Selection and maintenance of conveyor belts for transportation of coal in mines

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1 Selection and maintenance of conveyor belts for transportation of coal in mines Item Type text; Thesis-Reproduction (electronic) Authors Pundari, Nagubandi, Publisher The University of Arizona. Rights Copyright is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 01/07/ :33:44 Link to Item

2 SELECTION AND MAINTENANCE OF CONVEYOR BELTS FOR TRANSPORTATION OF COAL IN MINES by Nagubandi Pundarl A T h esis Subm itted to th e F a c u lty of th e DEPARTMENT OF MINING ENGINEERING In P a r t i a l F u lfillm e n t of th e R equirem ents For th e D egree of MASTER OF SCIENCE In th e G raduate C ollege THE UNIVERSITY OF ARIZONA 1962

3 STATEMENT BY THE AUTHOR T his th e s is has been subm itted in p a r t i a l f u l f illm e n t of req u irem e n ts f o r an advanced d egree a t th e U n iv e rsity of A rizona and i s d ep o sited in th e U n iv e rsity L ib rary to be made a v a ila b le to borrow ers under r u le s of th e L ib ra ry. B rie f q u o ta tio n s from t h i s th e s is a re allo w ab le w ith o u t s p e c ia l p erm issio n provided th a t a c c u ra te acknowledgm ent of source i s made. R equests fo r p erm issio n fo r extended q u o ta tio n from or re p ro d u c tio n of t h i s m anuscript in whole or in p a r t may be g ran te d by th e head of th e m ajor departm ent or th e Dean of th e G raduate C ollege when in th e ir judgment th e proposed u se of th e m a te r ia l i s in th e i n t e r e s t s of s c h o la rs h ip. In a l l o th e r in s ta n c e s, however, p erm issio n must be o b tain ed from th e a u th o r. SIGNED: APPROVAL BY THESIS DIRECTOR T his th e s is has been approved on th e d a te shown below: H. Ev. KRUMLAUF // P ro fe sso r of Mining E n g in eerin g f Dat e

4 SELECTION AND1MAINTENANCE OF CONVEYOR BELTS FOR TRANSPORTATION OF COAL IN MINES r ' By. ro.-; :',c ' N. P undarl - f v.: ; c ' :/ 1.. : : " \o:', c. " J' ;. ABSTRACT The f a c to r s th a t a f f e c t th e s e le c tio n of pro p er b e ltin g f o r tr a n s p o r ta tio n of c o a l in mines a re d isc u sse d in d e t a i l. The c o r r e c t d esig n in g of b e lts to g e th e r w ith c a re fu l i n s t a l l a t i o n and m aintenance of conveyors a re s tr e s s e d. ' ' " - : ;..:, Model te ch n iq u e s of s e le c tin g proper b e ltin g under th e s p e c ifie d c o n d itio n s and of e s tim a tin g c o s ts of owning and o p e ra tin g b e l t haulage equipm ent a re developed and i l l u s t r a t e d th ro u g h th e use of sample problem s. A lso, ty p ic a l c o s t c h a r a c t e r i s t i c curves f o r c o n v e n tio n a l b e lt haulage system s a re c o n s tru c te d ; and methods f o r red u cin g conveyor haulage c o s ts a re enum erated. C onclusions r e garding choice of i n s t a l l i n g b e lt conveyors and t h e ir econom ical f e a tu r e s a re drawn. S uggestions f o r f u tu r e study of d if f e r e n t kin d s of conveyor haulage system s a re l i s t e d. i i

5 ACKNOWLEDGMENTS The au th o r ta k e s t h i s o p p o rtu n ity to ex p ress h is deep sense of g r a titu d e to th e fo llo w in g members of th e f a c u lty o f ; th e U n iv e rs ity of A rizona, Tucson, A rizona, fo r s tim u la tin g rs u g g e s tio n s and c o n s tru c tiv e c r itic is m s during th e course of-, t h i s study and in th e p re p a ra tio n of t h i s m anuscrip t: H. E.i Krumlauf, P ro fe sso r of M ining E n g in eerin g ; and E. R. D revdahl and J. C. D otson, A sso c iate P ro fe sso rs of Mining E n g in eerin g. r;.7 The au th o r i s g r a te f u l to h is b r o th e r, Mr. N. R anganayakulu, D ornakal, I n d ia,.f o r, f in a n c ia l a s s is ta n c e to u n d ertake t h i s G raduate Study a t th e U n iv e rs ity of, J A rizona.. U. i ' i i

6 TABLE OF CONTENTS C hapter! ; - Page I INTRODUCTION I I REVIEW OF THE LITERATURE ' " v.. b_ E v o lu tio n of conveyor b e lt haulage system in c o a l m ines 4 A dvantages of b e lt haulage system 10 F u tu re tre n d s in b e lt haulage system s * 13 I I I SELECTION OF BELT WIDTH AND SPEED l8 IV DETERMINATION OF BELT HORSEPOWER REQUIREMENTS 24 Power to d riv e th e empty b e l t Power to move m a te r ia l h o riz o n ta lly along th e conveyor Power to e le v a te or lower m a te r ia l or power to be g en erated in low ering i t 31 Power to d riv e th e tr ip p e r A c c e le ra tio n horsepow er Summary of b e l t horsepower c a lc u la tio n s 36 P e rm issib le an g les of in c lin a tio n fo r h au lin g c o a l on b e l ts.... «39 V SELECTION OF PROPER BELT l D eterm in atio n of b e l t s tr e s s e s D eterm in atio n of maximum number of p lie s of b e l ts f o r p ro p er tro u g h in g and s t i f f n e s s.... 5l k «i v

7 C h a p t e r P a g e D eterm in atio n of s iz e of d riv in g drums and p u lle y s ;,. S e le c tio n of p ro p er b e lt c o n s tru c tio n " : m a te r ia l -... S e le c tio n of proper cover q u a lity and th ic k n e s s. r -:... B e lt s e le c tio n problem s... - _ j 53 5^ VI DISCUSSION ON BELT HAULAGE ECONOMICS AND - COST ESTIMATION.... E stim a tio n o f b e lt haulage c o s ts.... Problem on c o s t e s tim a tio n of b e l t haulage system.... Cost c h a r a c te r i s tic s of b e l t haulage system '.. How to red u ce conveyor haulage c o s ts VII V III INSTALLATION AND MAINTENANCE OF CONVEYOR BELTS FOR EFFICIENT OPERATION... I n s t a l l a t i o n p rocedure... P ro te c tio n of b e l ts.... B e lt m aintenance g u id es.... CONCLUSIONS AND SUGGESTIONS'FOR FUTURE STUDY BIBLIOGRAPHY AND SELECTED REFERENCES 105 v

8 T able I II III IV LIST OF TABLES Page Recommended b e l t speeds and allo w ab le lu m p -sizes of ru n -o f-m in e c o a l V alues of com posite f r i c t i o n f a c t o r, C and c o n s ta n t, L V alues of horsepower to d riv e empty conveyor V alues of h o riz o n ta l horsepower to convey c o a l V V alues of horsepower to e le v a te m a te r ia l 32 VI V alues of c o n s ta n t,ai.... 3^ VII Average tr ip p e r l i f t s V III Maximum p e rm is s ib le an g les of conveyor in c lin a tio n DC V alues of c o e f f ic ie n t of f r i c t i o n of b e lts 45 XI XII X V alues of,f* f a c to r Maximum p e rm is sib le te n s io n r a tin g s fo r d if f e r e n t b e l ts Minimum p lie s to su p p o rt lo ad and maximum p lie s f o r proper tro u g h in g X III Recommended conveyor top cover th ic k n e s s 62 F ig u re LIST OF FIGURES Page 1 Ropenframe conveyor s tr u c tu r e C a b le -b e lt conveyor d riv eh ead arrangem ent 9 3 C ro s s -s e c tio n of a loaded b e l t B e lt te n s io n s in a running b e l t & 6 T y p ical c o s t c h a r a c te r i s tic curves of conv e n tio n a l b e l t haulage sy stem (rig id -fram e ty p e ) & 84 v i

9 ... CHAPTER I -.» '.. -,,, INTRODUCTION..In any b e l t haulage system th e conveyor b e l t i s subje c te d to th e g r e a te s t s t r a i n, i s th e most e a s ily damaged, i s th e.m o st ex p en siv e, and has th e s h o r te s t l i f e of any p a r t of th e whole system. The b e l t i s th e only p a r t of th e conveyor which a c t u a l l y h andles th e m a te r ia l, and i s p r a c t ic a lly th e only item which has to be renew ed. The l i f e of th e b e l t, and hence th e haulage c o s t, depends on th e b e l t being c o r r e c tly s p e c ifie d f o r th e job and th e c a re and m aintenance th a t i t re c e iv e s. B e ltin g of im proper d esig n to save f i r s t c o s t w i l l have s h o rte r l i f e and g iv e s r i s e to h ig h er haulage c o s ts. I t should be n oted in t h i s co n n ectio n th a t average conveyor b e l t r e p r e s e n ts ap p ro x im ately h0% of th e e n t ir e b e l t haulage i n s t a l l a t i o n. The purpose o f t h i s stu d y i s to d is c u s s a l l th e f a c to r s th a t a f f e c t th e s e le c tio n o f c o r r e c t b e ltin g f o r a giv en duty and i t s good m aintenance. P ro p e rly designed and w e ll m aintained b e l ts giv e good perform ance a t low u n it c o s ts.. - * ' "! V * l The m ajor f a c t o r s e n te rin g in to p ro p er s e le c tio n of conveyor b e l ts such as b e l t w id th, speed, c a p a c ity, c a rc a s s q u a lity, te n s io n and horsepow er re q u ire m e n ts, cover q u a lity and th ic k n e s s, economics and o th e r im p o rtan t f a c to r s a re 1

10 2 d isc u sse d In d e t a i l, i n t h i s t h e s i s. No attem p t has been. made to compare th e u n it c o s ts of c o a l tr a n s p o r ta tio n by b e l t conveyors w ith th a t o f.any o th e r system. I t i s consid e re d in t h i s stu d y th a t under c e r t a in circu m stan ces b e l t conveyors a re e f f i c i e n t means of underground haulage when p ro p e rly d esig n ed and m a in ta in ed.. I t i s w ith t h i s assum ption th a t a l l o th e r in v e s tig a tio n s a re made.and im p o rtant conc lu s io n s a re drawn. O ther d esig n c o n s id e ra tio n s of b e l t haulage system, such as ty p e of d r iv e s, takeup d e v ic e s, lo a d in g arran g em en ts, ty p e of i d l e r s and t h e i r sp acin g, and o th e r a u x ilia r y equipment re q u ire d have n o t been In v e s tig a te d in t h i s s tu d y. of th e s e item s a re w e ll sta n d a rd iz e d f o r any s p e c if ic d u ty, and - i t i s only in th e s e le c tio n of c o s tly b e l ts w here m ista k e s a re o fte n made. These m istak es r e s u l t in i n e f f i c i e n t b e l t o p e ra tio n and in c re a se d haulage c o s ts. Hence th e im - p o rtan c e of p ro p er b e l t s e le c tio n to g e th e r w ith proper in s t a l l a t i o n and good m aintenance a r e.s tr e s s e d in t h i s stu d y r ' * ' - 'v 1, r,,.» v -. l v, More em phasis i s g iv en to sim p le, quick' and c o rre c t A ll methods of e s tim a tin g th e main s p e c if ic a tio n s of b e l t conv ey o rs f o r tr a n s p o r ta tio n of ru n -o f-m in e c o a l in m ines. f a r as p o s s ib le th e u se of com plicated c h a rts and ta b le s As have been av o id ed. Most of th e form ulae used f o r d eterm in in g v a rio u s b e l t s p e c if ic a tio n s a re n o t in ten d ed as a b a s is of d esig n in g new i n s t a l l a t i o n s w ith o u t re fe re n c e to th e

11 3 m a n u fa c tu re r, s su g g ested m ethod. The m anufacturer may p ref e r to work out th e req u irem e n ts of th e system by an o th er method. The methods used in t h i s stu d y fo r d eterm in in g c o r r e c t b e l t s p e c if ic a tio n s a re v ery h e lp fu l in o rd er to d ecid e i f conveying i s p o s s ib le or s u ita b le or econom ical under c e r ta in s p e c if ie d c o n d itio n s. These methods a re a ls o h e lp fu l to en able changes to be made econom ically in th e e x is tin g conveyor haulage system w ith o u t causin g undue b e lt f a i l u r e s. The method of c a lc u la tio n s a re kept as fundam ental as p o s s ib le, and a l l sim p lify in g assum ptions and ap p ro x i m ations have been c l e a r ly s ta te d, so th a t th e s e c a lc u la tio n s can be m odified to s u i t c o n d itio n s and ty p e s of equipm ent n o t s p e c ifie d in t h i s stu d y. I t i s hoped t h a t t h i s t h e s is w i l l d em o strate th e ease w ith which r e l i a b l e methods of e s tim a tin g b e l t sp e c i f ic a t i o n s a re made a v a ila b le to th e r e a d e r. P r a c tic a l examples of d eterm in in g c o r r e c t b e l t s p e c if ic a tio n s and c o s t e s tim a tio n of a com plete b e l t haulage system a re g iv en to a s s i s t in a b e t te r u n d erstan d in g of th e p ro p er d esig n of b e l t conveyors.

12 CHAPTER I I REVIEW OF THE LITERATURE EVOLUTION fig Tgg CONVEYOR BELT HAULAGE SYSTEM IN COAL The tr a n s p o r ta tio n of m a te r ia l by b e l t conveyors was f i r s t ex p lo red in th e m iddle of th e n in e te e n th c e n tu ry. By 1905 b e l t conveyors w ere being used underground in England but were n o t in use in th e U nited S ta te s u n t i l about They were o r ig in a lly used in th e U nited S ta te s in p an el rooms to convey c o a l from th e fa c e to th e e n try and th e n to c o l le c t c o a l in e n tr ie s from ch ain to shaker co n v ey o rs. D u rin g.t h i s p e rio d of e v o lu tio n many changes have o ccu rred in th e g e n e ra l la y o u t of th e conveyors. The f i r s t conveyor haulage c o n s is te d o f le a th e r and canvas b e l ts s lid in g on wooden tro u g h s. L a te r wooden r o l l e r s re p la c e d th e tro u g h and th e y - in tu r n were re p la c e d by c a s t ir o n r o l l e r s. T his l a t e r devlopm ent g r e a tly encouraged th e use of conveyor haulage of c o a l and o th e r m in e ra ls. For many y e a rs b e l t conveyors have proved to be an e f f i c i e n t, econom ical and s a fe method f o r underground tr a n s p o r ta tio n of c o a l. S ig n if ic a n t developm ents in th e d e sig n and c o n stru c tio n of conveyor haulage system s have been and a re being made to d e a l w ith v a rio u s f a c t o r s th a t a f f e c t o u tp u t.

13 5. S ince th e beginning of conveyor haulage tr a n s p o r ta tio n in m ines, v a rio u s ty p e s of b e l ts have been m anufactured, of which th e fo llo w in g a re w orth n o tin g : 1. C otton and s y n th e tic f ib e r c a rc a s s b e l t s. 2. U niplane c o tto n cord b e l ts f o r hig h te n s io n i n s t a l l a tio n s where o u te r p ly s tr e s s e s may c o n trib u te to th e u ltim a te d e te r io r a tio n of th e c a rc a s s. 1 ; _ ;... i ' 3. U nusual b e l t w eaves, such as one w ith a th rea d ed high modulus c o tto n f a b r ic running le n g th -w is e in th e c a rc a s s and w ith nylon f i l l th re a d s to d ecre ase th e crim ping in th e le n g th -w ise member. ^ 4-. S te e l c a b le b e l t s u t i l i z i n g high te n s io n a irp la n e ty p e c a b le s a s,th e te n s io n c a rry in g members. 5. F i r e - r e s i s t a n t, b e l t s u sin g n eoprene, te ry le n e and poly v in y l c h lo rid e (p.v ic.) poly e s te r s y n th e tic f ib e r m a te r ia ls.. '' ',..-y '..... v 6. G lass c a rc a s s b e l ts f o r o p e ra tin g w ith m a te ria ls a t th e te m p e ra tu re s around 500 d eg rees F a h re n h e it.. Many a tte m p ts have a ls o been made in th e d e sig n of th e su p p o rtin g s tr u c tu r e of th e b e l t haulage system. S ince 195$ th e ro p e-fram e conveyor s tr u c tu r e s have become alm ost sta n d ard f o r some b e l t haulage i n s t a l l a t i o n s in underground m ines. (See f i g. l ). Lower c a p i t a l c o s t p lu s th e sav in g s in b o th tim e and money th a t can be r e a liz e d from f a s t e r i n s t a l l a t i o n, e x te n s io n, and r e lo c a tio n make ro p e su p p o rted b e l t haulage an a t t r a c t i v e o ffe rin g and have le d

14 '6 ROPE-:

15 to i t s ra p id acceptan ce by th e m ining in d u s try. However, th e use of ro p e-fram e b e l t haulage f o r perm anent, m ain- " haulage i n s t a l l a t i o n s i s uncommon and th e rig id -fra m e, co n v e n tio n a l b e l t haulage i s s t i l l proving e f f i c i e n t and 7 econom ical in t h i s f i e l d. -.. : v, : The o th e r improvement in th e d esig n of b e l t haulage system i s th e developm ent of th e c a b le - b e lt conveyor.3 / 2 / In t h i s d esig n (see f i g. 2 ), two e n d le s s.s te e l- w ir e rope lo o p s, one on each s id e o f th e conveyor, a re a tta c h e d to th e running b e l t by p re sse d s t e e l c l i p s. These ro p es ta k e th e t e n s i l e s tr e s s in th e b e l t and in c re a s e th e l i f e of th e b e l t. The rope loops a re c a rrie d on to p and r e tu r n ro p e p u lle y s. These ro p es a re disengaged from th e b e l t a t th e te rm in a ls of th e conveyor by a p a ir of skewed or sp layed p u lle y s c a rrie d in a f a b r ic a te d s t e e l fram e. The ro p e s, which u n t i l th en have been c a rry in g th e b e l t, p ass around th e v e r t i c a l p u lle y s w h ile th e b e l t p asses around th e drum between th e p u lle y s. The ro p es th e n p ass around th e skewed p u lle y s whose to p s a re splayed s u f f i c i e n t l y to enable th e ro p es to p ass forw ard to th e d riv in g w heels. They th e n r e tu r n to p ic k up th e b e lt as i t le a v e s th e u n d e rsid e of th e b e lt drum. I t i s n o t 1 / T. D. E l l i o t, "Development of th e c a b le - b e lt conveyor" Iro n and Coal T rades Review. Vol 176. No A p ril h, 19% pp. 309:137-* 2 / "Three y e a rs of h o is tin g w ith th e P rin c e ss C able- B e lt", Coal Age, Vol 6 3, S ep t. 1958, pp

16 8 p r a c tic a b le to extend th e c a b le - b e lt conveyor in s h o rt le n g th s as f a s t as o th e r ty p e s. T his i s due to th e n e c e s s ity of s p lic in g a d d ito n a l ro p e. R egarding economics of such a type of b e lt haulage system no d e ta ile d study has been made. However, i t i s claim ed th a t under s im ila r working c o n d itio n s a sm all amount of saving in horsepower i s n o ted in th e c a b le - b e lt conveyors when compared to c o n v e n tio n a l ty p e b e l t conv e y o rs. The sta n d ard c a b le - b e lt conveyors, in b e lt w idths from 2 4 -in c h to 4 8 -in c h, u sin g d riv in g ro p es from one in ch to o n e -a n d -h a lf in ch es d iam eter w ith conveyor le n g th s up to 4000 f t., have been i n s t a l l e d in a number of c o l l i e r i e s in England during re c e n t y e a rs.

17 ? 13' coavsio?- JG3BT2

18 10 ADVANTAGES OF BELT HAULAGE SYSTEM ' ; In p lan n in g a haulage system, I t should be determ ined f i r s t w hether s u f f i c i e n t tonnage i s a v a ila b le f o r a number of y e a rs to j u s t i f y th e i n s t a l l a t i o n o f b e lt conveyors. The are a should be mapped and determ ined by crop l i n e s, property" l i n e s, g rad es e t c. and th e n a d e c is io n w hether to i n s t a l l com plete b e lt conveyor haulage or to use a comb in a tio n o f tr a c k h au lag e, s h u t t l e,c a r s and b e l ts i s made. The in tro d u c tio n of b e l t haulage system s in underground c o a l m ining has made p o s s ib le b e t te r methods of m ining to s u i t lo c a l c o n d itio n s, and in c re a se d fa c e m ech an izatio n. The su ccess or f a i l u r e of a modern c o a l mine depends, to a g r e a te r e x te n t, on th e e f f ic ie n c y.o f c o a l tr a n s p o r ta tio n. The f a s t e r th e c o a l i s produced a t th e fa c e by modern m ining m ethods, th e f a s t e r i t should be removed from th e fa c e and tra n s p o rte d to th e s u rfa c e a t minimum c o s t. Today b e l t conveyors a re th e most advantageous and econom ical means of moving c o a l in underground m ines, and th ey form th e hub of th e underground haulage system s th a t handle a la rg e p ercen tag e of U.S. m ining o u tp u t. The b e lt conveyor haulage system p o sse sse s many advantages and d e s ira b le f e a tu r e s over th a t of o th e r ty p e s of tr a n s p o r ta tio n system. The more im p o rtan t advantages a re l i s t e d below: 1. C ap acity : Because of i t s continuous o p e ra tio n, no o th e r method of haulage has such a wide range of c a p a c itie s

19 11 as th e b e l t conveyor system. W ith b e l t conveyors, th e amount of m a te r ia l c a r r ie d depends on th e b e l t w id th, speed and w eight of th e m a te r ia l conveyed. Owing to h ig h a b ra s iv e r e s is ta n c e of ru b b er used in th e cover c o n s tru c tio n of b e l t s, ru n -o f-m in e (h e r e a f te r c a lle d r.o.m.) c o a l of a l l s iz e s can be handled w ith o u t cau sin g s e rio u s damage or wear to th e b e l t. : ' '. 2. A d ap ta tio n to ground p r o f i l e : B e lt conveyors can fo llo w le v e l or p itc h e d t e r r a i n w ith eq u al ease up to 30$ g ra d e s. Compare t h i s to th e norm al economic lim ita tio n s of 20$ g rad es f o r tru c k s and 3$ g rad es f o r r a ilr o a d tr a n s p o r ta tio n. In some mines where, th e seams a re s te e p ly d ip p in g, t h i s f a c to r alo n e can make b u lk tr a n s p o r ta tio n econom ically f e a s ib le only w ith -co n v ey o rs. ;. 3. Simple e r e c tio n and minimum space: Underground b e l t conv eyors allow th e use of sim ple rig h ts -o f-w a y, narrow e n tr ie s and low.head room. No tr a c k s have to be la id or t r o l l e y w ires s tru n g. L i t t l e g rad in g i s n e c e ssary and o fte n sim ple ro o f su p p o rt can be u se d. The b e l t conveyors hold a unique p o s itio n in th e reco v e ry of th in -seam c o a l where d riv in g o f la rg e e n tr ie s to accom odate o th e r means of haulage would make th e o p e ra tio n uneconom ical. : \ H-. F l e x i b i l i t y : The w e ig h t of su p p o rtin g s tr u c tu r e s and th e conveyor equipm ent i t s e l f i s sm all when compared w ith th e volume of c o a l c a r r ie d. Hence i t i s e a s ily extended or r e t r a c t e d, d ism an tled, moved and reassem b led. However,

20 12 g e n e ra lly b e lt conveyors a re sem i-fix ed and do n o t provide, maximum f l e x i b i l i t y needed in some m ining o p e ra tio n s unle s s th e y a re used in c o n ju n c tio n w ith some other, ty p e s of tr a n s p o r ta tio n system, such as s h u ttle c a r s, lo a d e rs and movable b e l t h ead s. : : 5. S a fe, smooth, s i l e n t, and sim ple o p e ra tio n : No method of haulage i s in h e re n tly as s a fe as b e l t haulagethe : a c c id e n t r a t e w ith b e l t co n v ey o rv.h au lag e.is, extrem ely low. Freedom from v ib r a tio n s and q u ie t o p e ra tio n of b e l t haulage red u ces p e rs o n a l f a tig u e and i r r i t a b i l i t y. D ust problem s along th e p a th of th e conveyor a re g r e a tly red u ced, and, where lump d e g ra d a tio n i s im p o rta n t, th e smooth t r a n s f e r and tr a n s p o r t of b e l t haulage low ers lump break ag e. P ro p erly designed, conveyor system s have push b u tto n c o n tro ls and can be s e l f c o n tro llin g to a la rg e e x te n t by e l e c t r i c a l i n t e r lo ck in g arran g em en ts. 6. E arly w arning of impending danger: Probably no o th e r haulage g iv e s such an e a rly w arning of p o s s ib le f a i l u r e. U nlike th e a e r i a l tramways of which i t is s a id never have a minor a c c id e n t, or th e r a ilr o a d where a washout o f i b a l l a s t or a d erailm en t may s t r i k e w ith o u t-warning', th e b e lt conv ey o r, i f m ain tain ed p ro p e rly, r a r e l y : s u f f e r s a sudden breakdown. The b e lt. i t s e l f s ig n a ls i t s need f o r replacem ent in ample tim e to have a standby b e l t read y fo r i n s t a l l a t i o n. 7. Minimum m aintenance and power re q u ire m e n ts: Two to th re e men per m ile p er s h i f t a re norm ally s u f f i c ie n t f o r

21 13 d a ily r o u tin e m aintenance and o p e ra tio n. The r e tu r n ru n of th e b e l t on a slo p e b alan ces th e to p e ru n and, because of low ta r e w eight o f th e moving p a r t s, conveyors can p ro v id e 1 tr a n s p o r ta tio n w ith th e lo w est p o s s ib le consum ption of pow er. B e lt haulage needs only o n e -h a If th e power re q u ire d by o th e r m ethods...., 8. Econom ics: I f th e problem i s to g e t high p ro d u ctio n a t low er c o s ts, th e conveyor b e l t haulage may be th e answ er. The low u n it c o s t per to n of m a te r ia l tra n s p o rte d by b e lt haulage o fte n makes i t th e most econom ical means o f moving c o a l. Long term sav in g s in la b o r c o s t and m aintenance a re p o s s ib le w ith th e b e l t haulage system. The o th e r im m ediate savin g s from b e l t haulage a re re d u c tio n in g rad in g a n d. - b ru sh in g, th e e lim in a tio n o f s tr in g in g t r o l l e y w ire s, la y in g o f tr a c k and of c u ttin g i n t r i c a t e haulage ways. ' : The s u b je c t of b e lt haulage economics i s d isc u sse d in d e t a i l elsew here in t h i s t h e s i s under a s e p a ra te heading. The main d isad v an tag e of b e lt conveyors i s h ig h " i n i t i a l c a p i t a l ex p e n d itu re which means la r g e r tonnages must be a v a ila b le f o r a lo n g e r p e rio d to i n s t a l l b e l t conveyors. and to m inim ize haulage c o s t s. A lso u n fo re seen random breakdown d u rin g o p e ra tio n may a f f e c t th e whole o u tp u t. FUTURE TRENDS IN BELT HAULAGE SYSTEM... The p o p u la rity of b e l t conveyors f o r tr a n s p o r ta tio n

22 of c o a l in m ines has in c re a se d during th e :p a s t decade, and a number of s ig n i f ic a n t developm ents a re ta k in g p la c e in th e underground b e l t h a u la g e.; The b e l t conveyors a re growing :- s te a d ily in s iz e, th e horsepow er of th e motor i s in c re a s in g, lo a d in g m ethods, b e l t speeds and b e lt c o n s tru c tio n m a te ria l a re im proving and w i l l handle la r g e r o u tp u ts a t minimum c o s t. The fo llo w in g a re th e g e n e ra l tre n d s tow ard desig n in g ; f u tu re haulage system s; :. v. ;, : : : : 1. S h if t from r i g i d to rope supported b e lt equipm ent; The concept of mounting c a rry in g I d le r s on two s ta tio n a r y and p a r a l l e l w ire -ro p e s in s te a d of on a r i g i d framework i s. fin d in g growing use in th e c o a l m in in g.in d u stry due to low er c a p i t a l c o s t and savin g s in i n s t a l l a t i o n c o s t. Conveyor b e lt m an u factu rers have estim a ted t h a t d u rin g 1961 roughly of new conveyor equipm ent sold f o r p an el and b u tt e n try haulage was of th e r o p e : suspended ty p e. -However, the- s h i f t from r i g i d to ro p e-fram e id l e r s tr u c tu r e s f o r secondary and mainlin e b e lt haulage i s v ery slow Trends tow ard w ider b e l t s and h ig h er sp eed s; The h ig h er w id th -sp eed com bination i s becoming in c re a s in g ly in d is p e n s ab le in order, to p rovide, th e surge, c a p a c ity needed.fo r highspeed dumping, la r g e c a p a c ity s h u ttle c a rs, and o th e r tr a n s f e r r in g equipm ent. In some of th e German o p e n -p it c o a l mines s t e e l cable re in fo rc e d b e l ts up to 87- in ch wide c a rry 15,000 t o n s ;of o v er-b u rd en m a te r ia l per hour a t. speeds ran g in g

23 from 900 to 1100 f t. p er m inute and u t i l i z i n g up to H h o rs e p o w e r.^ 3. Growing i n t e r e s t in 35 deg. and 4$ deg. c a rry in g i d l e r s : These I d le r s a re being used in th e above ground equipm ent. In th e underground w orkings of th e mine where th e o p e ra tin g c o n d itio n s a re n o t as good as on s u rfa c e, 45 deg. i d l e r s p ro v id e g r e a te r c a p a c ity w ith o u t in c re a s in g b e l t w id th or speed. They may a ls o h elp to red u ce th e c o s t of s p illa g e c le a n -u p, an expense w hich approaches $30,000 per y ear fo r some m in es. The o th e r improvements in th e i d l e r d esig n a re v a rio u s ty p e s of f l e x i b l e c a te n a ry i d l e r s f e a tu r in g moulded ru b b er s p ir a l s in s te a d of a s e r ie s of ru b b er d is c s. These i d l e r s a re being used in c o n ju n c tio n w ith ro p e-fram e b e l t haulage s tr u c t u r e s. 4. Development o f a r tic u la t e d and cascade conveyors:*^the developm ent o f th e co n tin u o u s m iner and a ls o accompanying em phasis on th e im provem ent o f conveying mediums has r e s u lte d in th e d e sig n o f a r tic u la t e d and cascade conveyors. One v e rs io n of an a r tic u la t e d conveyor developed f o r th e boring ty p e of co n tin u o u s m iner c o n s is ts of a s e r ie s of 3 / E. R. T ra x le r, "Conveyor b e l t horsepower and o p e ra tin g d is ta n c e s co n tin u e to in c re a s e in f u tu r e ", E n g in eerin g and Mining J o u r n a l. Vol 162, No. 8, August 1961, pp. 86 f. 4 / Deep m ining Guidebook " P r a c tic a l tre n d s in tr a n s p o r ta tio n ", Coal Age, V ol. 6 3, No. 7A, M id-july 1958, p. 77*

24 16 in te rc o n n e c te d b e l t conveyors on w heels-each w ith i t s own, d riv in g a n d -p ro p e llin g m otors. _" -. : The cascade system i s s u b s ta n tia lly s im ila r. Here th e conveyor need n o t be in te rc o n n e c te d, though h itc h e s a re provided to p erm it th e s e r ie s to be p u lle d behind th e boring u n it in th e rem ote m ining a r e a s. To avoid in s e r tin g and r e moving conveyors one a t a tim e, th e l a t e s t id e a in rem ote m ining a re a s i s to s to r e th e conveyors in a s tr u c tu r e w ith c ir c u la r ram ps. As th e machine goes in to th e m ining a re a i t p u lls th e conveyor off, pushing them back onto th e ramps on th e way o u t. 5. B ridge conveyors and p o rta b le b e l t heads: The development of th e b rid g e conveyor u n it was th e f i r s t ste p in b rin g in g th e conveyor in to th e p ic tu re as means of se rv in g lo ad in g m achines and co n tin u o u s m in ers. The n ex t ste p was to d esig n room conveyor so t h a t i t could be e a s ily extended to keep up w ith th e fa c e u n i t. The b rid g e conveyor i s th e connecting lin k betw een th e fa c e conveyor and continuous m in er. At th e t a i l s e c tio n of th e face conveyor i t r id e s on tr a c k s ; a t th e d isc h a rg e conveyor of th e lo a d in g u n it or continuous m iner i t i s su p p o rted by a b a l l and so ck et f a s te n in g. $ o th p o in ts o f c o n ta c t allo w a 90 deg. movement to e ith e r s id e. In any c a se, th e b rid g e Is always p o s itio n e d to accep t c o a l and d isc h a rg e i t onto th e fa c e co n v eyors. A new developm ent w ith ro p e.su p p o rte d conveyors i s

25 17 th e p o rta b le b e l t head. The d riv e s e c tio n in c lu d in g m otor, c o n tr o lle r and power tra n s m is s io n f a c i l i t i e s i s made p o rt a b le by m ounting as a com plete u n it on a r a i l tr u c k. The p o rta b le head on i t s tru c k i s trammed to a sp o t in th e f i r s t c ro s s -c u t inbye of th e main l i n e. In t h i s p o s itio n i t i s 60 to 100 f t. from th e b e l t d is c h a rg e. The tru c k i s anchored in p la c e w h ile rem aining: on th e r a i l s. 6. Use of conveyors f o r tr a n s f e r of men: Under p ro p er sa fe g u ard s, movement o f men on b e l ts i s proving b o th sa fe and e f f ic ie n ts p e c ia l lo w "speed (up to 200 f.p.m.) and low c o s t b e l ts a re now being employed in tr a n s f e r r in g men on le v e l roadways and up s lo p e s. T his system should be so designed th a t th e b e l t cannot be r e s t a r t e d w ith o u t a check fo r p o s s ib le h a z a rd s. There should be emergency sto p cord or sto p system a l l along th e b e l t so th a t any man can sto p i t a t any tim e: ample c le a ra n c e and smooth unencumbered fo o tin g should be p ro v id ed a t a l l lo a d in g and unloading p o in ts. F in a lly, in a d d itio n to a l l th e above p re c a u tio n s, no movement o f men by b e l ts should be p e rm itte d u n le s s a re s p o n s ib le p erso n i s p re s e n t. i / I b i d.. PP. 72-9) P assim.

26 CHAPTER I I I SELECTION OF BELT WIDTH AND SPEED When th e i n s t a l l a t i o n of a b e lt haulage system is decided upon, th e f i r s t ste p in i t s proper d esig n i s th e s e le c tio n of b e lt w id th and speed commensurate w ith f u tu r e o u tp u t to be handled, inasmuch as b e lt w idth and speed govern th e h au lin g c a p a c ity of th e b e l t. From th e stan d p o in t of econom ics, th e id e a l b e l t conveyor should o p e ra te f u l l y loaded a t maximum p e rm is sib le speed w ith i t s w idth as narrow as p o s s ib le to h au l th e g iv en o u tp u t. The o p e ra tio n of a b e l t below i t s c a p a c ity r e s u l t s in low er haulage e f f ic ie n c y and g r e a te r wear fo r a g iven tonnage conveyed. For any p a r tic u la r problem concerning th e underground h au lin g of c o a l by b e l t conveyors, i t i s p o s s ib le to recommend more th a n one com bination of b e lt w id th and speed. However, th e w idth and speed of th e b e l t s e le c te d must be s u f f i c ie n t to move th e c o a l as f a s t as s h u ttle c a rs or o th e r tr a n s f e r conveyors th a t may be used in c o n ju n c tio n w ith th e b e lt can d isc h a rg e th e i r lo a d s upon i t ; o th erw ise d elay s w ill o c c u r. To p rev en t th e s e d e la y s, s a fe ty d ev ices may be used on th e b e l t s. These a re ( i) tr a n s f e r conveyors (e n try b e lts ) capab le o f ta k in g maximum s h u ttle car d isc h a rg e are in s t a l l e d to feed to th e main b e lt a t th e proper r a t e s, or 18

27 19 ( I I ) tw o-speed m otors a re I n s ta l le d w ith an au tom atic tim in g c o n tro l to speed up th e b e l t w h ile th e s h u ttle c a rs a re d is ch arg in g ; t h i s tim in g c o n tro l i s th e n c u t back a u to m a tic a lly. Almost a l l b e l t conveyor c a lc u la tio n s s t a r t w ith a c o n s id e ra tio n of th e c a p a c ity of th e b e l t. The f a c to r s w hich a f f e c t th e b e l t c a p a c ity a re b e l t w id th and speed, th e shape of th e lo ad ed c ro ss s e c tio n, b u lk w eight of th e m a te ria l to be conveyed, and tro u g h in g angle of i d l e r s on which th e b e lt ru n s. There a re two methods of d eterm in in g b e l t c a p a c ity :. 1. The averag e b e l t c a p a c ity in to n s/h o u r I s computed by d iv id in g t o t a l to n s moved p er s h i f t by th e hours per :. : s h i f t : " 2. "Peak c a p a c ity " i s u s u a lly ex pressed in to n s /m in u te. The peak c a p a c ity i s th e maximum amount of m a te r ia l th a t w ill be lo ad ed on to th e b e l t a t a l l of th e lo ad in g p o in ts in any one m in u te. The average or a c tu a l o u tp u t per hour w i l l alw ays be l e s s th a n th e "peak c a p a c ity ". But th e b e l t w id th and speed must be s e le c te d on th e b a s is of th e peak c a p a c ity which i s th e o u tp u t f o r id e a l com binations of lo a d in g. I f th e b e l t i s to be s e le c te d oh th e b a s is of th e average c a p a c ity, i t i s n e c e ssary to c o n tro l th e d riv e of th e e n try b e l ts as ex p lain ed a b o v e.- This p re v e n ts th e e n try b e lts from d isc h a rg in g onto th e main b e l t i f th e main b e lt i s a lre a d y f u l l y lo a d e d B e lt - W idth: - The form ula f o r d eterm in in g th e b e l t w id th,

28 20 as g iven by N a tio n a l E l e c t r i c a l M anufacturers A sso c ia tio n (N.E.M.A.), i s as fo llo w s : B e lt w id th ( in in c h es) s 13 i/h e re : 1 0, 000? S x U / 5 P z peak lo ad in to n s per m inute S = speed of th e b e lt in f t/m in u te U z w eight of th e broken m a te r ia l in Ib s /c u b ic f t. 2. B e lt Speed: The maximum recommended b e l t speeds fo r v a rio u s b e l t s iz e s a re giv en in ta b le (x). For c o a l mining conveyors, speed i s u s u a lly lim ite d to about 2^0 f t/m in. in g a te ro ad s and ^75 f t/m in. on tru n k ro ad s in B r itis h c o a l mines & 3. L um p-size: For th e maximum allo w ab le lu m p -size ru n -o f- mine c o a l i t i s u s u a lly p r a c t i c a l to t o l e r a t e an o c c a sio n a l lump o n e -h a lf th e b e l t w idth in i t s w id est dim ensions. The ta b le ( i ) shows th e recommended maximum allo w ab le lu m p -sizes f o r d if f e r e n t b e l t w id th s. The maximum lu m p -size which can be handled by a conveyor can a ls o be determ ined by th e fo rm u la:2/ (W - 6) A llow able lu m p -size ( in in c h e s) s \2) Where W z b e l t w id th in in c h e s. 4. B e lt C a p a c ity : ( i ) The N.E.M.A. form ula f o r determ ining 6 / N a tio n a l Coal Board, "R ela tin g a roadway b e lt conveyor to i t s d u ty ", In fo rm atio n B u lle tin No. 58/197. N a tio n a l Coal Board, H obart House, Grosvenor P la c e, London, S.W.l. 2 / N. Brook, "E stim a tio n of conveyor s p e c if ic a tio n s ", C o llie ry E n g in e e rin g T Vol 3 6, No. 429, November 1959, p p. 4 b 6-9 2

29 21 b e l t c a p a c ity f o r 20 deg. tro u g h in g i d l e r s i s as fo llo w s: T = Ux(W -5)2 (3) NOTE: or peak c a p a c ity. Where: T ^ c a p a c ity in to n s (o f 2000 l b - t o n ) / hour a t 100 f t/m in. b e l t sp eed. U * w eight in l b s. per c.ft. of th e... m a te r ia l to be conveyed. W = b e l t w id th in in c h e s.,the above c a p a c ity form ula c o n s id e rs maximum The recommended c a p a c itie s under which th e b e l ts a re to be o p erated must be about 10$ low er th a n th e tonnage d eriv e d by t h i s fo rm u la. For 35 deg. tro u g h in g i d l e r s and deg. uneq u al- r o l l tro u g h in g i d l e r s, th e c a p a c ity determ ined by th e above form ula must be in c re a se d by about 1$$ and 22$ r e s p e c tiv e ly. ( i i ) The re v is e d Goodyear f o rm u la ^ f o r b e l t capac i ty f o r 20 deg. sta n d ard e q u a l- r o ll tro u g h in g i d l e r s i s as fo llo w s: T = 5.,75(W ) 1 *^6x S x U (4) 200,000 Symbols as g iv e n above. 8 / Handbook qf b e l t i n g. Akron, Ohio, The Goodyear T ire and Rubber Co., IncV, 1953» P 51 '

30 22 -: - t. BELT PIG. 3 CROSS-SECTION OF LOADED BELT ( T il) A fotmula f o r d e te rm in in g 7approxim ate b e lt c a p a c ity as advocated by some m ining en g in eers can be de- VP iv6cl QS follows: ' '... L et V a b e l t w id th in in ch es a a th e edge d is ta n c e of b e lt n o t under lo ad. > (se e F ig. 3)., t : U s w t. of th e m a te ria l in I b s / c. f t. S s b e l t speed in f t./m i n. The shape of th e rib b o n of m a te ria l on th e belt" i s as shown in F ig. 3* This a re a of rib b o n i s appro x im ately e q u iv a le n t to a r e c ta n g le whose s id e s a re (W-2a) by W/9 (see F ig. 3)

31 T h e re fo re, th e c a p a c ity of th e b e lt i s g iv en by; 23 T = (W -2a)x(W /9)x(S /lw x(u /2000)x60 For m ining conveyors th e edge d is ta n c e *a* i s about 3 in c h es (or more a c c u ra te ly "a" = 0.055W in c h ). S u b s titu tin g th e v a lu e o f 3 in ch es fo r "a" in th e above eq u atio n and rounding o f f th e c o n sta n t g iv e th e c a p a c ity fo rm u la; m - (^-6)xWxSxU ; :. ^ (5) TABLE I MAXIMUM RECOMMENDED SPEEDS AND ALLOWABLE LUMP-SIZE OF R.O.M. COAL FOR DIFFERENT SIZES OF PLY-TYPE BELTS m m - r - r t e.i j e m b m p j b m i i r h i i i i" iii I I T ' i ir~ ~ - - i rrn m i Hill I B e lt W idth Maximum b e l t speed (f.p.m.) la m p -sizes ( in in c h e s) in in ch es Goodyear U.S. Rubber Average I f uniform I f mix- :, V.::. V ' : - ';, '. ed w ith f in e s 2b ' 6 10 ' b oo, 575 8, y

32 : CHAPTER IV ' DETERMINATION OF BELT HORSEPOWER REQUIREMENTS The, b e l t w id th and-speed f o r a g iven c a p a c ity i s f i r s t decided as d isc u sse d in th e l a s t c h a p te r; and th en th e t o t a l horsepow er re q u ire d to hau l th e m a te r ia l i s c a l c u la te d. This b e lt d riv in g power i s u s u a lly d iv id ed in to th e fo llo w in g com ponents: 1. Power to d riv e th e empty b e l t, he 2. Power to convey th e m a te ria l h o riz o n ta lly along th e b e l t, h^ 3. Power to e le v a te th e m a te r ia l on slo p e s or th e power to be g en e ra ted in low ering th e m a te r ia l, hr!+. A d d itio n a l power to d riv e th e t r i p p e r, i f a tr ip p e r i s used and i s to be d riv e n by th e b e l t m otor. t h i s tr ip p e r horsepower be eq u al t o, h^ L et 5. Power to a c c e le r a te th e lo aded b e l t a t s t a r t, ha The c a lc u la tio n s f o r a l l th e above b e l t horsepower components a re g iv en in d e t a i l below. POWER TO DRIVE THE Emm The power re q u ire d to d riv e th e empty b e lt depends 2b

33 25 on th e f r i c t i o n a l lo a d s due to ( i ) th e w eight of th e moving p a r ts such as i d l e r s, p u lle y s, drag of th e s k i r t b o ard s, drag caused by any m inute m isalignm ent of p u lle y s or i d l e r s, (11) th e w eight of th e m a te r ia l on b e l t, and ( i l l ) th e in t e r n a l f r i c t i o n of th e rib b o n of th e m a te r ia l as i t s h i f t s and re sh a p e s i t s e l f in p assin g over th e i d l e r s. * The c a lc u la tio n of a l l th e s e f r i c t i o n a l f o rc e s depends on an assum ption of a com posite f r i c t i o n f a c t o r ". The accu racy of t h i s assum ption d eterm in es th e accuracy of - '.. ' /v... - th e r e s u l t s o b ta in e d.. Most components of f r i c t i o n a l fo rc e s v ary d ir e c tly w ith th e len g th, of th e conveyor. However, th e re a re a few components which a re independent of b e lt le n g th and, th e r e f o r e, may be added as com ponents. The horsepow er to d riv e th e empty b e l t, he t o t a l f r i c t i o n a l fo rc e (lb s ) x b e lt speed (f.p.m.) r 3 3,0 0 0 Where: = CxQx (L^Lq)xS : (6) 33,000 C com posite f r i c t i o n f a c to r as "explained above. U su ally th e v alu e of C mayr.be ta k en However, fo r more a c c u ra te v a lu e s o f C, see p L - c e n te r - to - c e n te r d is ta n c e of b e l t * te rm in a l p u lle y s, in f t.

34 D eterm in atio n of v alu e Q: L0= A c o n s ta n t which r e p r e s e n ts f r i c t i o n a l lo s s e s th a t a re always to be in clu d ed in th e com posite f r i c t i o n a l f o r c e s. These f r i c t i o n a l lo s s e s a re independent of b e l t le n g th and a re commonly known as " te rm in a l f r i c t i o n a l l o s s e s ". U su ally LoSl5 0 f t. may be ta k e n. For more a c c u ra te v a lu e s see ta b le I I, p. 27- Q = w eight of th e moving p a r ts of th e conveyor system in I b s / l i n e a r f t. of th e b e l t, (see below ). 2 6 The v alu e of Q i s v ery d i f f i c u l t to o b ta in w ith accu racy. The approxim ate v a lu e of Q may be ta k e n as n u m e ric ally eq u a l to th e w id th of th e b e lt in in c h e s. Hence f o r a 1+8- in ch b e l t th e v a lu e of Q = 48 l b s. p er lin e a r f t. b e l t le n g th. A more a c c u ra te v alu e of Q can be determ ined by th e fo llo w in g fo rm u la:2 / Q = 2B / W ]/li / W2/ I 2 Where: B = b e l t w eight in I b s / l i n e a r f t. - W]= w t. of th e re v o lv in g p a r ts of th e c a rry in g i d l e r s in l b s. W - w t. of th e re v o lv in g p a r ts of th e r e tu r n i d l e r s in l b s. 2 / I b i d., p a g e 6 9.

35 l l = av erag e spacing of th e lo ad c a rry in g i d l e r s, in f t. Ip s av erage spacing of th e r e tu r n i d l e r s, in f t. 27 TABLE I I VALUES OF COMPOSITE FRICTION FACTOR, C, AND CONSTANT, LQ C lass of equipm ent V alue o f C V alue of L_ (In f t. ) For conveyors w ith a n t i f r i c t i o n id l e r i n s t a l l a tio n s on tem porary, p o r- a b le or im p e rfe c tly a lig n e d s tr u c t u r e s. For conveyors w ith high grade a n t i - f r i c t i o n i d l e r s on perm anent or w e ll a lig n e d s tr u c t u r e s. For conveyors as in (2) b u t w ith g rad es r e q u irin g r e s t r a i n t of th e b e l t when lo a d ed ^75 W ith th e above form ula (6 ), th e horsepower re q u ire d to d riv e th e empty b e l t, he, can be c a lc u la te d. The ta b le I I I g iv e s th e v a lu e s of hq f o r d if f e r e n t b e l t s iz e s a t 100 f.p.m. b e l t speed. The horsepow er a t o th e r b e l t speeds may be c a lc u la te d by m u ltip ly in g th e v a lu e s in ta b le I I I by a f a c to r o b tain ed by d iv id in g th e new b e l t speed by 100.

36 28 TABLE I I I APPROXIMATE VALUES OF HORSEPOWER TO DRIVE THE EMPTY BELT AT " a SPEED OF 100 FEET PER MINUTE JjCV, B e lt w id th ( in in c h es) H o riz o n ta l c e n te r - to - c e n te r d is ta n c e of te rm in a l p u lle y s ( in f e e t ) _ b e lt ' ' w-.jl ' ' oo ; >-, j --\ 0.5 ' l. o j, / " ^ /, ; 2. ;.. 9" NOTE: This ta b le i s based o n.th e form ula fo r c a l c u la tin g empty b e l t horsepow er where 0=0.03 and Lor l 50 f t. POWER TO MOVE THE MATERIAL HORIZONTALLY ALONG THE CONVEYOR * A fte r determ in in g th e empty b e lt d riv e horsepow er, th e n e x t s te p i s to d e te rm in e -th e horsepower to move th e lo ad of m a te r ia l h o r iz o n ta lly. As th e horsepow er to d riv e th e empty b e l t, he, i s g iv en by he = CxQx(L/Lp)xS (formu^a 6) th e 33,000 v alu e of th e h o riz o n ta l horsepow er, hm, can a ls o be c a lc u la te d by th e same fo rm u la w here th e sym bols C, L, L0 and S have th e

37 same meaning as b e fo re, b u t th e v alu e of Q changes due to a lo ad of th e m a te r ia l p u t on th e b e lt.' The v alu e of Q I s = c a lc u la te d in th e fo llo w in g way: - L et T * o u tp u t in to n s/h o u r and S = b e l t speed in T h en 'th e w eight of th e m a te r ia l on th e b e lt i s... eq u al to -T to n s/h o u r or. 2000T p o u n d s/h o u r...as..the. b e l t speed in f e e t p e r m inute i s S, th e speed in f e e t per hour i s eq u al to 60S f t. T h erefo re, th e w eight of m a te r ia l on the-., b e l t, Q ( in l b s ), f o r each f t. of b e lt le n g th = (2000T)/60S. Hence th e h o riz o n ta l horsepow er, hm, i s g iv e n 'b y " 0, ] h CxQx (L^Lq) x S - 1 o m :.. 33,000 : :. r -C. v :.,; ' J Cx^ 2 (L /L 0 ) xs ' - 33,000 j. ; :* Cx(L/Ln )xs.v. :.. v.'j 990, 5,:., ',.(7) NOTE: Here th e v a lu e of C i s recommended as compared to f o r empty b e l t s sin c e th e.p re s e n c e of th e lo a d w i l l modify: th e tro u g h in g c h a r a c te r i s tic s of th e b e l t. The ta b le IV g iv e s th e v a lu e s of h^ to h au l r.o.m. c o a l a t d if f e r e n t b e l t le n g th s and c a p a c itie s.

38 3 0 TABLE:H :: ;.Lx,::"-; }... l HORSEPOWER VALUES TO CONVEY THE R.O.M. COAL ON A HORIZONTAL BELT AT ANY SPEED V T ons/, T o ta l_ b e lt_ le n g th _ lin _ fe e tl hour o > -x I.--:- *: : : : : u: : ; ^ > 5 6 : O l.O i. o NOTE: T his ta b le I s based on form ula (7) where C = 0.03 and L0 = 150 f t. : V1 ' ; uvl

39 POWER TO ELEVATE OR LOWER MATERIAL OR POWER TO BE GENERATED IN LOWERING JX :v. By th e d e f in itio n of horsepow er, i t i s th e r a t e of doing work (measured in f t - l b s p er m inute dr per second) in r a is in g or low ering a.lo a d. Let; th e m a te r ia l to be conveyed i s eq u al to T to n s per hour or 2000T/60S lb s p er m inute. Then th e r a t e -of doing th e work n e c e ssary to r a i s e or low er 2000T/60S lb s per m inute th ro u g h a d is ta n c e.h f t. i s : ^ - ' : h f t - l b s ^3e2^ m inute - *-.^... * = 2000T x u Y 1 *; 6 "&S; 33 f OOO horsepow er ^ " ' ' ' " '= hp " ' - - V ' V T h e re fo re, th e power to r a i s e or low er th e m a te r ia l, hj,, i s g iven by r :.-.J..,' h y -r (TxH)/990 (8) ) NOTE: The horsepower v a lu e, h r., * 4~\ i s a lso ; \ c\ a lle d > g ra v ity horsepow er. In th e above form ula th e v alu e of H i s co n sid ered as th e d iffe re n c e in e le v a tio n between th e lo ad ing s ta tio n and th e d isc h a rg e p o in t. When th e b e l t p r o f ile i s u n d u la tin g, d iv id e th e p r o f i l e in to segm ents determ ined by m ajor b reak s in th e g rad e. ad v erse grade segm ent. Then f in d th e l i f t f o r each From th e sum of th e s e in c liv id u a l l i f t s, c a lc u la te t h e t o t a l l i f t, H, to determ ine th e v a lu e

40 of bp by th e above fo rm u la. The ta b le V g iv e s th e v a lu e s of hp fo r d if f e r e n t o u tp u ts and a t d if f e r e n t s lo p e s. 3 2 :. : TABLE V HORSEPOWER VALUES TO ELEVATE MATERIAL OR POWER GENERATED IN LOWERING THE MATERIAL Tons/ hour L i f t or drop1 (In f e e t ) ^ b-0.0 ' :0 : ' ^ NOTE: The above ta b le I s based on form ula ( 8 ). POWER TO DRIVE THE TRIPPER..t: ---- A tr i p p e r I s a m echanical d ev ice f o r unloading, a b e l t conveyor a t p o in ts o th e r th a n over th e head p u lle y. I t l i f t s

41 3 3 a p o rtio n o f th e b e l t o ff th e r e g u l a r. conveyor carry in g, id le r s and bends i t around th e tr ip p e r p u lle y.1' 1The m a te r ia l i s d isc h arg ed over th e tr ip p e r p u lle y (a s though i t were th e head p u lle y ) and in to a chute which i s a p a r t of th e t r i p p e r. Depending upon th e d esig n of th e tr ip p e r c h u te, th e m a te r ia l ; - " may be d ischarg ed to one sid e of th e b e l t conveyor, or s e le c tiv e ly to e ith e r s id e, o r.t o both s id e s sim u lta n e o u sly. Many models of t r ip p e r s a re a v a ila b le, but a l l can be c l a s s i f ie d in to th e fo llo w in g f iv e g e n e ra l ty p e s:... ( i ) : motor p ro p e lle d t r ip p e r s " ^ ( i i ) hand p ro p e lle d tr ip p e r s. ( i i i ) s ta tio n a r y tr ip p e r s (iv ) (v) ro p e -h a u l tr ip p e r s b e l t p ro p e lle d tr ip p e r s Of a l l th e s e ty p e s th e l a s t one, ( v ), b e l t p ro p e lle d tr ip p e r s a f f e c t th e t o t a l power req u irem en t of th e conveyor system. I f..the b e l t p ro p e lle d tr ip p e r, is. i n s t a l l e d,.the power, t o.. d riv e th e tr ip p e r i s o b tain ed from th e b e l t by means of a gear t r a i n which connects th e d riv e w heels to th e tr ip p e r p u lle y (th e d ir e c tio n o f th e tr ip p e r t r a v e l can be re v e rse d by s h if tin g g e a r s ). T his p o w e r is determ ined by th e fo llo w in g fo rm u la :3=2/ ' '... a ': v.0 B e lt p ro p e lle d tr ip p e r h p., h t = (9) 1 0 / H. E. P rim er, A ll about b e ltin g - Handbook M B-17, 1957, R o c k fo ile r C enter, New York 20, N.Y., U nited S ta te s Rubber Company, P., 22.

42 Where; A = a c o n s ta n t which v a r ie s w ith b e l t w id th. (See ta b le VI f o r v a lu e s of,ai ) S = b e l t speed in f.p.m. T = o u tp u t in to n s per hour r'. / H = tr ip p e r l i f t in f t. which v a r ie s w ith b e l t w id th. (See ta b le V II f o r v a lu e s ::.... o f *H') : - TABLE VI : VALDES OF CONSTANT 'A ' ' ; :. ; r r.: B e lt w id th (in in c h e s) V alue of A1 24 :. : : v : * ; TABLE V II - ;; AVERAGE TRIPPER LIFTS (VALUES OF, H*) B e lt w id th (in in c h e s). T rip p er h e ig h t (in f t ) if

43 ACCELERATION. HORSEPOWER. : - c. ' cr-nr.:;: 3 5 The a d d itio n a l horsepower re q u ire d to a c c e le r a te th e loaded b e l t, ha, i s determ ined by th e fo llo w in g f o r m u la :^ / - - ( L ) x ( S (Q / M) x (100) (100) t (10) Where: Q = w t. of th e b e lt and moving p a r ts ( in lb s :r: - p er lin e a r f t. of co n v eyor). See page 26 f o r f u l l e x p la n a tio n o f th e v alu e of -v.-- Q. v/..,-::. " '' L : S z b e l t speed in f.p.m. M r av erage lo a d in lb s per f t of conveyor. : I t i s determ ined from th e fo llo w in g form u la: u _ where T i s th e average r ;; v " s o u tp u t in to n s /h o u r. L. = t o t a l le n g th of th e conveying b e l t in f t, v i t = tim e in seconds to a c c e le r a te th e b e lt from r e s t to f u l l lo a d. (T his tim e i s :: :r. ' 1 u s u a lly lim ite d to 2 to 5 se c o n d s). This a c c e le r a tio n horsepow er, ha, i s r a r e ly added to th e o th e r b e l t horsepow er req u irem e n ts to o b ta in th e t o t a l b e l t horsepow er. Where th e a c c e le r a tio n r a t e i s u n u su a lly high or o th e r in d ic a tio n s a re th a t th e horsepower re q u ire d f o r a c c e le r a tio n may be uncommonly la r g e, i t must th e n be determ ined and in c lu d ed in th e t o t a l b e l t horsepow er. th e a c c e le r a tio n horsepow er i s le s s th a n 50%. of..th e sum of I f 11/ J H alsted S tr e e t Company, 1961,. W. Hardy, B e lt Conveyor C om putations., Chicago 9, I l l i n o i s, Goodman M anufacturing P» 5

44 he / hy, / h%., i t i s ig n o red sin c e m o to rs.a re norm ally cap ab le of d e liv e rin g power 50$ in excess of t h e i r continuous ' r a t i n g s. 3 6 A lso, a d d itio n a l c o n s id e ra tio n must be giv en to th e e l e c t r i c a l equipm ent when a conveyor w i l l be s ta r te d many tim es d u rin g th e s h i f t. An abnorm al number of sto p p in g and s ta r t in g tim es w ill te n d to h eat th e motor beyond i t s norm al r a tin g and must be co n sid ered when s e le c tin g m otors f o r th e conveyor system. SUMMARY BELT HORSEPOWER CALCULATION'S The t o t a l b e l t horsepow er, h, i s th e sum o f th e in d iv id u a l power item s he, hm, hr, h^, and ha ~. U su ally th e v a lu e s of h t and ha a re n o t in c lu d ed in th e t o t a l b e l t h o rse- : : 3 ;. :... power when th e tr ip p e r i s n o t p re s e n t or n o t o p erated by th e b e l t motor and when th e a c c e le r a tio n horsepower determ ined by form ula (10) i s le s s th a n 50$ of th e sum of he, h^, and hr. (A) Horsepower R equirem ents f o r H o riz o n ta l Conveyors: For h o r iz o n ta l- b e lt conveyor i n s t a l l a t i o n s th e power i s re q u ire d only to overcome th e f r i c t i o n in running th e empty b e l t and to c a rry th e m a te r ia l along i t. T h erefo re, t o t a l motor horsepower fo r h o riz o n ta l conveyors v:;;; - he ^ *V : (1 1 ) m otor e f f ic ie n c y

45 (B) Horsepower R equirem ents f o r E le v a tin g Conveyors: - The t o t a l m otor horsepower fo r e le v a tin g conveyors he / bin / hp motor e f f ic ie n c y (12) (C) Horsepower R equirem ents f o r D escending (or D eclin in g ) Conveyors: Two c o n d itio n s must be co n sid ered in co n n ectio n w ith a loaded d e c lin e d conveyor: ( l ) When th e g ra v ity horsepow er, hp, i s LESS th a n th e f r i c t i o n horsepower ( th a t i s, le s s th a n sume of he and hjjj), some power i s re q u ire d -fro m th e motor to,d r iv e th e loaded conveyor on d e c lin in g g ra d e s. i: This horsepower i s ^ (he V!%) (ht ).(13) (2) When th e g ra v ity horsepow er, bp, i s GREATER th a n th e f r i c t i o n horsepower (he / h g ), th e horsepower r e quired, in th e b e l t to r e ta r d th e loaded conveyor a g a in s t c- ", /' g r a v ity a c tin g on th e lo ad i s 1 3 / 37 (hr) (ko / h j, ) (I'O As (he / h m) approaches th e v alu e of hp, th e loaded 1 2 / U. S. R ubber, A ll about b e ltin g f o r Coal Mining Handbook M, 6314-B -l, 1957j R o c k fe lle r C e n te r, New York 20, N.Y. U nited S ta te s Rubber Company, p. 65* 1 3 / I b i d.

46 conveyor w i l l have a g r e a te r tendency to c o a st when th e power to th e motor i s sh u t o f f. When h r. i s g re a te r th an (h e,,/ hg.) a brake must be u sed I t i s obvious th a t in o rd er to a r r iv e a t th e a c tu a l motor horsepow er needed to d riv e th e b e l t conveyor in a l l th e above cases th e tra n s m is s io n and o th e r lo s s e s between th e motor and d riv e p u lle y must a ls o be co n sid e re d. The o v e r a ll e f f ic ie n c y of th e motor may be ta k en as eq u al to 80$. The s ta r t in g to rq u e req u irem en t of a conveyor i s an im p o rtan t f a c to r in s e le c tin g th e d riv e m otor. The g e n e ra l purpose s q u ir r e l cage motor w i l l f u l f i l l th e req u irem en ts of most a lte r n a tin g c u rre n t i n s t a l l a t i o n s. However, some conveyors r e q u ir e an i n i t i a l s t a r t i n g to rq u e which exceeds th e o u tp u t of t h i s ty p e of m otor. Such req u irem en ts n e c e s s ita te th e use of h ig h -to rq u e s q u ir r e l cage or w ound-rotor in d u c tio n m otors. These a lte r n a tin g c u rre n t m otors o f fe r c e r t a i n advantages over d ir e c t c u rre n t m otors on some a p p lic a tio n s. However, d ir e c t c u rre n t m otors a re fre q u e n tly used in c o a l mines where v a r ia b le speed req u irem e n ts a re n e c e s s a ry. O pen-type m otors a re n o t p e rm is s ib le f o r use in hazardous lo c a tio n s ; m otors th a t a re i n s t a l l e d a t lo c a tio n s where ex p lo siv e q u a n titie s of c o a l d u st or methane gas may be p re s e n t r e q u ir e s p e c ia l c o n s tru c tio n such as flam e p ro o f ing and i n t r i n s i c a l l y sa fe " f e a tu r e s.

47 39 PERMISSIBLE ANGLES OF INCLINATION FOR HAULING COAL ON BELTS The an g le of in c lin a tio n depends on th e fo llo w in g f a c to r s : (1) Shape and s iz e of th e m a te ria l to be conveyed - I r r e g u la r ly shaped m a te r ia l has le s s tendency to r o l l back th a n sm o o th ;sy m m e tric a lly shaped m a te r ia l. However, sy m m etrically shaped m a te r ia l can be conveyed up ste ep g rad es w ith o u t f o il- b a c k i f embedded iri a c o n s id e ra b le amount of f i n e s. (2) M oisture - Wet m a te ria ls ten d to s lid e back on in c lin e d conveyors. (3) Speed and lo ad in g - M oderate b e l t sp eed s, uniform ly c o n tro lle d fe e d -lo a d in g, and lo a d in g on a h o riz o n ta l s tr e t c h of th e b e lt iprovide th e g r e a te s t e f f ic ie n c y on s te e p ly in c lin e d r u n s.. In g e n e ra l, th e maximum angle of in c lin a tio n a t which th e m a te r ia l can be conveyed i s approxim ately 10 to 15 degrees l e s s th a n th e an g le of rep o se of th e m a te r ia l. The fo llo w in g ta b le V III l i s t s p e rm is sib le an g les over which c o a l can be conveyed w ith o u t undue s p illa g e.

48 TABLE V I I I MAXIMUM PERMISSIBLE ANGLES OF CONVEYOR INCLINATION M a te ria l to be conveyed Maximum p e rm is sib le an g le ( in d eg rees) 1. A n th ra c ite Coal (a) ru n -o f-m in e 16 (b) f in e s 20 (c) lumps only Bitum inous Coal (a) ru n -o f-m in e 18 (b) f in e s 20 (c) lumps only 16 r

49 CHAPTER V SELECTION OF PROPER BELT The proper s e le c tio n of b e lt width and speed fo r a given output and th e c a lc u la tio n of t o t a l b e lt horsepower has been shown in the previous chapters. A fter determ ining the t o t a l b e lt horsepower requirem ents, the f i r s t step in s e le c tin g the correct b e lt i s to know the maximum s tr e s s e s th a t w ill be developed in the b e lt w hile hauling the m a teria l. A b e lt carcass of proper con stru ction i s then s e le c te d to w ithstand th ese s t r e s s e s. F in a lly a b e lt covering i s s e le c te d to p ro tect the b e lt carcass again st ex tern a l wear, h eat, m oisture or other in ju rio u s prop e r tie s of the m a teria l to be conveyed. The s e le c tio n of the proper b e lt fo r a given duty i s very important to minimize tra n sp o rta tio n c o s ts. To determ ine the co rrect s p e c ific a tio n s of the b e ltin g, i t i s necessary to know the maximum operating ten sio n under which the b e lt w i l l work. In the operation of any b e lt conveyor there i s a d ifferen ce in b e lt ten sio n between the p oint where i t f i r s t con tacts the d rive p u lley and the p oint where i t le a v es the p u lle y. These ten sio n s known as " tig h t side" te n sio n, T^, and "slack side" ten sio n Tg, are in d ir e c t r e la tio n s h ip to one an oth er. The

50 d iffe re n c e.b e tw e e n th e t i g h t sid e te n s io n and s la c k sid e te n s io n i s known as e f f e c tiv e " te n s io n, Te. These th re e b a s ic b e l t te n s io n s must be determ ined b e fo re choosing c o r r e c t b e l t. However, th e re a re o th e r minor bielt.tensions th ro u g h o u t th e b e l t ru n t h a t may a f f e c t s u c c e s s fu l b e lt o p e ra tio n under s p e c ia l c o n d itio n s. These l a t e r b e l t te n s io n com putations a re n o t d e a lt w ith in t h i s stu d y and should be r e f e r r e d to th e conveyor b e l t m anufacturers* e n g in e e rs. DETERMINATION OF BELT STRESSES There a re many methods of c a lc u la tin g b e l t s tr e s s e s or te n s io n s. Most of th e la r g e r b e l t m an u factu rers p u b lis h a d esig n m anual covering t h i s s u b je c t. But many of th e se methods r e q u ir e th e use of c h a r t s, ta b le s, nomographs, e t c. A lso, th e s e m anuals in c lu d e l i t t l e, i f any, in fo rm atio n concern in g th e b e l t te n s io n req u irem en ts f o r poly v in y l c h lo rid e covered b e l t i n g, sin c e t h i s ty p e of covering has been r e c e n tly in tro d u ced as f i r e r e s i s t a n t b e ltin g. In t h i s s e c tio n a sim ple method of computing v a rio u s im p o rtan t b e l t te n s io n s re q u irin g a minimum number of c h a rts and ta b le s i s g iv en. (1) E ffe c tiv e B e lt T ension: The e f f e c tiv e te n s io n, TQ, i s th e p u ll on th e b e l t to overcome th e f r i c t i o n a l lo s s e s caused by th e movement of... th e b e l t and i t s lo a d in p assin g over i d l e r s and any l i f t of th e lo ad on a g rad e. The e f f e c tiv e te n s io n, Te, i s th e d iffe re n c e between t i g h t sid e te n s io n and s la c k s id e te n s io n

51 of th e b e l t. That i s,» - 43 : ;.To= CT1 - T 2 ) ( 1 5 ) : A lso, T. =?. 33.?QQ2. S (16) Where: h - t o t a l b e lt horsepower-, 8 «b e l t speed in f.p.m. (2) Maximum o p e ra tin g te n s io n : T ight s id e te n s io n, T^, i s th e te n s io n in th e b e lt as i t f i r s t c o n ta c ts th e p u lle y. The maximum b e lt, te n s io n i s th e h ig h e s t te n s io n in th e whole b e l t loop and t h i s te n s io n d eterm in es th e re q u ire d t e n s i l e s tr e n g th of th e b e lt to w ith sta n d th e w orking s t r e s s. In h o riz o n ta l or n e a rly h o riz o n ta l b e l t s th e maximum o p e ra tin g te n s io n may be tak en as eq u al to T^. In o rd er to determ ine th e maximum o p e ra tin g te n s io n (h e n c e fo rth d esig n ate d w ith symbol T ^), th e v alu e of e f f e c tiv e te n s io n Te, must be m u ltip lie d by a f a c to r, F (which w ill be ex p lain ed l a t e r ). 'T hat i s,. Maximum o p e ra tin g te n s io n T^ = Te x F (17) F ig. 4 B e lt T ensions In a Running B e lt

52 i R e fe rrin g to F ig. 4, i s t i g h t s id e te n s io n and Tg th e s la c k s id e te n s io n. When th e b e lt i s about to s l i p on th e d riv in g d ru a, th e r a t i o to and Tg w ill re a c h i t s maximum v alu e and i s g iv en by th e form ula: T 1 T 2 Where: 4 T _ (18) = an g le of wrap in ra d ia n s / I * c o e f f ic ie n t of f r i c t i o n between b e l t and d riv in g p u lle y e base of th e N aperian lo g a rith m S ince Vs and T h e re fo re,... H 3 11 I I Or F = (T^ - T2 ) (from form ula 15) Te x F ; (from form ula 17) *- ^ - * * - ^»*. t h / ( * i ). r ri / (n - 1) 3&/.(19) Where n = T h is,v a lu e of F and th e im plied v a lu e of Tg i s th e minimum v alu e to p reclu d e s l i p on th e d riv in g drum. In p r a c tic e s lip i s p rev en ted by usin g in th e d esig n a sm aller l V S ince = 'e 6 (from form ula 18) th e re fo r e, T2 T1 = T2 x ^ *" Then T1 = x ^ = "2 r. & = n (Tr i 2 ) T ig x / ) - i 2 t 2 % ^ - a (n- 1) Where n - ^

53 1 value fo r the c o e ffic ie n t of f r ic t io n between b e lt and drum than Is a c tu a lly obtained in s e r v ic e. 4 5 The'approximate v a lu es of the c o e ffic ie n t of f r ic t io n fo r various b e lts i s given in th e fo llo w in g Table IX: --, - ' * VALUES OF COEFFICIENT OF FRICTION B e lt Cover P la in drum Lagged drum Rubber covered b e ltin g Poly v in y l ch lorid e (p.v.c.) covered b e ltin g : In th e eq u a tio n (19) th e v a lu e s of 0 can v ary from 180 deg. to 270 d eg. f o r a s in g le d riv e depending on th e snub p u lle y arran g em en ts; and f o r m ulti-drum d riv e s an an g le of wrap of 220 deg. per d riv in g drum i s th e u s u a l v a lu e. The ta b le X g iv es th e v a lu e s of F based on form ula (19) and on ta b le IX fo r c o e f f ic ie n t of f r i c t i o n v a lu e s.

54 4 6 TABLE X VALUES OF "F" FACTOR Angle of -wrap Rubber covered b e ltin g p.v.c. covered b e ltin g P la in Lagged P la in Lagged ( in d eg rees) drums drums drums - drums 220,., , ^ o 1.1 7, i #27 ; ; ; * We have a lre a d y e s ta b lis h e d th e fo rm u la: -~F x Te where T_ - 4 x 33>000 (s e e form ula 1 6 ). I t i s ap p a ren t from ' - ' 6 S t h i s form ula t h a t th e h ig h er th e b e lt speed, th e sm a lle r w i l l be th e maximum te n s io n f o r th e same to n n ag e. P r a c tic a lly t h i s means th a t f o r a given tp h (to n s p er h o u r), th e lo ad bed on th e f a s t moving b e lt i s th in n e r and th e re w i l l be le s s w eight on th e t o t a l le n g th a t one tim e. Hence th e p u ll to move th e b e l t w i l l a ls o be l e s s ; f o r exam ple, a b e lt tra n s p o rtin g 300 to n s p er hour a t 300 f.p.m. r e q u ire s a t e n s i l e s tr e n g th only o n e -h a lf th a t of a b e l t tr a n s p o rtin g th e same tp h b u t a t l$ d f,. p.m. A fte r d ecid in g th e d e s ire d b e l t w id th and th e maximum b e l t te n s io n, th e n e c e ssary p ly w eight and number of

55 ^7 p ile s can be d eterm in ed. The t e n s i l e s tre n g th of th e b e lt i s co n sid ered to be in th e b e lt c a rc a s s..the ru b b er covers and skim c o a tin g in th e c a rc a s s a re m erely to bind th e f a b r ic p lie s to g e th e r and to p r o te c t th e c a rc a ss from imp a c t, a b ra s io n, m o istu re and d i r t. The. conveyor b e lt i s commonly made up of s e v e r a l p l i e s o f c o tto n, ray o n, n y lo n or com bination of th e s e woven in to a f a b r ic and sometimes r e in fo rc e d by c o tto n cord s or s t e e l c a b le s as in "Campass cord" b e l t s. The p ly s tr e n g th i s s p e c ifie d in pounds p er, in c h -w id th and i s d e sig n a te d as th e p e rm is sib le working s tr e s s. ( p.w.s.). I f p.w.s. i s exceeded in th e norm al b e lt ru n th e f i b e r w i l l te n d to s e p a ra te from i t s b in d in g in th e c a rc a s s. The p e rm is s ib le w orking s t r e s s i s determ ined as fo llo w s: p.w.s.* ( 20) - W ', ' :...: where T^ i s th e maximum"operating te n s io n in pounds, and W i s th e b e l t w id th in in c h e s. A lso,. Tx " = fx p in lb s p er in c h of w id th ( 21) Where: f = maximum w orking s tr e s s /p ly /in c h - w id th p * number o f p l i e s in th e b e lt The v a lu e o f -th e maximum w orking s t r e s s in th e b e l t depends upon th e fo llo w in g f a c t o r s : (a) th e q u a lity of m a te r ia l used in th e b e l t c a rc a s s. (b) th e ty p e of jo i n t used f o r end to end b e l t jo in in g

56 "Hook J o in ts " w ith m e ta llic f a s te n e r s have a s tre n g th of about 50$ o f th e o r ig in a l b e ltin g and "S p liced J o in ts " can have a s tr e n g th up to 75$ of th e o r ig in a l b e l t s tr e n g th, depending on th e number of p lie s in th e b e l t. (c) th e method of b e lt te n s io n in g arrangem ent. ( i ) In screw ty p e te n s io n in g, th e b e l t i s s tr e s s e d by a screw arrangem ent u n t i l s u f f i c i e n t te n s io n i s developed in th e b e ltin g. The a c tu a l te n s io n in th e b e lt cannot be gauged by th e te n s io n d ev ice o p e ra to r, and so th e u su a l p r a c tic e i s to co n tin u e te n sio n in g th e b e lt u n t i l s lip does n o t occur a t th e d riv in g drum. I t should be n o ted th a t th e b e l t i s e a s ily o v e r-s tre s s e d by t h i s m ethod. ( i i ) The g ra v ity ty p e te n sio n in g i s designed to apply only th e s la c k sid e te n s io n Tg on th e s la c k s id e o f th e b e l t : The v alu e o f T2 i s much low er th a n th e maximum fo rc e in th e b e lt and can be a p p lie d d i r e c t l y by w eighted r o l l e r s or in d ir e c tly by th e lo ad ed w ire ro p e s. This method of te n s io n ing cannot over s t r e s s th e b e l t and so i t allow s a h ig h er v alu e of p e rm is s ib le w orking s t r e s s to be u sed. (d) th e cy c le tim e o f th e b e l t. As th e cy c le tim e in c re a s e s th e b e l t te n s io n r a tin g must be in c re a s e d. The ta b le XI g iv e s th e v a lu e s of maximum working s tr e s s r a tin g s f o r ty p ic a l conveyor b e l t s.

57 MAXIMUM PERMISSIBLE TENSION RATINGS PER INCH WIDTH FOR DIFFERENT 'KINDS OF BELT CONVEYORS CD IO, V) 0 I s 0.3 +> 0 H o (D I s g A 0) CU si -p H I O 5 s Pi g n bc <D 5 m 0 a cd Q> XJ p <D 1 CD Eh I a g s to H > J&d o 3 Q A 0 0 Jd w +» (d CM m CM m CM co CM CO CM C O CM CO H CO O co CO CM IN- CM! = i. z z IN O vo l f \ vo CO J* irx IA IN a vo irx vo CO j - J - irx IA IN o vo 1A vo CO J* 1T\ IA IN o vo 1A vo co J - J - 1A IA v0 o vo & vo CO J - J - IA vo Os vo & IA CO CO J - IA 1A oo l f \ CO CO CO -± IA & 3 7 i CM IA CO VO no H CM co CO J* IA IA H xh CXJ o H CO co J* IA IA CO CM CM vo CM CO CO c o j - s & (B) CAMPASS CORD BELTS: Here th e v a lu es a re g iven per In ch -w id th of BELT Cord number = % r io ^ O v v\ if\ S3 E S ir\ cs ir\ \ i R S CM CM ik ITS CM %4 g 0 JC 1 I 0 w > S'- 1 i./ 1! G I I N O ' : W.3 E : :V ' S? K : : ' e s v ' ir ^ -' : - \\ r co m irx ov mv so & s s IA O IA IA IA 6 IA CO VO ' ^ /-;% E r c. ^.! 1 s I i 1 a - A s & 1 & 1 S. %A vo K i IA O CO CN IA VO i O CO IA IN vo VO IA 8 t a a l f \ VO E O H trx co 1 1A s.. I IA & I 3 a 3 * I! $ 1A O g H 1 H irx g : H B #4 IA 8 S % 8 VO CO 8 #4 O H O 8 H 8 no no j- tr\

58 50 3» Slope B e lt T ension: '. W ith a l l In c lin e d conveyors th e w eig h t-o f th e b e l t on th e slo p e causes te n s io n a t th e to p of th e slo p e. The slope b e l t te n s io n, Ts, depends on th e w eight of th e b e lt and th e f r i c t i o n of th e r e tu r n i d l e r s. W ith a f r i c t i o n coe f f i c i e n t of 0.03 f o r th e r e tu r n id le r s ^ th e slo p e b e lt te n s io n can be determ ined by th e fo llo w in g form ula Ts = C x L x (0-1 /1 5 ). (22) Where: G = g ra d ie n t o f th e slo p e ex p ressed as a f r a c t i o n ^ L = b e l t le n g th in f e e t C r b e l t w eight i n pounds p er l in e a r f t. (se e below f o r th e d e te rm in a tio n of ; b e l t w eig h t) Should th e v a lu e of slo p e te n s io n, Ts, as c a lc u la te d by th e above form ula exceed th e v alu e of s la c k s id e te n s io n, Tg, th e n th e maximum b e lt te n s io n, T^, w ill be eq u al to (Te / Ts ) and th e b e l t should be designed a c c o rd in g ly. The v alu e of Ts r a r e ly exceeds Tg even fo r conveyors on ste e p slo p e s u n le s s a th ree-d ru m d riv e i s used. D eterm in atio n of B e lt W eight: - The v alu e o f b e l t w eig h t, C, v a r ie s w ith th e ty p e of b e lt c o n s tru c tio n and m an u factu rer* s s p e c if ic a tio n s. 1 5 / N. Brook, o p. c l t. «p. 1*90

59 I f no In fo rm atio n as to th e w eight of b e lt Is a v a ila b le an approxim ate v a lu e may be determ ined by th e fo llo w in g form ula: 3 ^ / C r W f l U L l / q) I b s / l l n e a r f t. (23) 1200 "Where: * b e l t w idth in in ches w = duck w eight in ounces (u s u a lly su p p lie d ) p = number of p l i e s in th e b e lt NOTE: q * w eight of th e to p and bottom cover of th e b e lt ( in lb s ) per f t. long and p e r in c h wide of b e l t. U su ally th e v alu e of q = l b s. when to p and bottom cover th ic k n e ss = 1/32 In ch. The above form ula must be used only to determ ine th e w eight of p ly type b e l t s. For s t e e l cab le re in fo rc e d b e l ts, th e e x tra w eight of th e s t e e l members must be co n sid ered. DETERMINATION OF MAXIMUM AND MINIMUM NUMBER OF PLIES OF BELTS FOR PROPER TROUGHINO AND STIFFNESS The ch o ice of number o f p lie s in a norm al m u ltip ly b e lt Is governed n o t only by th e s t r e s s but a ls o by th e tro u g h in g and s t i f f n e s s c h a r a c t e r i s t i c s of th e b e l t. In o th e r w ords, a b e l t may p ro v id e s u f f i c ie n t s tr e n g th In te n s io n but owing to s iz e and w eight of m a te r ia l i t may be too flim s y. C onversely, a b e l t may be so heavy or th ic k th a t i t w ill n o t be tro u g h a b le in th e re q u ire d w id th. In 16/ i& ia

60 TABLE X II - 'MINIMUM PLIES TO SUPPORT LOAD OF R.O.M. COAL UP TO INCH MAXIMUM.LUMP-SIZE AND MAXIMUM PLIES FOR PROPER TROUGHING Duck w eight and p ly qual.ity B e lt w idth (in in ch es) Minimum p lie s to su p p o rt load Maximum p lie s f o r p ro p er tro u g h in g 28 o z._ Heavy 28 o z. 32 oz c o tto n - c o tto n - c o tto n - U stex c o tto n - c o tto n - c o tto n - U stex - nylon nylon nylon nylon rayon nylon n y lo n n y lo n n y lo n <.. ' '. ; Heavy ray o n 2k ; V : ; U _, 12 : NOTE: 1. Campass cord and s t e e l cab le b e l ts by t h e i r n a tu re, more tro u g b a b le th a n p ly -ty p e b e l t s and each w idth of th e s e I s d esig n ed w ith s u f f i c ie n t body to p ro v id e l a t e r a l s t a b i l i t y 2. The v a lu e s above a re based on 20 deg. e q u a l- r o ll t coughing i d l e r i n s t a l l a t i o n. A c u ta lly th e d e sig n o f a c a rc a ss fo r s u f f i c i e n t s tr e n g th to su p p o rt th e lo ad p rovided th e prop er tro u g h in g. c h a r a c t e r i s t i c s.. Hence i t may n o t be n e c e ssary to check th e b e lt f o r minimum or maximum p ly re q u ire m e n ts.

61 53 t h is case an a lte r n a tiv e i s to use a Campass cord or s t e e l cable b e lt w h ich 'w ill trough in the d esired w idth, or e ls e a wider b e lt w ith fewer p lie s may be used i f i t i s w ith in th e minimum and maximum p ly lim it a tio n s. ' The ta b le X II g iv e s the minimum and maximum p ly lim ita tio n s of ty p ic a l rubber covered b e lts to carry ru n -o f- mine c o a l. For p.v.c. covered b e lts th ese v a lu es may be 1',. ' '.. 1 ' r' found from the fo llo w in g form ulae:1 2 / Maximum number of p lie s Minimum number of p lie s 7-5W w 3-5W w (2W (25) Where: W = b e lt width in inches w r duck w eight in ounces DETERMINATION OF SIZE OF DRIVING DRUMS AND PULLEYS, The s iz e of drums and p u lley s required depends on th e number o f p l i e s and duck w eight used in th e b e lt cons tr u c tio n. These s iz e s must be such th a t i t should not cause the outer p ly of the b e lt to exceed i t s e l a s t ic lim it during the bend and su ffe r p ly sep a ra tio n. Hence th ick ca rca sses (i.e. larger number of p lie s ) req u ire la rg e diameter p u lley s and thinner ca rca sses (i.e. fewer p lie s ) need sm aller and l e s s expensive p u lle y s.. The thinner carcass of rayon w ill 1 2 / Ik M -

62 $ 4 have the same maximum p erm issib le ten sio n per inch per ply as the th ick er carcass of co tto n. Sometimes i t i s d e sir able to use th in carcass b e lts fo r u t iliz in g older p u lley s of sm aller s iz e, i f a v a ila b le at no extra cost. Otherwise th e thinner carcass of rayon or nylon having the same stren gth as a th ick carcass of co tto n would in v o lv e the purchase of a more expensive b e lt. The fo llo w in g formulae serve th e gen eral guides fo r determ ining the s iz e of drums and p u l l e y s : ^ /, f' ::v (ii) Diameter o f d riv in g,drums ( in in ch es) = y... R ' 6 Diameter of driven drums (in in ch es) r v x? : 8 (ill) Diameter of snub p u lley s (in in ch es) = \ ' '. Where: w = duck, w eight in ounces. u ; p = number of p lie s in a b e lt (2 6 ).(27) ( 28) SELECTION g F PROPER BELT CONSTRUCTION MATERIAL Of the many tie lts a v a ila b le, se v e r a l of th ese may s u it the predetermined ten sio n requirem ents. The conveyor b e lts are made of cotton fa b r ic, rayon, nylon and other 1 8 / I b i d., pp , p assim.

63 s y n th e tic f ib e r m a te r ia ls, s t e e l cab le re in fo rc e d members, f i r e - r e s i s t a n t b e l ts u sin g p. v. c., te ry le n e and neoprene, - e tc. In th e s e le c tio n of b e l t, "proper te n s io n i s n o t only th e f a c to r to be co n sid ered and i t does n o t n e c e s s a r ily confirm th e u ltim a te s tre n g h t of b e l t. In o rd er th a t some knowledge may be had o f some of 1th e o th e r f a c to r s in volved in th e s e le c tio n of a s u ita b le b e l t, th e fo llo w in g c o n d itio n s th a t a ffe c t'w o rk in g te n s io n s a re b r i e f l y d isc u sse d : 1. F a tig u e of B e it Duck: In any b e l t I n s t a l l a t i o n th e te n s io n member.of th e b e l t p asses from h ig h er to a low er or low er to a h ig h er te n s io n re g io n somewhere in i t s haul d is ta n c e. Thus th e re w i l l be c y c lic te n s io n changes depending upon th e b e lt speed and le n g th. When th e f a b r ic i s s tr e s s e d to more th an 50^ of i t s u ltim a te s tre n g th f a i l u r e from f a tig u e occurs r a p id ly S tre tc h : The more h ig h ly th e b e lt i s s tre s s e d th e more i t w ill s t r e t c h. The e x tra s t r e s s causes more fre q u e n t ta k e - : '. ' : VV ' ;,. - t,. ; up ad ju stm ents by th e screw ty p e takeup or more t r a v e l f o r au to m atic ta k e u p. 3* S p lic e L im ita tio n s : Conveyor b e l ts may be s p lic e d 1e n d le s s u by means of m etal f a s te n e r s ' or by v u lc a n iz in g. The p la te ty p e m e tal f a s te n e r s has p u ll- o u t s tr e n g th th a t i s le s s th a n th e s tr e n g th of th e duck i t s e l f. T his f a c to r i s ta k en in to c o n s id e ra tio n by th e te n s io n r a tin g s g iv en in Table X I.

64 The b e l ts of campass cord or s t e e l cab le re in fo rc e d c o n s tru c tio n.a re made " e n d le ss" by v u lc a n iz e d s p lic in g ONLY. The s tr e n g th in th e s p lic e cannot be as g re a t as th e sum of 5 6 th e s tre n g th s of th e in d iv id u a l cords or c a b le s. The f a b r ic p ly b e l ts may a ls o be v u lc a n iz e d "e n d le ss" w ith a diamond or b ia s ty p e s p lic e. W hile t h i s method does n o t p ro v id e a s p lic e as stro n g as an u n d istu rb e d b e l t s e c tio n s, however, i t i s very stro n g and f r e e from th e l o c a l s tr e s s e s found in a m etal fa s te n e d j o i n t. The use of v u lc an iz ed j o i n t in c re a s e s p e rm is s ib le te n s io n r a tin g as compared to a m e tal fa s te n e d j o i n t. The ta b le XI g iv e s th e te n s io n r a tin g s f o r th e v u l can ized s p lic e b e l t s. P u lle y Bending F o rc es: The form ulae 26 th ro u g h 28 on page 54 a re e s ta b lis h e d in o rd er to o b ta in th e same degree of bending s t r e s s r e g a rd le s s of th e b e lt th ic k n e s s. m a tte r what th e p u lle y d iam eter may b e, th e o u te r p l i e s of v - ' th e b e lt must e lo n g a te as th e b e l t i s b en t around th e p u lle y. The e x tra s tr e s s in th e o u te r p lie s induced by bending i s dependent on th e diam eter of th e p u lle y, th e th ic k n e s s of th e b e l t, and th e e l a s t i c c o n s ta n t of th e b e lt te rm in a l. Hence th e p e rm is s ib le working s t r e s s must be le s s th a n th e u ltim a te s tr e n g th of th e duck to allow fo r th e se bending s t r e s s e s. No The campass cord and s t e e l cab le b e l ts a re so c o n s tru c te d th a t th e p u lle y bending s tr e s s e s a re r e l a t i v e l y in s i g n i f i c a n t.

65 57 5. A c c id e n ta l Damage to B e lt: In underground c o a l h au lag e, b e l ts a re su b je c te d to many h azard s. B r i e f l y. th e fo llo w in g f a c t s a re d isc u sse d as an a d d itio n a l a id to b e tte r s e le c tio n of b e lts to guard a g a in s t p o s s ib le dam ages.. (a) P ieces of tram p iro n and o th e r hard m a te ria ls may p ie rc e th e b e l t, break th e c a rc a s s, c u t th e to p cover or cause o th e r o p e ra tin g damages and red u ce th e working th ic k n e s s of th e b e l t. U su ally i t i s n o t co n v en ien t to sto p and r e p a ir a b e l t th e in s t a n t i t i s damaged. Hence a b e l t i s expected to ru n u n t i l a convenient sto p p in g tim e can be a rra n g e d. T h e re fo re, th e c a rc a s s must have a s u ita b le f a c to r of s a fe ty in clu d ed in th e allo w ab le s tr e s s of th e. f a b r i c, co rd or s t e e l c a b le s to p ro v id e a re s e rv e f o r..tempor a r y o p e ra tio n under such c o n d itio n s. (b) D e te rio ra tio n of b e l t c a rc a ss ta k e s p la c e due to fu n g a l grow th on '.b elts w orking in m o ist and humid cond itio n s in m ines.. I t i s a breakdown of th e c e llu lo s e of th e c o tto n or ray o n f i b e r to p ro v id e nourishm ent f o r th e fu n g a l grow th. Hence th e u s e ;o f som e:m a te r ia l in th e b e l t cons tr u c tio n which w i l l a l l e v i a t e t h e ; g ro w th.o f fungus i s h elp f u l to guard a g a in s t such d e te r io r a tio n. W ith th e advent of th e u se of rayon in th e b e l t c a rc a s s, th e d ir e c t e f f e c t of th e p resen ce of m o istu re had to be ta k e n in to acco u n t. The c o tto n f a b r ic in th e p resence of m o istu re does n o t lo s e i t s s tre n g th but a c tu a lly i s somewhat s tro n g e r assum ing no b a c t e r i a l d e t e r io r a tio n. C onversely, depending upon th e

66 5 8 p ercen tag e of m o istu re p re s e n t In th e m in e,:rayon may lo s e a n.a p p re c ia b le p ercen tag e of i t s dry s tr e n g th. Adhesion between th e p l i e s and f l e x l i f e a ls o a re a f f e c te d by extrem ely wet c o n d itio n s. Hence rayon b e l ts should n o t be used under such, c o n d itio n s. In s t e e l cable re in fo rc e d b e l t s, a d if f e r e n t ty p e of d e te r io r a tio n may o c c u r, namely c o rro s io n. M echanical damage of th e ru b b er cover by gouging or open s p lic in g, i f n e g le c te d, can become a s e rio u s f a c to r because of th e r e s u ltin g c o rro s io n of c a b le s encased in th e b e l t. (c) F ir e H azards: Many f i r e s have o ccu rred in c o a l mines and some of th e s e have b een,caused by b e lt, conveyors. As a m a tte r of f a c t conveyor f i r e s a re exceeded in number only by spontaneous com bustion of c o a l or carbonaceous mat e r i a l. Hence a l l underground b e l ts should be f i r e - r e s i s t a n t. The U. S. B ureau o f Mines has recommended th e u se o f.n e o prene and poly v in y l.c h lo r id e ( p.v.c.) in th e c o n s tru c tio n of f i r e - r e s i s t a n t b e l t s. N otw ithstanding a l l th e s e cons id e r a tio n s f o r s a fe ty re q u ire m e n ts, th e b e l ts s e le c te d must f u l f i l l th e d u ty f o r which i t i s to be u sed.. * A new hazard has been p re d ic te d d u rin g re c e n t y e a rs. One of th e p r o p e r tie s of p.v.c. used in f i r e - r e s i s t a n t b e l ts i s i t s hig h e l e c t r i c a l in s u la tio n q u a l i t i e s or i t s hig h r e s i s t i v i t y. On some conveyors, m ostly o p e ra tin g in dry c o n d itio n s, an e l e c t r o s t a t i c charge i s found to be g e n e ra te d.

67 59 This charge w i l l g iv e r i s e to u n d e s ira b le and sometimes dangerous sp a rk in g s which may cause conveyor f i r e s. Hence th e concept o f developing a n t i - e l e c t r o s t a t i c m a te ria l fo r b e l t c o n s tru c tio n i s being r e a liz e d to guard a g a in s t s t a t i c e l e c t r i c i t y t h a t causes conveyor f i r e s. A lso, w ith th e higher b e l t speeds th e chance of dangerous sp ark in g s i s more lik e l y to o ccu r. The b e l ts must be ru n w ith in th e maximum recommended speeds commensurate w ith o th e r e f f ic ie n c y f a c t o r s. I t i s found t h a t e l e c t r o s t a t i c sp ark s w i l l not be produced when th e b e l ts a re ru n below 475 f t. p er m in u te. SELECTION OF PROPER QUALITY AND THICKNESS OF BELT COVER The l i f e of th e b e lt depends, to a g re a te r e x te n t, upon th e s e le c tio n of c o r r e c t to p and bottom cover q u a lity and th ic k n e s s. The to p cover must be of s u ita b le com position and s u f f i c ie n t th ic k n e s s. I d e a lly, i t i s d e s ira b le to f u r n is h a cover q u a lity and th ic k n e s s such th a t i t s s e rv ic e l i f e w ill m atch th e s e rv ic e l i f e of th e c a r c a s s. The cover th ic k n e s s i s im p o rta n t, n o t only from th e sta n d p o in t of w ear, but a ls o as a cushion to absorb th e lo a d in g im pact of m a te ria l to be conveyed. A la y e r of f a b r ic having a s p e c ia l weave c a lle d b reak er p ly i s o fte n imbedded in th e co v er. The b reak er p ly ab so rb s im pact and p r o te c ts th e c a rc a ss and cover a g a in s t gouging. The s e le c tio n of pro p er cover q u a lity and th ic k n e s s i s sometimes d i f f i c u l t because of many v a r ia tio n s of working c o n d itio n s. E xperience w ith

68 p rev io u s b e lts w i l l h elp i n th e s e le c tio n of th e p ro p er b e lt co v er. T his e x p e rie n c e ' should in d ic a te many, c lu e s fo r f u tu r e s e le c tio n. Loss of cover by a b ra s io n w h ile th e c a rc a ss i s r e l a t i v e l y i n t a c t would in d ic a te th a t succeeding b e lts could p r o f ita b ly c a rry a h e a v ie r or a b e tte r q u a lity c o v e r. Severe c u ttin g of th e cover w ith o u t s e rio u s a b ra s io n lo s s would in d ic a te e ith e r a lo ad in g problem or a need f o r more cover th ic k n e s s. I t would, o r d in a r ily, be more econom ical to improve lo a d in g c o n d itio n s. F a ilu r e due to o th e r causes of a cover t h a t i s r e l a t i v e l y i n t a c t would show e ith e r an im proper cover or th e need to red u ce th e c o n d itio n s producing th e f a i l u r e... The bottom cover th ic k n e s s of a b e l t depends m ainly on th e lik e lih o o d of damage caused by th e m a te ria l conveyed g e ttin g betw een th e b e l t and i d l e r s and p u lle y s. A b rasiv e m a te ria ls r e q u ir e a h eav ier cover th a n n o n -a b ra siv e m a te r ia ls. The g e n e ra l c le a n lin e s s of th e i n s t a l l a t i o n should a ls o be c o n sid e re d. Where th e b e l t i s kept c le a n and s p illa g e or p ile -u p s a re u n lik e ly, i t i s le s s im p o rtan t to have a th ic k bottom c o v e r. In g e n e ra l, a 1/16 in c h th ic k bottom cover i s q u ite s a tis f a c to r y f o r h andling r.o.m. c o a l w ith b e l t o p e ra tio n under good c o n d itio n s. However, b e lts w ith a h ig h ly s tr e s s e d c a rc a s s such as ray o n, campass cord or s t e e l cable should have th e e x tra p r o te c tio n of 1/16 in c h a d d itio n a l th ic k n e s s of bottom co v e r. 6 0

69 61 To a s s i s t in th e s e le c tio n of p ro p er th ic k n e s s of to p cover fo r b e l t s c a rry in g c o a l, ta b le X III has been p rep ared based on b e l t s p e c if ic a tio n s o f Goodyear T ire and Conveyor B e lt M anufacturing Company. v: In concluding t h i s c h a p te r, i t should ag a in be noted th a t b e sid e s d eterm in in g proper b e lt w id th, speed, motor " s iz e s, and. maximum o p e ra tin g te n s io n of th e b e l t, o th e r r e quirem ents such as b e l t tr o u g h a b llity and s t i f f n e s s, s iz e of d riv in g drums and p u lle y s, q u a lity of b e lt c o n s tru c tio n. m a te r ia l, b e lt cover th ic k n e s s, and p h y s ic a l working cond itio n s in th e mine must a ls o be co n sid ered sim u ltan eo u sly th ro u g h o u t b e l t s e le c tio n p ro ced u re. a re i n t e r r e l a t e d an d. in te rd e p e n d e n t. A ll of th e s e f a c to r s

70 6 2 TABLE X III RECOMMENDED CONVEYOR TOP COVER THICKNESS FOR CARRYING COAL 2L Cycle tim e (= ~ ) Lumpsize ( in in ches) f o r com plete re v o - lu tio n of b e l t. *, L - b e l t le n g th in f t. S = b e l t speed in f.p.ra. B itum inous Coal D ust i " t o 2 "to 6" & to-i" li- M 5" over Dust t o i " A n th ra c ite Coal g-"to 2 "to l i " /32 3/16 5/16 3 /8 3/16 3 /8 1 / /16 3/32 3/16 1 /4 3/32 3/16 3 /8-6" & over 0.6 1/16 3/32 1 /8 3/16 3/32 1 /8 1 /4.. 3 / /16 3/32 1 /8 3/16 3/32 < 00 s 9/ /16 3/32 1 /8 3/16 3/32 1 /8 3/16 7/ and over 1/16 3/32 1 /8 3/16 3/32 1 /8 3/16 3/16 BELT SELECTION PROBLEMS Example 1. S e le c tio n o f s u ita b le b e ltin g f o r underground main h au lag e. The fo llo w in g in fo rm a tio n i s p ro v id ed. 1. R ig id -fram e c o n v e n tio n a l b e l t conveyor w ith 20 deg. tro u g h in g i d l e r s.

71 6 3 ; ' 2. /L e n g th of h au l: 3000 f t..:3.bulk w t. o f c o a l :. 50 lb s p er cubic f t. 4. S ize of. lumps: up to 1 2". 5. G radien t of road-w ay: 1 in 50 a g a in s t th e loaded b e l t. 6. B e lt speed r e s t r i c t i o n s : ' n o t more th a n 4-50 f.p.m. 7* Two lo a d in g p o in ts on th e b e lt w ith peak lo ad in g of 3 0 tp h and 350 tp h r e s p e c tiv e ly. Ho tr ip p e r i s n e c e s s a ry. Step I D eterm ine th e t o t a l b e l t c a p a c ity, speed, w id th, and allo w ab le lu m p -siz e. The Peak c a p a c ity of b e l t» 300 / 350 s 750 tp h or to n s/m in u te. 15 Assuming a b e l t speed of 4-50 f.p.m., th e b e l t w idth in in ch es - j ; = 1 10,000P. f s x U * 5 (form ula 1) Al0,000 x 12.5, = a J 4-50 x / 5 = or 36 in ches 1 ' ; W - 6 ' A llow able lu m p -size * r (form ula 2) in ches

72 6 4 Step I I D eterm ine th e t o t a l b e l t horsepow er to convey th e c o a l under th e g iv en c o n d itio n s. C x Q x (L / L0 ) x S ( i) he = (form ula 6) 33,000 _ % 36 x (3000 / 1 50) x ,0 0 0 = hp. - 0 X (L / Lp) x T (11) hm ~ 990 (form ula 7) ( i i i ) hp _ x (3000 / 150) x = 71*50 hp. - y x H 990 (form ula 8) - (S ince g ra d ie n t = 1 in 50, th e r e f o r e, _ L _ 3000 _, H ' " I T " 6 0 f t ' - 45*50 hp. (iv ) ht = zero (S ince no tr ip p e r i s co n sid ered ).2 _ (Q / M) x (L/100) x (S/100)' (v) ha - (form ula 10) x t 2 (36 / 55*5) x (3000/ 100) x (450/100) x 3 29 hp.

73 Because t h i s a c c e le ra tio n, horsepower i s le s s th a n.50%: of th e sum of he, hg,, and hr i t may be ig n o red. 6 5 T h erefo re, t o t a l b e l t motor horsepower a t 80% motor e f f ic ie n c y : ' *, _ / / _ QOfto " 200 hp* Step I I I D eterm ine th e proper, b e lt s p e c if ic a tio n s. U sing a th ree-d ru m d riv e (an g le of wrap = 660 d eg.) w ith p la in drums and p.v.c. b e ltin g, F = (from i : v. ta b le X ). ; - S in c e, TV = x ^ 3 ^ x 33, = 13,200 lb s. (N ote: The slo p e te n s io n Ts of th e b e lt i s n o t cons id e re d h ere as i t does n o t exceed th e s la c k sid e te n s io n T2 ) Now ' f x p = JL (fo rm u la 21) = M i f -0.0 = 367 lb s p er in c h of b e lt 5 3d, w id th Taking v a lu e s of p (number o f p lie s in th e b e lt) - 5, 6, 7,... ^ ; The p.w.s./p ly /in c h - w id th = = 7 3.3, 6 1.1, 5 2.4,....

74 f 66 R e fe rrin g to t a b l e X l : t h e fo llo w in g b e l t ty p e s can be s e le c te d : (a) (b) (c) 7 -P ly, *+8 oz. c o tto n or heavy rayon b e ltin g No. 100 campass cord b e ltin g No. 150 s t e e l cable b e ltin g The a c tu a l s e le c tio n o f b e lt to be used i s p o s s ib le only a f t e r c o n sid e rin g o th e r f a c to r s such. as takeup d e v ic e, b e l t jo in tin g method, p h y s ic a l w orking c o n d itio n s in th e mine and o th e r f a c t o r s. Example 2. F ind th e g r e a te s t le n g th of conveyor p e rm is s ib le u sin g 6 -p ly, b2 o z. c o tto n f a b r ic c a rc a ss b e ltin g of 36 in ch es in w id th w ith ru b b er covering and conveying 400 tp h a t a speed of 350 f.p.m. up an in c lin e 1 in 50. The system u ses m e ta llic hook jo in t s 'a n d au to m atic counterw eig h t takeup d ev ice w ith no t r i p p e r. Step I D eterm ine th e t o t a l b e l t horsepow er. H ere, C = ;.Q = 36; L ~?; L0 I 150; S = 350; T = 400; H =. Jr,-..; 5 0 ' :: - (i) hq z 0.03 x 36 x (L / 150) x ,0 0 0 ; ( W 150) x hp- 100

75 ( l i ) hm = 0-03 X (L / 150) X 400 k ^.... l., ( i l l ) hr (L / 1^0) x x L _ 0.82L 990 X 50 * 100 The tr i p p e r and a c c e le r a tio n horsepow ers a re n o t cons i d e r e d.' ' '' T h erefo re, th e t o t a l b e l t horsepow er: = l.l 4 ( L / 150) / 1.21(1, / 150) / 0.82L = I r m / 3 2 h p. 100 Step I I D eterm ine b e l t s tr e s s e s and th e b e l t le n g th. From t a b le XI th e maximum a llo w a b le te n s io n f o r a 42 o z. c o tto n b e lt in g i s 45 lb s per in c h -w id th per p ly. S ince & = f x p (form ula 21) W T h e re fo re, T^ = f x p x W z 45 x 6 x 36 = 9,500 lb s Assuming a two-drum d riv e (an g le of wrap z 440 d e g.) w ith p la in drums, F = (from ta b le X) S ince T^ = F x Te (form ula 17) T h e re fo re, T0 = T^/ F = 9,5 0 0 /1.1 7 = 7,600 lb s

76 6 8 A lso, Le = t o t a l b e l t h p,(h ) x 33,000 8 (form ula 16) T o ta l b e l t hp. = Te x 8., 7,600 x , ,0 0 0 T h e re fo re, 3 _ - /. 353 = Zj.^92. x...3i (from p rev io u s ,000 p a g e :) On s im p lify in g, th e le n g th of th e conveyor L, i s 2,200 f t. ' : ' * '

77 CHAPTER VI DISCUSSION ON BELT HAULAGE ECONOMICS AND COST ESTIMATION... The' f in a l d e c isio n to employ a b e lt conveyor w i l l o ften depend upon the r e la t iv e c o sts of a l l methods of tra n sp o rta tio n. When used under the proper co n d itio n s, b e lt conveyors can move m a teria l more econom ically than most other methods. They consume l e s s power per u n it of work and the handling c o s ts in comparison w ith other system s are l e s s. However, b e lt conveyors have c e r ta in operating lim ita tio n s, and th e ir use i s not th e so lu tio n to every haulage problem; they have the a b ilit y to handle la rg e tonnages at low u n it c o s ts. Since they have a high c a p ita l co st they are not e f f ic ie n t fo r p art-tim e operation or fo r handling sm all tonnages. Hence, in planning a haulage system, i t should be determined f i r s t whether s u f f ic ie n t tonnages are a v a ila b le fo r a number of. years to j u s t if y the in s t a lla t io n of b e lt conveyors and, se c o n d ly, t o determ ine th e approxim ate breakeven p o in ts between conveyors and other types of mine. haulage. Here a model technique i s developed which b a s ic a lly i s intended to enable the engineer to estim ate the output and approximate co st of owning and operating a conveyor haulage system. These c o sts can then be compared w ith other system s o f mine haulage to. determ ine w hich.system or: 69.. ',.

78 70 com bination of system s i s most l i k e l y to p ro v id e th e lo w est u n it co st: f o r - t h e tr a n s p o r ta tio n of c o a l under th e cond itio n s being in v e s tig a te d. No attem p t has been made in t h i s study to compare th e u n it c o s ts of o th e r haulage sy s tems w ith th o se of conveyors; such a com parison i s beyond th e scope of th e p re s e n t stu d y. B efore an a ly zin g ow nership and o p e ra tin g c o s ts of b e l t haulage system, c e r ta in o th e r im p o rtan t economic f a c to r s must be d is c u s s e d. The economic l i f e of th e conveyor equipm ent depends on ( i) th e r a t e a t which th e equipment i s am o rtized and ( i i ) th e r a t e a t which th e m aintenance and r e p a ir c o s ts in c re a s e w ith th e age of th e equipm ent. These f a c t o r s a re d isc u sse d below. The d e p re c ia tio n c o s t i s a fu n c tio n o f th e f i r s t c o s t and l i f e o f th e equipm ent. The i n i t i a l c a p ita l in v e s t ment must be determ ined only a f t e r c o n s id e ra tio n of a l l th e c o s t f a c to r s in v o lv e d. As re g a rd s th e l i f e of th e conveyor equipm ent, i t i s d i f f i c u l t to p r e d ic t t h i s l i f e a c c u ra te ly. However th e American Mining Congress Conveyor Committee in t h e i r r e p o r ts over th e p a s t 8 y e a rs have c o n s is te n tly used a d e p re c ia tio n p e rio d of 10 y e a rs f o r conveyor fram e-w ork and a l l m echanical and e l e c t r i c a l equipm ent. The ru b b er b e ltin g i s d e p re c ia te d on a 5 y ear b a s is. The b e lt manuf a c t u r e r s c o n sid e r th e above f iv e - y e a r l i f e o f b e ltin g to be to o s h o r t, b u t ex p erien ce has shown th a t i t i s a f a i r

79 71 average l i f e ' f o r b e ltin g used In th e main and In te rm e d ia te haulage s e rv ic e. A number of d e p re c ia tio n methods a re a v a ila b le to d eterm in e y e a rly d e p re c ia tio n c o s t of th e equipm ent. The most im p o rtant of th e s e a re th e s t r a i g h t - l i n e, sin k in g fu n d, p ro d u c tio n u n its and d e c lin in g b alan ce m ethods. I t i s extrem ely d i f f i c u l t to keep up to d a te w ith th e U. S. Bureau of I n te r n a l Revenue1s re g u la tio n s.g o v e rn in g th e use of proper m ethods. The m aintenance c o s ts, in c lu d in g r e p a i r s, p lay a dom inant r o le in th e economic l i f e of th e equipm ent. The annual r e p a ir c o s ts may r i s e w ith th e age of th e equipm ent. Even th o u g h "th e r e p a ir c o s ts do r i s e each year - th ey r i s e only u n t i l th e f i r s t heavy r e p a i r s a re made. At. t h i s tim e i t i s p o s s ib le to show th a t as th e number of cy c les of heavy r e p a ir s in c re a s e, th e r a t e of r i s e of m aintenance c o s ts over th e t o t a l elap se d tim e may le s s e n. E v en tu a lly o v e r a ll m aintenance c o s ts w i l l le v e l o f f. Hence a uniform r a t e of o p e ra tin g m aintenance c o s t may be co n sid e red. R egarding I n t e r e s t, ta x e s and in su ra n c e c o s ts of.... :.. th e equipm ent, w hether money i s or i s n o t borrowed i n i t i a l l y. f ' : to buy th e new conveyor equipm ent, a 6^ i n t e r e s t r a t e i s a f a i r av erag e to be in clu d ed in th e an n u al ow nership c o s ts. The an n u al c o s t of ta x e s and in su ran c e may be tak en as eq u al to bfo of th e A v erag e Investm ent* c a lc u la te d as fo llo w s: A verage Investm ent = n / 1 (29) 2 x n

80 72 Where:n%= th e l i f e of th e conveyor equipm ent (10 y e a rs f o r conveyor fram e, m echanical and e l e c t r i c a l p a r t s, and 5 y e a rs fo r th e ru b b er b e l t i n g ). ESTIMATION 0 BELT HAULAGE COSTS ; I. Ownership C o sts: A r u le of thumb fo r e s tim a tin g c o s t of a com plete conveyor system i n s t a l l e d i s ab o u t S p er fo o t of le n g th f o r a c o n v e n tio n a l b elt'.co n v ey o r.using a 24-in c h b e l t. The; c o s t change i s about $50.00 f o r each 6 -in c h change in th e b e l t w id th. A more a c c u ra te method of c a lc u la tin g ow nership c o s ts i s g iv en below: (a) Cost of Equipm ent: T h is.in c lu d e s th e c o s t of p u lle y s, speed re d u c tio n tra n s m is s io n, m o to r s,c o n tr o l s, ta k e u p s, b ra k e s, e t c. The eq u ip m en t-co st v a r ie s w ith th e s iz e o f.th e conveyor. The fo llo w in g c o s t in fo rm a tio n has been su p p lie d to th e au th o r by th e Goodman M anufacturing Company, H alsted S tr e e t, Chicago 9, I l l i n o i s : Up to 6o hp.. = $ per hp.$ ".. 61 to 75 hp. = $ p e r hp.$ 76 to 200 hp. z $ I (30) p er h p.i over 200 hp. ' :Z $ p er hp.$ (b) Equipm ent: Cost o f S tru c tu r e s, I d l e r s, and o th e r S upporting

81 73 For c o n v e n tio n a l b e l t haulage s tr u c tu r e s ( rig id -fra m e ), th e c o s t in d o lla r s ' - ' z (0.8 0 x b e l t w id th in in ch es x le n g th of s tr u c tu r e in f t.) - - (31) For ro p e-fram e b e l t conveyor s tr u c tu r e s, th e c o s t in d o lla r s,z (0.50 x b e l t w id th in in ch es x le n g th of s tr u c tu r e in f t. ) (32) (c) Cost of B e ltin g : The c o s t of b e ltin g v a r ie s w ith th e duck w eig h t, number of p l i e s, ty p e of b e l t cons tr u c tio n m a te r ia l, m a n u fa c tu re r, fo o tag e to be purchased and o th e r f a c t o r s. The a c tu a l c o s t of a b e l t fo r any p a r t ic u la r duty can be determ ined w ith accuracy and i f th e a c tu a l c o s t i s known, th en t h i s should be used. However, a f a i r e s tim a te of th e c o s t of b e ltin g can be found as fo llo w s: : ) ' The c o st of b e ltin g (p ly ty p e) p er f t. in d o lla r s = ( x T-l / ) x W (33) Where: T j z maximum o p e ra tin g te n s io n of b e lt in lb s /in c h -w id th. W Z b e l t w idth in in ches (d) E re c tio n c o s ts :.U vvr:;.. i ( i) C leaning old mine openings and e la b o ra te

82 7 4 s i t e p re p a ra tio n s a re excluded c o s ts. When th e b e l t conveyor can be extended as th e working fa c e advances, th e e r e c tio n c o s ts may be ta k en a t l i $ to 2$ of th e c a p ita l to be in v e s te d f o r e x te n sio n under id e a l c o n d itio n s. (11) I f w irin g, c le a n in g, g rad in g and f i l l fo o tin g c o s ts a re in c lu d e d, th e i n s t a l l a t i o n c o s t may v ary from V5$ to 40$ of th e sum of th e equipment (item, a t above) and b e l t (item rc* above) c o s ts depending on th e amount o f work to be d one. (e) C o n tin g en c ies: The c o n tin g e n c ie s a re in clu d ed to cover th e u n fo re seen c o s ts. These c o s ts may be tak en as eq u al to 2$ of th e sum of th e equipm ent, b e l t, and e re c tio n c o s ts.. T h erefo re th e t o t a l Ownership C osts = (a) / (b) / (d) / (e) p lu s (c ); Using th e s tr a i g h t l i n e method, th e y e a rly dep r e c ia tio n c o s t: - (a) / (b) / (d) / (e) _ (c) p lu s y e a rs 5 y e a rs Y early fix e d c o s ts z y e a rly d e p re c ia tio n c o s t / c o s t of i n t e r e s t, ta x e s and in su ra n c e, z y e a rly d e p re c ia tio n c o s t / 10/5 of Average Investm ent"

83 WOTS: There a re many more c o s ts of owning a comp le te b e l t conveyor system. These in c lu d e tr a n s f e r s t a t i o n s, supply tr a c k, c a r s, and lo co m o tiv es, and, i f needed, surge b in s, fe e d e rs, and lin in g s in them, power s ta tio n s f o r b e lt d r iv e s, intercom m unication and r e la te d f a c i l i t i e s, and equipment c a r r i e r s. The c o s ts of a l l th e se item s a re n o t consid e re d in th e above c o s t e s tim a tio n p ro ced u re. I I O perating C osts: U nlike ow nership c o s ts, th e o p e ra tin g c o s ts, except f o r power c o s t, a re n o t p ro p o rtio n a l to th e b e l t le n g th, c a p a c ity, g ra d ie n t and so f o r t h. A ll th e o p e ra tin g c o st f a c to r s of conveyor haulage a re g iv en below. (a) Power C ost: G en e ra lly a l l th e roadway conveyors a re e l e c t r i c a l l y d riv e n. There a re v ery few conveyors in England t h a t a re now ru n by o th e r meansv A ttem pts to o b ta in a c tu a l consum ption of power proved u n s u c c e s s fu l. T h erefo re, th e energy req u irem e n ts must be d eriv e d on a t h e o r e tic a l b a s is assuming a known running tim e. Lacking th e l o c a l power r a t e j $0,008 per k ilo w a tt-h o u r may be used as an average power r a t e, and th e t h e o r e t i c a l power c o s t may be determ in ed as fo llo w s: Y early power c o s t in d o lla r s a t o t a l m otor h p x 0.7^6 x hours o p e ra te d /y e a r 7 5 x v;:: OH)

84 76. (b) O p eratin g ;L ab o r C o stsi For a l l ty p es of conveyors th e o p e ra tin g la b o r c o n s is ts of one man a t each tr a n s f e r p o in t fo r every s h i f t th e conveyor i s in o p e ra tio n. The wage r a te s :v a r y from p la c e to p la c e. At p r e s e n t, an average of $ per hour i s assum ed. f r in g e b e n e f its. T his r a t e in c lu d e s a l l ; (c) M aintenance and R ep airs C ost: ( i ) M aintenance la b o r c o s t: Only ro u tin e la b o r on conveyors may be c o n sid e re d. N on-routine la b o r f o r m ajor b e l t rep lacem en ts and o th e r works must be consid e re d s e p a r a te ly. This ro u tin e la b o r f o r d a ily m aintenance i s of two k in d s. F i r s t, u n s k ille d la b o r i s used fo r p a tr o llin g and clean in g th e s p illa g e ; f o r t h i s purpose one or two men per m ile of conveyor p er s h i f t i s a f a i r av e ra g e. Secondly, s k ille d la b o r i s used f o r th e m aintenance of th e m echanical and e l e c t r i c a l p a r ts of th e conveyor equipm ent. One m echanical f i t t e r and one e l e c t r i c i a n per m ile of th e conveyor per s h i f t a re s u f f i c i e n t. This t o t a l m aintenance fo rc e of 3 to 4 men per m ile p er s h i f t i s a ls o expected to do some o th er odd jo b s, such as s m a ll-b e lt rep lacem en ts and b e l t s p l i c i n g.. The wage r a te s, may be ta k e n f o r a l l men as $2.50 p er hour as s ta te d. ( i i ) M a te ria l c o s t f o r m aintenance: From th e r e cords of components and b e l ts re p la c e d in th e p a s t an attem p t i s made to determ in e th e l iv e s of th e m ajor components

85 77 of th e conveyor system ; b u t t h i s v e n tu re i s f u r th e r comp lic a te d, in some c a s e s, by th e ever changing d esig n of c e r ta in p a r ts of th e conveyor equipm ent. Hence an average m aintenance c o s t may be u sed.. ' The main c o s t of m aintenance i s, of c o u rse, th e r e placem ent of th e b e ltin g. The b e l t i s co n sid ered to have a l i f e of 5 y e a rs, w hereas th e l i f e of th e o th e r elem ents of th e e n t ir e i n s t a l l a t i o n i s 10 y e a rs. This means th e re w ill be one rep lacem en t of th e whole b e ltin g in 10 y e a rs. Using th e c o s t of th e o r ig in a l b e ltin g (item *c? in ow nership c o s ts ), th e y e a rly b e l t rep lacem en t c o s t can be c a lc u la te d. I t w ill be eq u a l to o n e -te n th of o r ig in a l b e l t c o s t. B esides y e a rly b e l t rep lacem en t c o s t, th e re w ill be sm all c o s t f o r sp a re p a r ts on th e conveyor s tr u c tu r e, lu b r i c a t i o n s, e t c. This c o s t may be tak en to be eq u al to 2$ of th e equipm ent c o s t (item *31 in th e ow nership c o s t s ). The t o t a l y e a rly o p e ra tin g c o s ts % (a) / (b) / (c) U n it c o s t/to n = YeaTly ow nershlp and o p e ra tin g c o s ts t o t a l to n s moved p er y ear PROBLEM ON TgE COST ESTIMATION & BELT HAULAGE SYSTEM Example: C a lc u la te th e u n it c o s t of conveying c o a l fo r example ( l ) on page 62. : I Ownership c o s ts :

86 7 8 (a) C ost o f equipm $1^5*00 p e r hp. = 200 x Ik? = $2 9,000 ( b ) " Cost of s tr u c tu r e = (0.80 x b e l t w id th x le n g th of s tr u c tu r e ) = (0.8 0 x 36 x 3,000) = $86,500 (c) Cost of b e ltin g * ( x / ) x 36 x (3000/ 3000/ ), -r ( x 367 / ). x 36 x, 6150 = $93,000 - (d) Cost of i n s t a l l a t i o n z 20^ of (equipm ent / b e lt) c o st r 20^ of (29,000 / 93,000) z $24,400 (e) C o n tin g en cies z 2% of (equipm ent / b e l t / i n s t a l l a t i o n ) = 2% of (29,000 / 93,000 / 24,400) -c ; r :: : /. = $2,928. :'y :, T o ta l ow nership c o s ts z 29,000 / 86,^00 / 93,000 / 24,400 / 2,928 = $237,828 Y early d e p re c ia tio n based on s tr a i g h t l i n e method. ( a ) / ( b ) / ( d ) / ( e ), (c) 10 y e a rs 5 y e a rs

87 7 9 _ 144,828, 93, = 133,083 Average Investm ent (ex clu d in g b e l t c o s t) = 144,828 x I P - / ^ x 5 = $ 79,500 (form ula 29) Average in v estm en t f o r b e ltin g 93,000 x dj 2 x 5 :: - - = #55i75o T o ta l average in v estm ent - z 79,000 / 55,750 : : - - = 1135,250 Yearly in t e r e s t, ta x es and insurance co st = 10^ of t o t a l average investm ent '. ;. 1 = 10;S of 135,250 = - 13,525 Yearly fix e d c o s ts = yea rly d ep recia tio n / y early in te r e s t, ta x e s, e t c. / 33,083 / 13,525 : $46,608 I I Operating c o s ts : (a) Y early power c o s t (based on 2000 hours per y ear) = $(200 x x 2000 x ) * -$ 2,4 9 0 : ' : : ".

88 8 0 (b) Y ea rly o p e r a tin g la b o r c o s t = S ( x 2000) = $ 5,000. : (c ) Y ea rly m ain tenance and r e p a ir c o s t s :. ' ( i ) M aintenance la b o r c o s t - (3 men) = 3 x x 2000 = $ 1 5,0 0 0 ( i i ) M aintenance m a te r ia l c o s t f o r r e placem en t and lu b r ic a t io n - r 10$ o f b e l t c o s t / 2$ o f equipm ent C O S t... : : v : L. :.. : = 10$ o f 9 3,0 0 0 /2 $ o f 2 9,0 0 0 = 9,300 / 580 s 9,880 ' T h erefo re t o t a l m aintenance and r e p a ir c o s t Z item ( i ) / item (ii) above = 15,000 / 9,880 = $ 2^,880 T o ta l o p e r a tin g c o s t s = 2,4 0 0 / 5,0 0 0 / 2 4,8 8 0 = $ 3 2,3 7 0 T h erefo re t o t a l ow nership and o p e r a tin g c o s t s per year. = 4 6,6 0 8 / 32,370 = $ 78,978 T o ta l to n s moved per 750 tp h * 2000 x 750 1, 500,000 T h erefo re c o s t / t o n o f c o a l hau led = = 1, 500,000 $0,053 per to n

89 81 NOTE: Or c o s t/to n /m ile = x 28. e.et. 3,0 0 0 (len g th of haul) Z $0.093 per to n per m ile. A ctu ally the c o s t/to n -m ile w i l l be l e s s than th e above fig u r e sin c e maintenance labor co st i s not d ir e c tly p rop ortional to len g th of haul. COST CHARACTERISTICS OF BELT HAULAGE SYSTEM Based on the above c o st estim ation procedure, a range o f hypothetical*1 d u ties rep r ese n ta tiv e of co n d ition s under which the conveyors w ill run are in v e stig a te d to determ ine the b e lt haulage co st c h a r a c te r is tic s. The use of th e term h ypothetical" should be c le a r ly understood th at i t i s the conveyor in s t a lla t io n s which are h y p o th etica l. The c o s ts are r e a l, based on the above co st estim ation procedure which i s developed from a ctu a l conveyor in s t a lla t io n s and manufacturers* q u o ta tio n s. With a l l th ese and the fo llo w in g assum ptions ty p ic a l c h a r a c te r is tic curves have been constructed (see F ig s. 5 and 6) from ca lcu la ted u n it c o s ts a t f iv e p o in ts fo r each curve: (1) C onventional type b e lt haulage system (i.e., rigid -fram e supporting stru ctu res) w ith 20 deg. troughing id le r s. (2) S tra ig h t lin e d ep recia tio n method i s u sed. (3) No salvage or r e s a le valu e of the equipment i s

90 82 co n sid ered. (M-) I n t e r e s t, ta x e s and in su ran c e c o s t i s ta k en a t : Vyfo of th e "Average In v e stm e n t". ; ; (5) M aintenance la b o r - t o t a l of th r e e men as s p e c if ied: below: one e l e c t r i c i a n.. ; :! one m echanical f i t t e r one man f o r p a tr o llin g and c le a n in g s p illa g e (6) Labor r a t e f o r a l l c a te g o rie s i s ta k e n a t $2.50 per hour in c lu d in g a l l f r in g e b e n e f its. (7) A ll o th e r c o s t f a c t o r s a re tak en as s p e c ifie d in th e c o s t e s tim a tio n p ro ced u re. HOW TO REDUCE CONVEYOR COSTS? I t has a lre a d y been s tr e s s e d th a t f o r co n tinuous o p e ra tio n, hig h p ro d u c tio n, and low u n it c o s t th e b e l t haulage system i s th e b e s t s o lu tio n f o r tr a n s p o r ta tio n of c o a l in m in es. But h ig h er u n it c o s t may r e s u l t because of im proper d esig n and i n s t a l l a t i o n or poor m aintenance and o p e ra tio n. W ith c a r e f u l d e sig n o f th e b e lt haulage system and p ro p er m aintenance, most o f th e b e l t haulage c o s ts can be kept to a minimum. The fo llo w in g a re some of th e o th e r ways of f u r th e r red u cin g th e b e l t haulage u n it c o s t w herever p r a c tic a b le and p o s s ib le. ( l ) Use of narrow b e l t w idths and in c re a se d sp eed s. A ctu al lo a d in g tr a n s p o r t req u irem e n ts must be s tu d ie d f o r each in d iv id u a l c a s e. The s iz e and shape of th e m a te r ia l

91 HnXlZTS EECAIT - L i _ 1. ' T - r r u! i ic OUTPUT:Tons p er Hour Ifkisai T i-r-ri t ig a a r i

92 rrrt i LLi OUTPUT* TONS Per HOUR