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 BUSINESS PROBLEMS OF THE COAL M1N1NC INDUSTRY
IS e tc Y o r k , F e b r u a r y , 1 9 3 1 V o l u m e 3 6
Nu m b e r 2
Theme Song— 1931
T o INDUSTRY in g e n e ra l, p e rh a p s n o th in g b e tte r b ecam e th e y e a r ju s t closed th a n its d e p a r tu r e . A n d yet, on th e p u re ly p h y sical side, th e b ala n c e sh ee t o f th e coal in d u s try in 1930 w as n o t w holly u n fa v o ra b le .
In a y e a r w h en r e tr e a t w as th e g e n e ra l o r d e r o f th e d ay fo r business in its w a r a g a in s t d e p re ssio n , th e sh rin k a g e in v o lu m e o f p ro d u c tio n a n d th e decline in prices o f coal w e re am o n g th e m o st m o d e s t r e p o r te d by any m a jo r in d u stry . M o re o v e r, as sh o w n in th e p ag e s follow ing, p ro g re s s in m e c h a n iz a tio n a n d in p r e p a ra tio n w as n eith ei h a lte d n o r m a te r ia lly slow ed up by th e p re v a ilin g p essim ism o f th e 1930 seers o f b u si
ness p ro sp e c ts.
D e v e l o p m e n t s o f 1930, h o w e v er, d o a c c e n tu a te w h a t m u st be th e m a jo r p r o b lem o f th e coal in d u stry in th e com ing y e a r.
T h a t p ro b le m is th e a p p lic a tio n o f p ro fit en g in e e rin g to th e vo lu m e o f p io d u c tio n w hich can re a so n a b ly be expected in 1931.
Vo l u m e su g g ests m ass p ro d u c tio n . B u t th e tw o te rm s a r e n o t necessarily syn
on ym o us, an d , unless th is is cleai ly u n dei -
sto o d , th e re is d a n g e r o f in d u lg in g , as m any business m en h av e d o n e in th e p a s t, in an o rg y o f p ro d u c tio n p ro d u c tiv e o f n o th in g b u t p ro fitle ss v o lu m e.
If m a s s p r o d u c t i o n m e th o d s a r e to be successful in th e coal in d u stry , th e a p p li
ca tio n m u st be in th e d ire c tio n o f a g r e a te r c o n c e n tra tio n th a n h a s been com m on in th e p a st. T h e a p p lic a tio n m u st be on e w hich re co g n izes ex istin g lim ita tio n s on im m e d ia te exp an sio n in m a rk e t d e m a n d an d h as as its fu n d a m e n ta l id ea c o n c e n tra te d p ro d u c tio n m e th o d s w hich w ill p e r m it sales a t a p ro fit.
P r o f i t , to o lo n g lo st s ig h t o f in th e ra c e fo r vo lu m e, m u st d o m in a te p la n n in g a n d p e rfo rm a n c e if th e co al in d u s try is to be p u t in a p o sitio n to m e e t successfully th e g r e a te r p ro b le m s w hich w ill c o n fro n t it in th e y e a rs to com e. T h a t p ro fit can be re a liz e d on ly by th e fu lle s t em p lo y m en t o f a ll th e m a n a g e ria l a n d e n g in e e rin g skill w hich th e in d u s try po ssesses a n d th e m ech an ical aids w hich re d u c e u n it co sts o f p ro d u c tio n w ith o u t im p a irin g th e e a rn in g p o w e r o f th o se d e p e n d e n t up o n th e in d u s try fo r th e ir liv e
lih o o d .
Seeing PreparationThroughin Answer to Competition
CLEARING SKIES
+ Forecast for Business in 1931 A
P O S T -M O R T E M on businessin 1930 would be a bit p rem a
ture. B usiness w as sick enough, in all its p arts, the w orld o v e r; but, as in the case of M a rk T w ain, reports of its dem ise w ere grossly exagger
ated. A ll th a t is in o rd er is an esti
m ate o f the degree of its illness, a diagnosis o f its causes, and some prognosis of the probable course of the m alady fro m now on.
In try in g to find o u t how sick a patien t is, the doctor doesn’t usually depend w holly upon the p atien t’s description of his feelings, b u t tries to check up on it by taking his te m p eratu re, pulse, blood pressure, etc.
B usiness in 1930 felt a g rea t deal w orse th an it was. T h is discrepancy is usual in depression p e rio d s; b u t it w as m uch m ore m arked th is tim e.
J u s t as the spread o f popular medical know ledge has m ade a g re a t m any people im agine they are sicker than they really are, so it is possible th a t the m ore extensive discussion of busi
ness conditions and the publication of business statistics in th e press has tended to m ake business m en m ore aw are of depressions th an they used to be.
A t any rate, the business recession in 1930 did n o t affect the figures as m uch as it did our feelings. T he level of business activity in the U nited S tates never actually falls as m uch below the norm al level as we im agine fo r any g reat length of tim e. T h is is because the busy-ness involved in ju st keeping a nation o f 125,000,000 people going is extrem ely large— o f astro nomical p ro p o rtio n s in com parison w ith th a t of o ther countries. T he total business tu rn o v e r in this country probably aggregates a ro u n d $1,0 0 0,- 000,000,000 a year. T h is is like a huge reserv o ir w ith an alm ost infinite num ber o f inlets and outlets, and it
requires some m uch m ore d rastic in terferen ce w ith the w ate r supply or the rainfall th an w e have know n since the W o rld W a r greatly to affect the level of the w ater in it. T h is is as tru e o f booms as it is o f depressions.
So, if we take as a w ater-m ark the level of general business activity which w ould have existed in this country if the average annual ra te of increase over the past fifty years had continued d u rin g 1930, and call th a t norm al, the best and m ost com prehen
sive m easurem ents we have indicate th a t the actual level d u rin g th a t year was on the average only 1 0 p er cent below norm al. A n o th e r w ay to get an idea of the ex ten t o f business de
pression d u rin g 1930 is to com pare the actual am ount of production and trad e in certain lines fo r the y ear as a whole w ith the average fo r the p re ceding five years. T h e accom panying table shows these com parisons f o r a w ide variety of lines o f in d u stry and business, together w ith som e com posite indicators. A veraged out, such com parisons show about th e same th in g : if th e average fo r th e 1925-29 period was a norm al level, 1930 was about 10 per cent below that.
A closer analysis indicates tw o im po rtan t facts about th e year. T h e first is that, from the point of view of general business, the depression did not really begin until the m iddle of the year. T h e first h alf w as fairly good; the second h a lf w as v ery bad.
T h is is clearly seen in the accom pany
ing ch a rt show ing th e course of g en
eral business activity d u rin g th e year as m easured by T h e B u sin ess W e e k ’s w eekly index. U sin g only ro u g h fig
ures, business averaged about 5 p er cent below norm al d u rin g th e first h alf and about 15 p er cent below d u r-
By VIRGIL JORDAN
E co n o m ist, M c G r a w -H ill P u b lish in g Co.
ing the second half. T h is is im portant to note, because it gives a h int as to how long the real depression has lasted and how long it m ay be e x pected to last. I t is im p o rtan t fo r ano th er reason which I shall m ention later in discussing the causes of the depression.
A second point to be noted is that the slum p affected the different as
pects of business activity very u n equally. T h e basic industries produc
ing raw m aterials, equipm ent, and all the m eans o f production called capital goods declined m uch m ore than the production and distribution of con
sum ers’ goods, w hich m ake up w hat is called general trade. T h is is usual in depressions, ju s t as in boom p eri
ods, but it w as strikingly show n d u r
ing 1930. T h e table illustrates this in m any w ays: B uilding construction was off 27 p er cent from the average o f the preceding five y e a rs; locomo
tive shipm ents, 27 p er c en t; autom o
bile production, 2 2 per c en t; steel production, about 14 p er c e n t; al
though the total volum e of m an u fac
tu rin g as a whole w as dow n only about 11 per cent. In co n trast w ith this, the value of checks draw n and cashed in cities n o t affected by the slum p in stock tra d in g w as dow n only about 2 p er cent an d dep artm en t sto re sales only 3.9 p er cent.
In both these cases if low er prices or g re a te r value of the dollar w ere allowed for, th e volum e o f tu rn o v er probably would show up above the average o f the five preceding years.
E lectric pow er production, w hich re
flects not only in d u strial activity but also general tra d e and the dem and fro m th e g reatest in d u stry of all—
F ebruary, 1931 — C O A L A G E 55
the home— w as nearly 18 p er cent above the five-year average and only about 1 per cent below the norm al or expected level on the basis of the average annual increase over m any years.
A ll this m eans that, taking the year as a whole, it is probable th at the quantity of goods consum ed by the citizens of this country d u rin g 1930 w as very little if any below the n o r
mal am ount, and th a t the real slump was in the dem and fo r and production of so-called capital goods, w hich fell
expect them to yield. W hen these tw o facto rs are in balance, the p ro duction of capital goods will ru n along norm ally and general business is likely to be fairly stable an d p ro s
perous. I f m oney is so abundant th a t it costs less th an it yields w hen invested in fixed capital, you have th e m akings of a boom period ; and vice versa, w hen it costs m ore th an it really yields, you have the m akings of a depression period.
T h is is w hat happened in 1928 and 1929. B eginning as long ago as 1925
off about 1 0 p er cent on the average below the norm al level.
T h is m ay seem puzzling, b u t it w orks out fairly sim ply w hen you consider the decline in prices of con
sum ers’ goods. R oughly, th e total cash income of w orkers averaged about 10 per cent low er in 1930 than in the preceding five y ears, b u t the average cost of living also w as about 10 per cent low er, so th a t th e total purchasing pow er probably rem ained about the same. T h e slum p w as really a decline in the q uantity of capital goods produced and sold— buildings, plant, m achinery, utilities, and fixed capital o f all kinds. T h is is w hat m akes the difference betw een n o r m ally prosperous conditions and d e
pression, not the v ariations in the am ount o f food and clothing and such things consum ed. T h e capital goods m entioned account fo r about 30 per cent of in d u strial production, and the rem ainder varies very little. T h is may be one reason fo r the fact th a t even at the extrem e depths o f depression the volum e of in d u strial o utput in this country has never fallen m uch below 70 per cent of norm al.
T hese facts give us som e clew to th e underlying causes o f the dep res
sion. T h e q uantity o f capital goods th at a re bought, and th e re fo re p ro duced, depends u p o n tw o fundam ental factors. O n e is how m uch it costs to borro v the money to buy them w ith : the other is how m uch th e purchasers
the m arket rate of interest on long
term money fo r real investm ent in fixed capital began to be noticeably g reater th an the actual yield. T h ere w ere m any reasons fo r th is w hich I cannot go into here, b u t the evidence is clearly to be seen in the steady decline in residential building since 1925. By 1928 and 1929 th e d is
crepancy became so m arked as the result o f the abnorm al an d artificial dem and fo r m oney in the stock m arket boom to carry excessive issues of pyram ided securities w hich did not represent real investm ent, th a t such
B u sin e ss in 1930
(E a se d on fu ll y e a r or e le v e n m o n th s) P er c e n ta g e
o f 1925-29 A v era g e G eneral trad e ... .. S9.S T o ta l p roductive a c tiv ity ... 79.8 In d u str ia l production ... SS.8 B u ild in g c o n t r a c t s ... * . 72.8 Iron an d s t e e l ... S5.2 A u t o m o b ile s ... 77.4 L ocom otives (sh ip m e n ts) ... 7 2.S N o n -ferr o u s m eta ls ... S7.0 B itu m in o u s coal ... S3.3 T e x tile s ... S4.0 L eath er an d s h o e s ... 93.9 P a p er an d p rin tin g ... 99.0 T obacco m a n u fa ctu res ... 110.7 E lec tric pow er production ... 117.6 B rick ... 53.9 L um ber ... 62.6 M erchandise c a r lo a d in g s ... 93.1 A ll o th e r c a r lo a d in g s ... 79.6 D ep artm ent sto re s a l e s ... 96.1 F iv e and Ten C ent S tore c h a in s . 112.1 B a n k d eb its ou tsid e N e w York
C ity ... 9S.0
L ife In su ra n ce s a l e s ... 10S.3 W h o lesa le prices, a ll co m m o d ities SS.3 F a c to r y em p loym en t ... S5.9 N e w ca p ita l i s s u e s ... 91.0
investm ent was drastically checked in this country, and especially abroad.
T h e result w as a progressive de-
‘cline in the production of capital goods of all kinds, p articu larly build
ing. Since such production is the determ ining facto r in the dem and fo r labor and raw m aterials th e w orld over, em ploym ent fell off and com m odity prices declined rapidly. I t is m ore th a n a coincidence th a t the de
clines in em ploym ent, in com m odity prices, and in new security issues d u r
ing 1930, as com pared w ith the av e r
age of the preceding five years, w ere all of about the same proportions.
T
H E fundam ental cause of this business depression w as the steady and drastic contraction of credit which took place in this co u n try and the w orld over the m iddle o f 1928 on, tending to raise the m ark et rate of in terest fo r long-term capital to uneconom ic levels, and thereby checking the production of capital goods.
T h e saving facto r th a t helped to cushion the decline in the first h a lf of 1930 w as the stim ulation of public construction and of a good deal of industrial and u tility construction w ork as the result of the P re sid e n t’s conferences in N ovem ber, 1929. T h is w as m ade possible p artly by the fact th a t m any stro n g corporations had large cash surpluses fo r the purpose and did not have to borrow and p artly because governm ents in this country do not care very m uch w hat they have to pay fo r m oney fo r such purposes, so th a t the in terest ra te is n o t a real factor. T h at is w hy public co n stru c
tion w ork is looked to as a m eans of so ften in g business depressions, b u t it only illustrates the economic forces involved in them . T h e m ildness of th e recession d u rin g th e first h alf of 1930 w as largely a reflection of the fact th at public agencies, and they alone, w ere w illing and able to b o r
row m oney fo r the production of capital goods. A s a m atte r of fact, the level of building construction practically touched norm al by Ju n e, 1930, as the resu lt of this influence.
T h e same influence has continued since and will be m ore m arked d u rin g the first half of this year, b u t the depression has since gone so fa r that public construction alone can do rela
tively little to raise the general level of business activity.
T hese things help som ew hat to give an idea of the probable length o f the depression and of the facto rs th a t are likely to b rin g about recovery. T h e m ajo r depressions of the p ast in this
( Turn to page 42)
56 C O A L. A G E — V o l.3 6 ,N o 2
SUITING THE PLANT
+ To the Preparation Job
B
E F O R E deciding on the technical requirem ents of a clean
ing and p rep aratio n plant it is necessary to m ake a survey of the m arkets into w hich th e coal fro m the p lan t is to go, in o rd er to find ju st w hat kind of coal is desired. In a com m ercial operation the economic problem s of coal cleaning an d p rep aratio n and the m arketing of the p roduct outw eigh technical consider
ations.
U n fo rtu n ate ly , no section of the public has a positive stan d ard on w hich to base the acceptability of a coal, but the probable a ttitu d e of any g ro u p of consum ers can be judged in advance by its criticism of the service already rendered. T h e designer o f a plant to p rep a re coal fo r the m arket, the builder, ow ner, and op erato r of one will be w ise if he endeavors to learn from th e m ark et reactions to his ow n o r sim ilar products ju s t w hat the p articu lar public he is serving will dem and.
T h a t public is n o t alw ays best pleased w ith the p u rest coal sub
m itted. I t m ay be m ore greatly con
cerned about a flaky lam ination V,: hi.
thick on the face of the coal th an it is about alm ost invisible im purities well d istrib u ted th ro u g h th e piece, or about lenses of p y rite hidden in the h eart of the lum p th a t only some specific-gravity test w ould disclose or w ashing rem ove. I t has been said th a t som eone picked out fo r rejec
tion in a consignm ent of Illinois coal the w o rst pieces he could find and analyzed the ag gregate and then made an analysis of those th a t w ere left, only to find th a t he had rejected the b e tte r coal and retained the less desir
able. B u t w as th a t tru e ? T h e m ar
ket recognized the visual test and would question any other, even though b etter, w h eth er a calorific, an ash, o r a specific-gravity appraisal.
F ebruary, 1931 — C O A L A G E
So long as the public is th u s m inded it will be necessary to hand-pick coal of the larg er sizes, breaking dow n the coal th a t has the p o o rer ex tern al a p pearance. In fact, m uch good coal is wasted in the reject from th e m odern picking table. B roken dow n and washed, it will yield 60 p er cent of clean coal fo r the m arket. I t m ay be as m uch as 80 p e r cent in some instances, fo r the cause of the re je c
tion usually is only a m ere skin of shaly lam ination th a t raises th e spe
cific g rav ity b u t little, rarely enough to cause rejection in m echanical clean
ing, unless an unusually low specific- gravity cleaning is provided.
T his article by M r. M orrow is the first o f a series by coal operators, consulting engineers, and the editorial staff o f Coal A g e discussing the fu n d a m ental problem s o f m odern coal preparation. T h e next article to be published will cover structural and construc
tio n problem s in build in g m o d e r n coal - preparation plants. A m ong the o th er ques
tions w hich w ill be treated in this series are : m aterials h a n dling technique, electrification, pow er transm ission, refuse dis
posal, m aintenance, b lending and m ixing, crushing, re-treat
m ent, dew atering and drying, dust recovery, chemical and physical control, screening, and the redesign of obsolete plants.
— T h e Editors.
By J. B. MORROW
P rep a ra tio n M a nager P ittsb u rg h Coal Co.
P ittsb u rg h , Pa.
T h e force at an anthracite cleaning plant frequently hand-picks the p ro d uct o f the cleaning u n it so as to re
move “cappy coal,” o r treats the product either on a spiral or a jurnp- the-gap picker so as to rem ove the flat and shale-faced pieces th a t are clean enough w ithin and as a whole to give th e required heat on b u rning, but w hich have the d irt so painfully disclosed as to arouse the ire o f the purchaser.
L am inated coal in a rising c u rre n t is likely to be lifted, because o f the large area it exposes to the upw ard m ovem ent. W h e re th is fo rm o f m o
tion is not m arked, the lam inated coal will be stratified solely by its relative buoyancy as com pared w ith round coal. In alm ost every form of wet ■ o r d ry cleaner th ere is an upw ard m ovem ent o f the w ater or air som e
w here in the process of cleaning, and the lam inated coal is lifted unduly.
H ow ever, in such p a rts of th e process as result in alm ost horizontal p ro p u l
sion, the lam inated m aterial tends to drop and d rag on the bottom an d so to rem ain below, perm ittin g the round coal to bound freely over it.
Som etim es, because of upw ard cu r
ren ts o r because of an internal pu rity th a t com pensates fo r the external boney cap, all of the lam inated coal is n o t dropped and then some hand- cleaning m ay be necessary. C rushing and re-treatin g of th is coal and of the m iddling reject saves m ost o f the coal, but, on account of th e reduction in size, does not salvage by any m eans as large a p roportion o f its entire value as it does of its w eight.
B u t, to re tu rn to the question of m arket, it is necessary to learn w ith
| ju st w hat coal the product of the new 57
cleaning ami preparation plant will have to compete. It is n o t enough to know the kind of coal a consum er com pany will accept from its ow n mine ov cleaning plant, because th at com pany may he averse to leaving its in
terio r coal underground, o r m ay have an in fe rio r coal area, o r again may he.
unw illing to go to the expense of installing a w ashing plant, if it has none, or a b etter one it it is already equipped. In such cases all it can do is to stille com plaint. But the com
m ercial plant, it it is to do business w ith this com pany o r another in the same industrial field, must be ready to m ake a class of coal that will in duce the electric, gas, railroad, or m etallurgical com pany, w hichever it is. to discard its ow n coal as to get the benefit of the lowered freig h t rate p e r therm al unit and a fuel of better quality,
S T A N D A R D S o f quality may be ditlici
k ) diftieuit to determ ine. Any con
sum er will declare that he desires no ash o f su lp h u r in his coal. H e know s he cannot get w hat he would desire.
In fact, he will low er his stan d ard s almost to any degree if none o f the coal he can get will come u nder m ore r e a s o n a b l e specifications. C onse
quently. w hile he is striving fo r the unattainable he is w illing to com prom ise, and though he know s h e has to tak e less th a n his ideal, he is re ti
cent to state ju s t w hat concession he is w illing to m ake fo r fear th at he will concede m ore than is necessary, H ow ever, he h as h a d long e x p e ri
ence o f w hat he has been obliged to accept, and he is alw ays ready to w el
com e a product that will bo a shade b e tte r as to ash o r su lp h u r th an th a t w hich he has form erly purchased, but specifications o t this kind arc compromises; only a n d subject to change as th e onaH ty o t th e coal on th e •. ket im proves o r declines.
O r * r.'Av m ake a specification to t bra<s e - bronze, because it is a syn
th etic product th e proportions ot
which can be varied at will, b u t w ith coal there are lim itations, and the specification is based largely on w hat the purchaser m ay reasonably hope to obtain. F o r this reason it is diffi
cult to say ju st how m uch sulphur and ash there may and should be fo r the m etallurgical or the gas m arket.
It is necessary also for plant m an
agers and designers to know w hat size of coal the m arket dem ands, so th at in preparation— for prep aratio n is not wholly o r even m ainly cleaning
— this may be kept in m ind. T h ere are m arkets which dem and large coal, partlv because the largest coal they have’ had in the past has happened to be the cleanest. Som etim es the large coal comes fro m the p u re st p a rt of the seam. T h a t is m erely a coin
cidence. one th a t is ra th e r stran g e than natural, fo r the im pure p a rt of the seam usually gives the largest lumps, but when men have been in the habit of finding size and p u rity com bined they naturally think these tw o qualities have a universal connota
tion. and it is difficult to induce them to believe that egg may be ju s t as clean as. or cleaner than. lump.
O th ers using a coal th at decrepi
tates and spontaneously ignites, as do the lignite, sub-bitum inous and low- rank bitum inous coals of the W est, naturally p refer th at the coal they purchase shall be large. T h e y will dem and this even if the coal they receive comes from tru e bitum inous fields and from regions w here the coal is sem i-bitum inous an d docs not decrepitate o r sc.lt'-ignite. T o get into m arkets such as these w ith a well-graded egg requires education an d time, which may be costly in
deed. It may be added th a t some coals have well-m arked cleats so close together that, no m atter how m uch care m ay he taken, large lum ps can
not be obtained, at least in quantity.
Tn some fields the coal is naturally triab le a n d clean and, en terin g into m arkets w here such coal is esta b lished, th ere is less prejudice as to
size, and a w ell-prepared egg m ay find ready acceptance.
I t stands to reason th a t the laig ei sizes of coal should be fre e r of extraneous m atte r th a n the sm aller sizes, because it can be m ore clearly seen and rem oved. T h e a n th racite field, w hich has had so m uch m ore experience th an the bitum inous coal field, has long ago recognized this.
T h e public dem ands less bone in its large coal, and indeed m echanical equipm ent usually cleans th e large coal w ith m ore effectiveness, even w hen the sizes are cleaned together.
T h e lum ps seeih to be cleaned at a som ew hat low er specific g rav ity th an the finer m aterial. T h u s the sink p e r
centage w ith 2-|x4-in. coal m ay ru n 0 .5 p er c en t; w ith I x2-Mn. coal, 1 per c e n t; and w ith 0 o r f-in . to 1-in.
coat, 2 p er cent.
A
n t h r a c i t e o p erato rs fuii>- re-„ alize th at cleaning cannot be a b solute and have provided certain m o d est tolerances, such as have been set u p in alm ost every in d u stry , especially those th a t have to do w ith the o u t
p u t of n atu ral and not synthetic products, though, even w ith the latter, tolerances a re not unknow n. T h e bitum inous coal m an. how ever, either sells a coal cleaned only in th e m ine o r one th a t he declares, by im plica
tion a t least, is absolutely clean. Such a pretension only m akes trouble. T h e doctrine o f probability, o r chance, in the behavior of a h u m an being o r a piece of coal w hen the la tte r is being inspected, m echanically cleaned.^ o r sized and the irre g u la rity o f feed should be given som e recognition.
A m om entary in atten tio n o f the picking-table operative, a m isleading p resentation o t th e piece o f coal, o f w hich only one face is in full view , the distraction of the eye in th e case o f hand-picking, and the v ario u s con
ditions in the coal fro m th e m in e as to ash content and ra te o f te e d in the case of m echanical cleaners m ak e 1 0 0-per cent p erfo rm an ce imlikely-
In the an th racite field coal is frankly sold on visual inspection—
the ground on w hich it is accepte ' o r rejected. B itum inous coal is n o t so sold h u t ra th e r on h e a t value an d ash content, and yet fo r dom estic use is ju g( visu al stan m ore than by any o th e r fa c to r. I t seems th a t it should alw ays be sold on precisely th e sam e g ro u n d s a s a re used in determ ining its acceptability on receipt.
Sim ilarly, in th e a n th ra c ite region th e re a re tolerances as to sire , because the o p erato r cannot p re p a re his coal
C O A L A G E — ? ' o ! J 6 S o 2
to any exact size w ith o u t undue b reakage and excessive screen area, o r even then.
B itum inous o p erato rs s h o u l d specify and dem and sim ilar toler
ances, fo r in practice they will have to tak e them w hether the purchaser likes them o r not, and as th ere will be segregation in the car, m uch of the undersize will be found in the h o p p er and will greet the purchaser as th e doors are low ered fo r his in
spection. T h e presence of this fine coal is su re to cause com plaint from th e p u rch aser w hich will be unusually difficult to com bat, fo r w as not this a consignm ent of sized coal and, as the p u rch aser understan d s the ex p res
sion, th a t m eans w ith o u t any u n d er
size w hatever. H e should be obliged to realize by the actual w ording of his contract, o r by the trad e practice of th e region fro m w hich the coal comes, th at in practice th ere m ust be u n d ersize— coal, th a t is, th at adheres to and rides on coal of larg er size, coal th a t blinds the screen, and coal th a t has one diam eter m uch longer th an the o ther and, therefo re, screens w ith difficulty.
H a n d - cleaning, carefully p e r
form ed, m ay produce a coal that visually accords w ith standards, but th e ex tran eo u s m a tte r th at m ay be le ft in cleaning will ru n higher in ash th a n th e sink fro m the cleaned coal.
A picking table should be run so slow th a t it will n o t exceed the ability of th e picker to clean the coal. 1 he rate o f m ovem ent will depend m uch on the size of the coal and on the character a n d cleanliness o f the coal to be picked. In any case th e coal'shouid n o t be m ore than one layer deep fo r sa tisfacto ry operation, and w ith large lum ps th e operative should be able to see the side of the lum p as well as its u p p er surface.
B
E F O R E p rep a rin g to build a cleaning p lan t a large num ber of analyses o f the coal in the seam by layers should first be m ade, so as to see if som e of these layers should be elim
inated, fo r som e coal is of such a high in h eren t ash and sulphur content th at no cleaning can undo th e unkindly processes of n a tu re T h e best that can be done w ith such coal is to leave it, p referab ly unm ined, w ithin the w orkings as either ro o f o r floor coal, fo r o ften , b u t not alw ays, such unim provable coal is found either at the to p o r bottom of the seam. H o w ever, in some cases by cleaning these layers-, o r a p a rt of them , w ith the o th er portions of the bed it may be possible to use them .
February, 1931 — C O A L A G E
J. B. M o rro w
Som e of the coal m ay be both very fine and clean. T h a t is tru e of some fragile coals. In loading the coal, m oreover, it m ay not be contam inated by scale from the ro o f o r floor but come to the cleaning plant in excel
lent condition fo r the m arket. In th at case it m ay be well to leave this p a rt of the coal entirely unprocessed.
It can be screened out and added to the coarser coal a fte r the la tte r has been cleaned. D ry coal, how ever, it may be said in passing, in byproduct ovens has the disadvantage of ex ploding and blow ing back w hen charged and of producing an undue p roportion of carbon on the top of the coke column.
O ne can scarcely take too m any sam ples in a m ine the p ro d u ct of which is to be studied fo r cleaning.
A good practice is to take 60, o r even 10 0, and to take th a t num ber from each of the five o r six stra ta of which the seam is com posed, if th ere is any such a num ber of layers. In each of these analyses the facts are d e te r
mined as set fo rth in the table.
T he “R aw Coal ( a c t u a l ) ” is r e c o r d e d in t h e “ P e r - C e n t - o f - W e i g h t ” c o lu m n a s 1 0 0 p e r c e n t , a n d t h e “R aw Coal ( c a l c u l a t e d ) ” i s t h e s u m o f t h e p e r c e n t a g e s i n t h e l a s t t h r e e h o r i z o n
tal lines of th a t c o lu m n ; th a t is, it is the sum o f the float a t 1.40 specific gravity, the coal betw een 1.40 and 1.60 specific g rav ity , and the sink at the la tte r density. T h e calculated fig
u re is used solely as a check on the accuracy o f the determ inations.
I t m ay seem strange th at only two gravities are taken instead of m any w ithin th a t range, but it has been found quite possible to interpolate values. T h e ratio betw een the ash in the float at any given gravity and the ash in the sink a t th a t gravity lies betw een (1) the ratio of the ash in the float at 1 .4 0 to the ash in the sink at th a t g rav ity and (2) the ratio of the ash in the" float a t 1 .6 0 to the ash in th e sink a t th a t same gravity and is in reg u lar p roportion to the gravity value.
H ence, given the percentage value of the ash in the float, it is possible to find by p roportion the specific g rav ity tm d the q uantity o f ash in the reject and also th e specific g rav ity at w hich the coal m u st be floated to get the req u ired ash percentages in the float. T h is system has had e x tensive test w ith a large range of coals and been found to accord w ith the facts. F ro m this know ledge m ay be obtained a figure fo r the percent
age of ash in the float fo r any given recovery w ithout direct test.
I
T IS well to know the analysis of the ash, especially w hen p rep arin g a m etallurgical f u e l; fo r exam ple, th e calcium oxide percentage is im portan t. Calcium carbonate is a helpful body in the blast furnace. In fact, it alw ays is added as a flux, if not p resent in sufficient q uantity already in the iron ore. W h y object to it then in coal fro m which coke fo r the fu rn ace is to be m ade? J u s t fo r this re a s o n : th e calcium carbonate reduces to calcium oxide in the oven, b u t as soon as it is sprayed w ith w ater in the cooling o f the coke it slakes and expands and so m ay m ake crevices in the coke th a t will cause it to spall, m aking excessive fines, o r will w eaken
Form fo r S tudy o f th e C oal in a M in e P re lim in ary to C lea n in g
Pa rt of Coal Tested Top Breast e- R aw coal (a ct u a l). . 10 0.0 R aw coal (calculated) 10 0 . 0 F lo at 1. 40s p.s r 9 7 . 4 Fl oa t 1.60sp.?r... 1.0 Sink 1.60 sp.iir 1. 6
4 . 7 4 . 6 3 . 7 19.8 5 2 .6
X
1.20 1.14
1.01
2 . 7 ! 9. 16
Volatile C on te nt
-3ea 3 ‘C s i*“
Q —
British
Th ermal U nits -A n a l y si s of A s h -
i '. i 37 ‘. 7 39! 6 14,550 15,280 47.8 35.5 . .. 42.4 ¿4.u ... 39.0 20.5
ft O
1 3.3 2 . 6 1 6 .8 9.1 2 6 . 9 7 . 8
2.520 2,180 2,310
59
the coal being p rep ared and on the size o f the coal lost. L osses should alw ays be counted in dollars, n o t in tons. T h e engineer th in k s in tons, but the econom ist in m onetary values.
In building cleaning plants and in operating them , dollar losses m u st be stacked ag ain st dollar costs if one would build o r operate w ith due economy. T h is m ust be rem em bered in sizing up a record of cleaning-plant perform ance.
I t m ust be rem em bered th a t the actual cleaning equipm ent m ay re p re sent only a sm all p a rt of a com plete plant. T h e cost of the au x iliary equipm ent will be found to be g re a te r th a n th a t o f the actual clean
ing u nit. W h e re this is th e case, too m uch stress should not be laid on it when it has to bear the burden of be taken that all the precautions the cost of the Iattei. In a d ry - the w eight in the furnace. T he rela- exercised to fill specifications are not cleaning plant, screening m achinery is tion of the calcium -oxkle content to vitiated by lack of proper handling an item alm ost as larg e as tabling, and that of the silica also is suggestive ot" or a certain am ount of rescreening at d u st collection as large as either, trouble from fusing. ' - the receiving point w herever the coal T h o u g h the general practice is to
T oday there is a'd isp o sitio n to ask is not m ixed at the tipple. IJ n fo r- re g a rd the cleaning end as th e alpha not only what is the so ften in g tem - Innately, railroad tran sp o rtatio n is an d om ega of the tipple, today far p eratu re of the fusion cone but w hat not by any m eans gentle. T h e coal m ore m oney is likely to be spent on is the fluid tem perature, so perhaps is loosely’ laid in the car and will dum ping, loading, drying, picking, it would be well to find, tabulate, and descend some inches in tra n s it.' A s disposing of refu se, and o ther au x - consider both w hen m aking the stir- the coal in the bottom o f the hopper iliary services than on the actual rev o f the seam. As the cleaning is under a load of 500 lb. per sq u are cleaning, fo r the cleaning equipm ent plant rarely if ever w orks on an aver- foot, it is natural that th e re will lie has arriv ed a t such perfectio n th a t it age sam ple of the entire m ine but m uch breakage w ith this w eight set- operates alm ost autom atically on its som etim es has to w ork tem porarily, tling down even an inch o r so d u rin g p art o f the output,
m ainly on the product of some one the early impacts between cars.
part, it is well to design the cleaning T h e re also will be segregation, but " D E C A U S E o f recent em phasis 011 plant not 011 average conditions b u t on w ith a mixed coal the voids are well L ) cleaning, th ere has been a disposi- conditions som ew hat less fo rtu n ate filled, and in tran sit the coal, being tion to overlook o th er phases of p rep - than norm al, so th at w ith all the properly Ledded in fines, is not so aratio n . O n e m ight have a cleaning chances unfavorable the result de- badly broken and there is a m inim um p lan t th a t w ould reach its objectives sired will Ik- attained. T h u s, if the tendency to segregation. in every detail and yet not have a average ash content o f the raw coal U sually the sales engineer can de- tipple o r breaker th a t w ould give is ¡0, it may be well to base one’s vise a form ula or recipe th at will fill satisfaction. T o m eet m ark et d e
design on an ash content o f 15. the buyer’s needs. Com plaints fre - m ands, the featu res o f prep aratio n O ne m akes an im portant e rro r, quently arise m erely from the fact o th er than cleaning need carefu l con- however. if one believes today th at that the purchaser has been buying sideration, both in design and oper- w heu coal is cleaned the w ork is the w rong sizes o r m ixtures of coal ation.
done. P rep aratio n includes m ore to suit his conditions. A s one w anders th ro u g h a large th an cleaning. Som e m ight be dis- W h en selecting a cleaning plant ore concentrating plant and notes the posed to speak o f cleaning and pre- m any conditions should receive con- various kinds of equipm ent in use, paring as tw o separate yet co-ordi- sideration. F o r instance, it m ust be one realizes th a t the m ill designer is nate operations, fo r sizing and m ix- rem em bered in these days of irre g u - em ployed by the com pany and th a t mg of sizes accurately a n d u niform ly for run n in g tim e th a t depreciation he selects fro m one m a n u fa c tu rer is alm ost as im portant as cleaning, d u rin g the idleness of a plant is a w hat he needs f o r one process and l-or instance, fo r the dom estic stoker facto r of im portance. W ill the p lan t from an o th er m an u fa c tu rer w h at in it serves n o t at all to have the rig h t hear u p well under idleness o r will his opinion will serve best fo r som e p roportions, w ith the coarse size in th ere be excessive depreciation? o ther purpose, and so all th ro u g h one p a rt o f the fire or in one cliarg- In planning a small cleaning plant, the mill and the beneficiating plant, ing and th e finer size in th e other, one should not aim fo r excessive re- T h e mill m en know th e ir o re and In fact, the fum es m ay travel back finem ents which can be justified only they know w h at tre a tm e n t it needs, along the feed screw and m ake in a large p lan t w here a big tonnage In the coal in d u stry one m anufac- trouble if enough fine coal is not pro- is handled by a few men. O ne can h ire r's m achinery is likely to be used vided to p rev en t any such action, afford in such a sm all plant to let a alm ost throughout. T h e re is n o t so The caking o f coal in the producer som ewhat h igher proportion o f coal m uch o f the selective w ork done by also is helped by the pro p er percent- go to bank in o rd er to reduce the the prep aratio n engineer th a t is so age o f fines. carry in g charges o f the installation. notably present in the layout o f the
It is in p o rtan t. how ever, th a t care E v ery th in g depends 011 the cost of concentrating plants of an o re m ine.
C O A L A G E — Vol36,No.2
M ECHANIZATION
+ Developments in 193 0 M arked By M ore Intensive Planning
A L L facto rs considered, mine m echanization in its broad as- 1 J L p e c ts m ade satisfacto ry p ro g ress in the bitum inous in d u stry during
1930. T h e activity w as m ore notable fo r its gain in constructive trends tow ard the supplem enting and bal
ancing of equipm ent— fo r a better p roduct first and fo r low er over-all costs last— than fo r its contribution to production volume. T h e re w as an abundance of evidence to support the belief th a t operators have learned the lesson th a t successful m echanization does not stop w ith the installation of equipm ent fo r loading coal but it m eans o th er necessary im provem ents below and above ground. T h e year, th e refo re, m arked the beginning of an era o f sounder m echanization policy.
O ne o p erato r prom inent in m echan
ical m ining explained the situation as follow s: T h e y ear of 1930 em pha
sized th a t m echanization is not a panacea fo r all op eratin g troubles. In elim inating some difficulties, it in tro duces o th e rs of a m ore serious n a ture. T h e line of least resistance certainly does not p oint tow ard m echanized m ining. Installations al
ready m ade of m echanical equipm ent, p artial and com plete in large and small m ines, m ake the w hole field of m echanization look u n duly attractive.
T h ey do not, how ever, reveal the real difficulties w hich the average operator will encounter in his pow er plant, his tipple, his haulage equipm ent, op erat
ing supplies, supervision, etc. T he p ast y ear sobered the o p erato r p u rsu in g m echanized m ining. H e has taken an inventory of his favorite schemes and ideas, has discarded the im prac
tical, and stands ready to progress on a m ore substantial basis.
In tern ec in e com petition and the
com petition of substitute fuels from without- is beginning to influence the m echanization policy of shrew d op
erators. Faced w ith a loss in o utput which m ade th e developm ent o f ad d i
tional capacity of no purpose, they showed a tendency to p erfe ct existing operations ra th e r than to enlarge them. T h is step tow ard im proving efficiency w ithout sw elling production prom ises to be one of the m ost f ru it
ful germ s of stabilization planted in 1930.
E xcept in a few isolated cases, com petition from the expansion o f gas distribution w as n o t sufficiently felt to have had m uch bearing on m ech
anization last year. B ut it is a pow er which m ust be reckoned w ith in the fu tu re. T o fight effectively against this new elem ent in its m a r
kets, the in d u stry is compelled to m odernize its plants w ith increas
ing speed. T h is and the fact th a t the scope of requisite physical im prove
m ents is w ide call atten tio n to the urgency of im m ediately w orking out plans fo r the financing o f new equip
ment. T o stim ulate the m echaniza
tion advance, it has been suggested that the m a n u fa ctu rers develop de
ferred paym ent plans, as a few already have, to assist responsible buyers. A n o th er proposal m ade is
th a t the pow er com panies, which profit from m echanization, be asked to u n d e rw rite credit papers. A th ird possibility is com m ercial credit services.
S everal com panies w ere added to the list o f those who have been p ay
ing bonus o r incentive wages. B ut even w ith these additions the list still em braces relatively few nam es. O ne com pany rep o rts constructive results fro m th e functioning o f a g ro u p pre^
m ium plan based upon a fa ir daily m an -sh ift production. A ll m en em ployed in and about each individual m achine a re considered in the group a n d prem ium s are com puted over the sem i-m onthly pay period.
In the case of shaking conveyors, w ith the loading crew undercutting, drilling, shooting, and tim bering the places, a prem ium is paid equal to half the established labor cost per ton. T h e aggregate prem ium fo r a period is p ro -rated betw een the men on the basis o f m an -sh ifts actually w orked by each. N o attem p t has been m ade to enforce the earning of a p re m iu m ; yet about 44 p er cent of the tonnage loaded by this m achine type is on the prem ium basis. T h e plan has yielded daily individual w o rk er p re m ium s ran g in g from 20c. to $3. F o r the first half of D ecem ber th e average prem ium w as 8 6.8c. p er m an sh ift and covered 45.6 p er cent of the to n nage com ing u n d er the prem ium . T h e m achines are num bered, and e arn in g o r non-earning o f prem ium s fo r each is posted. A s a fu rth e r m eans to set fo rth clearly the rew ard fo r diligence, prem ium s earned by in dividuals are paid by a separate check.
A t a certain plant, w here loading m achines are double-shifted, g reat strid es have been m ade in personnel tra in in g and direction. S ta n d a rd s of w orkm anship have been set up and these are enforced. V ario u s activ
ities have been analyzed and respon
F ebruary, 1931 — C O A L A G E 61
sibilities aticl au th o rity fo r each ex- actingly placed. P rin ts are furnished on im p o rtan t jobs and these are sup
plem ented by w ritten instructions.
V erbal ord ers have been reduced to a m inim um ; w ritten instru ctio n s are the practice all the w ay dow n the line.
Discussion continued on the rela
tive safety of m echanized loading w ith respect to hand loading, b u t no agree
m ent w as reached. A research study o f this problem is now u nder way at the U n iv ersity o f Illinois. A t the W ash in g to n m eeting of the A m erican M ining C ongress it w as proposed that th is organization g a th er statistics to decide the question. J. D. Zook, president and com m issioner of the Illinois Coal O p e ra to rs’ L ab o r A sso
ciation, stated at this m eeting th a t such figures should be collected by governm ent authority. A recom m en
dation w as m ade th a t the figures should be broken dow n by occupations fo r a clear picture o f the results of m echanization on. safety.
S
A F E T Y w ith respect to m achines received serious attention in U tah.D u rin g the y ear the S ta te In d u strial Com m ission issued an o rd e r th a t a f te r Ja n . 1, 1932, only equipm ent approved by the Ù . S. B ureau of M ines m ay be used in "g assy ” m ines in U tah. U n d e r the order, o p erato rs o f “gassy” m ines are required to have an electrician keep in daily contact w ith equipm ent a t th e w orking face.
R epairs m ust be m ade above ground and the electrician m ust m ake a daily record o f equipm ent in use.
L a st y ear the U . S. B ureau of M ines w as asked to pass judgm ent on the perm issibility o f m ore equip
m ent th an in an y previous year. I t issued 36 approvals w hich covered practically every m a jo r m achine type.
F o r fu rth e r details see p. 78, this issue.
V ariatio n s in daily production have been tax in g th e ingenuity o f m anage
m ent a t m echanized mines. M ore and hea /ie r equipm ent, together w ith
ex trao rd in ary facilities fo r m ain tain ing it, has added m uch to capital in vestm ent, so th at th e advantages gained by high degree of m echaniza
tion are discounted by idle time.
Planning and scheduling of o p era
tions are the w ays out o f this difficulty, and rep o rts have come in of progress in these channels. O p e ra tion control calls fo r laying out the w ork of every m an, from m achine ru n n ers to track and tim b er m en Supervision m ust be m ore intent and companies no longer countenance superficial observance of processes by foremen.
In the w orking out o f plans, how ever, it has been discovered th a t because of the principle o f dim inish
ing re tu rn s a change which benefits one phase of operation m ay react to the disadvantage of others. R u n n in g tim e generally, but not always, is a tru e m easure of efficiency. W h y have tw o gathering locomotives, in th e e x trem e case, behind a loading m achine?
O r w hy a cutting m achine a t every narrow , conveyor-m ined face? T h e answ er is simply th a t practical efficiency sometimes o u tstrip s the theoretical.
A t one plant w here supervision and scheduling have been carried to refine
m ent, section lines are distinctly m arked. E ach section has a forem an and the forem an is held absolutely accountable fo r w hatever tran sp ires in his territo ry . Section h ead q u ar
te rs is connected w ith a d isp atch er’s office by telephone fo r centralized control of tran sp o rtatio n and o ther m ining activities. A t this plant pow er cost has been reduced 1c. a ton thro u g h m eter control of peak loads.
G athering locomotives are operated in a sequence fixed by the dispatcher and peak loads are thus m inim ized.
A n unusual reduction in m aintenance cost has rew arded this practice.
W h ere due regard has been paid to scheduling, the proportion betw een gen erato r capacity and connected horsepow er has been kept surprisingly
low. S pread in g operations over off- peak hours has become increasingly im p o rtan t and desirable and is g ra d ually b ringing about a tra n sitio n to tru e m ultiple sh iftin g . Incidentally, double sh iftin g rem ains confined to com paratively few m ines, chiefly to long-face w ork, developm ent, and e x traction of long-standing pillars.
T h a t thin coal bulks less as the bugaboo of present m ining w as made m an ifest d u rin g the p a st year. M a chines, p articu larly conveyors, en larged the area and low ered the seam thickness lim its of economical m ining.
N ow , coal dow n to the w orking height of cutting m achines is being taken in lim ited a r e a s ; recovery o f 30-in. coal is relatively common. A voidance by m odern m ethods of y ard ag e and dead- w ork penalties, the fact th a t m uch of the thin coal le ft in previous o p era
tions is of high quality, and dem and fo r quality ra th e r than volum e p ro duction are the d eterm ining factors.
In some cases pro d u ctiv ity on the basis of m an -sh ifts has been m ore th a n doubled by th e use of m achines in th in coal. R ecent im provem ents in equipm ent design, especially the low ering in heig h t of m ining m a
chines, locomotives, and m ine cars, have greatly accelerated this activity.
I
T IS said th a t the track-m ounted cu ttin g m achine is the logical successor of the sh o rt wall cu tter, ju s t as the la tte r succeeded the b re ast ty p e ; it also is believed th a t the superseding of the first type fo r the second will be at a ra te fa ste r th an w as th a t of the second fo r th e th ird . A t any rate, track-m ounted cu tters are being in stalled in all fields, in thick coal and in thin. R ead ju stm en t of w age bases fo r cutting-m achine ru n n e rs has been a stim ulus to the in troduction of these m achines.
B ut in In d ian a labor has held out a hand to stay this progress by o b ject
ing to the use of this m achine in con
nection w ith hand loading. By co n tra c t the m achine is allow ed in com bination w ith m achine loading only. I t is an ill-advised g estu re a t
tem pting to th w a rt m echanization, w hich cannot be halted w hen econom ic forces decree its consum m ation. F o r tunately, labor in general takes a constructive view point in th e m atter.
Several new types o f loading m a
chines w ere introduced. O n e is the C larkson track-m ounted loader, w hich uses belting, traveling in 24-in.
I-beam s, instead of m etal flights in its conveyor construction. G ath erin g arm s m ounted on chains crow d the coal onto the fro n t convevor. T h e
62 C O A L A G E — V o l.3 6 ,N o .2
M y ers-W h aley “ A u to m at” is a new coal-loading m achine incorporating a one-piece shovel w hich is operated by tw o sets of d riv in g rods, one fo r m ov
ing the shovel back and fo rth and the o th e r fo r tiltin g the shovel to dis
charge position ( Coal A g e , V ol. 35, p. 1 3 6 ). In the light-w eight class ap
p eared th e Jeffre y 4 4 -C loader ( Coal A g e , Vol. 35, p. 4 6 5 ), and the U tility sem i-loader ( Coal A g e , V ol. 35, p.
4 1 3 ), both of which in operation are supplem ented by som e degree of hand shoveling.
T
H E tendency in pit-car loader design is tow ard heavier and m ore rugged construction. A tten tio n to perm issibility of equipm ent continues and m uch atten tio n has been given to the fro n t o r loading end to allow' tw o o r m ore m en to shovel w ithout in te r
ference. C hanges in conveyor con
stru ctio n involved utilization o f m ore d urable m aterials and o th e r refine- . m ents m ore th an the developm ent of newr types. F airfield E ngineering Co. b ro u g h t o u t a new sectional drag type face conveyor designed fo r speedy m oving aro u n d pillars ( Coal A g e , V ol. 36, p. 1 0 )-.
P illa r ex tractio n w ith mobile load
ing m achines cannot yet be said to be a general practice. In the M id-W est, w h ere th e re is a concentration of these units, little pillar coal is taken.
In m any m ines elsew here, the m a
chines a re applied only to p artial e x tractio n o f pillar coal. In view of this situation, it is in terestin g to note th at tw o com panies in P ennsylvania have in au g u rated m achine loading on the open end of pillars, a m ethod which appears as inviting as long-face w ork w ith conveyors from the standpoint of theoretical sim plicity and yield per cut. T h e ro o f in both instances can be described as fairly sound.
O n e of these com panies by open- ending on an oblique has succeeded in establishing a 1.450-ft. pillar line u n d e r a cover of 350 ft. T he other com pany has been w o rk in g pillars open-ended at an angle of 75 deg. off the center line of face room s as m eas
u re d a t the pillar point. I t w as found, how ever, th a t in p illar ex tractio n on an angle to the slips of the seam, the coal cannot be readily released from the solid. T o overcom e this difficulty, a new layout has been started in w hich the pillar ends will parallel the seam face and yet be at an angle of 4 5 deg. to th e room course at the point of sm allest angle.
T h e p ro jec ts of these two com
panies, both of w hich are considered experim ental, should shed some light F ebruary, 1931 — C O A L A G E
on the degree to w hich rap id ex tra c tion of pillars affects ro o f control in mechanical loading. W ill resu lts be as favorable to loading m achines as they have been to conveyor ex traction of pillar coal by open-end m ethods?
T he real test, of course, will com e a fte r a large area has been pillared.
O ne of the new m ining layouts fo r mechanical loading w hich took on prom inence d u rin g th e y ear is th e checkerboard system developed at a m ine in In diana. In th is system room s a re driven 30 ft. w ide, leaving 40-ft. pillars w hich are pocketed by 20-ft. crosscuts on 4 0 -ft. centers.
T he 20-ft. stum ps rem aining are le ft to hold th e ro o f and are n o t recov
ered. T h is arran g em en t allow s 40 per cent o f the coal recovered to be loaded into trip s of cars ( Coal A g e , Vol. 35, p. 8 5 ).
In conveyor m ining, o p erato rs have grow n m ore p artial to room -and-pil- lar system s— som etim es w ith m odifi
cations— a t the expense of typical long-face layouts. T h e fo rm er have proved them selves, b u t in general th e latter have not. E conom ies from long faces appear about as f a r off as ever in th e past, except in scraper mining, w here extended faces have given best results.
O ne com pany in M ary lan d con
tinued the successful use of steel-arch tim bering u n d er broken cover in tw o of its B ig V ein seam m ines. T h is arch is shaped like an inverted U and the ends are rested on sm all steel plates on the floor o f the heading.
H ardw ood boards, som etim es treated w ith preservative, are used as lag-
A n Acknowledgment
T his, the T w en tieth A nnual R e
view and Progress N u m b er, is the result o f co-operation given the editors by m en o f th e in d u s
try and associated agencies. I t is fitting th a t this invaluable assistance be acknow ledged.
T herefore, appreciation is here expressed to the executives, m anagers, superintendents, and engineers in the industry itself, and to the individuals in related activities w ho contributed so generously o f their tim e an d ef
fort. So m any joined in the com pletion o f this w ork th a t it is n o t possible to m ention all by name.
ging. In cross-section the m em ber is T -shaped, 3 in. b road and 2f- in.
deep, w ith a thickness of | in.
O f all its applications in this coun
try , the m erits of the collapsible steel prop have perhaps been seen to best advantage in long-face layouts.
W h e re it has been used system atically in this kind of w ork it is generally accepted as a good thing. A better recom m endation could h ard ly be given to urg e its use, if not in pillar extraction, xin the driving of room s and entries, w here dem ands are less severe. I f fo r nothing else, it has its use fo r keeping ro o f safe at the face w hile the men and m achines are at w ork. A com pany in P ennsylvania keeps a set of screw jacks on loading units fo r th is very purpose.
I t is to be reg rette d th a t the in d u stry as a w hole has m ade so little headw ay in the utilization of steel as a su b stitu te fo r w^ood in m ine tim bers.
M echanization has plainly show n th a t the po o rer grades of w ooden tim bers cannot be safely used and th a t the b e tte r grades are too expensive.
T h ese tw o fa cto rs will eventually bring about w ide use o f recoverable steel roof supports in this country, as they already have across the seas (see p. 82, this issu e).
P
N E U M A T IC coal picks m et w ith increasing fav o r largely in thin seam s fo r breaking dow n, shearing, and u n d ercu ttin g coal. O ne com pany has a large num ber o f picks in operation fo r undercutting. In A labam a m ining these tools have increased the productivity of face m en roughly one- th ird ( Coal A g e , V ol. 35, p. 7 5 ).
T h e ir w eight is about 25 lb. and th eir strokes about 3,000 p er m inute.
D u rin g th e y e a r the U . S. B ureau of M ines issued an approval plate fo r a one-m an electric d rill of G erm an design fo r 250-volt d.c. service. A few' electrically operated ro ta ry coal drills w ere installed in the anthracite region. Also, a pow er-driven ex- panding-barrel type of wedge, used in place of explosives fo r b reaking dow n coal, w as developed ( Coal A g e , Vol.
35, p. 3 5 7 ).
M ine-car capacity in new installa
tions has been steadily increased.
E x p erien ce has show n th a t u n d er favorable circum stances a car costing, say, $250, m ay replace a serviceable car costing h alf th a t am o u n t an d pay fo r itself in as little tim e as a year.
T h e gain is th ro u g h all-around im provem ent of operations. F o r best results, it has been show n th a t cars m ust be designed expressly fo r th e specific job.
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