become of secondary importance. I f pricing activities were entirely eliminated, the services rendered in the oth er fields nam ed would more than justify and repay the cost. N o govern­

ment bureau can be expected to do this job;

only a very few o f the la rg e r producing com­

panies could a tte m p t to duplicate it. A bandon­

ment of the w ork would be wild extravagance

— not economy.

440 C O A L A G E — V ol.40, N o . l l

SAFETY A N D EFFICIENCY

+ A t A l l e g h e n y P i t t s b u r g h M i n e s

G o H a n d i n H a n d

O

m ents o f production is exem pli­

fied at th e S pringd ale m ine and plant of the A lle g h e n y P ittsb u rgh Coal Co., L ogans F erry, P a., w hich , w ith 540 em ­ ployees, produces about 3,600 tons daily.

That safety and efficiency stem from the same root, in the b elief o f th e heads of this operation, is w ell attested by the fact that th e m in in g en gin eer has been charged w ith th e safety w ork and now carries th e additional title o f “ safety engineer.” H e had a sin g le assistan t before th e ch an ge w as m ade and now has tw o, so that th is additional function w ill n ot be slighted . E v e ry w eek he makes a report on an y featu res in op­

eration that are u nsafe and on any un­

safe practices h e or h is assistan ts have observed. T h is report g o es to the fo re­

man, the superintendent and the general superintendent, so that any improper condition m ay be k now n and corrected.

T h e roof o f th e T h ic k F reep ort seam in A lleg h en y C ounty, it is gen erally conceded, h as som e quite desirable characteristics. A t S pringd ale it usually consists o f a cannel slate about 14 in.

thick im m ediately over the coal, w h ich in m ining is le ft undisturbed. T h is is surm ounted by 10 to 30 ft. o f black slate topped by a th ick body o f sandstone.

T h e cannel a t th is m ine gen erally is strong and adheres to th e slate above it, furnishing a g ood su pp ortin g m aterial.

U nder such sev ere stress as m ay be e x ­ perienced in som e h ead in gs in case of delayed roof breaks, th e cannel m ay fracture and fall, but u su ally it is a re­

liable m easure and fre e from “kettle- bottom s.” B ut, w hen th e cannel does fall, the shale ly in g above it is w ith diffi­

culty retained in place, for it is rotten and w ill n ot stand w ith o u t support. A s a rule it m ust be arched back up to the sandstone. In som e places, h ow ever, the sandstone appears im m ediately over the coal bed and, on rare occasion s, d is­

places som e o f th e upper coal bench.

W ith a s o f t fireclay floor at least 6 ft.

thick and p o ssib ly far m ore, for it has

n ot been explored, such a strong roof is extrem ely difficult to break, and un­

less and until an area as large in one dim ension as the thickness of the over­

burden is extracted, the roof w ill not break to the surface and relieve the w eigh t. T h e fireclay w hen lifted is found to contain much w ater, w hich rises in th e excavation to a certain defi­

nite level b elow w hich pum ping w ill low er it w ith extrem e difficulty. T h is m ay account in som e degree fo r the fluidity of the clay bottom under pres­

sure.

T h e coal seam com prises in the main tw o benches— a bottom bench of a som e­

w hat weak, pulverulent coal 3^ ft. thick (in clu d in g in that m easurem ent a foot of floor coal m ade non-com m ercial by the presence o f tw o or three little slate b a n d s), a 12-in. binder o f h igh -ash coal too poor for com m ercial use and a 2 2 -ft.

bench o f hard, clean top coal, m aking in all 7 ft. o f w hich 5 ft. is com m ercial and 6 ft. is rem oved in m ining. In rooms, crosscuts and cut-overs, the binder is cast back into the gob, but in all head­

in gs it is brought to the surface for disposal in w aste heaps, w here thus far

Fig. 1— Hoisting shaft at Springdale mine

it has failed to fire. A bou t 3 per cent of the gro ss tonnage hoisted in the sh aft is w aste m aterial o f th is type.

In the first seven m onths o f th e pres­

ent year, 459,785 tons o f coal w a s pro­

duced w ith ou t a fatality ( in A u g u st, there w as n ot even a lost-tim e a c c id e n t).

T h e m onthly report of the P en n sylvan ia D epartm ent of M in es placed th is com ­ pany first am ong bitum inous operations of the en tire S tate for its record of n on- fatal accidents caused by fa lls “d irect or indirect.” D ire ct falls include on ly those at the w ork in g face. It had no direct, indirect or m aterial falls. S in ce that tim e a fatality has occurred w h ich prob­

ably w ill be rated as the resu lt of a direct fall, thou gh it appeared som e feet back o f the w ork in g face.

T h e seam is undercut on the top of the slate bands to w h ich referen ce has been made. U n til the pillars are draw n, this 12-in. bench of dirty coal supports

fcSBi fA

N o v e m b e r, 1935 — C O A L A G E 441

the w eig h t of the props and does not allow the floor to heave, but when, in pillar draw ing, break-row s of timber are set as the fulcrum on w hich the roof is to be broken, the props push down into the floor several feet, so that their recovery is everyw here im possible and is never attempted. O nce the con­

tinuity of the coal covering the clay be­

low is broken, it oozes out from under the unbroken coal areas and leaves them defenseless. Som etim es, to protect the roof, second-hand and worn 60-lb. rails are set over the posts.

Stress is placed on inspection of all timber. It m ust be straight, free from knots and cross-grainin g, be not less than 3^ in. in diameter or its equivalent at the sm all end, and m ust nowhere e x ­ ceed 5£ in. in diameter. Saw n caps are provided and used over all posts. T h ese are 1 in. thick, 4 to 6 in. w ide and 14 in. long. B ecause the bottom bench is soft, the binder quite frequently projects from the face after the face has been shot, so sprags have to be used for its support. T hese, w hich m ay be as many as three to a face, are set vertically.

R oom s are necked 12 ft. w id e and each neck is 35 ft. lon g w ith the sight lin e 2 ft. to the right of the left rib.

W hen the room is w idened it is made 5 ft. w ide to the left of the sigh t line and 11 ft. w ide to the right, and the only posts used are set in a line at 4-ft.

centers 4 ft. from the right rib. T h e road is placed in the center o f the room.

T h is leaves am ple and convenient gob space for p ilin g the binder. Tim bers are kept alw ays w ithin 6 ft. o f the face.

A ccordingly, they do not interfere w ith cutting or loading operations.

Rooms are driven at 90-ft. centers, so the pillars are 74 ft. w id e and crossed by 15-ft. crosscuts at 100-ft. centers, g iv in g pillars 74x85 ft. T h ese pillars are n ow being drawn on retreat from the boundary w ith break lines w hich e x ­ tend in a straight line from one entry to the n ex t; these entries are at 2 ,0 0 0 -ft.

centers. M uch trouble accom panies the m aking of the first break in any panel.

It has been found that the angle of breaking draw is at tim es as much as 15 deg. T hus, as overburden runs from 600 to 800 ft., the crevice at the surface 7 » would h e between 160 and 214 ft. be­

yond the excavation line.

U n til recently it has been the practice (se e F ig . 3 ) to lay tracks in any cross­

cut as the break line approached the crosscut beyond it, and to drive a road­

w ay up the center o f the pillar, tim ing its advance so that it would be com ­ pleted through to the next crosscut w hen the break line reached that point, but this involved w eakening of the pil­

lar, m ore stress on the floor, much dif­

ficulty in throw ing coal to the car from the remoter parts of the pillar and two right-angled turns in the roadway which had to be negotiated by cars and gath ­ erin g locom otives. A s the bottom often heaved until the motorman could not

Fig. 3— Former method of removing pillars— by splitting

see over the tops of the cars, it is easy to im agine that derailm ents and acci­

dents occurred and that m uch expense w as involved in liftin g track, low erin g bottom and relayin g rails.

Consequently, it is now the practice to drive cut-overs 15 ft. w id e through the pillar, lea v in g a pillar 12x74 ft. again st the goaf for prompt rem oval in four sections. T h e present w idth o f pillars between room s, how ever, is subject to revision, though the change w ill be de­

layed by the fact that necks have been driven in m any butt headings, and the distances thus established m ust be m ain­

tained. T im in g has been arranged sub­

stantially as set forth in F ig . 4. A s no definite stint is set for each man that m ust be com pleted every day— that is, as there is no “clean-up” system , but each man does h is utm ost during the running period— the w ork cannot be subjected to close tim ing, but m ust de­

pend largely on the judgm ent of the foreman as to the characteristic produc­

tion of the several men em ployed. S h ift­

ing o f men is essential often to keep the face line straight. In this operational chart nothing is intended to be indicated except sequence. T he several advances do not in any w ay represent daily p ro g ­ ress. T h e angle of the break lin e is kept 40 deg. off the line of the face fracture.

Springdale m ine provides coal for a sin gle power plant and therefore op­

erates regularly. Its output is planned on the basis of four days’ operation per week. R unning thus steadily, the lo n g break lines can be advanced w ith onlv short periods of idleness. E x c ep t w h ere there is exceptional stress, the face

every m orn in g of operation is in better condition for w ork in g than it w ould be in m ines w ith sim ilar p hysical con d i­

tion s and like m ethods o f op eration but w here lon ger intervals of in activ ity in ­ tervene. T h o u g h th e d riv in g of room s and h ead ings is alm ost w ith o u t hazard from falls, the stren gth o f th e roof m akes n ecessary the utm ost care in p ost­

in g and in k eep in g a straigh t break line during pillar w ithd raw al, especially w hen the roof in an y section has not been broken already up to th e surface.

In the m ine at presen t are o n ly five break lin es. T h ere are 19 a ctive head­

in gs and 156 room s and pillars, w ith two men to each w ork in g place, yet th e 3,600- ton output is readily made, but, as som e of these places are n ot w ork in g every op eratin g day, the output per m an figures 12.45 tons per loader. T h is la rg e tonnage from a concentrated area m akes it pos­

sible to supervise the en tire production w ith one forem an, three section foremen, one n ig h t forem an and to exam in e the m ine for gas w ith five fire b o sses; yet the w ork can be done effectively.

D esp ite the ex cellen t roof, the big flanking pillars on either side o f the “flat”

en tries— n ever less than 205 ft. w ide—

and the 38-ft. chain pillars, there are some w eak spots in the roof of the headings, and here steel I-beam s are used set on 12x l 2 -in. pilasters m ade o f 6 x 6 x l 2 -in.

“red-dog” blocks constructed by local m anufacturers from the burned shale p iles w h ich surround n eigh b orin g mines.

A ll headings are 12 ft. w id e.

Springd ale m ine is definitely gassy, m aking over three quarters o f a m illion cubic feet of m ethane every 24 hours, but, by use of safety lam ps, adequate venti­

lation, good red-dog stoppings, line brat- tic in g and careful in spection , the g as is kept under control. T h e m ain return at present carries 0.19 per cent methane, w hich is on ly about one-fifth as large a percen tage o f g a s as that w hich careful m anagers regard as th e lim it for safe operation. H o w e v e r , the m ost gassy split has 0.24 per cent of m ethane. These low percen tages are obtained by passing 276,000 cu.ft. of air per m inute through the w ork in gs at 2.8-in . w ater gage. The m ain return sh o w s 285,500 cu.ft. and the sum m ation o f the variou s sp lits 195,200 cu.ft., sh o w in g that 70 per cent o f the air reaches the face of the w ork in gs, includ­

in g 7,200 cu.ft. w h ich is used for ven ti­

latin g the ch a rg in g stations, etc., around the intake airw ay. T h e air velocity no­

w h ere exceed s 2,060 ft. per m inute.

T h e m ain fan, w h ich is o f exhaust type, m easures 6 x 12 ft., is reversible and runs at 160 r.p.m. T h is ventilates the m ine proper. A sm aller force fan, w h ich su pp lies additional air to that al­

ready detailed, is used to course the two tu n n els w h ich con n ect th e m ine on the L o g a n s F erry sid e of th e A llegh en y R iver w ith th e sh aft at Springd ale. T h is sm all fan is a 6 -ft. straigh t-flow unit w h ich d elivers 25,000 cu .ft. o f air per m inute w ith 0.3-in . w ater g a g e. T h e air Sandstone

*\Black state tO'to 30' Carmel state t-2"

L-Coat 2'-6"

‘¿■Dirty coat 12"

\-Coat 2'-6“

x ~Slatycoall2"

'Ctay 6'r coal cross- Fig. 2—Room layout, left;

section, right

442

C O A L A G E — V o l.40 , N o .11

F i g . 5 Main ventilator supplies air to workings goes dow n the top section o f the man-

and-material slope to the autom atic doors w hich separate the ven tilatin g currents o f the tunnel from those o f the mine. It ven tilates the tw o tunnels and passes up the m ain shaft, carrying w ith it any dust w hich the revolvin g dump at the foot o f that shaft m ay create.

A t this m ine the intakes and returns at the surface are so far apart that there is no risk that the m ethane w h ich leaves the m ine by the return w ill be sucked into the intake and be recirculated through the m ine or that the dust in the return w ill be carried back into the mine and deposited in the airw ays. T h e main current enters the m ine in the bottom section o f the m an-and-m aterial shaft 300 ft. from the air shaft, and the air is en tirely free of both m ethane and coal dust, b ein g about a m ile from any tipple or dump. T h e sm aller force fan takes its air on one side o f the A lle ­ gheny R iver w here there is no dust and delivers it laden w ith the dust o f the dump to the su rface on the other side of the river. U nfortu nately, it is n eces­

sary to cause the air o f the m ain fan to double on its tracks. W h en a n ew area is opened to operation it is hoped that a shaft can be provided that w ill make it no longer n ecessary to bring the air back to a point on ly 300 ft. aw ay from which it enters the m in e; such a shaft will provide in that m anner w hat w ill approach on e-w ay ventilation.

T o reduce air resistan ce all m ain en ­ tries con sist o f four headings, each pair of headings on one sid e o f the entry be­

ing intakes and the other pair returns.

T h is applies to th e m ain butt entries and to the faces— here term ed “flats,”

though they are hardly m ore level than the butts. R oom entries con sist o f tw o headings only. A s the roof is good, both the intake headings of the m ain butts are used for haulage as far as the eleventh butt intersection, w ith no stop­

p ings in the crosscuts between them ; so the trips in p assin g interpose little interferen ce w ith intake ventilation. A ll returns have been equipped w ith rock- dust barriers h avin g vanes and tripping devices, all o f w hich cause air to eddy and interpose resistance. It is the inten­

tion to rock-dust these headings w ith a h igh-pressure dust distributor so that the barriers can be rem oved and v en ti­

latin g conditions further improved. T h e rock dust in the barriers tends to cake, and it is feared that it m ight n ot make a curtain of fine dust if disturbed by an explosion. T o assu re that it w ill act as desired, the dust has to be renewed fre­

quently, w hereas by rock-d ustin g the headings th is recurring difficulty w ill be elim inated. H au lage is restricted to in­

take airw ays.

U tm ost care has been taken to drive the roads straight, thus p reventin g tur­

bulence, alw ays a source o f m ore loss of pressure than m ere surface friction.

N ea r the intake slope, w here the air is travelin g at its h igh est speed, m any o f the ribs, w hich norm ally w ould be rough because o f the irregular butt fractu res, h ave been trim m ed w ith the accuracy that d istingu ish ed the art o f m in in g early in the nineteenth century, but some o f these ribs, unfortunately, h ave scaled in places, rou gh en ing som ew h at their otherw ise perfect alignm ent. C urtains for d irectin g air to th e fa ce of the w ork ­ in gs are h u n g from the r o o f and not nailed to posts.

T o reduce the resistan ce at th e base o f th e 169-ft. m ain-return air shaft, w hich h as a cross-section of 176.7 sq.ft., the bottom o f the sh aft w a s curved out in the four d irection s from w h ich the air entered in to it, but it w a s feared that the air resistance n evertheless w as in ­ creased by u n n ecessary ed d ying at th is point. G eorge M cC aa, m ine inspector o f the district, su ggested erectin g a fou r­

sided pyram id at th e b ottom o f th e shaft w h ich w ould serve to direct the variou s air stream s, each in th e rig h t direction.

T h e m anagem ent w as uncertain as to the best form of pyram id to install, so exp erim en ts w ere m ade w ith w ood structures h a v in g d ifferen t an gles to the plane of the floor, and it w as found that a 30-deg. slope to that p lane g a v e best results. W ith 45-deg. in clination s, som e ed d ying at th e foot o f the shaft w as still found. T h e sid es o f the pyram id run out into th e fou r h ead in gs w h ich m eet at the shaft base. T h e shape finally adopted is a truncated pyram id, 6 ft.

square at the top and 8 ft. h igh . Its introduction increased air flow from 245,000 to 280,000 cu.ft. per minute^—

over 14 per cent— sh o w in g h o w la rg e a loss can be incurred in a sh ort len gth o f roadw ay w h e re air is tra v e lin g at speed. B ut, as this w ood con stru ction in trodu ces a fire hazard, of w h ich no N o v e m b e r, 1935 — C O A L A G E

443

one is m ore conscious than the m anage­

ment, the pyramid w ill be made with steel plates, w hich already have been ordered.

A s the batteries in the motor barn, repair shop and charging rooms gene­

rate exp losive gas, care has been taken to g iv e to each a separate split of air w hich is carried by pipes at the rear of each of these rooms direct to the return.

Both flame safety lamps and electric cap lamps are provided for all bosses, firebosses, shotfirers and cutters, 62 in all of the form er type of lamp being in use. Others carry electric safety lamps, o f w hich there are 600, 471 being ac­

tually in use.

Perm issible powder of glycerine dynamite type is used for shooting with three shots drilled under the cannel roof in advancing rooms. T h e center hole, w hich is loaded w ith 2 \ or more cart­

ridges, is fired first and then the two side holes, w hich are charged each with 2 j or less cartridges, each cartridge containing 4.38 oz. o f explosive. N o. 6 caps are used as detonators w ith 8-ft.

lead w ires wound on a spool for each shot. Form erly, an additional shot was placed under the middle parting, but the more sim ple method of shooting seem s to g iv e the desired effect. A s none of the coal from this m ine goes on the m ar­

ket, but all is used at the W est Penn power plant adjacent, where the coal is crushed for use on underfeed stokers, little is gained by methods that would break the coal less.

Miners drill their own shotholes and carry in their ow n cartridges in wood boxes, but shotfirers, of whom there are nine, load the holes and carry the detonators and batteries by w hich the shots are fired. T h e cars by which the miners are hauled into the m ine w ith their cartridges are special w agons with wood seats, plain— not sw ivel—

couplings and an insulated coupling be­

tween first car and locom otive. W ith plain couplings the cars are less likely to overturn in case of derailment than with sw ivels. T hese cars are switched into a sidetrack, w here they aw ait the end o f the shift. W hen the tim e comes for the men to leave the m ine they enter the cars and w ait till the locom otive is coupled to the trip and they are hauled out. S o there is no unseem ly haste and possible accident.

A ll cartridges are stemmed to the mouth of the hole w ith clay dummies.

These are not put into paper receptacles, for by a strict adherence to the letter these are held not to be perm issible un­

der _ the terms of the Pennsylvania m ining law, because paper is not incom ­ bustible. The clay is wetted, worked into sausage-like dummies by the miner, presented to the shotfirer in the bowl of a shovel held near the face and rammed into the hole w ith a w ooden tamping bar. A ll shots are fired by batteries. B e­

fore firing, tests are made for gas w ith the flame safety lamp. Shotfirers, as

F ig . 6— D e f le c t o r p y r a m id at b a se o f a ir sh a ft

stated, carry both flame and electric safety lamps.

A ll coal is cut to a depth of 7 ft. over the bands in the bottom of the coal by perm issible lon gw all undercutters h avin g cutter bars 7£ ft. long. P erm issib le equipment, to be safe, m ust be d iligently inspected. W ith feeler g a g es the w idths of clearances, through w hich an y ga ses exploding in interior cham bers can escape to the exterior of the m achine, are tested so that they m ay be kept w ithin the required lim its and so that gases as they em erge w ill be cooled by the metal surfaces to a tem perature w ell below the ignition point. Inspection also is made to see that no bolts are om itted or loose, because should the clearances be w ide enough for the em ission of

the glid ers, at the su g g estio n o f A rthur H all, m ine superintendent, a re inset w ith ’ M eehanite, this m etal con tain in g graphite, w h ich g iv e s good conductance and a sm ooth contact. It has been found that w ith any kind o f contactor, when the trolley w ire is oiled, sp ark ing is re­

duced or elim inated.

T roub le and accidents, one resulting in a broken back, h ave resu lted from m otors breaking lo o se from th eir sus­

p ensions from failu re of su spension bars, bolts or sp rin gs. M otors m ay be thrust up again st cover plates or m ay fall to the track. C lose in spection m ay or may not anticipate such defects w ith repairs.

So a safety d evice, co n sistin g of a strong su spension crossb ar jo in in g the frame on eith er sid e and bolted thereto, has been provided for each m otor. T h is bar has bolts and ch ain s attached to the ca sin g fram e o f the m otor w h ich w ill prevent the m otor from fa llin g to the track. It also has a buffer block that w ill hold th e m otor should it sw in g in the opposite direction.

Probably the m otorm an w ill be cog­

nizan t should th e regular suspension bar, bolts or sp rin gs fail, but even i f he should not be, no dam age w ou ld result.

T h e locom otive still can be run out to the repair pit w ith th e m otors hanging

-W-

F ig . 7— S u s p e n s io n b a r k e e p s m o to r s f r o m f a l l i n g t o tr a c k

over-hot gas, or should they becom e w ide enough by reason of internal pres­

sures and insecure retention by bolts in ­ adequately tightened to pass such over­

hot gas flames, the m ethane in th e w ork ­ in g place m ay be ignited. F lam es also may pass through an unoccupied bolt hole.

S ix -to n storage-battery locom otives, som e h aving 80 cells and som e 74, b rin g loaded cars to partings in the butt-entry headings, w hence th ey are taken by 8- ton trolley locom otives alo n g th e “flat- road” or face entries to the m ain butt roads; here m ain-line 15-ton locom o­

tives, of w h ich there are six , haul the loads to the revolvin g dump at the shaft.

Gliders are used, instead o f trolley w heels, on all s ix locom otives ; these w ere provided the m otorm en on their request after the first one had been in ­ stalled. N o t only do they furnish the power required for locom otive opera­

tion w ith reduced resistance, becau se of their lengthened contact, but th ey fo llo w the w ire and sw itch es w ith le ss, fr e ­ quent dew irem ent, make no sparks and make back-poling im possible. S om e o f

on the em ergen cy su spension bar. T h is safety equipm ent is sh ow n in F ig . 7.

L ocom otives w ere form erly repaired at the m ain shop on th e surface, but it w a s found that w hen on e go t out of order it w as not con ven ien t to send it to the shop till the end o f the w eek, so it w as patched up and m ade to operate as best it m ight, w h ich m eant that it gave inefficient serv ice and developed in the interim furth er d isq u ietin g and expen­

siv e sym ptom s. M oreover, h oistin g a h eavy loco m o tiv e up the man-and- m aterial slop e w a s n ot a w h olly safe p erform ance for frequent repetition.

F or th is reason a repair pit w as pro­

vid ed in sid e the m ine so that the loco­

m o tiv e can g o to the doctor promptly w h en ever ills develop.

Cars are of tw o types, a riveted steel car o f 100-cu.ft. cap acity w ith plain b earin gs and 18-in. w h eels and a welded steel car o f 123-cu .ft. capacity having rolled ed g es and roller b earings with 14-in. w h eels. In neither car is the bot­

tom m olded around the w h eels to give ad dition al w id th . T h e track g a g e is 44 in. A s the car supply is at a ll tim es ade­

444 C O A L A G E — Vol.40, No.11

quate and no effort is made to induce the m iners to build up their coal, the cars are not topped to an y extent. A s a result, w ith straight, strong tracks, good sw itches and solid-bottom cars, the track always is clean. T h e new cars are en ­ tirely sm ooth on their exteriors, and so cannot catch anyone as they pass along the road.

E ven the m iners’ check hook is a m issing m enace. T w o h oles are drilled close to each other through the fron t of ever}- car. T h rou gh one o f these is passed a lead w ire from an exploder, of which there are m any in every room.

This en gages tw o holes in the m iner’s check. T h e w ire is then passed through the other hole and the tw o ends are twisted firmly, h old in g the check im ­ movably. A t the w eig h scales the check is broken loose w ith a pry. A m iner, if he w ill, can rem ove the check from an­

other m iner’s car, but w ith th is arrange­

ment all h e w ould h ave w ould be a valueless disk o f m etal, for w ith this arrangem ent h e could not replace the stolen check w ith h is ow n w ithou t first em ptying the car, because the check holes are placed near the car bottom.

So at this m ine no one “steals cars,” and there is no risk o f lacerations or en­

tanglements w ith check hooks.

In m ost cars the brake blocks are set so as to push the w h eels aw ay from each other, thus d istortin g th e car and in­

creasing the w heelb ase. Cars at this mine have a brake that p resses on the tops of the w h eels and thus avoids that defect (s e e F ig . 9 ) . O n the dump, which revolves through 360 deg. and dumps tw o cars a t a tim e, a certain longitudinal strain is kept on th e cou­

plings so that the p ins o f the sw ivels will not drop out. T h e cars, b ein g of two types h a v in g w h eels d ifferin g in diameters by 4 in., w ould not locate themselves properly in the dump w ith a fixed stop at its entrance if it w ere not that provision has been m ade by w hich the w heelbase o f th e truck h a v in g the small w h eels is 4 in. m ore than the wheelbase o f th e truck h a v in g the larger wheels. T h is corrects for the difference in diameter, and dum ping o f cars now of one type and n o w o f another proceeds without difficulty.

In the m ain h ead in gs (w h ic h are driven on th e b u tt) and in the face or

“flat” h ead ings, 60-lb. rail is used, set mainly on w ood ties laid at 20-in . cen ­ ters. In the room h ead ings, 40-lb. rail also is set on w ood ties w ith 24- to 30-in. centers, but steel ties are used at the points o f sw itch es and for a foot or more beyond th e fr o g to assu re per­

fect g age. In the room s, 30-lb. rail is provided w ith steel ties set at 3-ft.

centers. A ll sw itch es are factory-m ade, p i o s e at room m ouths h ave N o . l \ frogs, and all others are N o . 3 fro g s.

On the m ain h aulage, fro g s are plated or o f m an gan ese steel.

D isp atch in g o f trip s w ith a block- signal system is anoth er sa fety pro­

vision, but it has an even greater advan­

tage in increased efficiency. Trip size is carefully regulated. Storage-battery locom otives pull one or tw o cars at a tim e from each w ork in g face, the lighter trolley locom otives pull 14 to 15 cars to a trip and the m ain trips behind the heavy trolley locom otives are lim ited to 28 cars.

T h e double air doors in the tunnels are m echanically operated by the pass­

in g trips and are set 600 to 700 ft. apart, so that one pair o f doors is closed before the other is opened. T o assure that the cars w ill be on the track on approaching the doors, rerailin g devices are per­

m anently installed. In all rooms safety blocks are provided to prevent cars from running a w ay and pinning men between the fa ce and the end o f the car.

T o prevent the man car at the head of the m an-and-m aterial h oist from g e t­

tin g aw ay and running down the in­

cline a solenoid-operated sw itch, nor­

m ally open, is provided at the loading point. W hen the sw itch is open a green lig h t is show n in sid e the h oist house.

W h en the hoistm an lets the car down the slope, he throw s this sw itch by a m ovem ent of h is fo o t on a pedal and a red ligh t is show n.

T h e tracks have recently been con­

nected w ith short U -b olt 4 /0 welded bonds placed under rails, this being made possible by th e fact that all rail join ts are placed over a gap between ties instead o f restin g on a tie. T h e old sid e bonds, w h ich passed from rail to rail around the fishplates and w hich w ere good practice w hen installed, are still in place in m ost instances, and they help also to decrease resistance. N o t only, how ever, are th ey longer and therefore m ore resistan t to the passage

of current than the shorter U -b ond s but the flanges o f the w heels have cut them in places and any derailm ents are lik ely to tear them loose. T h e sh ort U -b on d is down under the rail w h ere it is w ell protected from all form s o f abuse. T h e U -bond costs 42c. as m aterial and 86c.

to install, m aking a total co st o f $1.28, w hereas the old bond cost 88c. and 58c.

to install, the total cost b ein g $1.46. T h e w elded U -bond w ill g iv e about h alf the resistance o f the old pressed bond w ith good w ork in each instance. S in c e the U -bonds w ere installed, arm ature and field failures have decreased con sid er­

ably and an electrical savin g o f $350 per m onth has been made. C ross bonds are provided at 200-ft. intervals. O n the room headings, h ow ever, to avoid ig n it­

in g gas, no w eld in g is done. P ressed 2 / 0 bonds are used to connect the rails.

D irect-cu rrent potential is 250 volts.

T h is is provided at tw o substations, one on the su rface and one underground at the 11th butt. F rom the first substation to the slope bottom, a distance of 650 ft., the direct current is carried b y one 1,000,000-circ.m il, one 750,000-circ.m il and one 500,000-circ.m il cable. F rom that point to the 11th butt in tersection is installed one 1,000,000-circ.m il cable, tw o 500,000-circ.m il cables and tw o trol­

ley lines totalling 423,000 circ.m ils.

A ll th ese feeders are positive. T o the underground substation is carried a 3-conductor, 2,300-a.c. cable, 5,000 ft.

long, buried 2 f t deep in the clay floor.

A t the w ork in g faces the purpose is to m aintain at least 200 volts under load.

Should th is fail to be provided, cables o f sufficient capacity are added to assu re that th is voltage w ill be m aintained.

F rom th e bottom o f the m an-and- m aterial slope to the substation on the

November, 1935 — C O A L A G E 445

I\fyholecsk.a^

| to be set ¡n shop a ft e r [ brake mechanism R / e is equalized^

L-4'x4'x% for holding cars in \ rotary dump j

/ \

l i stationary coupling ; pin v/ith % cotter pin te-IOg ->P

l - i'/yW/i'x'/j bent, cut a n d weld corner - — ->K--- 4 '- 6 " — ... - ...^ ...2 ' j /6

IO-IOi

t

M- 5-5% -

K ...

M'idiam.C.l. wheels w ith 2%-diam. a llo y steelax/es.

R o lle r b e a rin g s

Top o f r a i ! -y _______________ __ _____ _ I «— - - 2'-9" — - J * --- 2 ' - 9 ' ' - \ - - > \

W --- J-7p wheel g a g e ... >il K - - : 3 -8 "r a i l g a g e - ...->4

p j g < 9— M in e car s h o w in g b r a k e m e c h a n is m

surface the return current is carried by one 1,000,000-circ.m il cable, one 500,- 000-circ.m il cable and the two 60-lb.

rails. T h e return current from the four 60-lb. rails o f the haulage system is car­

ried to the underground substation by a 1,000,000-circ.m il cable. T h e m ine uses 390,000 kw.-hr. per month, or 5.7 kw.-hr.

per ton. Its installed substation capacity is 960 kw.

E lectric lights are provided at all sw itches and other important points.

Great care is taken to ground these carefully, passing the return current down to the floor by a ground w ire fastened to the heading rib. T h is w ire is buried in the floor and passed toward the rail, where it is clamped firmly to an electric bond in the haulage track.

A ll machinery, portable as w ell as sta­

tionary, is well grounded, and rubber mats are provided at all sw itches, on w hich the operative m ust stand. In m ost permanent installations these mats rest on stools a few inches high w hich lift the operative clear of the ground and make shock impossible. A ll metal- cased telephones are grounded as m etic­

ulously as machines.

In each substation, rubber and leather gloves are provided, to be used when pulling sw itches and disconnects on high-tension lines. T hese gloves are tested every three months by the W est Penn Pow er Co. to see that they m ain­

tain the required resistance. N ew m oisture-proof telephone cables are be­

ing installed which w ill not be buried but hung from the roof. A ll pumps are being equipped w ith starters. Gears also are guarded. In the repair-pit shop all tools w ill be kept in a recess to be covered w ith a steel door, and another recess sim ilarly guarded w ill house the w elding equipment.

R ock-dusting is being m ore aggres­

sively practiced at this mine as the years pass. N o t only w ill self-tripping barriers give place to general rock- dusting of returns but more dust is be­

in g used on travelin g roadw ays and rooms than before. W hereas in previous years 30 tons sufficed per month, in the first six months of the present year 50

tons m onthly has thus been used. R ock- dust m en w ear respirators and one certified man in the rock-dust distribut­

in g crew of three enters each place ahead of the m achine to test for gas.

T hough a blast of return air from the sm aller of the tw o fans enters the pit over w hich the revolvin g dump op­

erates, sw eeps over the chute down w hich the coal slides and carries the dust up the shaft to the surface, it is thought w ell to w et the coal dow n on the dump w ith sprays. T h e re volvin g dump m akes a com plete revolution in 8 seconds, but on only a fourth of the revolution is the coal discharged. So w ater is needed on ly for 2 seconds, but so much w ater is required that only a 6-in. line can supply it.

A 6-in. valve is difficult to open and close for so short a period w ith the necessary promptitude, so a 2-in. valve operated by the m otion of the dump is m ounted above th e 6-in. va lv e to pro­

vide w ater that p ressing on the gate of this large valve w ill open it w ide. O n ly enough w ater to bring the quantity up to 4 per cent is used, and this percentage is helpful rather than detrim ental in the operation of the W est P en n underfeed stokers on w hich the coal is consumed.

T h e m ovem ent of one p rojection of the revolvin g dump opens the 2-in. valve, w hich the m otion of another p rojection closes (se e F ig . 8 ) .

P ossib ilities of fire are carefully watched. A ll accum ulations o f refuse are duly avoided. In the repair-pit shop below ground n oth ing but the w ork bench is of w ood, and this is so h eavy as to be slow -burning. A ll ch argin g rooms, pumprooms, substations, etc., are m ade of incom bustible m aterial and fitted w ith steel doors. Certified m en inspect the m ine on idle days lest an electrical fire start in the cannel roof.

O n other days the m en at w ork w ould report the condition and ex tin g u ish the fire. A 200-gal. F oam ite-F ire F oam car is kept at the m ine bottom and is m ain ­ tained in condition by the m achine boss at the locom otive repair shop. A 2^-gal.

tank of the sam e type is h u n g at the entrance to each butt entry and a 1-qt.

P yren e fire-figh tin g equipm ent is car­

ried on every locom otive and m ining m achine. S u rface b u ild in gs also have 2-j-gal. tanks, and fire p lugs around the property com plete this protection.

S afety hats, safety sh oes and g oggles are not m andatory, but their use is en­

couraged, and all are quite generally used and kept in stock at the m ines.

S om e of the m iners are u sin g respira­

tors. M en g rin d in g at the em ery and Carborundum w h eels are required to w ear g o g g le s, and a g la ss plate further protects them at w ork. A d h erin g grains of ab rasive dust on the underside of the plate gla ss te s tify forcib ly to the need­

fu ln ess o f its p rotective presence.

F iv e M cC aa breath ing apparatus re­

cently have been in stalled in place of older equipm ent. A carbon-m onoxide detector o f n e w d esign h as been pro­

vided for use in case o f a m ine fire. A t the m outh of ev ery room heading a rescue cham ber w ith a sm all 4x4-ft.

op en in g and about 100 ft. long-, barely h ead in g w idth, h as been excavated in the 205-ft. flanking pillar o f the ad­

jacen t face en try and ru n nin g parallel thereto. T h e op en in g can be blocked w ith a door by the b eleaguered m iners, this door b ein g stored in the chamber, the cap acity o f w h ich is increased by d riv in g tw o sh ort “n eck s” on each side, those d riven tow ard the face entry hav­

in g tw o sm all ea sily blocked holes which lead into th e return. B u lletin boards are placed in variou s places around the m ine w ith p osters provided by the W est P en n P o w er Co. A ll m iners are checked in to and out of the m ines.

M eetin g s o f forem en are held every m onth to d iscu ss accid en ts occurring d u rin g th e p reced in g period and means of a v o id in g sim ilar accidents. T h ey study the reports of the sa fe ty engineer, R. E . Jon es, on dangerous conditions and their correction , also violation s of safety p ractice observed by him and his assistan ts in m akin g their rounds of the property. N o sa fety m eetin gs of em­

p loyees are held, as it is found that such m eetin gs h ave not resulted in any bet­

term ent of conditions.

( Concluded on page 461)

446 C O A L A G E — Vol.40, No.11

AERO-MECHANICS

+ Sheds N ew Lisht

O n Ventilation of M ine s

I

ments h is ow n pressure-drop, or re sis­

tance, form ula. A s a result a number were proposed to exp lain and predict friction pressure and friction losses.

Several o f these form ulas have been used at one tim e or another for the calculation of the friction pressure en ­ countered in m ine ven tilation ducts. A t the present tim e the form ula in m ost general use is a variation o f C hezy’s original pressure-drop form ula,

K L O V 2 R = ---

A

in w hich R is the pressure drop in pounds per square foot, K is a friction coefficient, L is the length o f the duct in feet, 0 is the perim eter o f the duct in feet, V is the air v elo city in feet per minute, and A is the cross-section al area of the duct in square feet. T h is form ula accurately ex p re sse s the variation in pressure for a g iv e n duct w hen the velocity is varied. It is not so satisfac­

tory, h ow ever, in ex p la in in g resistance variation w ith ch a n g in g duct condi­

tions. V ariation o f w all roughness makes necessary considerable adjust-

Courtesy United Engineering Trustees, Inc.

F ig . 1— T u r b u le n t f lo w a lo n g a s t r a ig h t p ip e

m ent in the value of K if this form ula is to hold.

R esistan ce to flow of air through a duct is com m only believed to be w holly caused by actual rubbing o f the fluid or air on the w alls o f the duct. T h is con ­ ception of air friction is incorrect. L ess than ten per cent of a g iv en resistance loss arises from w all friction, the rest b ein g due to turbulent flow.

W h en air travels through a m ine en­

try at very lo w speed, the air particles m ove regularly in paths p aralleling the w alls of the entry. T h is type of flow is term ed “lam inar.” If the velocity e x ­ ceeds about 5 ft. per minute, w hich in ­ cludes all practical m ine-ventilation v elocities, irregular secondary m otions

By A . L. BARRETT

P ittsburgh Coal Co.

L ibrary, Pa.

are introduced in directions perpendicu­

lar to the a x is o f the entry. T h e condi­

tion representing turbulent flow is show n in F ig . 1*. T h e lim itin g velocity b etw een lam inar and turbulent flow is determ ined by the R eynolds num ber w h ich is a function of the duct size, the kinem atic viscosity, and the air velocity, but the value g iv e n applies to average m ine entries, and all m ine ven tilatin g currents w ill be turbulent. E v en in a perfectly sm ooth aircou rse this turbu­

lence cannot be avoided. H o w ev er, ad­

ditional turbulence is caused by rou gh ­ ness, obstructions, turns and rapid changes in cross-sectional area, and th is turbulence can be reduced, as w ill be show n.

A study of the flow con d itions around an obstruction exp lain s the causes of the tw o types of flow , as w ell as the change in the m agnitude of K in C hezy’s form ula w ith a m odification in duct surface. W h en flow is ju st startin g from zero v elocity around a blunt body, a purely lam inar flow results, as in F ig . 2. A ll particles o f the air are in m otion

• P ig s . 1-6 are from “A p p lied H y d ro - and A ero -M ech a n ics,” b y O. G. T ien tie n s, p u b ­ lish e d b y M cG raw -H ill B o o k Co.

F ig . 2— F lo w ju s t sta r te d fr o m l e f t t o r ig h t a r o u n d a b lu n t b o d y . F lo w i s a lm o s t e n t ir e ly la m in a r

Courtesy United Engineering Trustees, Inc.

F ig . 3— S t i l l f lo w in g f r o m l e f t t o r ig h t b u t t u r b u le n c e h a s s ta r te d o n r ig h t

Courtesy United Engineering Trustees, Inc.

November, 1935 — C O A L A G E 447