Coal Age : devoted to the operating, technical and business problems of the coal-mining industry, Vol. 29, No. 21

C ^oal A ^g

McGr a w- Hi l l

i BhSmI^ G Co“ p a n y ' Inc- D e v o t e d t o t h e O p e r a tin g , T e c h n ic a l a n d B u s in e s s

Ja m e s H . McGr a w. P r e s i d e n t r 0 1 Da w s o n Ha u.

B. J . M e h r e n , V i c e - P r e s i d e n t P r o b le m s o f t h e C o a l-M in in g I n d u s t r y E n g i n e e r i n g E d i t o r

Volume 29 NEW YORK, MAY 27, 1926 Number 21

Where Statistics Would Help

A

T h ere are, h ow ever, ce rta in sta tis tic a l a c tiv itie s th a t the fed era l g o v e rn m en t properly m ig h t expand or in a u g u ra te. C on cern in g th e se th ere could be no ch al­

len ge. T h e se s t a tis tic s rela te to p roduction, d istr ib u ­ tio n and con su m p tion . T he g o v ern m en t is, o f course, and h a s b een fo r som e tim e , co llectin g and p u b lish in g w eek ly d ata on p rod u ction . T he only c r itic ism w h ich m ay be leveled a g a in s t th o se fig u res is th e ir lack o f detail. A b ig step fo r w a r d w a s tak en w h en th e pro­

duction fig u re s w ere broken dow n in to to n n a g es by sta te s. B u t th e a n a ly sis sh ou ld go fu r th e r . T h e sta te figu res sh ou ld su p p ly in fo r m a tio n a s to th e ou tp u t o f th e im p o rta n t p ro d u cin g d istr ic ts. T h e Bureau! o f M ines a lrea d y is w o r k in g on th is p a rticu la r problem , and it sh ou ld be en cou raged in its u n d ertak in g.

I t is sev era l y e a r s sin c e a n y a tte m p t w a s m ade to p u blish data on d istr ib u tio n . Y e t su ch data are a n e ces­

sa ry com p lem en t to th e p rod u ction figu res. T h e la tte r tell on ly h a lf th e sto ry . T h ere are no in su rm ou n tab le difficulties to th e co llectio n and com p ilation o f d istr ib u ­ tio n s ta tis tic s . It is m erely a q u estion o f s e ttin g th e proper m a ch in er y in m otion . F o r y ea rs th e Illin o is and In d ia n a Coal Traffic B u rea u , a railroad o rg a n iza tio n , h as been co m p ilin g su ch data w ith resp ect to th e d is­

trib u tio n o f th e p rod u ction o f th o se tw o sta te s. T he Ohio B u rea u o f Coal S t a t is t ic s h a s been p e r fo r m in g a sim ila r b u t le ss v o lu m in o u s se r v ic e fo r cer ta in oth er fields. In n e ith e r ca se, how ever, are th e s e m o n th ly re­

p orts a v a ila b le to th e g e n e r a l pu b lic or to th e coal in ­ d u stry a t la rg e.

T he a c tiv itie s o f th e se b u re a u s in th e ir lim ite d areas s u g g e s ts h ow th e problem o f c o lle c tin g s ta tis tic s , n a tio n a l in scope, sh ou ld be m et. T h e ra ilro a d s have th e b a sic data. T h e ta sk o f a sse m b lin g it fr o m th e c a r r ie r s’ record s w ou ld b e c o m p a r a tiv ely sim p le. T he task o f c o lla tin g in d iv id u a l rep o rts fro m th o u sa n d s o f o p erators ev e ry m on th w ould be a lm o st im p o ssib le.

M oreover m a n y p ro d u cers se llin g th r o u g h sa les a g e n c ie s do n o t k n o w th e final d e stin a tio n o f p a r t o f th e ir to n n a g e . T h e I n te r s ta te C om m erce C om m ission m ig h t w ell is s u e an order r e q u ir in g th e r a ilr o a d s under it s ju r is d ic tio n to fu r n is h it w ith m o n th ly d istr ib u tio n

rep orts. In fa ct, no oth er agen cy is so w ell situ a ted fo r the collection and p u blication o f th is in form ation .

W ith com plete data on production and d istrib u tio n available, th ere still w ould rem ain sta tis tic s on stock s in th e hands o f consum ers and consum ption. T hese s ta tis tic s are e ssen tia l to a w ell-rounded pictu re. T hey are n ecessa ry i f th e in d u stry is to conduct its b u sin ess in te llig e n tly and if th e consum er is to place h is orders w isely . T he coal in d u stry cannot supply th ese figures.

The consum er alone h a s th e data. The B ureau o f the C ensus, in co-operation w ith th e B ureau o f M ines, has m ade som e stu d ies o f th is situ a tio n , but th e stu d ies to date have been n eith er com prehensive enough nor issu ed w ith sufficient freq u en cy to serve as a sen sitiv e b arom eter of con d ition s. T he w ork should be expanded and quickened.

Post-Convention Soliloquies

A

Q uick p la n tin g stim u la te s grow th . A con ven tion a m onth old has little o f its v ita lity le ft, so tr y and a r ­ ran ge a ffa irs in a m anner th a t w ill p erm it o f quick action . Com panies, w h ich have se n t m en should take care th a t th e g a in m ade is n ot lo st by in action .

T here is need th a t th e problem s o f th e in d u stry be seen in a la rg e w ay. L ittle im p rovem en ts in p ra ctice are good, but v ita l ch a n g es are b etter. Som e str ik in g d evelopm ent should be planned; fu r th e r data should be accu m u lated ; v is its should be m ade to places w h ere im proved op eration is in actual p ractice. T he p ile o f le tte r s on th e desk should be prom ptly reduced, so as to leave th e m an ager and su p erin ten d en t tim e to plan.

It is to be rem em bered th a t th e b u sin e ss o f an alert m in e official is not to tra v el th e old w ell-b eaten p ath s o f h is pred ecessors, but to break a new road to efficiency.

H ave you no reserv e o f im a g in a tio n ? W ill you le t your n e g a tio n s be m ore num erous and m ore p o ten t th a n your affirm ations? H ave you atten d ed th e con­

ven tio n w ith a firm co n v ictio n t h a t w h a t is n ew is n ot true, and w h a t is tru e is n ot new ? I f so th e con ven tion is lost to you. T he w orld m oves alon g. T h ere have been hundreds w ho q u estion ed all th a t w a s o rig in a l, bu t th e fe w w h o sa w and b elieved w h a t w a s w o rth se e in g and b e liev in g advanced in d u stry and profited, and w ith th em th e w orld.

In con ven tion s th e w isd o m o f m any m en is pooled.

W e learn w h a t h as succeeded, and i f a n y th in g h as fa ile d w h y it did not succeed. F ro m th is w e can ch art a s a fe cou rse to la rg er accom p lish m en t, b u t no one su c ­ ceeds w ho does n ot act. It is perhaps e a sie r to r e st im m obile, b u t th o se w h o do so g e t n ow h ere. T he con ven tion a t C in cin n a ti w ill m ove m a n y m en fo rw a rd and leave th e re st to m uddle alon g u n h ap p ily to w a rd

751

752

C O A L A G E

Guessing or Knowing

stan d still g r a v ita te rapidly to th e rear w h ere are ,—^q q qF T E N th e m in e fo rem a n does n ot know at found the m isfits and n e’er-do-w ells w h ose la m en tation s I ^ .n th e day ju g t h o w m a n y m en th ere are w ould have us believe th a t the coal in d u stry is w ith o u t ^ ^ w orkingg and in w h a t se c tio n th e s e m en m ay be aw ards and opp ortu n ities fo r any. found> How> th en , can h e a r r a n g e h is tr ip s and h is

- g a th e r in g fo r ces? In th e ea rly m o r n in g h e assu m es th a t all th e p laces are cu t t h a t sh ou ld h a v e been cut

Free of Detail

Som e com panies keep a research en gin eer to m ake t h is m ay be avoided if , ea r ly in th e d ay, th e in q u iries into new m ethods o f a ch iev in g resu lts. _ H e telephone is used to a d v a n ta g e b y som eon e w ho en- can spend a w eek or a m onth v is itin g th e w o rk in g s deavors to a scerta in h ow m a n y m en are ou t. F u rth er under con sid eration and other m in es a t rem ote p oin ts. inf orm atio n w ill be a v ailab le i f th e m en check in to th e H e prepares estim a tes. H e su g g e sts th e n ecessa ry sur- m ine and t h e n ig h t fo rce lea v es a record as to w h a t h as v eys. H e consults w ith m a n u fa ctu rers’ rep resen ta tiv es. been done du ri n g th a t s h ift. S o m etim es p la ces are not H e d iscu sses th e su g g e ste d im provem ent w ith m en w ho cut; a sw itch is n o t laid , w a te r com pels a m an to lay h ave tr ie d it, i f any have done so, and in th e end h e offi m en are s jck or h a v e sic k n e ss a t h om e. W hen th ese g a th e r s up h is data and p uts h is conclusions in to a fa c ts are a scertain ed , d riv ers can be d isp a tch ed here c a refu lly planned report, and then, a fte r con su ltation , 01, t h e r e ; roadm en se n t to clean u p ; tr a c k la y e r s d irected h is c h ie fs decide on th e m erits of th e su g g e ste d im - to lay s w it c h e s ; b ra tticem en s e n t to m end a fa lle n stop- provem ent, k eep in g in m ind th e retu rn on the necessary p in g or build one in th e n e a r e st ou tb y cr o ssc u t w h erever cap ital in vestm en t, w hich should be about 15 per cen t a new crosscu t h as been com pleted.

fo r s a fe ty and should have long enough life to return A fte r an h ou r’s in v e stig a tio n , th e m in e fo rce can be th e cap ital expended. T h is is th e m odern w ay. Our ap p ortion ed w ith efficiency. P e r h a p s th e fu ll com ple- coal m in es have all too fe w research en gin eers. m en t o f g a th e r in g u n its is n ot n eed ed , and th e forem an _ w ill be saved fro m th e n e c e ssity o f lo o k in g fo r a m iner to replace som e m otorm an or d riv er w h o h a s la id off

A Virtue in Delay

E

r eg u la te th e sig n a ls at th e variou s cro ssin g s by an elec- O b tain in g th a t k n ow led ge sh ou ld be n o t th e fo rem a n ’s trica l cu rren t, so th a t all w ould in d icate “S top ” a t one but a su b o rd in a te’s d uty. T h e fo r em a n sh ou ld be given tim e. B u t w hen th e schem e w as tried , all th e str e e t th e data so th a t he can a c t on th em . N o th in g aids cars on th e avenue w ere stopped and sta rted at th e m orale m ore th a n a fa st-w o r k in g fa c t-fin d in g arran ge- sam e m om ent and as th ere w ere m any o f th em th e m ent. M any a m an le a v e s th e m in e b eca u se h e finds he sta r tin g b rou gh t such a heavy load on th e su b sta tio n cannot w ork as soon as h e reach es h is place and doubts th a t th e plan w a s discarded. F urtherm ore, th e c it y ’s i f he w ill g e t serv ice. H e com es o u t to a r g u e w ith th e plan tended to d isru p t C leveland’s d iv ersity fa cto r. b oss w h en h e should kn ow th a t h e can s ta y in h is place

M uch th e sam e effect is experienced w hen pow er fa ils and g e t th e serv ice h e n eed s. H e sh ou ld b e told ju s t in th e m ine and is suddenly restored. E v ery m otor- w hen he w ill g e t it. M any a n e e d le ss tr ip w ill be saved m an, ev ery m achine cu tter, every pum pm an w a n ts h is i f som eone is co llectin g fa c ts and d is tr ib u tin g w o rd fro m m otor, cu tter or pump, w h ich ever it m ay be, to g e t im m e- th e b oss t h a t th e se rv ice w ill sh o r tly be fo r th c o m in g ,

d ia tely in to action . It tak es m ore pow er to sta r t th a n A n y th in g th a t p rev en ts m en fr o m ju m p in g loaded to run m ach in ery, so th e demand fo r pow er is abnorm al tr ip s to com e to th e su r fa c e d e crea ses th e p o ssib ility fo r th e first m in u te a fte r th e restoration o f th e cu rren t, o f accid en t. F u rth erm o re, w h en p rop s a re d elivered T he D a v is Coal & Coke Co. has m et th e difficulty w ith prom ptly in a n sw er to a telep h o n e dem and th e m in er is i t s m otorm en by in stru ctin g h a lf o f th em to w a it one le ss lik ely to ta k e a ch an ce in a n im p ro p erly tim b ered m in u te a fte r pow er is restored b efore a ttem p tin g to room . M any a w ord p a ssed to a m o to rm a n f a ils to sta r t. In consequence a pow er fa ilu r e does n o t cau se reach th e r ig h t p erson a t th e su r fa c e and b y a p p o in tin g a h ea v y peak. T he m en respond q u ite readily, w h ich a m an to receiv e su ch in fo r m a tio n a c tio n is m ad e m ore p erhaps is stra n g e, because th e average m otorm an irk s certa in . T he telep h on e and a m a n to a n sw e r it h a v in g at w a itin g and w a n ts to be up and doing. a pad on w h ich h e can ta k e n o te s and a ruled and It h as been su g g ested , how ever, th a t it m ig h t be pos- ta b u la ted sh e e t on w h ich he ca n c o r r e la te in fo rm a tio n sib le to put a tim e-lim itin g relay on a locom otive th a t w ill sa v e a b oss m uch an n o y a n ce and h elp h im plan h is w ould m ake it dead till a certain fixed len g th o f tim e w ork m eth od ically. T h e m in e fo r e m a n a lw a y s has a fte r th e pow er is re-estab lish ed . T h at w ould, how ever, p len ty to do and e v e r y a s s is ta n c e sh o u ld b e afforded com e in to actio n every tim e th e tro lley w h eel w a s him in th e d o in g o f it. P e r h a p s t h is se r v ic e can be a d ju sted to th e w ire. So perhaps it is b est to leave th e restr ic ted in a sm all m in e to c e r ta in h o u rs, b u t in th e m a ttei in th e hands o f th e m otorm en and o th ers. early m o rn in g it sh ou ld c e r ta in ly b e afforded.

May 27, 1926

C O A L A G E

H ow M in es w ith U n d e r g r o u n d D u m p s A re T r y in g T o E lim in a te C oal-D ust H azard

N o C o m p lete Cure H a s B ee n F ound, but S h a fts A re B e in g M ade D ea d as to V e n tila tio n , A u to m a tic D oors In sta lle d to K eep D u st from M ine and C oal I s B e in g W e tte d at F a ce and D um p

B y C. W . O w in g s * a n d V . C. A llis o n f U. S. B u re a u of M ines, P itts b u rg h , P a.

I N THE LAST FIV E YEARS there has been a growing use of underground dumping in shaft coal mines where large production is desired. This is largely due to the economies resulting from dumping into underground bins and hoisting the coal with skips or conveyors and to the fact th a t more coal can be hoisted from a single opening in this way than is possible w ith the usual method of car hoisting. How­

ever, as many hoisting shafts are used as intake or downcast airways, the coal dust resulting from dumping operations is carried back into the mine, augmenting the ever-present danger of a coal-dust explosion, unless some provision is made to intercept the dust.

The danger from accumulations of coal dust is ap­

parently fully realized by coal-mine operators and in every installation visited, provisions have been made to nullify this hazard. The Bureau of Mines has made a preliminary survey of a num ber of schemes for combat­

ing the coal-dust hazard th a t have been put into prac­

tice in mines equipped w ith underground dumping sys­

tems. The purpose of this paper is, by describing the methods now in use, to bring to the attention of operators contemplating the use of such a system some of the difficulties involved in its use.

The explosibility of coal dust when in a dense cloud

P u b lish ed b y p erm issio n of D ire c to r, B u re a u of M ines. T he in fo rm atio n c o n tain ed in th is a rtic le , in re g a r d to specific m ines is used th ro u g h th e c o u rte sy of th e m in e m a n a g e m e n ts concerned an d w ith th e ir fu ll p erm ission.

The h ead p ie ce show s th e flam e e m e rg in g fro m th e E x p e rim e n ta l Mine of th e B u re a u of M ines a t B ru c e to n , P a ., fro m a n explosion caused b y a llo w in g fine coal d u s t to fa ll fro m a V -sh a p e d sh e ll onto a flam e o r elec tric a r c lo c a te d a b o u t 6 ft. o u tb y th e shelf.

• A s s is ta n t m in in g engineer, f A s s is ta n t fu el chem ist.

is universally recognized by coal-mining men. For coal dust to ignite or explode, there are three necessary fac­

tors, namely, a source of ignition; a sufficient quantity of dry coal dust and an agent which will raise the coal dust into a dense cloud.

There are two general sources of ignition common to coal mines—open lights and arcs from electric wires or electrical equipment. According to Tracy in 1892, at Durham, England, a cloud of coal dust, raised by men shoveling pulverized coal in a coal bin, was ignited by open lights hung near the bottom of the bin. The resulting explosion killed three men. A t a western coal mine material from an old dump was being loaded by steam shovels, and in order to loosen the m aterial, shots were fired. This resulted in unburned coal dust, which had been loaded from the tipple onto the top of the rock pile, being raised in a dense cloud which, coming in contact with the flames of the burning refuse, ignited and burned nearby workmen.

The Bureau of Mines has repeatedly dem onstrated th a t an open light will ignite a cloud of coal dust in the absence of gas. One method of making such a te st is as follows: N ear the portal of the main entry a t the Experimental Mine, Bruceton, Pa., coal dust is piled on a V-shaped shelf laid across the entry near the roof.

An open-flame lamp is suspended about 6 ft. outby the shelf. By means of compressed a ir the coal dust is blown in a dense cloud down upon the flame. Imme­

diately the dust ignites and burns rapidly, a swirling,

boiling mass of flame passing out of the entry. An

observer standing inby the point of ignition is made

fu lly aw are of th e p ressure b ein g developed by the crackling o f h is ear drum s and by th e w ay in w hich h is body is sw ayed back and forth by th e p ressure w ave

developed. .

A sim ila r te s t is m ade, su b stitu tin g an electric arc lamp fo r th e open-flame lamp. The resu ltin g ig n itio n o f the d ust is sim ila r to th a t obtained by u sin g the open-flam e lamp. In th e headpiece th e m ass o f flame from one o f th ese te s ts is show n issu in g from th e m ine m outh, the volum e o f th is m ass o f flame b ein g about 1,600 cu .ft.

The ex h ib itio n coal-dust explosion g a llery o f th e bureau has been exten sively used over th e U n ited S ta tes in th e la st tw o years in effectively d em on stratin g the

Fig. 1— Miniature Reproduction of Mine Gallery

T h i s b o x , w h i c h I s 6 f t . l o n g a n d o f 6 x 6 i n . c r o s s - s e c t i o n , i s p r o v i d e d w i t h m e a n s t o b l o w c o m p r e s s e d a i r i n t o a p i l e o f c o al d u s t w i t h i n t h e b o x t h u s r a i s i n g a c l o u d . A n o p e n - f l a m e l a m p p l a c e d i n s i d e t h e " g a l l e r y ” i g n i t e s t h e d u s t , c a u s i n g a n e x p l o s i o n w h i c h c a n b e c l e a r l y s e e n t h r o u g h t h e g l a s s w a l l s . A s n o g a s i s p r e s e n t , t h e d u s t i s d e m o n s t r a t e d t o b e c a p a b l e o f c a u s i n g a n e x p l o s i o n w i t h o u t t h e a i d o f g a s .

e x p lo sib ility o f coal dust from open flam es in th e ab­

sence o f gas. T h is gallery is 6 f t . long and 6x6 in.

square, w ith all fou r sid es o f g la s s ; th e rear end m ay be tig h tly closed. O ne-half oz. of coal d ust is placed upon th e floor o f th e gallery at th e rear and blow n by com ­ pressed a ir down over a carbide lamp placed 18 in.

in b y th e open end o f th e gallery. The coal-dust cloud ig n ite s and a m ass o f flame, som etim es o f a volum e of 200 cu .ft., issu e s from th e m outh o f th e gallery. T h is m in iatu re en try w ay is show n in F ig . 1.

T hese te s ts prove the p robability th a t exp losion s w ill occur from th e ig n itio n o f coal d ust w hen no g a s is present. T h ey su b sta n tia te th e conclusions reached a fte r the S tark ville (C olo.) explosion o f 1910, th e D olo­

m ite N o. 3 m in e explosion a t D olom ite, A la., in 1922 and the D aw son N o. 1 M ine explosion, D aw son, N . M., in 1923. The second explosion m entioned w a s caused by cars b reak in g loose, r u n n in g down a slope, w reck in g th em selves and stir r in g up a coal-dust cloud, w h ich w a s ig n ite d by an electric arc o f a ruptured pow er cable.

T he first and th ird explosions w ere caused by w recked tr ip s k nocking out tim b ers and also r a isin g dense coal- d ust clouds w h ich w ere ig n ited by arcs fro m sh ort- circu ited tro lley w ire s. T hese accid en ts confirm th e exp erim en tal resu lts, w h ich show th a t coal d u st can be ig n ite d w ith open lig h ts or electric arcs in th e absence o f ex p lo siv e g a s.

U nderground dum ping p resen ts a sim ila r hazard. In th e d um ping operation, freq u en tly a dense cloud o f coal d u st is put in to su sp en sion . In m any m in es open-flam e lam ps are w orn b y th e w orkm en. E lectrical equipm ent fo r d um ping is freq u en tly in stalled and even w h ere

pneum atic dum ps are em ployed, e le c tr ica lly d riven car hauls are used nearby.

T he m ine m ay, th e r e fo r e, h a v e an e x tr e m ely hazard- ous con d ition — a know n sou rce o f ig n itio n and the likelihood o f a dense coal-d u st cloud. I t is a solu tion o f th is problem th a t c o n fro n ts th e coal-m in e op erators w here underground d u m p in g o f coal is p ra cticed or is in contem plation.

It is in te r e stin g to ob serve th a t ev ery m in e v isite d during th is p relim in a ry in v e s tig a tio n had adopted som e m ethod to p reven t th e coal d u st th a t is fo rm ed in underground d um ping fro m tr a v e lin g back in to th e m ine w ork in gs. T h ere are tw o p r e d o m in a tin g sy ste m s w h ich are o ften com bined. One is to put a dum p on a sep arate sp lit o f a ir and th e oth er to u se a w a te r sp ray.

A notable exam ple o f h a v in g th e dum p on a sep arate sp lit is th e H arm ar M ine o f th e C on su m ers M in in g Co., H arm arville, P a . W hen th e tw o -ca r r o ta ry dum p and skip h o ist w ere first in sta lled a s th e s h a f t w a s d ow ncast, coal d ust accum ulated in d a n g ero u s q u a n titie s a t th e s h a ft bottom and on th e in ta k e a ir w a y s. In order to overcom e th is con d ition , th e h o is tin g s h a f t w a s m ade n eu tral and 12,000 c u .ft. o f a ir per m in u te w a s passed over th e dump, ap p roach in g it fro m both sid es.

Cu t a Ho l e i n Co n c r e t e Li n i n g

A bout 10 ft . in b y th e s h a ft a h ole ab ou t 5x5 f t . w as cu t in th e con crete lin in g , a llo w in g th e a ir to p ass th rou gh a crosscu t, over an o v erca st and th en ce to the fa n s h a ft ( F ig . 2 ) . T h e cro ss-se c tio n o f th e cro sscu t is about 6x12 ft., and th e su d d en d ecrea se in v elo city o f th e a ir in p a ssin g fro m th e sm a ller to th e larger area cau ses a la rg e q u a n tity o f th e d u st to s e ttle on th e floor. T h e a ir e x h a u st fro m th e dum p p la y s upon th e th resh old o f th e 5 x 5 -ft. h ole and th u s p reven ts accum ulation o f d u st th ere. F ig . 2 is a sk etch sh o w in g th e la y o u t a t th e s h a ft b ottom and th e d irectio n o f the a ir th ro u g h th e b yp ass.

T he s h a f t e n try h a s been lin ed w ith co n crete and th o ro u g h ly rock-dusted. A n y coal d u st s e t t lin g on th e w h ite su r fa c e w ould be rea d ily d iscern ed , b u t on ly s lig h t q u a n titie s w ere se en on th e in b y sid e o f th e dum p.

T he atm osp h ere is v e r y clear d u r in g d u m p in g . In order to fu r th e r rem ove th e coal d u st fr o m th e air p a ssin g th ro u g h th e b yp ass, th e com p an y is co n sid e r in g in sta llin g a w a te r sp ra y a t th e 5 x 5 -ft. port.

A G E ^ 0L' ^

F ig. 2— Dust Prevention at Harmar Mine

T h e s h a f t h a s b e e n m a d e n e u tr a l a s f a r a s v e n ti l a t i o n is co n - c e r n e d , b u t a h o l e 5 x 5 f t . i n c r o s s - s e c t i o n , h a s b e e n c u t in th e c o n c r e t e l i n i n g o f t h e s h a f t b o t t o m , w h ic h h o le is c o n n e c t e d w ith t h e r e t u r n . I n t o i t a i r i s d r a w n f r o m t h e m i n e . T h e a i r e x h a u s t p l a y s o n t h e t h r e s h o l d o f t h e h o l e a n d t h u s p r e v e n t s d u s t fro m a c c u m u l a t i n g a t t h a t p o i n t .

Ma y

27. 1926 C O A L A G E 755

F ig. 3— Powhatan Dump Is at Foot of an Upcast Shaft; Much Dust Settles on Timbers

e m p t y t r a c k t o t h e d u m p w h e r e i t j o i n s i n t h e h o i s t i n g s h a f t a s w e l l a s o n a l l t h e a i r c o m i n g t h r o u g h c h u t e A a n d t h r o u g h s u r f a c e s o n t h e s h a f t b o t t o m . T h e l a t t e r t h e t r a c k w a y f o r l o a d s . T h i s a i r p a s s e s i s f l u s h e d w i t h w a t e r e v e r y n i g h t , a n d a u p t h e s h a f t . I n t h i s i n s t a n c e t h e d u s t

a c c u m u l a t e s o n t h e s t a i r w a y a n d b u n t o n s T h r e e a u t o m a t i c m i n e d o o r s h a v e b e e n

i n t r o d u c e d t o p r e v e n t t h e d u s t f r o m e n t e r ­ i n g t h e m i n e w h e n t h e a i r i s r e v e r s e d . A n a u x i l i a r y f a n o f a c a p a c i t y o f 5 0 , 0 0 0 c u . f t . p e r m i n u t e c a u s e s a i r t o f l o w a l o n g t h e

w a t e r l i n e i s b e i n g l a i d f o r t h e f l u s h i n g o f t h e s h a f t f r o m t h e s u r f a c e .

T he S p rin g d a le M ine o f th e A lleg h en y P ittsb u r g h Coal Co., L o g a n s F erry , P a ., is unique, in th a t the h o istin g s h a f t is reached by a p a ir o f en tries driven under th e A lle g h e n y R iver. T he coal is dum ped by a tw o-car p n eu m a tic ro ta ry dum p in to ch u tes w h ich load d irectly in to a double-deck sk ip . A th ick cloud o f d ust is ra ised d u rin g th is op eration .

A n a u x ilia r y fa n , d e liv e r in g 50,000 c u .ft. o f air per m inute v e n tila te s th e se u n d er-river en tr ie s th e air p a ssin g up th e h o is tin g sh a ft. A t p rese n t only sin g le doors are placed on th e h a u la g e roads at th e b e g in n in g of th e sp lit. W h en ever th e se doors are opened th ere is a re v ersa l o f th e a ir cu rren t, w h ich ten d s to draw th e coal d u st back in to th e m ine.

P la n s h a v e been m ade to in sta ll au to m a tic doors fo rm in g an a ir lock o f sufficient le n g th to accom m odate a tr ip o f cars, th e reb y e lim in a tin g th e reversal o f th e air c u rren t. A s th e riv e r e n tr ie s are v ery w et, little dust p a sse s in to th e m a in p a rt o f th e m in e, w h ich is rock-dusted.

Au t o m a t i c Do o r s Ke e p Du s t f r o m Mi n e

T he P o w h a ta n M in e o f th e P o w h a ta n M in in g Co., P ow h atan , O hio, dum ps th e coal in to a sk ip h o ist by m eans o f a tw o -ca r r o ta ry dum p a t th e bottom o f an upcast s h a ft. M uch coal d u st is ra ised in to su sp en sion w h ile th e coal is b e in g dum ped. In order to p reven t th is coal d u st fr o m r e tu r n in g in to th e m ine, au tom atic doors h a v e b een in sta lle d on th e tw o s h a ft en tr ie s and a c o n n ectin g c h u te B ( F ig . 3 ) and an a u x ilia r y fa n , d eliv erin g 50,000 c u .ft. o f a ir per m in u te, ca u ses air to flow a lo n g th e em p ty tra ck to th e dump, w h ere it jo in s th e a ir co m in g th r o u g h ch u te A and th e loaded track, and fro m th e n c e p a sse s up th e s h a ft. M uch of the coal d u st th r o w n in to su sp en sio n w h en d um ping accu m u lates on th e sta ir w a y and b u n to n s in th e h o is tin g sh a ft, a s w e ll as on all s u r fa c e s a t th e s h a ft bottom . E v ery n ig h t th e s h a f t b ottom is flu sh ed w ith w a te r and on th e su r fa c e a w a te r lin e is b e in g laid to th e top o f th e s h a f t to p rovid e a m ea n s o f flu sh in g out th e sh a ft.

T he s h a f t e n tr ie s a re ro ck -d u sted . Coal d u st a ccu ­ m u lates on th e s u r fa c e s o f th e s e e n tr ie s , e sp e c ia lly fro m th e dum p in b y to ch u te A , due to th e r ev er sa l o f a ir w h en ever th e a u to m a tic d oors a re opened.

M ine N o. 3, N a tio n a l M in in g Co., C ow den, P a ., w h ich u ses sk ip h o is ts , h a s a r o ta r y dum p a t th e b ottom o f a sh a ft, w h ich is d o w n ca st. T h e dum p is, th e r e fo r e , on th e in ta k e a ir, b u t th e a ir v e lo c ity over th e dum p is low . In a n a tte m p t to p r e v e n t th e d u st, fo rm ed in d u m p in g th e coal, fr o m b e in g ca rr ied back in to th e

m ine, w a ter sp rays w ere first tried b u t th e y w ere aban­

doned fo r th e p resen t m ethod.

S teel p lates sap arate th e s h a ft fro m th e dump and in th is plate have been cut tw o op en in gs, 1 f t . 6 in . x 3 f t. O pposite th e dump is a cro sscu t in w h ich is placed a concrete stop p in g. A bleeder o p en in g 15 x 22 in. p erm its a sm all q u an tity o f a ir to sh o rt-circu it and p ass in to th e retu rn airw ay.

Ro c k Du s t Si f t s Do w n o n Co a l Pa r t i c l e s

D irectly over th is opening is placed a steel hopper ( F ig . 4 ) w ith a cap acity o f about 350 lb. o f rock dust.

A p erforated iron strap , 2 in. w id e is placed in th e bottom o f th e hopper, to each end o f w h ich is attach ed a steel rope w h ich p a sse s over a p u lley and th en ce to th e w eig h basket.

A s the w eig h b a sk et m oves, th e iro n stra p also m oves back and fo rth , th e h oles r e g iste r w ith h oles in th e bottom o f th e hopper th ereb y ca u sin g rock d u st to s if t dow n over th e op en in g and m ix w ith th e coal-d u st cloud.

I t w ill be n ecessary, how ever, to in sta ll an a g ita to r to p reven t th e rock d u st from pack in g. T h e rock-dusted e n try on w h ich th e dump is located sh o w s th a t little coal d ust p a sses back in to th e m ine.

T h e in sta lla tio n o f a sin g le-ca r ro ta ry dum p and skip h o ist in th e H arw ick Coal Co.’s m in e at H arw ick , P a ., im m ed iately p resen ted a g r e a t coal-d u st hazard. In a sin g le day coal d u st w ould accum ulate fro m i to I in.

th ick fo r 100 f t . in b y th e dump. To overcom e th is con d ition a 12-in. p ipe w a s connected to th e u p cast s h a ft and b ro u g h t to th e dump. A stro n g su ctio n w a s obtained a t th e end o f th is pipe, b u t b e in g located a t th e ro o f and a g a in st th e le f t rib, con sid erab le q u a n titie s o f th e d u st p assed in to th e en tr y beyond.

T he dump is on a str o n g in tak e cu rren t, and th e n e c e ssity o f p r e v en tin g th e coal d u st r e tu r n in g in to th e m in e is fu lly ap p reciated . T he p ipe w a s n o t e n tir e ly su ccessfu l, so a rra n g em en ts have been m ade to in sta ll w a ter-sp ra y c u rta in s. A lso a canopy or hood m ay be placed over th e dum p and connected w ith th e su ctio n p ipe or a h orizon tal s lit run across th e e n try at th e ro o f and connected w ith th e u p cast s h a ft th ro u g h th e pipe.

W hen th e H . C. F r ic k Coke Co. co n so lid a ted its C olonial N o s. 1, 3 and 4 m in es and in sta lled th e now - fa m o u s b elt conveyor, 22,930 f t . lon g, m ean s w ere tak en to provide enough coal to keep th e b elts loaded a t all tim e s. T w o ro ta ry dum ps, 374 ft . lon g w ere in sta lled , w ith a ca p a city o f fro m th irty -fiv e to fo r t y c a r s each.

T he coal d u st fo rm ed in d u m p in g su ch a la r g e num ber o f cars is n o t g rea t. R ed s ig n a l lig h ts a t one end o f th e dum p m ay be e a sily seen fro m th e o th er end, 374 ft .

756 C O A L A G E VOL. 29, No. 21

F ig . 4 In D o w n c a st S h a ft a t N a tio n a l M ine N o . 3 R etu rn A ir Is B y p a sse d T h ro u g h D um p

T h e a i r v e l o c i t y i n t h e s h a f t i s l o w a n d i t w a s t h o u g h t t h a t w a t e r s p r a y s w o u l d b e a d e q u a t e t o p r e v e n t d u s t f r o m e n t e r i n g t h e m i n e . T h e s e f a i l e d , h o w e v e r . S o a i r w a s b r o u g h t t h r o u g h a c r o s s c u t a n d t h r o u g h t h e s t e e l p l a t e s b e t w e e n t h e s h a f t a n d d u m D w h e n c e i t p a s s e d i n t o t h e r e t u r n a i r w a y . T h e b i n s h o w n o n t h e l e f t i s k e p t s u p p l i e d w i t h p o w d e r e d r o c k . T h e m o v e ­

m e n t o f t h e w e i g h h o p p e r o p e n s h o l e s i n t h e b o t t o m o f t h i s b i n c a u s i n g t h e p u l v e r i z e d r o c k t o b e s p r i n k l e d o n t h e c o a l d u s t .

distant, while trips are being dumped. The small quan­

tity of dust is due to the thorough wetting of the coal at the face by the miner.

However, to prevent any dust returning into the mine, about 26,000 cu.ft. of air is brought into the dump at each end and then passes upward and out of openings, three of them on the right side and four on the left, to the return airways. At each opening is installed a water spray to beat down coal dust from the air passing into the return.

Another mine in the same district also uses water on the cutter bars of the miAing machines, and the miners sprinkle the coal before it is loaded out. As a further means of laying the coal dust, the rotary dump, which is used in connection with a skip hoist in a neutral shaft is covered with a steel hood.

• Cu r t a i n Sp r a y f r o m W a t e r Ri n g

As the cars are turned over the coal dust is beaten down by a curtain spray from a water ring composed of 2-in. pipe, placed on all four sides of the dump, in which ¿-in. holes are drilled every 3 in.; the water is under a pressure of about 95 lb. per square inch. No dust was seen anywhere on the bottom. The walls, although whitewashed about nine months previously, were fresh and white.

Where the hoisting shaft is downcast and the dump is on the intake airway, as in the Harwick and National No. 3 mines, there is a great tendency for the coal dust to be carried back into the mine. The use of a single suction pipe with no special nozzle or no hood or canopy over the dump has failed at the former mine. The bypass in the National mine appears to remove the greater part of the coal dust from the air. In each case there was considerable coal dust on the floor and down in the chamber below where the weigh basket was located. This coal dust must be loaded out every night.

The Springdale and Powhatan Mines, by making the shaft upcast prevents the dust from returning into the

mine, except when the connecting doors on the haulage roads cause a reversal of the air. Air locks will elim­

inate this feature, but accumulations of explosive dust in the shaft affect the most vital part of the mine.

Danger would result from an explosion in the shaft.

Dust accumulations at the shaft bottom and in the pit below the dump are added dangers. Some solution of the problem will doubtless be worked out.

A neutral shaft, as at the Harmar Mine, allows the dust to be collected through a bypass. However, here again we are confronted with dust accumulations on and below the dump. Undoubtedly the neutral shaft is the best means of providing for dust collection and elimina­

tion but a bypass with dry-collecting methods have not satisfactorily met the problem.

W a t e r a t F a c e a t Co l o n i a l Mi n e s

The Colonial Mines’ use of water at the face, is a step forward toward the solution, but above, on and below the dumps, there is an accumulation of dry dust.

The lessening of dust where water is used on the cutter bars of the mining machines and the sprinkling of the coal by the miner, as well as a strong water spray in an enclosed dump and a neutral shaft gives at least one solution of the problem. In the bins and the chambers surrounding them there was no dry dust, thereby reduc­

ing the dust hazard to a minimum.

Much dust is formed by cutting machines, by blasting and by the miner in picking down the coal and shovel­

ing it into the mine car. The dust problem at the underground dump is materially helped by the applica­

tion of water on the cutter bar and by the wetting the coal before it is loaded at the face. In the shaft the accumulation of dry dust may be much lessened by use of a water ring in connection with a neutral shaft, which, however, in winter would require a small split of warm return air to prevent the water from freezing.

The use 6f water may be impractical in some mines;

more especially where the dump is on the downcast which may result in freezing the water in winter.

Satisfactory removal of the coal dust formed in dump­

ing may be obtained under these conditions if the shaft or slope be made neutral, a bypass be provided at or near the dump, and a water spray installed to remove the dust from the air in the bypass.

In addition, the bypassed air should be allowed to expand immediately after leaving the dump and before reaching the return air. This is done at the Harmar mine and the result of this sudden decrease in velocity of the moving air is to deposit about 75 per cent of its coal dust before reaching the return airway. This method prevents coal dust being carried back into the mine, but has the disadvantage of allowing dry coal to accumulate around the dump.

Several large coal companies are investigating the possibilities of a dust-collecting system which will re­

move the coal dust from the bypassed air and deliver the cleaned air to the return airway. It is the opinion of several well-known ventilating and dust-collecting engineers that some such system could be adapted to mine conditions, one which would be practicable, and would collect at least 85 per cent of the dust.

It will be seen that the coal-dust problem from dump­

ing underground has not yet reached a fully satisfactory

conclusion for all conditions of shaft and ventilation

layout, but there is every reason to believe that in time

the problem will be solved.

M

27, 1926 C O A L A G E 757

C rozer R oad w ay s H a v in g R ea ch ed B o u n d a r ie s o f P r o p e rty ,

M in es N ow W ork in F u ll R etreat

D rainage and H aulage Grades Planned Before R oads W ere Driven — A dvancing-W ork Profit P aid D evelop m ent Cost— 4% -M ile H aul— Track L aid L ike Railroad as to L ines and Grades

By a Staff C orrespondent

T HE OPENING UP of the Crozer mines of the Crozer Coal & Coke Co., at Elkhorn, McDowell County, W. Va., which is midway between Blue- field and Welch, dates back to the early days of the Poca­

hontas field, when coal land sold for a song. At that time the Crozer Land Association acquired connected fee tracts aggregating over 10,000 acres underlaid with the Poca­

hontas No. 3 seam. This property has been mined for nearly forty years and will not be entirely exhausted a quarter century hence and perhaps not even then. The acreage is being mined by the Crozer Coal & Coke Co., the Upland Coal & Coke Co. and the Page Coal & Coke Co., all of which are subsidiaries of the land company.

Several companies also have leased from the Crozer concern. It is with the systematic methods by which this property has been operated in the past, as ex­

emplified by present methods at one of the plants, namely, that of the Crozer Coal & Coke Co., that this article deals.

The territory allotted to this plant consisted of 1,838 acres of thick coal belonging to the Pocahontas No. 3 seam. The mine started operations in 1887. Of this acreage, 1,064 acres have been mined out during the last thirty-eight years. Of the coal that remains 145 acres are in pillars and 629 acres in the solid. The average recovery during the past life of the property is

86.7 per cent, but in late years it has been about 90 per cent.

The operation consists of five mines, all of which lie under one hill. A fingered hollow almost completely divides the property into two territories which are con­

nected by a rather narrow neck. Of these two areas that which is adjacent to the Norfolk & Western R.R., which serves this operation, is by far the larger.

Within the boundaries of this larger territory are Mines Nos. 1 and 2. Mine No. 2 is exhausted to such an extent that in it the coal being mined is derived solely from the barrier and chain pillars of the main entry which is on the retreat. No. 3 mine is now en­

tirely mined out. During its life coal from it was hauled through the narrow neck which joins the two main territories and through No. 2 mine to the tipple.

De c i d e d t o Ad v a n c e En t r i e s t o Cr o p

No. 1 mine is depleted except for the barrier and chain pillars of the main entry and a few room pillars which are being mined in the final stages of the retreat toward this entry. As this main heading of No. 1 mine must serve as a part of the main haulway from Mines Nos. 4 and 5, the pillar coal which protects it will not be mined until after the latter operations are finished.

Mines Nos. 4 and 5 which lie in the smaller of the two main territories already mentioned, are comparatively new operations.

The development of these two mines was started in 1915 and was continued through the years of the World War when most of the coal produced at this plant came from Mines Nos. 1 and 2. It was decided at the be­

ginning of this period to advance the entries in these new mines, leaving the coal practically intact until the boundaries were reached, and then to remove by rooms and pillars the coal thus developed, working all the time on a full retreat.

The high prices for coal obtained during the last few years of the Twenties did not swerve the management from its predetermined plan. The company balanced the high cost of this development work in its two new mines by the lower cost of the coal from its old mines.

During the prosperous years, while the old mines were on the retreat, the new mines were being developed on the advance.

Today, as already intimated, little coal is being pro­

duced by the old mines, but the plant nevertheless pro­

duces about 1,700 tons per day. Most of this coal is bejng won in the new mines which, having been de-

One of the R oom s in the Crozer M ines

T h e s e a m i s 7 f t . 1 0 in . t h i c k . N o t e t h a t t h e s i g h t l i n e h a s b e e n e x t e n d e d t o t h e f a c e a n d t h a t a s u p p l y o f t i m b e r , c P p i e c e s a n d w e d g e s a r e k e p t o n h a n d . T h i s p l a c e i s 1 8 f t . w i a .

T h e h e a d p i e c e s h o w s t h e t o w n a n d p l a n t o f t h e C r o z e r C o a l &

C o k e C o ., a t E l k h o r n , W . V a . M o s t o f t h e p o w e r c o n s u m e d i n t h e C r o z e r m i n e i s g e n e r a t e d i n t h e s t e a m p l a n t s h o w n . i n p o ff ic e a n d s t o r e b u i l d i n g o c c u p i e s t h e c e n t e r o f t h i s p i c t u r e , i r j e r a i l r o a d i n t h e v a l l e y i s t h e N o r f o l k & W e s t e r n w h i c h i s e l e c ­

t r i f i e d a l o n g t h i s s t r e t c h .

7 5 8

C O A L A G E V

. 29, No., 21

B y T h is B rid g e a C ircu itou s R o a d w a y Is O b viated

T h i s s t e e l s t r u c t u r e i s 6 3 0 f t . l o n g a n d i n c o r p o r a t e s ^ a 2 1 0 - f t . s p a n . I t s e l e v a t i o n a b o v e t h e b o t t o m o f t h e v a l l e y i s l l o I t . B y i t s e r e c t i o n t h e r o a d w a s s h o r t e n e d a n d s t r a i g h t e n e d . i i a a i t n o t b e e n b u i l t , t h e t r a m w a y w o u l d h a v e b e e n c o m p e l l e d t o f o l l o w t h e o u t c r o p u p t h e r a v i n e , t r a c i n g t h e c o n t o u r o f t h e h i l l i n m o s t o f i t s m a n y e r r a t i c t u r n s .

veloped to their boundaries, are now on the retreat. In 1925 the Crozer plant produced 443,000 tons. In recent years prior to the last it maintained its standing as a big producer in the field, a fact which under the circum­

stances indicates the value of a nice balance between the high cost and lesser productivity of territory under development on the one hand, and the lower cost and greater productivity of territory being mined by rooms and pillars on the other.

P r o j e c t e d Li n e s a n d Gr a d e s

Prior to the beginning of the development work in Mines Nos. 4 and 5, the area to be traversed by these mines was surveyed. Levels also were taken to de­

termine what would be the most logical layout. This preliminary work was carefully collated so as to obtain in advance the data necessary for predetermining a lay­

out with particular reference to grades and drainage and to the possibility of easy access to the areas lying within promontories in the crop line. Accordingly, entries were projected on the map, and this layout has since been followed to advantage with scarcely any variation.

The success of this scheme shows that it is good policy to plan a mining operation with almost the same exactness with which a surface development is designed.

Many mines in regular seams are extended on short- time projections which are chosen without much regard for the future of the property. In contradistinction the program at Crozer embraced operations over long periods of time.

The Pocahontas No. 3 seam in these mines has an average thickness of 94 in. and contains two partings.

One of these is a 2-in. hard shale occurring about 9 in.

from the roof, which the miners call a sulphur band, and the other is a 4-in. bed of bony coal which occurs about 55 in. from the bottom. No attempt is made to

remove these impurities at the face. The separation is made by hand picking at the tipple and by means of a Bradford breaker in accordance with a procedure which is described elsewhere in these pages.

The mining system provides for the greatest possible degree of concentration in mining the rooms and pil­

lars. Rooms are driven only as needed and the pillars are drawn immediately in a retreat from the limits of the property and on a 45-deg. extraction line. Each room entry provides an average of nine working places, of which five are advancing rooms and four are retreat­

ing room pillars. Rooms are driven 18 ft. wide on 70-ft.

centers and are 330 ft. long. Entries are driven 12 ft.

wide on 70-ft. centers. The major entries are pro­

tected by barriers which in width vary from 150 to 500 ft.

Ni n e t y p e r Ce n t Re c o v e r y

Although the necessity for concentration of working places in the room-anjd-pillar system of mining has for many years been realized, until recently few companies followed this practice. The Crozer Coal & Coke Co. is- numbered among that few. By practicing concentra­

tion during the last 38 years, it has recovered 86.7 per cent of the coal in the area mined. Due to further refinements of its methods in recent years, its recovery has been about 90 per cent.

Practically none of the roof, which is of shale, is taken with the coal. The thickness of cover above these mines varies from 250 to 500 ft., of which 60 to 70' per cent consists of sandstone. The sandstone beds are more or less shaly, except the Eckman, which is massive. This bed varies from 20 to 50 ft. in thickness and occurs 75 to 100 ft. above the coal seam. Perhaps no other seam in the country breaks less readily.

Nevertheless it is being controlled without much diffi­

culty by concentration methods. This would not be the case, nor would the recovery be nearly as high, if the rooms had been driven promiscuously and pillars drawn irregularly.

The fact that a projection was determined before work commenced in Mines Nos. 4 and 5 has already been mentioned, but something should be said as to the accuracy with which the development is • made in ac­

cordance with that plan and as to the manner in which that accuracy is attained. All entries and rooms are driven on sights. On the entries, sight spads are put

Loaded Trip En R oute to T ipple

C o a l f r o m t h e f a c e t o t h e t i p p l e a t t h e C r o z e r m i n e s is h a n d l e d i n t w o l i f t s . I t i s h a u l e d o n e - t h i r d o f t h e w a y b y 1 5 - t o n l o c o ­ m o t i v e s t o a s i d e t r a c k w h i c h a d j o i n s t h e f a r e n d o f t h e b r i d g e a n d b y 2 0 - t o n l o c o m o t i v e s f r o m t h i s p o i n t t o t h e t i p p l e . H e r e i s s h o w n a 2 0 - t o n m o t o r c o u p l e d to a s t a n d a r d trip of 4 0 cars.

E a c h c a r h o l d s 3 i t o n s o f c o a l .

Ma y

27, 1926

C O A L A G E

759 in place by the engineering corps at intervals of 200

to 250 ft. Sight lines in rooms are painted by the trackmen. Levels are run every three months to deter­

mine diainage and grades. These are taken at intervals of 50 ft. on all entries and in all rooms which dip to excess.

Such details as listed above are more or less the routine of the engineering corps at any modern mine.

Howe\ ei, the duty and responsibility of the Crozer cor­

poration does not stop here. The engineering depart­

ment keeps in close touch with the operating manage­

ment and keeps informed as to the “strategy” which must be followed in driving rooms and pulling pillars.

The mine officials of course have their say in determin­

ing what this strategy shall be. The engineering corps not only locates proposed working places, but it also informs the underground officials as to when this or that room or entry shall be started and when work on a pillar shall be started or stopped.

Between visits of the corps the underground officials natuially must have jurisdiction, and furthermore may make an appeal against any decision of the former with regard to the sequence of working. This three-sided arrangement gives each of the factions which compose it an opportunity to make suggestions and obtain a clear knowledge of the purposes underlying the system of extraction.

At the beginning of a retreat from the boundaries, the hauls must of necessity be unusually long. The dis­

tance from the innermost point on the main haul in No.

A L o n g S t r a ig h t H a u l T h r o u g h N o . 1 M in e

D e r a i l m e n t s o n t h e m a i n h a u l a g e r o a d i n t h e C r o z e r m i n e s a r e p r a c t i c a l l y u n k n o w n . T h i s s t r e t c h o f s t r a i g h t t r a c k i s 5 ,8 0 0 f t . lo n g . T h e r a i l s w e i g h 5 6 lb . p e r y a r d a n d a r e l a i d o n 6 x 8 - in . o a k t i e s . A u n i f o r m g r a d e o f 0 .7 p e r c e n t a g a i n s t t h e l o a d s h a s b e e n e s t a b l i s h e d o n t h e s t r e t c h . N o t e t h e t r a c k c l e a n i n g s o n th e s i d e , w h i c h i s a f u r t h e r i n d i c a t i o n t h a t e v e r y p r e c a u t i o n is t a k e n t o m a k e h a u l a g e e f f i c i e n t a n d s a f e .

4 mine to daylight is about 5,000 ft.; in No. 5 mine this distance is about 7,200 ft. From the main portal of No. 4 mine, which also serves as an exit for trips from No. 5 mine, the haulage to No. 1 mine consists of an outside tram road, 3,100 ft. long, which spans by a bridge the mouth of a deep hollow. This bridge is a steel structure which is 630 ft. long and lies at a maxi­

mum level of 115 ft. above the hollow. Without this

bi idge the haulage would have been compelled to fol­

low a circuitous path along the crop line of this ravine.

The length of the main haul through No. 1 mine is about 8,300 ft., and from this mine to the tipple along an outside tram road the distance is about 3,750 ft.

The maximum haul from No. 4 mine to the tipple, there­

fore, is 20,150 ft. or 3.81 miles and from No. 5 mine to the tipple 22,350 ft. or 4.23 miles.

Lo n g H a u l Bu t F e w De r a i l m e n t s

Generally speaking, the chance of derailments is proportional to the length of the haul. Conditions be­

ing the same in a haul of one mile as in a haul of two, derailments in the latter are likely to occur twice as oiten as in the former. In the Crozer mines derail­

ments on the main 4-mile haulways are indeed rare.

The tracks in the rooms are laid with 20-lb. rails- and rest on steel ties; room entries are tracked with 30-lb. rails and the main haulways with 56-lb. rails.

The heavy rails in the latter case are laid on 6x8-in.

oak ties spaced at 15- to 18-in. centers. These main tracks are ballasted with cinders from the boiler house, the company generating the larger portion of the power used at its mines.

As shown by several accompanying illustrations of stretches of track, inside and outside the mine, the rails are aligned and ballasted with a precision which rivals that of steam railroads. Grades are flattened out as much as possible over long stretches which are generally

T ip p le R e c e n tly B u ilt to R e p la c e O lder S tr u c tu r e

L u m p , e g g , n u t , p e a a n d s l a c k a r e p r e p a r e d i n t h i s t i p p l e R e f u s e i s h a n d l e d f r o m a m i n e t r a c k w h i c h h a s b e e n b u i l t o n t h e e m b a n k m e n t b e t w e e n t h e t w o - s t e p p e d s t o n e w a l l s .

Good T ra ck M a k es D e r a ilm e n ts In fr e q u e n t

a b o u t*4 S n t « t 0 * iiiP S le ? n . t h e m a i n h a u l > t h r o u g h a d i s t a n c e o f h o w c a r e f u l l v t h l c a r e r u l l y t h e t r o l l e y w i r e h a s b e e n h u n g a n d a l i g n e d .*S ai? g'0/ )d t h a t h e r e s h o w n . N o t e

It