C o a l A g e
A M c G r a w - H i l l P u b l i c a t i o n — E s t a b l i s h e d 1911
DEVOTED TO THE OPERATING, TECHNICAL, AND BU SIN ESS PROBLEMS OF THE COAL MINING INDUSTRY
N ew Y o r k , March, 1 9 3 1
Vo l u m e 36 Nu m b e r 3
Long-Term Planning
T h e i n d u s t r i a l d e p r e s s i o n w h i c h s t a r t e d l a t e in 1 9 2 9 is a d i s t i n c t c h a l l e n g e t o t h e A m e r i c a n e c o n o m i c s y s t e m a n d b u s i n e s s p h i l o s o p h y . P r o g r e s s i v e l e a d e r s h i p in i n d u s t r y r e c o g n i z e s t h i s f a c t a n d is s e e k in g t o m e e t t h e c h a l l e n g e .
N o h e l p c a n b e e x p e c te d f r o m b e l i e v e r s in t h e e a s y f a t a l i s m o f t h e c y c lic s c h o o l o f r e c u r r i n g p e r i o d s o f c o m m e r c i a l d i s a s t e r w i t h t h e i r w i d e s p r e a d h u m a n s u f f e r i n g . L i t t l e a s s i s t a n c e is t o b e h a d f r o m t h o s e i n f e c t e d w i t h i t i n e r a n t p a c k - p e d d l e r o p p o r t u n i s m .
T h e c h a l l e n g e, i f s u c c e s s f u ll y m e t a t a ll c a n b e m e t o n l y t h r o u g h l o n g - t e r m p l a n n i n g w h i c h w i l l l i f t t h e v a ll e y s b y d e p r e s s i n g th e p e a k s . M a n a g e m e n t m u s t e x p a n d i t s v i s i o n b e y o n d t h e c o m p l e x p r o b l e m s o f t o d a y t o a n t i c i p a t e t h e u n e n d i n g t o m o r r o w s .
S u c h a c a m p a i g n c a lls , f i r s t , f o r a n a l y s i s o f u n d e r l y i n g p r i n c i p l e s ; s e c o n d , a p r o g r a m f o r f u t u r e a c t i o n , a n d , f in a lly , i n d iv i d u a l a n d g r o u p e f f o r t w h i c h w ill r e le n t l e s s l y f o llo w t h r o u g h . S u c h a c a m p a i g n d e m a n d s c l e a r - c u t d e f i n i t i o n o f m a j o r o b j e c t i v e s a n d u n d e r s t a n d i n g o f w h e r e r e s p o n s i b i l i t y f o r a c h i e v e m e n t lie s.
A s a c o n t r i b u t i o n t o t h e c r y s t a l l i z a t i o n o f c o n s t r u c t i v e p o l ic i e s a n d e n c o u r a g e m e n t t o p r o g r e s s i v e l e a d e r s h i p in m e e t in g t h e c h a l l e n g e o f t h e c y c l i c a t t a c k u p o n t h e A m e r i c a n e c o n o m ic s y s t e m , ' t h e M c G r a w - H i l l P u b l i s h i n g C o . h a s f o r m u l a t e d “ A P l a t f o r m f o r A m e r i c a n B u s i n e s T h i s d o c u m e n t i s p u b l i s h e d a s a s u p p e rn e t h i s i s s u e o f C o a l A g e .
T h i s p l a t f o r m is offered n either as a panacea fo r the autom atic cu rin g of all busi
ness ills no r as the counsel of perfection. It cannot even claim the cheap v irtu e of com plete novelty. B ut the general objectives w hich it sets dow n are fundam ental to the p reserv atio n o f our p resent economic system.
W i t h o u t steady raising o f living
stan d ard s, long-term planning fo r fu tu re b u si
ness grow th, prom otion of international business co-operation, and continued encouragem ent of p riv ate initiative, A m erican business can hardly hope fo r sound com m ercial and social develop
m ent. W ith them , th ere should be few brakes on progress.
W h e t h e r industrial society can com
pletely elim inate peaks and valleys is, of course, debatable. B ut it is an ideal w orth striv in g for, despite the croakings of the fatalists and the in
difference o f the opportunists.
T h e p l a t f o r m fu rn ish es a sta rtin g point fo r the d rive tow ard this ideal. B road as it necessarily is, since it is addressed to A m erican business as a whole, the objectives it states should be common to all business— to coal as well as to drygoods.
Co a l has much to gain by the applica
tion o f these principles to the conduct of its own business. G eneral adoption of the p la tfo rm by in d u stry in the m ass w ould be a boon to coal, since m uch of the present instability in m ining has its roots in the general business u n certain ty which long-term planning would elim inate.
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E le c t r ic a lly O p e ra te d R o ta ry D u m p B u i l t to A l l o w Passage o f a 15-Ton L o c o m o tiv e
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M ECHAN IZATION
+ O f Loading and Top Preparation Recaptures Lost Market
N O W comes W e st V irg in ia w ith a m ine new ly equipped fo r com plete inside m echani
zation and fo r m echanical cleaning 100 p er cent of the m ine output. T his is N o. 9, a 2,500-ton operation of the CarBon F u el Co. a t W evaco, on Cabin C reek, in K an aw h a County.
T h e en tire p ro je c t is based on the m aintenance o f u n ifo rm quality to sa tisfy a m a rk e t fo r a high grade byproduct coal.
T h e com pany w as organized in 1905 an d reached a peak tonnage of 900,000 in 1927. T h is e n tire output w as from the splint seam , and the sam e w as tru e fo r 17 o f the 25 years o f the com pany’s history. In 1916 the com pany first sta rte d m ining the Pow eflton seam , w hich is well know n fo r its high q uality as a byproduct coal. In 1924, m ining o f this coal w as stopped because of high cost of h and loading and th e inability to se
cu re u n ifo rm p rep ara tio n by hand m ethods.
R elative scarcity o f th is particular high-volatile b y p ro d u ct coal, because o f the lim ited to tal acreage, caused th e officials to keep close w atch on p ro g ress in the in d u stry w hich would p oint to a n econom ic plan fo r re
e n te rin g th is m ark et. I n 1928 it w as concluded th a t m echanization w as be
yond the ex p erim en tal stage, so an investigation w as launched to de
term in e th e econom ic possibility of a com bination o f th e m o st favorable m ethods o£ m in in g and outside p re p aratio n . A f te r m ore th a n a year o f stu d y an d consultation w ith ex
p erts it w as decided to open a new m ine equipped w ith m echanical load
ers and a Peale-D avis d ry cleaning plant.
No. 9 is spoken of as a new mine, although headings which w ere driven some years ago are used as the main entry. F ifty thousand dollars was spent fo r grading and new track. T o date, over $500,000 has been invested in the new p ro ject and th e final total will approxim ate th ree-q u arters of a million. T h e cleaning p lan t w as com pleted M ay 1, 1930, and th e present production, practically all develop
m ent w ork, is 800 tons p er day.
R ated capacity o f the cleaner is 250 tons per hour. I t is the intention to mine 2,500 tons in an eig h t-h o u r sh ift but to operate the cleaner fo r ten hours.
A s the entire o utput of the m ine is crushed to 1 in. in a B ra d fo rd breaker, prevention o f breakage was n o t a consideration in design o f the plant. A 1,000-ton concrete storage
bin a t the top of the hill, a portion of a reta rd in g conveyor, and tw o 50- ton steel loading bins of the fo rm er p lan t w ere utilized in the new layout.
M ine cars are unloaded w ithout uncoupling in a single-car rotary dum p operated by electricity. W e ig h ts are autom atically recorded as a source of d a ta fo r cost keeping ra th e r than fo r com puting w ages, as all m en are on a day rate. B y th e pro p er setting o f a fly gate, m ine refu se is directed over a reciprocating feeder and a pan conveyor into a 200-ton re fu se bin a t th e loading term inal o f an aerial tram , and th e coal is directed over a d istrib u tin g -ty p e pan conveyor into the 1,000-ton bin. T h is conveyor, e x tending above the cen ter o f the bin, is equipped w ith several unloading plows.
F ro m th e bottom o f th e bin. th e coal is carried dow n th e hill on a pan conveyor to a sh ak er located high in th e cleaning-plant stru c tu re , 1 hi?, sh ak er is equipped w ith a ty-in, lip screen to facilitate hand-picking of the lum p. T h is p ro d u ct an d a 1x2^- in. size discharge directly into the
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C oal is b ro u g h t fro m th e c o n crete bin by th e co n v e y o r h a v in g th e v e r tic a l a n gle.
R e fu se Is ta k e n b a ck u p th e h ill b y th e s tr a ig h t con veyor1.
M arch, 1931 - C O A L A G E
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S am pling R oom . A and A A re C hutes to T w o L oading B in s; B, Sam ple H o p p e r; C-C-C, Sam ple C onveyor to V ertical C one C ru sh e r; D , C hute fo r D ra w in g Sam ples F rom C onveyor fo r F loat and S ink T ests
B ra d fo rd breaker, which acts as a cru sh er and as the second step in the rejection of im purities.
T h e 1-in. to 0 from the breaker and a p ro d u ct o f the same size from the m ain shaker go to a 40-ton bin feeding the p rim ary table. R efuse from the p rim ary table passes through a 25-ton bin and onto a re-treatm en t table. M iddlings from both tables are retu rn ed to the feed bins of the respective tables. A ir blown th rough the tables is recirculated a fte r relief into the huge expansion space above the tables. Escape, if any, o f dust to the outside a ir from the circulating system is im perceptible.
F R O M the cleaning plant, the cleaned coal is carried by a pan conveyor to a separate building con
taining sam pling equipm ent, v ib ratin g screens, and the tw o 50-ton bins above the loading tracks. By m eans of the v ibrating screens the product can be separated into Ix-V and 4x0 if a special m arket should develop fo r these sizes. A t p resent the screens are bypassed and the production is being shipped as 1-in. to 0.
T h e sam pling equipm ent deserves special m ention because of the p ro vision fo r obtaining tru ly rep resen ta
tive samples. In a chute ju s t beyond the discharge of the clean coal con
veyor there is a fly gate and stopper arrangem ent by w hich the entire stream can be deflected into a small tw o-com partm ent bin. T h e lever actuating this gate is on a floor be
low, w here the operative cannot see the coal on the conveyor and th e re
fore is sp .red the possible tem ptation o f selecting the sam ple by appearance.
120
T h ree 500-lb. sam ples are taken while each railroad car is being loaded. In a crusher each sam ple is reduced to -£-in., and 95 p e r cent is autom atically rejected. T h e rem ain ing 25 lb. is reduced to 20-m esh in a g rin d er and is then collected in a 2-^-gal. pail. T h e th ree pailfuls are then mixed and halved several tim es in a Jones sam pler until a 2-lb. sam ple rem ains. T h is goes to a lab o ra
tory which the com pany m aintains near by, at Carbon. T h e laboratory is equipped fo r run n in g com plete proxim ate analyses.
Cleaning results of the plant have fulfilled all expectations as to ash re duction and uniform ity. T h is is es
pecially g ratify in g to the officials, in view of the fact th a t they realize th a t the mechanical loading complicates the attaining of this m uch desired uniform ity. A s is usually the case, the inherent ash varies slightly in different sections of the mine. W ith hand loading the coal m aking u p one railroad car would come from fifteen to tw enty different places in the mine, but w ith mechanical loading a m ine- c a r tr ip carrying sufficient coal to load one railroad car usually comes from about tw o places in close proxim ity.
T h e latter is tru e because the activity of a g athering locomotive is confined to one w orking place until th a t place is cleaned up. A lthough the coal in two railroad cars m ay come from widely separated places in the mine, the average difference in ash content seldom exceeds 0.5 per cent. T he averages of daily analyses never vary over approxim ately 0.2 per cent ash.
R efuse from the picking table, B rad fo rd breaker, and re-treatm ent
table is carried up the hill on a flight conveyor to the 200-ton re fu se bin.
T h e aerial tram is a T ren to n -B lei- chert continuous type m a n u factu red by th e A m erican Steel & W ire Co.
T h e present capacity of 60 tons per hour can be increased to 90 tons by adding buckets and installing a larg er tractio n rope.
T h e entire plant, including the item s of old equipm ent utilized, is o f con
crete and steel. T h e ro ta ry dum p an d hillside conveyors w ere built by the K anaw ha M an u fa c tu rin g Co., and the cleaning plant, including sam pling a p p aratu s and v ib ratin g screens, by the F a irm o n t M ining M achinery Co.
T h e coal com pany specified the elec
trical equipm ent and purchased and installed the w iring.
T h e 29 electric m otors o perating th e plant, and totaling 582^- connected horsepow er, are all of G eneral E lec
tric m an u factu re and are w ound fo r 220 volts a.c. M ost o f them are 900 r.p.m . N ineteen are type F T R squir- rel-cage and the largest o f th is type is 25 hp. E ig h t are the type M T slip -rin g ran g in g fro m 20 to 60 hp., and one, th a t driving the p rim ary fan, is a 100-hp. type T S 80 -p er cent p o w er-facto r synchronous m otor, iia ch o f the tw o M T m otors d riving the p rim ary table is rated 25 hp. con
tinuous, and 40 hp. fo r 8 m inutes.
T h e actual o p eratin g dem and of the plant is 320 kw.
Three 100-kva. and th re e 25-kva.
tra n sfo rm e rs handle the p lan t load.
M o to r-sta rtin g equipm ent consists of T ru m b u ll safety sw itches an d G en
eral E lectric m agnetic controllers.
P u sh buttons controlling th e cleaning plant are grouped on a panel betw een the tw o tables. P ilo t lam ps indicate w hen m otors are in operation. All w irin g is in rigid conduit. In the plant complete, including headhouse, th ere w as used 5,670 ft. of conduit in sizes from 4 to 4 in. inclusive, and 83,000 ft. o f insulated w ire.
S IX types o f m o to r-d riv e connec
tions are used. T hese a re nine g e a r reducers, six V -belts, ten flat belts, tw o Reeves variable-speed belts, one g e a r train, and one silent chain.
1 he silent chain is used on the B ra d ford breaker, th e Reeves tra n sm is
sions are used on the table feeders, and the g ear tra in is on th e aerial tram . M ost of the flat belts are on th e old equipm ent th a t w as utilized in the new layout. T w o Ideal lubrica
to rs handle the rem ote g reasin g o f all bearings in the cleaning plant, except m o to r bearings.
W o rk in g height in the m ine av e r
ages 9 ft. 2 in. E ig h teen to tw enty- C O A L A G E — V o l.36, N o .3
U nderground at M ine No. 9 of Carbon Fuel Co.
L o ad in g th e Second C u t o f a B re ak th ro u g h W ith a Jo y
Face o f 16-Ft. H e a d in g W ith S late R aked O u t A fte r H a v in g B een C u t an d S hot. N o te T h re e S h othoies in U p p e r B ench o f C oal
Face F u lly P re p a re d and S w ept o f Im p u ritie s R eady fo r S h o o tin g th e C oal
T h is G o o d m an P o w er S hovel W o rk s in 30-Ft. R oom s
M y e rs-W h aley L o a d in g O u t the T h ird C u t o f
an E n try B re a k th ro u g h
M arch, 1931 — C O A L A G E
121
A t Left, Incom ing P a n e l; at R ight, Synchronous M o to r and C o n tro ls of P rim ary Fan
fo u r inches of top coal is left and there is a 2 - ft. band of very hard slate about 3 ft. from the bottom . T his band is rem oved and the w orking place is sw ept clean before the coal is shot down. Coal is cut w ith track- m ounted slabbing m achines ju s t over or ju s t below the parting, and a fte r the slate is shot the la tte r is raked out by the same machine. A t one visit the loading m achine loads the slate and at the next visit it loads the coal. Coal cuttings are loaded by hand.
A
r present four loading units are operating in the mine. Two M yers-W haley loaders and one Joy loader are d riv in g 16-ft. headings and a Goodm an hydraulic shovel is d riv ing room s in experim ental blocks.T h e M yers-W haley and Joy units are being double-shifted. It is the e x pectation to drive room s 30 ft. wide and 200 ft. deep on 40-ft. centers, gobbing as much, of the slate as pos
sible along one rib and taking a slab
bing cut along the other, leaving a 3 -ft. pillar. Because the coal is very soft, sloughing of the ribs will soon cause a 3 -ft. pillar to weaken and allow roof caving. It is recognized th at natural conditions or lim itations of equipm ent may call fo r a change
to some other m ethod of w orking the rooms.
T he main entry consists of fo u r parallel headings and runs a p p ro x i
mately through the center of the body of coal assigned to the mine.
Four-heading cross-entries are tu rn ed to the right and left at rig h t angles and have all breakthroughs d riven at approxim ately 45 deg. to facilitate speed in transportation. T h e plan for these breakthroughs is projected fo r some weeks ahead, in o rd er to bring about speed of e n try driving and secure the desired haulage lay
out. Triple-heading b utt entries, off which the room s are driven, are turned to right and left 90 deg. off the cross entries, th u s m aking them parallel to the m ain entry.
Inside equipm ent in addition to the loading machines now consists of fo u r General Electric 8-ton cable- reel locomotives w ith contactor con
trol and open equipm ent, one Jeffrey M ain C on tro l Panel on G a llery B etw een
Prim ary and R e-treatm ent T ab les
15-ton m ain-haulage locom otive, one G eneral E lectric 15-ton locom otive w ith T im ken jo u rn al b earings and contactor control arran g ed fo r d y n a
mic breaking, fo u r G oodm an slab
bing m achines fo r center cutting, one S ullivan self-propelling coal drill, and th re e Chicago P n eu m atic p o rt
able electric coal drills. I t is the in
tention to use track -m o u n ted drills in room s and the others in headings.
T h e cost of a m echanical loading u n it consisting of a loading m achine, loco
motive, m ining m achine and drill is- in the neighborhood of $25,000.
O
N the m ain haulw ay, w hich is:about tw o miles in length, 60- and 75-lb. steel is used and th e 6x6-in.
x 6 -ft. ties have been im pregnated w ith W o lm an salts at the coal com p an y ’s tre atin g p lan t ( Coal A g e , V ol. 35, p. 3 4 3 ). P o sts, headers, and cap pieces used on this h a u lw ay also are of trea ted tim ber.
Jo in ts of both rails are double
bonded, in o rd er to tak e full adv an tage of the track as a conductor. T he bond on the inside o f the jo in t is a 2 / 0 long bond and th at on the o u t
side is a 4 / 0 U -shaped bond. B oth are electric w elded. E v e ry fifth rail is cross-bonded. T h e trolley w ire, consisting of “ N o. 9 ” section, is paralleled by a 500,000-circ.m il feeder. L ights w ith angle reflectors, to prevent glare in the eyes of the- m otorm en are installed opposite each m anhole.
M ine-car equipm ent consists of 300 com posite, solid-body cars of 152-cu.ft. capacity m ade by the K an aw h a M a n u fa c tu rin g Co. T h ey a re equipped w ith T im k en bearings, four-w heel brakes, and sp rin g d ra w b a r in one end.
T h e plant and all equipm ent in d i
cate a progressive a ttitu d e on the p a rt o f a m anagem ent w hich has been in charge of the com pany’s affairs fo r m any years. T h e president, C. A. Cabell, w as one of the fo u n d ers of th e com pany. L . N . T h o m as is vice-president in charge o f operation and W . G. M agee, vice-president in charge of sales. K . D . O u a rrie r is general su p erin ten d en t and C. A.
P e a rse is su p erin ten d en t in charge o f the N o. 9 mine.
122
C O A L A G E — V ol.36, N o .3 'SPOTLIGHTING
Variables and Constants In Coal Production Costs
T
H E broad use of the word“econom ics,” as applied to a p articu lar industry, covers such a w ide range th a t it m ay m ake for clarity if it is explained a t the be
ginning th at, as used in this article, its m eaning is restricted to denote the science w hich investigates the m eans by w hich an in d u stry or en ter
prise obtains the profits necessary or desirable fo r im provem ents, expan
sion, and dividends. A pplication of this science involves an exam ination of the stru c tu re and organization of th e business o r in d u stry w ith re fe r
ence to the factors w hich influence its earn in g ability.
E ach in d u stry and individual en terp rise has its ow n distinct eco
nom ic characteristics. In m ost in
d u strie s, and in m any private corporations, these have been studied, form ulated, and analyzed in either public o r p riv ate rep o rts, and are periodically b ro u g h t up to date. In th e coal in d u stry several such studies, m o re o r less com prehensive, have been privately m ade by individual com panies, b u t th e re has been little exchange of in fo rm atio n as to m ethods used o r results obtained w hich w ould guide o th ers in devising a sound pro ced u re fo r the develop
m en t of essential economic facts o r in m aking accu rate deductions from de
veloped facts.
T o the e x te n t th a t these facts are know n and p ro p erly used by the mine m anagem ent in determ ining the course of a com pany, e rro rs of ju d g m en t are autom atically elim inated.
T h e num ber of failu res which, year a fte r year, m ark th e h isto ry of the coal in d u stry , how ever, w ould appear to indicate a need fo r a b ette r u nder
standing o f the econom ic principles un derlying the production and m a r
keting of coal on the p a rt of those w ho have direction o f th is work.
By ERNEST L. BAILEY
It is tru e th at, d u rin g the disturbed economic conditions w hich existed during and im m ediately a fte r the w ar, m any m ines w ere opened w hich had no real chance to survive, be
cause of some fundam ental economic w eakness ; and these have c ontributed in im portant m easure both to the present depressed condition of the industry and to th e m orgue of de
funct mines. T h e circum stances under w hich m any o f these m ines w ere developed w ere such th a t no criticism is justified, as they w ere brought into existence to m eet w a r
tim e needs.
It is likewise tru e th a t since those days; in the face of a know n devel
oped productive capacity fa r in e x cess of the norm al peak requirem ents
W ith large in d u strial con
sumers definitely com m itted to the slim waste line in th eir fuel diet, alert coal-m ine m an
agem ent is becom ing m ore keenly conscious o f the fact th at financial success fo r the operator lies in the subordina
tion o f p lan n in g fo r p ro d u c
tion to p lan n in g fo r profit.
T he m ajor problem is n o t how much volum e can be pushed up but w hat can be done to sell at a profit the tonnage fo r which there is a ready and a logical m arket. M r. Bailey here outlines an approach to the solution of this problem in the abstract. T h e direct application o f the principles of profit engineering to a con
crete case in the coal-m ining industry w ill be show n in a n other article to be published in an early issue of Coal Age.
W a d lcig fi & B a iley, W a s h in g to n , D . C.
of the m arket, a num ber of new m ines have been opened and the ca
pacity of m any already existing m ines has been g reatly increased.
C um ulative forces will be directed tow ard the stabilization of the coal m ining in d u stry as a whole in the de
gree th a t the essential economic fac
to rs o f each individual m ine are developed and applied to th e conduct of its business. A t the root o f any economic investigation lies the con
ception of a stan d ard of earnings on invested capital com m ensurate w ith the risk involved.
F ro m the am ount o f m oney lost yearly in poorly conceived o r badly m anaged coal m ines, one m ight readily be led to in fe r th a t th e in vestors in this in d u stry do n o t d e
m and or expect the sam e evidence of stability and earning pow er th a t is dem anded by investors in o th er in
dustries. Such inference, of course, is erroneous, as the expectation o f a sound profit is the sole basis fo r any investm ent. T h e coal in d u stry differs only in th a t th e bases fo r expected profit are not ordinarily subjected to the same searching analysis neces
sarily applied w here public invest
m ent participation is expected.
M ost coal-m ine investm ents m ade in recent years fall into tw o classes : 1. Investm ents m ade fo r th e p u r pose of increasing productive ca
pacity, based on the th eo ry th a t increased production, giving rise to low er u nit costs, would resu lt in increased profits.
2. Investm ents fo r p lan t and m ine rehabilitation and m odernization, from w hich low er u n it costs could be expected to result.
T h e first class o f investm ent has
M arch, 1931 - C O A L A G E
123
been peculiarly enticing to m any coal producers. T h e usual line of reaso n ing is the com pany now has an in
vestm ent in plant and equipm ent of, fo r exam ple, $3 per ton of annual productive capacity; m any of the m ajo r units a re capable of substan
tially increasing p erfo rm a n c e ; the lim iting facto r to production prob
ably is a few item s of equipm ent, the provision of w hich w ould equip the m ine to produce 25 or 50 p er cent m ore coal, and the additional tonnage could be realized w ith an investm ent of only $1 p er to n of added annual capacity, leading to decreased costs, and increased profits.
I f production w ere the only factor to consider the reasoning would be entirely sound, as an .im proved load factor on fixed charges and lower o perating costs would result. E a rn ings, how ever, depend upon the ability to sell the product at a profit, and plant expansion is justified only w hen a profitable outlet is reasonably assured.
C
O A L d iffers from m ost basic com m odities in th a t the price, w ithin reasonable lim its, exercises little o r no influence on consum ption.T h e im p o rtan t g ro w th of substitute fuels in recent y ears has, in practically no im p o rtan t instance, been based on th e econom y of th e substitute. T h e p resen t price of coal a t the mine m outh could be doubled and. except in u n im p o rtan t districts, it w ould still rem ain th e co u n try ’s least costly fuel.
Because of certain characteristics peculiar to th e coal in d u stry , the law o f supply and dem and does not op
erate as a price stabilizer to the same degree as in o th er basic industries.
T h e tem p o rary closing of a devel
oped m ine o rdinarily is an expensive m easure, the contem plation of which too frequently leads to a decision to continue operation a t a loss until prices im prove. Seasonal fluctuations in consum ption (am o u n tin g to ap proxim ately 35 p e r c en t) also are an im p o rtan t factor. P roductive capacity o f the in d u stry m ust be kept above th e norm al peak requirem ents o f th e country in o rd e r th a t an ade
quate supply o f fuel at all tim es will be assured. A n industry' equipped fo r such peak requirem ents m ust necessarily operate a t reduced speed d u rin g the periods o f low consum p
tion, w hich, u nder existing condi
tions, also are th e periods o f low est prices.
T o expect the in d u stry as a w hole to w o rk out and apply any broad.
constructive m easures of im prove
m ent seems useless. Each individual producer m ust determ ine fo r him self the proper balance of all factors which enter into his p artic u lar costs of producing and selling coal and a d ju s t these to the variations in dem and and price.
F ro m an economic view point the determ ination of a proper selling price should be dependent not upon the m arket but upon the over-all cost of production and distribution. If, a fte r all sound cost-reduction m eas
ures have been applied, a p articu lar producer finds him self above the m argin, because of an artificially de
pressed m arket or by reason of a d verse natural conditions o r an
©Undertcood & Vnderxcood
E rnest L. B ailey
in ferio r product, only one logical step rem ains: th a t is to close dow n until a period of readjustm ent has bro u g h t about sufficient change in conditions to ju stify the resum ption of opera
tion.
T h ere will be unavoidable periods, however, when the total num ber of m ines required to m eet peak con
sum ption will not be able to operate at capacity because of fluctuating de
m and. T h e re fo re, it becomes nec
essary to analyze carefully the n atu re of production costs u n d er varying percentages o f capacity operation, in o rd er th a t an intelligent price m ay be quoted d u ring the off-peak season.
E ven though the producer consider it good business to continue in opera
tion and tem porarily take a loss on his product, he should at least know in advance a t w hat ra te o f operation an available price will result in the least loss.
A n analysis of production costs
will show th a t they fall into th ree general c la sse s:
1. C onstant T o ta l and Variable U nit Costs— C ertain item s of cost a re fixed as to am ount, regardless of the tonnage produced. T h ese are constant total costs and give rise to variable u n it costs dependent upon the production over w hich they are spread. T hey include such item s as taxes, insurance, depreciation, in te r
est, m inim um royalty (if in excess of earned ro y a lty ), re n ts fo r sales offices, and expenses of like character.
Salaries also fall in this class, b u t differ in th a t they are su b ject to a d ju stm en t. L e t us assum e th a t these fixed charges am ount to $10,000 per m onth fo r a m ine hav in g a m onthly capacity of 50,000 tons. I f the m ine w ere o perating at capacity th e u n it cost o f fixed charges w ould be 20c.
p er ton. I f , how ever, th e m ine is operating a t only 50 p e r cent capac
ity, th e u n it cost is 40c. p e r ton, or if at 25 p er cent capacity it becomes 80c. p er ton.
2. Constant U nit and Variable T o ta l Costs— C ertain o p eratin g costs (a n d sales costs if on a com m ission b asis) vary as to totals, but are con
sta n t as to units. T h ese include such item s of labor as a re paid fo r on a contract o r piece w ork basis, th e cost of w hich rem ains relatively constant regardless of the am o u n t o f coal produced.
3. Variable U nit and T o ta l C osts
— C ertain o ther op eratin g costs v ary w ith respect to both u n it and total values, and are influenced by th e to n nage produced. T h is class includes day labor, pow er, m aterials and su p plies, etc. A close exam ination of this class of costs will reveal th a t they p artak e som ew hat of th e ch arac
te r o f both th e o ther classes. T h a t is to say, w hile the m ine is o p eratin g a t all th ere will be a certain m inim um p a rt of each item th a t will rem ain relatively constant, reg ard less o f the volum e o f production, such as tipples expense, pow er, haulage, drainage, ventilation, etc. W h e n p ro d u ctio n attain s or passes th e figure fo r w hich this m inim um is adequate, a m ore n early constant u nit cost results.
T o estim ate th e u n it cost w hich m ay properly be expected to re su lt fro m varying percentages o f o p era
tion, each item of to tal cost m u st be studied and its v ariations w ith respect to o u tp u t determ ined fo r each in dividual mine. F ro m such an analy
sis a m inim um selling price fo r a given tonnage m ay be intelligently determ ined.
124 C O A L A G E - V ol.36, N o .3
■SECOND O F A S E R I E S O F A R T IC L E S O N T H E F U N D A M E N T A L S O F M O D E R N C O A L P R E P A R A T IO N
C O A L PREPARATION PLANT
+ The Structure That Houses It
E
V E R Y s tru c tu re bears a relation to its su rro u n d in g s, to' its com panion stru ctu re s, an d to its contents. E ach of .'these relationships m u st be considered by th e designer if he is an y th in g m ore th a n a^ m ere d ra ftsm a n , an d th o u g h th e utilitarian view point m u st alw ays, in the last analysis control th e design, th e re are g rea t differences in th e w ay a th in g is done and in the sp irit w ith w hich the problem is approached.
A s tru c tu re should have in itself a so rt o f beauty. W e a re likely to con
sider only th e m echanical _ req u ire m ents of the stru c tu re, b u t it is also possible to keep in m ind th e need fo r a certain sym m etry of p ro p o rtio n and outline w hich will m ake the stru ctu re pleasing to the eye and in harm ony w ith its su rro u n d in g s, converting a stru c tu re th a t is m erely u sefu l into one th a t is also b eau tifu l. T h e re is no reason w hy w e should cover our co u n try w ith arch itectu ral m onstros
ities. W h y cannot th e engineer ab
sorb a little of th e sp irit of th e arch i
tect, to w hom a stru c tu re is a w ork o f a r t as well as a m achine? T h e lines of sym m etry are based largely on th e in n er functions of the stru c
ture. A ll n a tu re m oves on th e lines of least resistance. A stru c tu re de
signed to c a rry loads an d stresses m ost econom ically and w ith m inim um deflections will generally be pleasing in p roportion and outline. M uch of our predisposition to “ dog houses’
and “ lean-tos” is due to sheer care
lessness or to a fa ilu re to visualize the industrial fu n ctio n s f o r w hich p ro vision m u st be m ade.
In its general design a stru ctu re should fit its su rro u n d in g s. I t should be harm onious in line an d color w ith the neighboring u n its of the plant. I t should use m aterials th a t offer h a r
m ony o r a pleasing c o n tra st w ith the environm ent and should express, M arch, 1931 - C O A L A G E
w ithout ostentation o r excessive adornm ent, som ething o f the serious purpose fo r w hich it is built. M ate
rials should alw ays be local w here possible, th u s giving a stru c tu re a definite local character. F o reig n m aterials o ften m ake a building look like a pom pous and unw elcom e stran g er in u n fam iliar surro u n d in g s.
T he design of th e fram ew o rk should be based on the equipm ent it
A nd rew s A llen
contains. H e re again is th e old ques
tion of the egg or the hen. Shall we build a stru ctu re and p u t the m a
chinery into it, or shall we design th e m achinery and build th e stru ctu re w ith an intim ate and essential rela
tion to each p a rt of it? B oth m ethods have their place. M any p rep aratio n structures contain equipm ent w hich consists of m any relatively sm all and self-contained units. W h e n arran g ed in groups they natu rally fav o r a structure having definite floors o r stories w here these units can be set
By ANDREWS ALLEN
A lle n & G arcia Co.
C o n su ltin g & C o n stru ctio n E n g in eers C hicago
and m ade trib u ta ry to th e general a rra n g em en t fo r h andling m aterial to an d fro m them .
T h e re are m any m echanical units in a m ining plant, how ever, w hich m ust be definitely provided fo r and w ro u g h t into the stru ctu re. P ro v i
sion fo r p ro p er flow of m aterial at suitable speeds and w ith o u t breakage fixes th eir vertical and horizontal re lation. T h e accessibility of p a rts w hich req u ire atten tio n determ ines the location of w alkw ays, p latfo rm s, and stairw ays. T h ese do n o t usually lend them selves to predeterm ined floor levels and a p rearran g ed spacing of colum ns. O n the o th er hand, no system of coal handling o r p re p a ra tion can be regarded as a finality.
T h e a rt is m oving fo rw a rd ra p id ly ; the requirem ents of th e m ark et change fro m y e a r to year, and som e
tim es fro m m onth to m onth. I f th e m achinery is too closely tied in w ith the stru ctu re, th e arran g em en t is too inelastic and changes are too difficult to make.
H e re is w here th e experience o f the designer comes in. H o w can the stru c tu re and m echanical re q u ire
m ents be properly harm onized and at the sam e tim e sufficient latitu d e be provided fo r fu tu re changes?
T h is requires m uch stu d y and a th o ro u g h consideration o f the changes w hich m ay be req u ired to su it fu tu re conditions. A m ple clear
ances betw een u n its will o fte n p rove a life-sav er w hen changes are neces
sary. I t is also im p o rtan t to allow am ple space and facilities fo r m ov
ing and handling any u n it into o r o u t of th e plant, and to consider th e loca
tion of possible fu tu re conveyor lines by w hich portions of m aterial m ay be
125
tra n sfe rre d to some new o r ex p eri
m ental equipm ent. W h en a stru ctu re has been am ply designed, as fa r as space is concerned, th ere usually will be little trouble in m aking changes to fit new equipm ent. W h en changes are necessary, the m odern cutting torch and welding outfit will m ake it possible to do a neat an d substantial revam ping job in half the tim e and fo r half the m oney it form erly cost.
O fte n the lim itations as to cost a re so stringent th a t it seems neces- sarv to crow d and skim p in planning an arrangem ent. I t usually happens, however, th at, w here such a program is undertaken, the saving in cost is m ore ap p aren t than real. A better p ro g ram generally will be to space the m achinery as it should be and use
T hus, a screen ru n n in g 100 r.p.m ..
w ith a 6-in. stroke will produce a horizontal force equal to 100 per cent of the w eight of th e screen itself plus the w eight of th at p roportion of the coal (usually on e-h alf) w hich can be regarded as being anchored to it.
W h en this force has been d e te r
mined, it should be taken dow n into the foundations and enough w eight provided to prevent u p w ard reactions at any column. S tru ctu ral steel m em bers should be proportioned to resist an impact equal to at least 300 per cent of the load. T h is, how ever, de
pends on the length of the bracing members. L ow er u nit stresses (th a t is to say, higher im pact values) should be used w here the distance from screen drive to foundation is
upon it, b u t it does not alw ays pay to do so. Good engineering dem ands th a t th e fu llest consideration be given to econom y of m aterial and labor. In d ep en d en t piers fo r heavy v ib ratin g u n its are freq u en tly used w hen the foundations are good and no t too deep.
W h e n such separate fo u n d atio n s an d stru c tu re s are constructed, light an d high stru ctu res escape those cum ulative vibrations w hich would otherw ise req u ire a heavier and m uch b e tter braced building. I f horizontally oscillating screens are set even a t a reasonable height above gro u n d and re st on separate foundations and stru c tu re s, m uch concrete m ust usually be added in o rd er to provide the w eight necessary to hold them dow n, w hereas if the screens are su p p orted on the m ain stru ctu re, th e floors and o ther co nstruction usually have sufficient w eight fo r this p u r pose.
cheaper m aterials, such as tim ber in place of steel, o r to use steel only w here it is necessary to keep the stru c tu re from d istortion o r w arping.
In general, shaker screens and th eir drives, centrifugal d ry ers o r cru sh ers, and sim ilar heavy vibrating m a
chinery should have th eir supporting stru ctu res specially designed fo r them.
A shaker screen, even if balanced, produces severe horizontal alternating stresses. T hese m ust be resisted by w ell-proportioned m em bers designed to take care o f all stresses, both in the m em bers them selves and in th e ir joints. T h e follow ing form ula fo r horizontal stresses from screens is in rational form , but the constants have been determ ined or modified by e x perience, w ith the idea of developing a form ula w hich can be followed in designing a stru ctu re fo r operating conditions :
F = W X A’2 X i - r 60,000 w here V
= h o rizo n tal fo rce in pounds ; IV — w eig h t of screen in pounds plus about h a lf th e load in g ( th a t p ro p o rtio n o f th e load w hich acts as if anchored on the screen ) ; R — rev o lu tio n s per m in u te ; .S' = length o f stro k e in inches.
m ore than 30 or 40 ft., unless the load can be absorbed by bins or heavy floors betw een the screen and
the foundation.
T he unit stresses o r im pacts adopted in a stru ctu re carry in g heavy vibrating m achinery should be chosen fo r deflection ra th e r than actual strength, and fo r this reason it is not necessary to carry the same im pact into the calculation of rivets, in w hich case 100 per cent im pact generally should be sufficient. C are need be taken only to see th a t the jo in ts are central and sym m etrical, and th at th e metal is heavy enough to hold the rivets. A little spring in a connection angle th a t is too thin can throw quite a whip into a stru ctu re w hich o th e r
wise would be strong enough.
W h eth er foundations o r stru ctu res shall be provided independent of the m ain building is largely determ ined by relative cost and convenience.
T h ere is no such w ord as “ im pos
sible” in stru ctu ral engineering. A stru ctu re can be designed of suffi
cient stren g th and stiffness to take any loads o r stresses th a t m ay come
W
H E R E screens are placed above bins, the w eight of the s tru c tu re helps g reatly to produce stability and stiffness, b u t w here screens are below the bins, the effect is precisely oppo- s:te. A little m otion in the screen or driv e su p p o rts m ay s ta rt cum ulative vibrations to an alarm in g degree. O f course, it w ould be u sefu l to know the vibration period of a s tru c tu re as a whole or in p art, but in practice it is alm ost im possible to d eterm in e this essential facto r in advance w ithin th e tim e available fo r m aking a design.W e m ay discover it a fte rw a rd in a disagreeable w ay if it happens to coin
cide w ith the v ibration period o f o u r m achinery. W h e n synchronous v ib ra tions are encountered, it is usually possible to counteract them e ith er by deliberately changing the v ibration period of the s tru c tu re o r the speed of the v ib ratin g m em ber, o r by p ro viding additional b racin g designed to
e x e rt force duly calculated to resist the v ibration of a know n w eight w ith period and am plitude determ in ed by observation.
A stru c tu re alw ays should be so designed th a t it will "take care o f acci
dental stresses, such, fo r instance, as the o v er-strain in g of a belt, rope, o r chain to the b reak in g point. In o th er w ords, the stru c tu re should n ev er be the w eak link. A s above stated, a m ining stru c tu re should be designed fo r stiffness and n o t p rim arily fo r stren g th . Beam s should be p ro p o r
tioned in ratio of d ep th to length to give the req u ired stiffness, unless th e requirem ent of stren g th should be g reater.
126 C O A L A G E — Vol.36, N o ,3
T h e resu lt should be a stru ctu re th a t does not sw ay perceptibly in any p a rt and w here the only im pression to o u r senses is a so rt of “healthy” m ill
ing v ib ratio n som ew here “betw een a shake and a so und.” W ith a stru c
tu re of this kind m aintenance of equipm ent is less troublesom e, for p a rts do not shake loose as they so o fte n do in flimsy stru ctu res. T he o p e ra to r can well afford to build a substantial s tru c tu re to house fine expensive m achinery, b u t often the stru c tu re is the last consideration left to the m achinery designer and the cost is lim ited to w hatever m oney may be le ft over.
F ew stru c tu ra l engineers are cap
able or experienced in designing stru c tu re s f o r sup p o rtin g heavy v ib ra
tin g m achinery, and every year stru c tu re a fte r stru c tu re has to be braced and stren g th en ed because of inade
q u a te stre n g th o r stiffness and lack of skill on the p a rt of the designer.
T h is is o ften tru e even w here there is am ple or even excessive metal in the stru ctu re.
M uch m ay be said of the form and type of construction in steel and con
crete. A s tru c tu re should be com
posed of relatively large members w ith w ide spacing. T h is is done to m inim ize the nu m b er of joints, to facilitate bracing, and frequently to save m etal. W h e re panels are not fixed by the requirem ents of m a
chinery or o th e r positive conditions, it m ay be possible to determ ine the economical panel spacing by a p re lim inary calculation balancing the w eight of colum ns ag ain st the floors and w orking fo r a spacing w hich will give a m inim um cost per square foot.
In steel th e b racin g should be diag
onal, eith e r single o r double, and c ar
ried to the g ro u n d in continuous lines so as to take care of any com bination of vib rato ry stresses.
Special care should be used to avoid the possibility of ro ta ry vibration. In one case in m y experience, a high stru c tu re on the top of which was a M arch, 1931 - C O A L A G E
fast-ru n n in g shaker screen vibrated seriously. O n analyzing the situ a tion I discovered th a t th e vibration was ro tary and a p a ir of vertical X braces a t rig h t angles to the axis of the screen and sym m etrically d is
posed to it cured the tro u b le com pletely. I t does not follow, therefo re , th a t the bracing to control vibration need necessarily be placed in the d irec
tion of the forces w hich cause the m ovement. W h erev e r vibration is en countered in a stru c tu re it is m y p ra c tice to study the situation carefully by m easuring or sensing the direction and am plitude of the deflection at each point, then carefully studying and com bining the results, and decid
ing accordingly.
Bracing m em bers should be capable of taking both com pression and te n sion. T hey should generally be double and sym m etrical to the colum n section. R od bracing or single-angle bracing can be used in roof w ork o r light stru ctu res w hich do not have to resist vibration, but they have no place in a stru ctu re carry in g vibratory load.
A pair of angles w ith batten s or lacing m akes a good brace and one can occasionally use an I-beam o r H - beam, o r even a channel connected by the flanges. C olum ns usually are composed of C-beam s or H -beam s.
w hich in recent years have come to such a variety of uses. T h e re are
places in some stru ctu re s, how ever, w here a p air of laced channels is still preferab le. T h is is especially tru e w hen th ere are tw o sets o f bracin g at rig h t angles to each o th er attached to the sam e column.
T h e stren g th and sim plicity o f the connections in such cases com pensate fo r the additional cost o f th e colum n sh afts. W h e re laced channels are used it is generally possible to use
“ tw o -riv et” lacing bars, so th a t th ere are no pockets fo r w ater o r coal dust.
By spacing the lacing b ars a t a w ide enough angle, it is alw ays possible to obtain plenty o f room fo r p ainting and cleaning th e inside o f th e colum ns.
C oncrete has contributed en o r
m ously to the stren g th and stability of m ining stru ctu res. It can be used alm ost anyw here except w here m ini
m um depths and close clearances or attachm ents o f m achinery are neces
sary. E ven concrete h ead fram es are a com plete success and provide rigidity and sufficient stren g th at low cost.
Steel m em bers subject to d e te rio ra tion can be incased in concrete to p re serve and stiffen them . Concrete floors are practically stan d ard in the b e tter class of m ining stru ctu res, and th ere is practically no lim it to the e x ten t to which concrete can be used, except w here it involves expensive
form w ork.
In steel, the use of electric w elding has already m ade g reat progress, and it will not be long b efore we shall have completely w elded m ining stru c tu res. T h is is a new a rt of fab rica
tion and will require a new technique.
So fa r its use has been largely a u x il
iary. All bridge trees fo r screens and heavy m achinery should be welded, even if also riveted.
C onveyor bridges and such m em bers as are expensive to fabricate by the old m ethods can be w elded as a m atter of economy. B ins can be welded in the field w ith only enough bolts to hold them to g eth er properly fo r welding. T ig h t bins are th u s p r o
vided at no additional cost. L ast, b u t not least, m uch shop detailing can be elim inated by w elding such light m em bers as stairw ays, g irts, railings, conveyor bridges, etc., th e design of w hich congests and slows u p a d r a f t
ing room , som etim es delaying the draw ings o f m ain m em bers fo r a few unim portant connections.
A s to covering, w e have n o t yet attained the C ontinental stan d ard of brick-filler w alls in steel stru ctu res.
P e rh ap s o u r stru c tu re s v ib rate so m uch that we are a fra id th a t brick or tile will n o t stand up. I f this is the reason, it is no th in g to be proud of.
O f course, the w eight of the stru c
tu re is increased by brick o r tile, but this is by no m eans a disadvantage, as o u r stru c tu re s generally are too light.
In m any cases in which I have made a com parison, the cost of brick o r tile curtain w alls is not at all out of line.
O u r stan d ard covering is co r
rug ated steel, usually galvanized.
T he best grades arc relatively cheap an d are fairly tight, though, of course, they do n o t hold th e heat.
R o o fs m ay be of th e sam e m aterial o r o f concrete tile, w hich is better and much m ore sightly. T ra n s ite and asbestos-protected m etal are excellent m aterials eith er f o r roofing o r siding.
I
T usually is desirable to provide tight skylights fo r lighting purposes only, a n d fo r ventilation it is better to use m etal ventilators and w indow s th an to attem p t to use op eratin g skylights o r saw - tooth construction, w hich so freq u en tly leaks.
T h e re is no reason today fo r not u sing steel w indow s a n d doors. Steel sash are cheaper and m uch b e tte r than wood, and steel d o o rs give m ore class
to a stru ctu re th an any o ther equal expenditure.
O utside p latfo rm s and stairw ays should be made of subw ay gratin g , w hich is safe, strong, and reasonable in cost. T h is practice should be fo l
lowed also fo r in terio r p la tfo rm s or stairw ays in dusty stru ctu res ; o th e r
wise, the best stairw ay construction consists of treads of inverted ch an
nels filled w ith concrete, and p la t
form s o f concrete on steel. W ood stairs and platform s are excellent in m any ways, easy on the feet, and in expensive. but frequently are objec
tionable because of the fire hazard and lack of perm anence.
In designing a stru ctu re, it m ust be borne in m ind th a t the m ere fact that steel and concrete are used does not necessarily m ake the building fire
proof. It is possible to experience a very hot fire in a stru c tu re th at has little wood about i t ; even only a few g irts, floors, or stairw ays. I f these are well soaked in oil an d co’-ered w ith coal dust, they will produce a fire c a b b ie of w arping o r seriously dam aging alm ost any steel o r con
crete structure. Som e of the fire hazard is elim inated by u sing steel.
T h e entire hazard can be rem oved only by proper protective coatings, such as are approved by the boards of fire underw riters or by th e use of autom atic sprinklers.
L ast and least we have tim ber con
struction to consider. It has carried us over a period of rapidly developing industries. It has served us w hen no other m aterials w ere available, and now m ust be satisfied to rem ain as an auxiliary m aterial and fo r use in tem porary or hastily built stru ctu res.
E ven the design of a tim ber stru c
tu re is largely fo r th e c a rp en ter and n o t th e engineer. V e ry few stru c tu ra l engineers know, a n y th in g about tim b er construction, as w as clearly in dicated by the resu lts of m any years of engineering license ex am ination in a certain state. T h e re w as alw ays one problem in tim b er construction, and the answ ers w ould have niade a good bedtim e story. T im ber,-how ever, is a w o n d erfu l m aterial. I t has unique possibilities in m any directions and w hen p roperly used should still fill an im p o rtan t place in engineering con
struction. F ew engineers know how to m ake a jo in t in -timber— w ell, let them learn.
T im b er w arps, shrinks, cracks, and decays. A know ledge o f its failings should regulate its use. A certain q u an tity of steel should generally be used in a tim b er stru c tu re to keep it tig h t and in line. T im b er, if of good quality, will last a long tim e w hen p ro p erly protected o r im pregnated w ith a preservative. I t should be used in engineering stru c tu re s hav in g a sh o rt projected life o r w here radical changes m ay be m ade th a t cannot be readily foreseen. H eavy, “ slow - b u rn in g ” construction is f a r p re fe r
able to flimsy steel, and is m uch less costly also. T h e re is an a r t of tim b er construction, and w hen rig h tly used tim ber is still one o f o u r m ost useful m aterials.
T h e design o f foundations is as im p o rta n t, perhaps, as any p a rt o f th e design. I t is necessary n o t only to go dow n to a stra tu m w hich will c a rry the desired load b u t possibly to brace the foundations to each o th er an d stiffen them by buttresses, o r o th e r
wise, so as to resist any horizontal forces th a t m ay come upon them .
C O A L A G E — V0U 6, -Vo
3
RECOVERED "LAST T O N
t t+ While Maintaining High Daily Production At Fordson Mine
R
e c o v e r i n g over 9 0 p er cent o f th e to tal recoverable coal, -m ain tain in g practically full p ro duction to w ith in seven m onths of p lan t abandonm ent, and loading 44 p er cen t o f norm al capacity on the v ery last day of operation, is the record o f th e F o rd so n Coal Co. at the K en ten ia m ine in H a rla n County, K y., w hich w as sh u t dow n Sept. 13, 1930. W ith in a m o n th and a h alf all b u t fifteen m en of those w illing to m ove h ad been placed a t o th er m ines o f th e com pany.B eginning w ith a d ate about 12 m onths b efo re shutdow n nothing but m ain haulw ay chain and b a rrie r pil
lars, th e la tte r of 70- to 150-ft.
w idths, w ere le ft to m ine. Instead of allow ing the recovery o f these to drag over several years, thereb y suffering the low p roduction penalty o f m ini
m um royalties, fixed overhead, and necessary d ay labor to operate the incline, tipple, and so on, it w as de
cided th e re w ould be an economic gain in building a considerable length of outside tra m ro a d , a ffording several
points o f attack to th e b a rrie r pillars, and in double or trip le sh iftin g n e a r the end as the available w orking places decreased.
T h e m ine is in h alf of a n arro w and irreg u lar area of th e W allin s seam, bounded by outcrop, lying p ra c tically horizontal and close to th e top of th e ridge. Below the 72 in. of clean coal th e re is a 10-in. stratu m of fireclay w hich d u rin g recovery caused some trouble by flowing o u t an d heav
ing the bottom . In different locations the roof condition varied from a diffi- cut draw slate to an excellent slate top up to 48 in. thick and overlaid w ith a sandstone approxim ately 20 ft.
thick. T h e cover varies up to several hundred feet.
K entenia w as purchased in 1920 by the F o rd M o to r Co. in terests fro m the B anner F o rk Coal C orporation.
H a lf of the available 650-acre area, know n as M ine N o. 1, w as w orked out in 1927. A m ap as of M ay 1, 1929, here reproduced, covers the o ther half, know n as N o. 2 mine.
N orm al single-shift capacity w as
T h e M in e W a s D iv id ed In to Sections an d B a rrie r P illa rs W e re A ttacked at Several P o in ts
A C T IV E T O T H E V ER Y LA ST
Some m ines seem to waste away o f o ld age. W h e n devel
opm ent ceases, to n n ag e drops an d all the advantages o f no entry d riving an d little upkeep are lost in th e expense o f o p eratin g tipples, roads, and planes fo r m eager o u tp u t. A t K entenia m ine, the coal was attacked a t several points in tensively, an d as a result to n nage stood about 50 p er cent o f norm al to th e closing day.
1,950 to n s p e r day. E x c ep tin g the operation o f one Jo y type 5 B U m a
chine, continued to ab o u t th e last m onth, th e o u tp u t w as hand-loaded.
T h e coal w as low ered dow n a long in
cline to the tipple in fo u r-c a r trip s operated in balance. H a n d loaded, th e cars average 6,000 lb .; and m a
chine loaded 5,000 lb.
Section A , show n on th e m ap, w as finished on M arch 20, 1930. H e re th e re w as a draw slate 3 in. to 36 in.
thick and containing slips, b u t above it w as a stro n g blue slate. F a irly close posting and quite a n u m b er of crossbars w ere necessary to hold th e draw slate.
Sections B and C h ad a bad ro o f w hich consisted of 12 to 48 in. of draw slate th a t could be held w ith props and crossbars only w hen over 18 in. thick. I n section B , 12-ft. room s on 50-ft. centers w ere driven off from and a t rig h t angles to th e m ain line and aircourse. A fte r cu ttin g th ro u g h , th e pillar w as b ro u g h t back as fast as possible. T w o sh ifts w ere em ployed and tw o m en w orked p er place.
V e ry little o f this section could be robbed open-ended.
In section C, th e room s w ere driven 12 ft. w ide on 6 0 -ft. centers. F o r th e m ost p a rt th e pillars w ere th en m ined open-ended, placing tw o to fo u r cars
M arch, 1931 — C O A L A G E
129
