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Selection and maintenance of conveyorbelts for transportation of coal in mines
A T h esis Subm itted to th e F a c u lty o f th e
DEPARTMENT OF MINING ENGINEERING
In P a r t i a l F u lf i l lm 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
STATEMENT BY THE AUTHOR
T his th e s i s has been subm itted in p a r t i a l f u l f i l lm e n t of req u irem e n ts f o r an advanced d eg ree a t th e U n iv e rs ity of A rizona and i s d ep o s ited in th e U n iv e rs ity L ib ra ry to be made a v a i la b le to borrow ers under r u le s of th e L ib ra ry .
B r ie f q u o ta tio n s from t h i s t h e s i s a re a llo w ab le w ith o u t s p e c ia l p e rm iss io n p rov ided th a t a c c u ra te acknowledgm ent of sou rce i s made. R equests f o r p e rm iss io n fo r ex tended q u o ta tio n from or re p ro d u c tio n of t h i s m anuscrip t 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 o r th e Dean o f th e G raduate C ollege when in t h e i r 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 o f s c h o la r s h ip . In a l l o th e r in s ta n c e s , however, p e rm iss io n must be o b ta in ed from th e a u th o r .
SIGNED:
APPROVAL BY THESIS DIRECTOR
T his th e s i s 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
SELECTION AND1MAINTENANCE OF CONVEYOR BELTS
FOR TRANSPORTATION OF COAL IN MINES
r ' By • . ‘ r o . - ; :',c
' N. P undarl - f
v.: ;■ c ' :/ • 1 • .. : : " \o:', c. " J' ; .ABSTRACT
The f a c to r s t h a t a f f e c t th e s e le c t io n of p ro p er
b e l t in g f o r t r a n s p o r ta t io 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 es ig n in g o f b e l t s to g e th e r w ith
c a r e fu l i n s t a l l a t i o n and m aintenance o f conveyors a re
s t r e s s e d . •' ' ■" - ■ : ; • . ■ .: ,
Model te ch n iq u e s of s e le c t in g p roper b e l t in g under
th e s p e c if ie 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 hau lage 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 p rob lem 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 cu rves f o r c o n v e n tio n a l b e l t
hau lage system s a re c o n s tru c te d ; and methods f o r red u cin g
conveyor hau lage c o s ts a re enum erated. C onclusions r e
gard ing cho ice of i n s t a l l i n g b e l t conveyors and t h e i r
econom ical f e a tu r e s a re drawn. S uggestions f o r f u tu r e
s tudy of d i f f e r e n t k in d s of conveyor hau lage system s a re
l i s t e d .
i i
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 t i tu d e to th e fo llo w in g members of th e
f a c u l ty o f ; th e U n iv e rs ity o f A rizona, Tucson, A rizona, f o r
s t im u la tin g rs u g g e s t io n s and c o n s tru c tiv e c r i t i c i s m s du ring
th e cou rse of-, t h i s • s tudy and in th e p re p a ra t io n of t h i s
m an u scrip t:
H. E.i Krumlauf , P ro fe s s o r of M ining• E n g in ee rin g ;
and E. R. D revdahl and J . C. D otson, A sso c ia te P ro fe s s o rs
of Mining E n g in ee rin 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 i n a n c i a l a s s is ta n c e
to u n d ertak e t h i s G raduate Study a t th e U n iv e rs ity of
A rizona., J
.... U .
i ' i i
TABLE OF CONTENTS
C hapter ! ; •- “ Page
I INTRODUCTION - - 1
I I REVIEW OF THE LITERATURE ' " v . . b_
E v o lu tio n o f conveyor b e l t hau lage systemin c o a l m ines 4
A dvantages of b e l t haulage system 10
F u tu re t r e n d s in b e l t hau lage system s * 13
I I I SELECTION OF BELT WIDTH AND SPEED ... . . . l8
IV DETERMINATION OF BELT HORSEPOWER REQUIREMENTS 24
Power to d r iv e th e empty b e l t . . . . 24k «•
Power to move m a te r ia l h o r iz o n ta l lyalong th e conveyor . . . . 28
Power to e le v a te or lower m a te r ia l or powerto be g en e ra ted in low ering i t 31
Power to d r iv e th e t r ip p e r . . . . 32
A c c e le ra tio n horsepow er . . . . 35
Summary o f b e l t horsepower c a lc u la t io n s 36
P e rm iss ib le an g le s of in c l in a t io n fo rh au lin g c o a l on b e l t s . . . . « 39
V SELECTION OF PROPER BELT . . . . 4 l
D ete rm in a tio n o f b e l t s t r e s s e s . . . . 42
D ete rm in a tio n of maximum number of p l i e s of b e l t s f o r p ro p er tro u g h in g and s t i f f n e s s . . . . 5l
i v
C h a p t e r
VI
VI I
V II I
D ete rm in a tio n o f s iz e of d r iv in g drums and p u lle y s ; , .
S e le c t io n o f p ro p er b e l t c o n s tru c tio n " : m a te r ia l • - . . .
S e le c t io n of p roper cover q u a l i ty and th ic k n e s s .
r -: . . .B e lt s e le c t io n problem s . . .
DISCUSSION ON BELT HAULAGE ECONOMICS AND - COST ESTIMATION . . . .
E s tim a tio n o f b e l t haulage c o s ts . . . .
Problem on c o s t e s tim a tio n o f b e l t • hau lage system . . . .
Cost c h a r a c t e r i s t i c s o f b e l t haulage system ' . •.
How to red u ce conveyor haulage c o s ts
INSTALLATION AND MAINTENANCE OF CONVEYOR BELTS FOR EFFICIENT OPERATION . . .
I n s t a l l a t i o n p rocedu re . . .
P ro te c t io n of b e l t s . . . .
B e lt m aintenance g u id es . . . .
CONCLUSIONS AND SUGGESTIONS'FOR FUTURE STUDY
BIBLIOGRAPHY AND SELECTED REFERENCES
• - _ j
53
5^
59
62
69
72
77
81
82
89
89
92
93
100
105
P a g e
v
LIST OF TABLES
T able Page
I Recommended b e l t speeds and a llo w ab le lu m p -s izes o f ru n -o f-m in e c o a l . . . . 23
I I 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 , L0 . . . . 27
I I I V alues o f horsepower to d r iv e emptyconveyor . . . . 28
IV V alues o f h o r iz o n ta l horsepower to convey c o a l . . . . 30
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^
VI I Average t r ip p e r l i f t s . . . . 34
V III Maximum p e rm is s ib le an g le s of conveyor in c l in a t io n . . . . 40
DC V alues of c o e f f ic ie n t o f f r i c t i o n of b e l t s 45
X V alues of ,F* f a c to r . . . . 46
XI Maximum p e rm is s ib le te n s io n r a t in g s fo r d i f f e r e n t b e l t s . . . . 49
XI I Minimum p l i e s to su p p o rt lo ad and maximum p l i e s f o r p roper tro u g h in g . . . . 52
X II I Recommended conveyor top cover th ic k n e s s 62
LIST OF FIGURES
F ig u re Page
1 Ropenframe conveyor s t r u c tu r e . . . . 6
2 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 . . . . 22
4 B e lt te n s io n s in a runn ing b e l t . . . . 435 & 6 T y p ica l c o s t c h a r a c t e r i s t i c cu rves o f con
v e n t io n a l b e l t hau lage sy s tem (rig id -fram e ty p e ) . . . . .
83 & 84
v i
................. CHAPTER I- . •» ' ■ ..
- , ,, INTRODUCTION
..In any b e l t hau lage system th e conveyor b e l t i s sub
je c te d to th e g r e a t e s t s t r a i n , i s th e most e a s i ly 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 o f any p a r t of
th e whole system . The b e l t i s th e on ly p a r t o f th e conveyor
which a c t u a l l y h and les th e m a te r ia l , and i s p r a c t i c a l l y th e
on ly item which has to be renew ed. The l i f e of th e b e l t , and
hence th e hau lage c o s t , depends on th e b e l t being c o r r e c t ly
s p e c if ie d f o r th e job and th e c a re and m aintenance th a t i t
r e c e iv e s . B e ltin g o f im proper d e s ig n to save f i r s t c o s t w i l l
have s h o r te r l i f e and g iv e s r i s e to h ig h e r hau lage c o s ts . I t
should be n o ted in t h i s co n n ec tio n th a t average conveyor
b e l t r e p r e s e n t s ap p ro x im ate ly h0% o f th e e n t i r e b e l t hau lage
i n s t a l l a t i o n .
The purpose o f t h i s s tu d y i s to d is c u s s a l l th e
f a c to r s t h a t a f f e c t th e s e le c t io n o f c o r r e c t b e l t in g f o r a
g iv en du ty and i t s good m ain tenance . P ro p e rly designed and
w e ll m ain ta ined b e l t s g iv e good perform ance a t low u n i t. • • - ••• ■ ■ ’ ‘ — *■' •"! V ’ * ’ l
c o s t s . The m ajor f a c t o r s e n te r in g in to p ro p er s e le c t io n of
conveyor b e l t s 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 l i ty , te n s io n and horsepow er re q u ire m e n ts , cover q u a l i ty
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
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 a ttem p t has been .
made to compare th e u n i t c o s ts of c o a l t r a n s p o r ta t io n by
b e l t conveyors w ith t h a t o f . any o th e r system . I t i s con
s id e re d in t h i s s tu d y th a t under c e r t a in c ircu 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 r ly 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 t ig a t io n s a re made.and im p o rtan t con
c lu s io n s a re drawn.
O ther d e s ig n c o n s id e ra t io n s of b e l t hau lage system ,
such a s ty p e o f 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 ac in g , and o th e r a u x i l ia r y equip
ment re q u ire d have n o t been In v e s t ig a te d in t h i s s tu d y . A ll
of th e s e item s a re w e ll s ta n d a rd iz e d f o r any s p e c i f ic d u ty ,
and - i t i s on ly in th e s e le c t io n of c o s t ly b e l t s w here•m is
ta k e s a re o f te n made. These m is tak 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 t io n and in c re a se d hau lage 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 t io n to g e th e r w ith p roper in
s t a l l a t i o n and good m aintenance a r e . s t r e s s e d in t h i s s tu d y ......... - r ' - - - - * ' - — 'v 1 ,■ r ■ , , .» v -■ . l v ,
More em phasis i s g iv en to s im p le , quick ' and c o r r e c t
methods of e s tim a tin g th e main s p e c i f ic a t io n s o f b e l t con
v ey o rs f o r t r a n s p o r ta t io n o f ru n -o f-m in e c o a l in m ines. As
f a r as p o s s ib le th e u se of com plica ted c h a r ts and ta b le s
have been av o id ed . Most o f th e fo rm ulae used f o r d e te rm in in g
v a r io u s b e l t s p e c i f ic a t io n s a re n o t in ten d ed as a b a s is of
d e s ig n in g new i n s t a l l a t i o n s w ith o u t r e f e re n c e to th e
3
m a n u fa c tu re r , s su g g ested m ethod. The m anufac tu rer may p re
f e r to work ou t th e req u irem e n ts of th e system by an o th e r
method. The methods used in t h i s s tu d y fo r d e te rm in in g
c o r r e c t b e l t s p e c i f ic a t io n s a re v e ry h e lp fu l in o rd er to
d ec id e i f conveying i s p o s s ib le or s u i t a b le or econom ical
under c e r t a in s p e c if ie d c o n d it io n s . These methods a re a ls o
h e lp fu l to en ab le changes to be made econom ically in th e
e x is t in g conveyor hau lage system w ith o u t cau sin g undue b e l t
f a i l u r e s . The method of c a lc u la t io n s a re kep t as fundam ental
as p o s s ib le , and a l l s im 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 t h a t th e s e c a lc u la t io n s
can be m od ified to s u i t c o n d itio n s and ty p e s o f equipm ent
n o t s p e c if ie d in t h i s s tu d y .
I t i s hoped t h a t t h i s t h e s i s w i l l d em o stra te 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 i c a t i o n s a re made a v a i la b le to th e r e a d e r . P r a c t i c a l
examples o f d e te rm in in g c o r r e c t b e l t s p e c i f ic a t io 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 t e r u n d e rs tan d in g of th e p ro p er d e s ig n of
b e l t conveyors .
REVIEW OF THE LITERATURE
CHAPTER I I
EVOLUTION fig Tgg CONVEYOR BELT HAULAGE SYSTEM IN COAL
The t r a n s p o r ta t io 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
bu t were n o t in use in th e U nited S ta te s u n t i l abou t 1930.
They were o r ig in a l ly used in th e U nited S ta te s in p an e l
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 l e c t c o a l in e n t r i e s from ch a in to shaker co n v ey o rs .
D u rin g .t h i s p e r io 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 o f th e conveyors. The f i r s t
conveyor hau lage c o n s is te d o f l e a th e r and canvas b e l t s
s l id 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 i r o n
r o l l e r s . T his l a t e r devlopm ent g r e a t ly encouraged th e use
o f conveyor hau lage o f 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 , eco
nom ical and s a fe method f o r underground t r a n s p o r ta t io n of
c o a l . S ig n i f ic a n t developm ents in th e d e s ig n and c o n s tru c
t io n o f conveyor hau lage system s have been and a re being made
to d e a l w ith v a r io u s f a c t o r s t h a t a f f e c t o u tp u t.
5.
S ince th e beg inn ing o f conveyor hau lage t r a n s p o r ta
t io n in m ines, v a r io u s ty p e s o f b e l t s have been m anufactu red ,
o f 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 t ic f i b e r c a rc a s s b e l t s .
2 . U nip lane c o t to n cord b e l t s f o r h ig h te n s io n i n s t a l l a
t io n s where o u te r p ly s t r e s s e s may c o n tr ib u te to th e
u l t im a te d e t e r io r a t io 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 h igh
modulus c o tto n f a b r ic runn ing le n g th -w is e in th e
c a rc a s s and w ith ny lon f i l l th re a d s to d ec re a se 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 h igh te n s io n a i rp 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 s in g n eop rene , te ry le n e and po ly
v in y l c h lo r id e (p .V ic .) po ly e s t e r s y n th e tic f i b e r
m a te r ia l s . . '' ' ,. .-y ' .. .... v ■
6 . G lass c a rc a s s b e l t s f o r o p e ra tin g w ith m a te r ia 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 s ig n of th e
su p p o rtin g s t r u c tu r e o f th e b e l t hau lage system . S ince 195$
th e ro p e-fram e conveyor s t r u c tu r e s have become alm ost
s ta n d a rd f o r some b e l t hau lage i n s t a l l a t i o n s in under
ground 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 l iz 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 t io n make ro p e
su p p o rted b e l t hau lage an a t t r a c t i v e o f fe r in g and have le d
' 6
ROPE
-:
7
to i t s r a p id accep tan ce by th e m ining in d u s t ry . However,
th e use of ro p e-fram e b e l t hau lage f o r perm anent, m ain- "
hau lage i n s t a l l a t i o n s i s uncommon and th e r ig id - f r a m e ,
co n v e n tio n a l b e l t hau lage i s s t i l l p rov ing e f f i c i e n t and
econom ical in t h i s f i e l d . - .. : v, :
The o th e r improvement in th e d e s ig n of b e l t hau lage
system i s th e developm ent of th e c a b le - b e l t conveyor.3 / 2 /
In t h i s d es ig 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 t ta c h e d to th e
runn ing 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 t r 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 r r ie d on to p and r e tu r n ro p e p u l le y s .
These ro p es a r e d isengaged from th e b e l t a t th e te rm in a ls of
th e conveyor by a p a i r of skewed or sp lay ed p u lle y s c a r r ie 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 a s se s around th e drum between th e p u l le 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
sp layed s u f f i c i e n t l y to enab le th e ro p es to p ass forw ard to
th e d r iv in g w hee ls . They th e n r e tu r n to p ic k up th e b e l t a s
i t le a v e s th e u n d e rs id e of th e b e l t drum. I t i s n o t
1 / T. D. E l l i o t , "Development o f th e c a b le - b e l t conveyor" I ro n and Coal T rades Review. Vol 176. No. 4689. A p ril h, 19% pp. 309 :137-*—
2 / "Three y e a rs of h o is t in g w ith th e P rin c e ss C able- B e l t" , Coal Age , Vol 6 3 , S ep t. 1958, pp . 106-08.
8
p r a c t ic a b le to ex tend th e c a b le - b e l t conveyor in s h o r t
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 i ty
o f s p l ic in g a d d i to n a l ro p e . R egarding economics o f such a
type of b e l t hau lage system no d e ta i l e d s tudy 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 sav ing in horsepower i s n o ted in th e c a b le -
b e l t conveyors when compared to c o n v e n tio n a l ty p e b e l t con
v e y o rs . The s ta n d a rd c a b le - b e l t conveyors, in b e l t w id th s
from 2 4 -in c h to 4 8 - in c h , u sin g d r iv 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 du ring r e c e n t y e a r s .
? 13'
coavsio?-JG3BT2
10
ADVANTAGES OF BELT HAULAGE SYSTEM ' ;
In p lan n in g a hau lage 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 i la b le f o r a number
o f 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 l t conveyors.
The a re a should be mapped and determ ined by crop l i n e s ,
p roperty" 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 l t conveyor haulage or to use a com-
b in a t io n o f t r a c k h au lag e , s h u t t l e ,c a r s and b e l t s i s made.
The in t ro d u c t io n of b e l t hau lage system s in under
ground c o a l m ining has made p o s s ib le b e t t e r methods of
m ining to s u i t l o c a l c o n d i t io n s , and in c re a se d fa c e
m ech an iza tio n . The su ccess o r 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
t r a n s p o r ta t io n . The f a s t e r th e c o a l i s produced a t th e f a 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 t r a n s p o r te d to th e s u r fa 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 o f moving c o a l i n underground m ines, and
th ey form th e hub o f th e underground haulage system s th a t
handle a la rg e p e rce n tag e of U .S . m ining o u tp u t . The b e l t
conveyor hau lage system p o sse sse s many advan tages and
d e s i r a b le f e a tu r e s over t h a t o f o th e r ty p e s of t r a n s p o r ta t io n
system . The more im p o rtan t advan tages a re l i s t e d below:
1 . C ap ac ity : Because o f i t s con tinuous o p e ra t io n , no
o th e r method o f hau lage has such a wide range of c a p a c i t ie s
11
as th e b e l t conveyor system . W ith b e l t conveyors, th e amount
o f 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 o f th e m a te r ia l conveyed. Owing to h ig h a b ra s iv e
r e s i s ta n c e o f 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 l le d r . o . m . ) c o a l o f a l l s iz e s can
be handled w ith o u t cau sin g s e r io 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 a l ease up to 30$ g ra d e s .
Compare t h i s to th e norm al economic l im i ta t io n s o f 20$ g rad es
f o r t ru c k s and 3$ g rad es f o r r a i l r o a d t r a n s p o r t a t io 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
a lo n e can make b u lk t r a n s p o r ta t io n econom ically f e a s ib le
only w ith -co n v ey o rs . ; .
3 . Simple e r e c t io n and minimum space: Underground b e l t con
v eyo rs a llow th e use o f sim ple r ig h ts -o f -w a y , narrow e n t r i e s
and low .head room. No t r a c k s have to be l a id or t r o l l e y
w ire s s tru n g . L i t t l e g rad in g i s n e c e ssa ry and o f te n sim ple
ro o f su p p o rt can be u se d . The b e l t conveyors hold a un ique
p o s i t io n in th e reco v e ry of th in -seam c o a l where d r iv in g o f
la rg e e n t r i e s to accom odate o th e r means of hau lage 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 o f su p p o rtin g s t r 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 i e d . Hence i t i s e a s i ly extended or
r e t r a c t e d , d ism an tled , moved and reassem b led . However, ‘
12
g e n e ra lly b e l t conveyors a re sem i-fix ed and do n o t p rov ide ,
maximum f l e x i b i l i t y needed in some m ining o p e ra tio n s un-
l e s s th e y a re used in c o n ju n c tio n w ith some o ther, ty p e s of
t r a n s p o r ta t io n system , such as s h u t t l e 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 t io n : No method
of hau lage i s in h e re n t ly as s a fe as b e l t h a u l a g e T h e :
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 , ex trem ely low .
Freedom from v ib r a t io n s and q u ie t o p e ra t io n of b e l t hau lage
red u ces p e rs o n a l f a t ig 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 o f th e conveyor a re g r e a t ly red u ced , and,
where lump d e g ra d a tio n i s im p o r ta n t, th e smooth t r a n s f e r and
t r a n s p o r t o f b e l t hau lage low ers lump b reak ag e . P ro p e rly
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 t ro l l in 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 a rran g em en ts .
6 . E a rly w arning of impending danger: P robably no o th e r
haulage g iv e s such an e a r ly w arning of p o s s ib le f a i l u r e .
U n like th e a e r i a l tramways of which i t •i s s a id never have a
minor a c c id e n t , or th e r a i l r o a d where a washout o f i b a l l a s t
or a d e ra ilm en t may s t r i k e w ith o u t-warning', th e b e l t con
v ey o r, i f m a in ta in ed p ro p e r ly , r a r e l y : s u f f e r s a sudden b reak
down. The b e l t . i t s e l f s ig n a ls i t s need f o r rep lacem en t 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 r e e men per m ile p er s h i f t a re no rm ally s u f f i c i e n t f o r
d a i ly r o u t in e m ain tenance and o p e ra t io n . The r e tu r n ru n of
th e b e l t on a s lo p e b a lan ce s th e to p e ru n and, because of low
t a r e w eight o f th e moving p a r t s , conveyors can p ro v id e 1
t r a n s p o r ta t io n w ith th e lo w est p o s s ib le consum ption o f pow er.
B e lt hau lage needs on ly o n e -h a If th e power r e 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 h igh p ro d u c tio n a t
low er c o s ts , th e conveyor b e l t hau lage may be th e answ er.
The low u n i t c o s t per to n of m a te r ia l t r a n s p o r te d by b e l t
hau lage o f te 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 hau lage system . The o th e r im m ediate
sav in g s from b e l t hau lage a re r e d u c t io n in g rad in g a n d . -
b ru sh in g , th e e l im in a tio n o f s t r in g in g t r o l l e y w ire s , la y in g
o f t r a c k and of c u t t in g i n t r i c a t e hau lage ways. ': ■
•The s u b je c t o f b e l t hau lage economics i s d isc u sse d
in d e t a i l e lsew here in t h i s t h e s i s under a s e p a ra te head ing .
The main d isad v an tag e of b e l t 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 i la b le f o r a lo n g e r p e r io d to i n s t a l l b e l t conveyors .
and to m inim ize hau lage c o s t s . A lso u n fo re see n random break
down d u rin g o p e ra t io n may a f f e c t th e whole o u tp u t .
FUTURE TRENDS IN BELT HAULAGE SYSTEM............
13
The p o p u la r i ty o f b e l t conveyors f o r t r a n s p o r ta t io n
of c o a l in m ines has in c re a se d du ring th e :p a s t decade , and a
number o f s ig n i f i c 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 t e a d i ly in s i z 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 l t c o n s tru c tio n m a te r ia 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 t r e n d s tow ard desig n in g ; f u tu r e
hau lage system s; : . v . ; , : : : : •
1 . S h i f t from r i g i d to rope supported b e l t equipm ent; The
concep t of mounting c a rry in g I d le r s on two s ta t io n a r y and
p a r a l l e l w ire -ro p e s in s te a d o f on a r i g i d framework i s .
f in d in g growing use in th e c o a l m in in g .in d u s try due to low er
c a p i t a l c o s t and sav in g s in i n s t a l l a t i o n c o s t . Conveyor b e l t
m an u fac tu re rs have e s tim a ted t h a t d u rin g 1961 rough ly of
new conveyor equipm ent so ld f o r p an e l and b u t t e n try hau lage
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 t r u c tu r e s f o r secondary and main
l in e b e l t hau lage i s v e ry slow . . .
2 . Trends tow ard w ider b e l t s and h ig h e r sp eed s; The h ig h e r
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 o rder, to p rov ide , th e surge, c a p a c ity needed .fo r h igh
speed dumping, la r g e c a p a c ity s h u t t l e c a r s , and o th e r t r 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 c a b le r e in fo rc e d b e l t s up to 87- in ch wide c a rry 15,000
t o n s ;o f o v er-b u rd en m a te r ia l per hour a t . speeds ran g in g
15
from 900 to 1100 f t . p er m inute and u t i l i z i n g up to H000
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 l e r s a re being used in th e above ground equipm ent.
In th e underground w orkings o f 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 a s on s u r fa 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 e lp to red u ce th e c o s t o f s p i l la g e
c le a n -u p , an expense w hich approaches $30,000 p er y ea r f o r
some m in es. The o th e r improvements in th e i d l e r d e s ig n a re
v a r io 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 i r a l s in s te a d of a s e r i e s of ru b b er d i s 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
hau lage s t r u c t u r e s .
4 . Development o f a r t i c u l a 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 improvement o f conveying mediums has r e
s u lte d in th e d e s ig n o f a r t i c u l a t e d and cascade conveyors.
One v e r s io n of an a r t i c u l a t e d conveyor developed f o r th e
bo ring 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 o f
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 ee rin 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 t i c a l t r e n d s in t r a n s p o r ta t io n " , Coal Age, V o l. 6 3 , No. 7A, M id-July 1958, p . 77*
in te rc o n n e c te d b e l t conveyors on w hee ls-each w ith i t s own ,
d r iv in g a n d -p ro p e llin g m oto rs. _" - ■ . : •
The cascade system i s s u b s ta n t ia l ly s im i l a 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
p rov ided to p erm it th e s e r ie s to be p u lle d behind th e boring
u n i t in th e rem ote m ining a r e a s . To avo id in s e r t in 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 t r u c tu r e w ith
c i r c u la r ram ps. As th e machine goes in to th e m ining a re a
i t p u l l s th e conveyor o f f , pushing them back onto th e ramps
on th e way o u t .
5. B ridge conveyors and p o r ta b le b e l t heads: The develop
ment o f th e b r id g e conveyor u n i t was th e f i r s t s te p in
b r in g in g th e conveyor in to th e p ic tu r e as means of se rv in g
lo ad in g m achines and co n tin u o u s m in e rs . The n ex t s te p was
to d es ig n room conveyor so t h a t i t could be e a s i ly extended
to keep up w ith th e fa c e u n i t . The b r id g e conveyor i s th e
connecting l i n k betw een th e f a c e conveyor and con tinuous
m in e r. At th e t a i l s e c t io n of th e f a c e conveyor i t r id e s on
t r 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 i t or
con tinuous m iner i t i s su p p o rted by a b a l l and so ck e t f a s te n
in g . $ o th p o in ts o f c o n ta c t a llo w a 90 deg . movement to
e i th e r s id e . In any c a se , th e b rid g e I s always p o s it io n e d
to ac ce p t c o a l and d isc h a rg e i t onto th e fa c e co n v ey o rs .
16
A new developm ent w ith ro p e .su p p o rte d conveyors i s
17
th e p o r ta b le b e l t head . The d r iv e s e c t io n in c lu d in g m otor,
c o n t r o l l e 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 r t
a b le by m ounting as a com plete u n i t on a r a i l t r u c k . The
p o r ta b le head on i t s t r u 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 o f th e main l i n e . In t h i s p o s i t io 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 t ru c k i s anchored
in p la c e w h ile rem ain ing : on th e r a i l s .
6 . Use of conveyors f o r t r a n s f e r o f men: Under p ro p er s a fe
g u a rd s , movement o f men on b e l t s i s p rov ing b o th s a fe and
e f f i c i e n t S p e c i a l lo w "speed (up to 200 f . p . m . ) and low
c o s t b e l t s a re now being employed in t r 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 de
signed th a t th e b e l t canno t 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 s to p cord or
s to p system a l l along th e b e l t so t h a t any man can s to 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 un load ing p o in ts .
F in a l ly , in a d d i t io n to a l l th e above p re c a u tio n s , no move
ment o f men by b e l t s should be p e rm itte d u n le s s a re s p o n s ib le
p e rso n i s p r e s e n t .
i / I b i d . . PP. 72-9) P assim .
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 o f a b e l t hau lage system i s
decided upon, th e f i r s t s te p in i t s p roper d es ig n i s th e
s e le c t io n o f b e l t w id th and speed commensurate w ith f u tu r e
o u tp u t to be hand led , inasmuch as b e l t w id th 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 s tan d
p o in t o f 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 s ib le speed w ith i t s w id th 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 hau lage
e f f ic ie n c y and g r e a te r wear f o r a g iven tonnage conveyed.
For any p a r t i c u l a r problem concern ing th e under
ground h au lin g o f 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 l t w id th and speed .
However, th e w id th and speed o f th e b e l t s e le c te d must be
s u f f i c i e n t to move th e c o a l as f a s t a s s h u t t l e c a rs or o th e r
t r a n s f e r conveyors t h a t may be used in c o n ju n c tio n w ith th e
b e l t can d isc h a rg e t h e i r lo a d s upon i t ; o th e rw ise d e lay s
w i l l 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 ) t r a n s f e r conveyors ( e n try
b e l t s ) cap ab le o f ta k in g maximum s h u t t l e c a r d isc h a rg e a re
i n s t a l l e d to fe ed to th e main b e l t a t th e p roper r a t e s , or
18
( I I ) tw o-speed m otors a re I n s t a l l e 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 t t l e c a rs a re d is
ch a rg in g ; t h i s tim in g c o n t ro 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 t io n s s t a r t w ith a
c o n s id e ra t io n of th e c a p a c ity o f 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 t io n , b u lk w eigh t o f th e m a te r ia l to
be conveyed, and tro u g h in g ang le of i d l e r s on which th e b e l t
ru n s . There a r e two methods of d e te rm 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 e r 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 l ly ex p ressed in to n s /m in u te .
The peak c a p a c ity i s th e maximum amount o f m a te r ia l
t h a t w i l l be lo ad ed on to th e b e l t a t a l l o f 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 ssa ry to c o n t ro l th e d r iv e of th e
e n try b e l t s as ex p la in ed a b o v e .- This p re v e n ts th e e n try
b e l t s from d isc h a rg in g on to th e main b e l t i f th e main b e l t
i s a lre a d y f u l l y lo a d e d . 1
1 . B e lt - W idth: - The fo rm ula f o r d e te rm in in g th e b e l t w id th ,
19
20
as g iven by N a tio n a l E l e c t r i c a l M anufactu rers A sso c ia tio n
(N.E.M.A.) , i s as fo l lo w s :
B e lt w id th ( i n in c h es) s 13 1 0 , 000? S x U / 5
i/h e re : P z peak lo ad in to n s per m inuteS = speed of th e b e l t in f t /m in u te U z w eight o f 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 r io u s b e l t s iz e s a re g iv en in ta b le ( x ) . For c o a l mining
conveyors, speed i s u s u a l ly l im 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 i t i s h c o a l
mines &
3 . L um p-size: For th e maximum a llo 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 s io n a l
lump o n e -h a lf th e b e l t w id th in i t s w id es t d im ensions. The
ta b le ( i ) shows th e recommended maximum a llo w ab le lu m p -s izes
f o r d i f 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 ________\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. fo rm ula f o r de term in ing
6 / N a tio n a l Coal Board, "R e la tin g a roadway b e l t conveyor to i t s d u ty " , In fo rm a tio n B u l le t in 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 s tim a tio n of conveyor s p e c i f i c a t i o n s " , C o l l ie ry E n g in e e rin g T Vol 3 6 , No. 429, November 1959, p p . 4 b 6 -9 2 •
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 a s fo llo w s :
T = 0.0032Ux(W -5)2 __________ (3)
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 . f t . 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 .
NOTE: ,The above c a p a c ity fo rm ula c o n s id e rs maximum
or peak c a p a c ity . The recommended c a p a c i t ie s under which
th e b e l t s a r e to be o p e ra ted must be abou t 10$ low er th a n
th e tonnage d e riv 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 a l-
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
fo rm ula must be in c re a se d by abou t 1$$ and 22$ r e s p e c t iv e ly .
( i i ) The re v is e d Goodyear f o rm u la ^ f o r b e l t capa
c i t y f o r 20 d e g . s ta n d a rd e q u a l - r o l l tro u g h in g i d l e r s i s as
fo llo w s :
T = 5.,75(W - 3 .3 ) 1 *^6x S x U (4)200,000
Symbols a s 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•'
22
- : -
t .
BELT
PIG. 3 CROSS-SECTION OF LOADED BELT
( T i l ) A foTmula f o r d e te rm in in g 7 approxim ate b e l t
c a p a c ity as advocated by some m ining en g in ee rs 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 l t n o t under lo ad . > (se e F ig . 3) ♦. , t :
U s w t. of th e m a te r ia 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 r ib b o n o f m a te r ia l on th e belt" i s as shown
in F ig . 3* This a re a of r ib b o n i s app ro x im ate ly e q u iv a le n t
to a r e c ta n g le whose s id e s a r e (W-2a) by W/9 (see F ig . 3)•
23
T h e re fo re , th e c a p a c ity o f th e b e l t i s g iv en by;
T = (W -2a)x (W /9)x (S /lW x(U /2000)x60
For m in ing •conveyors th e edge d is ta n c e *a* i s about
3 in c h es (o r more a c c u ra te ly "a" = 0.055W - 0 .9 in c h ) .
S u b s t i tu t in g th e v a lu e o f 3 in ch es fo r "a" in th e above
eq u a tio n and rounding o f f th e c o n s ta 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" i i i 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 -s ize s ( in in c h e s ) in in ch es Goodyear U .S. Rubber Average I f un ifo rm I f mix-: , V.:: . V . - - .. ... . 1 ■' : - ' ; , ’ ' • . ed w ith
________________________ ______________________________________ f in e s
2b 500 400 450 5 8
30 600 450 525 ' 6 10
' 36 600 500 550 y 12
b2 650 . . 5oo , 575 8 ,48
6 5 9. 550 600 10 16
54 650 600 625 11 20
650 600 625 12 24
: • 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 dec ided a s 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 l t d r iv 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 r iv e th e empty b e l t , he
2 . Power to convey th e m a te r ia l h o r iz o n ta l ly 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 s lo 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 r iv e th e t r i p p e r , i f a t r ip p e r
i s used and i s to be d r iv e n by th e b e l t m otor. L et
t h i s t r ip p e r horsepower be eq u a l t o , h^
5. Power to a c c e le r a te th e lo ad ed b e l t a t s t a r t , ha
The c a lc u la t io 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 Em m
The power re q u ire d to d r iv e th e empty b e l t depends
2b
on th e f r i c t i o n a l lo a d s due to ( i ) th e w eigh t o f th e moving
p a r t s such as i d l e r s , p u l le y s , drag of th e s k i r t b o a rd s ,
drag caused by any m inute m isalignm ent o f p u lle y s or i d l e r s ,
(11) th e w eight o f th e m a te r ia l on b e l t , and ( i l l ) th e
i n t e r n a l f r i c t i o n of th e r ib b o n o f 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 a ss in g over th e i d l e r s . *
The c a lc u la t io n of a l l th e s e f r i c t i o n a l f o rc e s de
pends 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 e term in es th e accu racy of- ' . . • ' ‘ - • - . . . . . . . ... /v . . . . -
th e r e s u l t s o b ta in e d . . Most components o f f r i c t i o n a l f o rc e s
v a ry d i r e c t l y w ith th e len g th , o f th e conveyor. However,
th e r e a r e a few components which a re independen t o f b e l t
le n g th and, th e r e f o r e , may be added as com ponents.
The horsepow er to d r iv 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 l t _ ___________ speed ( f . p . m . )
r 3 3 ,0 0 0
= CxQx (L^Lq)xS : ‘______(6)■ 33,000
25
Where: C ■ com posite f r i c t i o n f a c to r as "explainedabove. U su a lly th e v a lu e of C mayr.be ta k en 0 .0 3 . However, f o r more a c c u ra te v a lu e s o f C, see p . 27.
. 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 l le y s , in f t .
2 6
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 c lu 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 independen t o f 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 a lly 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 eigh t o f th e moving p a r t s o f 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 ).
D ete rm in a tio n o f v a lu e Q:
The v a lu e o f Q i s v e ry d i f f i c u l t to o b ta in w ith
ac cu racy . The approxim ate v a lu e of Q may be ta k e n as
n u m e ric a lly eq u a l to th e w id th o f th e b e l t 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 o f Q = 48 l b s . p e r
l in e a r f t . b e l t le n g th .
A more a c c u ra te v a lu e of Q can be determ ined by th e
fo llo w in g fo rm u la :2 /
Q = 2B / W ] /l i / W2/ I 2
Where: B = b e l t w eigh t 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 t s of th ec a rry in g i d l e r s in l b s .
W£- w t. o f th e re v o lv in g p a r t s 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 .
27
l l = av e rag e spacing of th e lo ad c a rry in g i d l e r s , in f t .
Ip s av e rag e spacing of th e r e tu r n i d l e r s , i n f t .
TABLE I I
VALUES OF COMPOSITE FRICTION FACTOR, C, AND CONSTANT, LQ
C lass o f 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 t io n s on tem porary , p o r- a b le or im p e rfe c tly a l ig n e d s t r u c t u r e s .
0 .030 150
For conveyors w ith h igh g rade 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 l ig n e d s t r u c t u r e s .
0 .022 200
For conveyors as in (2) b u t w ith g rad es r e q u ir in g r e s t r a i n t of th e b e l t when lo a d ed .
0 .012 ^75
W ith th e above fo rm ula (6 ) , th e horsepower r e q u ire d
to d r iv 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 i f 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 ta in ed by d iv id in g th e new b e l t speed by 100.
28
TABLE I I I
APPROXIMATE VALUES OF HORSEPOWER TO DRIVE THE EMPTY BELT AT
" a SPEED OF 100 FEET PER MINUTEJjCV ,
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 ) _
NOTE: The above t a b le I s based on form ula ( 8 ) .
POWER TO DRIVE THE TRIPPER..t:
---- A t r i p p e r I s a m echan ical d ev ice f o r un load ing , 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 l le y . I t l i f t s
3 3
a p o r t io n o f th e b e l t o f f th e r e g u l a r . conveyor ca rry in g ,
i d l e r s and bends i t around th e t r ip p e r p u l le y .1' 1 The m a te r ia l
i s d isc h a rg ed over th e t r 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 chu te which i s a p a r t of th e t r i p p e r .
Depending upon th e d e s ig n of th e t r ip p e r c h u te , th e m a te r ia l; - "
may be d isch a rg ed to one s id e of th e b e l t conveyor, or
s e le c t iv e ly to e i th e r s id e , o r . t o bo th s id e s s im u lta n e o u s ly .
Many models of t r i p p e r s a re a v a i la b le , bu t 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 i p p e r s " ^
( i i ) hand p ro p e lle d t r ip p e r s
. ( i i i ) s ta t io n a r y t r i p p e r s
( iv ) ro p e -h a u l t r ip p e r s
(v) b e l t p ro p e lle d t r 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 t r ip p e r s
a f f e c t th e t o t a l power req u irem en t o f th e conveyor system .
I f ..the b e l t p ro p e lle d t r ip p e r , i s . i n s t a l l e d , .the power, t o ..
d r iv e th e t r i p p e r i s o b ta in ed from th e b e l t by means of a
gear t r a i n which connects th e d r iv e w heels to th e t r ip p e r
p u lle y ( th e d i r e c t io n o f th e t r ip p e r t r a v e l can be re v e rse d
by s h i f t in g g e a r s ) . T his p o w e r is de term ined by th e
fo llo w in g fo rm u la :3=2/ .............. ...... ’ ' ' ............. ...‘a ': v ■■■.0B e lt p ro p e lle d t r i p p e r h p . , h t = -----
-990(9)
1 0 / H. E. P rim er, A ll about b e l t in g - Handbook M. 6314-B-17, 1957, R o c k fo ile r C en te r, New York 20, N .Y ., U nited S ta te s Rubber Company, P . , 22.
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 . r'■ • . /
T = o u tp u t in to n s per hour
H = t r 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.:
3 4
B e lt w id th ( in in c h e s) V alue of •A1
24 : .. ■: . 0 . 0030 :
30 0.0047
36 . • • v : 0.0058
42 0.0070
48 0.0082
* ; 0.0100
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 )
24
30
36
4 8 .
’ 5if
4 .0
4 .5
5 .0
5 .5
6.0
7 .0
3 5
ACCELERATION. HORSEPOWER. : - c . ' cr-nr.:;:
The a d d i t io n a l horsepower r e q u ire d to a c c e le r a te th e
loaded b e l t , ha , i s de term ined by th e fo llo w in g f o r m u la :^ /
■ - ‘ - ( L ) x ( S(Q / M) x (100) (100) 2
6 3 . 8t___(10)
Where: Q = w t. of th e b e l t and moving p a r ts ( in lb s■:r: - p e r l i n e a r f t . of co n v ey o r). See page
26 f o r f u l l e x p la n a tio n o f th e v a lu e of-v.-- Q. v/..,-::. " '' L :
S z b e l t speed in f .p .m .
M r av e rag e lo a d in lb s per f t o f conveyor. : I t i s determ ined from th e fo llo w in g
fo rm u la :
u _ -------- where T i s th e averager ;; 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 l tfrom r e s t to f u l l lo a d . (T h is tim e i s
:: :r . ' 1 u s u a lly l im i te d to 2 to 5 s e c o n d s ) .
This a c c e le r a t io 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 t io n r a t e i s u n u su a lly
h igh or o th e r in d ic a t io n s a r e t h a t th e horsepower re q u ire d
f o r a c c e le r a t io n may be uncommonly l a 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. I f
th e a c c e le r a t io n horsepow er i s l e s s th a n 50%. of..th e sum of
11/ J H als ted S t r e e tCompany, 1961,
. W. Hardy, B e lt Conveyor C om putations., Chicago 9 , I l l i n o i s , Goodman M anufacturingP ♦» 5 •
he / hy, / h%., i t i s ig n o red s in c e m o to rs .a re norm ally cap ab le
of d e l iv e r in g power 50$ in excess of t h e i r con tinuous '
r a t i n g s .
3 6
A lso , a d d i t io n a l c o n s id e ra t io n must be g iv 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 t a r t e d many
tim es d u rin g th e s h i f t . An abnorm al number o f sto p p in g and
s t a r t i n g tim es w i l l te n d to h ea t th e motor beyond i t s
norm al r a t in g and must be co n s id e red when s e le c t in 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 a lly 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 t r i p p e r i s n o t p re s e n t or n o t o p e ra ted by th e
b e l t motor and when th e a c c e le r a t io n horsepower determ ined
by form ula (10) i s l e s s th a n 50$ o f 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 l t conveyor i n s t a l l a t i o n s th e power
i s r e q u ire d on ly to overcome th e f r i c t i o n in runn ing 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 e re fo re , t o t a l motor horsepower fo r h o r iz o n ta l conveyors
v:; ;; - he ^ * V : ( 1 1 )m otor e f f ic ie n c y
37
(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 t in 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 (o r D ec lin in g )
Conveyors:
Two c o n d itio n s must be co n s id e red in co n n ec tio n w ith
a loaded d e c lin e d conveyor:
( l ) When th e g r a v i ty 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 , l e 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 . This horsepower i s ^
i:(he V !%) - 4 - (hT ) .(13)
(2) When th e g r a v i ty 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
qu ired , in th e b e l t to r e t a r d th e loaded conveyor a g a in s t• c - ", /'
g r a v i ty a c t in g on th e lo ad i s 1 3 /
(hr) - 4 - (ko / h j , ) ____________ (I'O
As (he / h m) approaches th e v a lu e o f hp, th e loaded
1 2 / U. S. R ubber, A ll abou t b e l t in 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 .
conveyor w i l l have a g r e a te r tendency to c o a s t when th e power
to th e motor i s sh u t o f f . When h r . i s g r e a te r th an (h e ,,/ hg.)
a b rake must be u sed .
. I t i s obvious t h a t in o rd e r to a r r iv e a t th e a c tu a l
motor horsepow er needed to d r iv e th e b e l t conveyor in a l l
th e above ca ses th e tr a n s m is s io n and o th e r lo s s e s between
th e motor and d r iv e p u l le y must a ls o be co n s id e re d . The
o v e r a l l e f f ic ie n c y o f th e motor may be ta k en a s eq u a l to 80$.
The s t a r t i n 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 t in g th e d r iv e m otor. The g e n e ra l
purpose s q u i r 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 l t e r n a t in g c u r r e n t i n s t a l l a t i o n s . However, some con
veyors r e q u i r 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 o f t h i s ty p e o f m otor. Such req u irem en ts n e c e s s i t a t e
th e use o f h ig h - to rq u e s q u i r r e l cage or w ound-ro tor in
d u c tio n m o to rs. These a l t e r n a t in g c u r re n t m otors o f f e r c e r
t a i n advan tages over d i r e c t c u r r e n t m otors on some a p p l i
c a t io n s . However, d i r e c t c u r r e n t m otors a re f r e q u e n t ly 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 t io n s ; m otors t h a t a re i n s t a l l e d a t lo c a t io n s
where ex p lo s iv e q u a n t i t i e s of c o a l d u s t or methane gas may
be p re s e n t r e q u i r 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 .
3 8
PERMISSIBLE ANGLES OF INCLINATION FOR HAULING COAL ON BELTS
The an g le of in c l in a t io n depends on th e fo llo w in g f a c to r s :
(1) Shape and s iz e o f th e m a te r ia l to be conveyed -
I r r e g u la r ly shaped m a te r ia l has l e s s tendency to r o l l back
th a n sm o o th ;sy m m e tr ic a lly shaped m a te r ia l . However,
sy m m etrica lly shaped m a te r ia l can be conveyed up s te ep g rad es
w ith o u t f o i l - 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 oistu re - Wet m a te r ia ls ten d to s l id e back on
in c l in e d conveyors.
(3) Speed and lo ad in g - M oderate b e l t sp eed s , un ifo rm ly
c o n t ro l le d f e e d - lo a d in g , and lo a d in g on a h o r iz o n ta l s t r e t c h
o f th e b e l t ip rov ide 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 l in e d r u n s . .
In g e n e ra l , th e maximum ang le of in c l in a t io n a t
which th e m a te r ia l can be conveyed i s app rox im ate ly 10 to
15 deg rees 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 II I l i s t s p e rm is s ib le an g le s over
which c o a l can be conveyed w ith o u t undue s p i l l a g e .
39
TABLE V I I I
MAXIMUM PERMISSIBLE ANGLES OF
CONVEYOR INCLINATION
M a te r ia l to be conveyed Maximum p e rm is s ib le an g le ( in d eg rees)
1 . A n th ra c i te Coal
(a) ru n -o f-m in e 16
(b) f in e s 20
(c) lumps only 16
2. B itum inous Coal
(a) ru n -o f-m in e 18
(b) f i n e s 20
(c) lumps on ly 16 r
CHAPTER V
SELECTION OF PROPER BELT
The proper s e le c t io n o f b e lt width and speed fo r
a g iven 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 t in g the correct b e lt i s to know the maximum s tr e s s e s
th a t w i l l be developed in the b e lt w h ile hauling the
m a ter ia 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 aga in st
ex tern a l wear, h eat, m oisture or other in ju rio u s pro
p e r t ie s of the m a ter ia l to be conveyed. The s e le c t io n of the
proper b e lt fo r a g iven duty i s very important to minimize
tra n sp o rta tio n c o s t s . To determ ine the co rrect s p e c if ic a t io n s
of the b e lt in 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 iffer en ce in b e lt ten sio n
between the p o in t where i t f i r s t con tacts the d rive p u lley
and the p oin t 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 s io n , T^, and "slack side" ten s io n
Tg, are in d ir e c t r e la t io n s h ip to one an oth er. The
d if fe re n c e .b e tw e e n th e t i g h t s id e te n s io n and s la c k s id e
te n s io n i s known as “ e f f e c t iv e " te n s io n , Te . These th r e 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 r e a re o th e r minor b ielt .ten sions
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 l t
o p e ra t io n under s p e c ia l c o n d i t io 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 l t w ith in t h i s s tu d y and should be
r e f e r r e d to th e conveyor b e l t m anufactu rers* e n g in e e rs .
DETERMINATION OF BELT STRESSES
There a re many methods of c a lc u la t in g b e l t s t r e s s e s
or te n s io n s . Most o f th e la r g e r b e l t m an u fac tu re rs p u b lis h
a d es ig 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 i r e th e use of c h a r t s , t a 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 a tio n con
ce rn in g th e b e l t te n s io n req u irem en ts f o r po ly v in y l c h lo r id e
covered b e l t i n g , s in c e t h i s ty p e of covering has been r e
c e n tly in tro d u ce d as f i r e r e s i s t a n t b e l t in g . In t h i s s e c t io n
a sim ple method of computing v a r io u s im p o rtan t b e l t te n s io n s
r e q u ir in g a minimum number of c h a r ts and ta b le s i s g iv en .
(1) E f f e c t iv e B e lt T ension:
The e f f e c t iv e te n s io n , TQ, i s th e p u l l 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 a ss in g over i d l e r s and any l i f t o f
th e lo ad on a g rad e . The e f f e c t iv e te n s io n , Te , i s th e
d i f fe re n c e between t i g h t s id e te n s io n and s la c k s id e te n s io n
43
of th e b e l t . That i s , » -
: ; . T o = CT1 - T 2 ) . ---------------------------------- ( 1 5 )
: A lso , T. = — ?. 33.?QQ2.S --------------------- (16 )
Where: h - t o t a l b e l t h o r s e p o w e r - ,
8 « b e l t speed in f .p .m .
(2) Maximum o p e ra tin g te n s io n :
T igh t s id e te n s io n , T^, i s th e te n s io n in th e b e l t
a s i t f i r s t c o n ta c ts th e p u l le y . The maximum b e l t , 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 e te rm in es th e re q u ire d t e n s i l e s t r e n g th of th e b e l t
to w ith s ta n d th e w orking s t r e s s . In h o r iz o n ta l or n e a r ly
h o r iz 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 a l to T^. In o rd er to de te rm ine th e maximum o p e ra tin g
te n s io n (h e n c e fo r th d e s ig n a te d w ith symbol T ^), th e v a lu e of
e f f e c t iv e te n s io n Te , must be m u lt ip l ie d by a f a c to r , F
(which w i l l be ex p la in 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
R e fe rr in 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 l t i s abou t to s l i p on
th e d r iv in g d ru a , th e r a t i o to and Tg w i l l re a c h i t s
maximum v a lu e and i s g iv en by th e fo rm ula:
. W ith a l l In c l in e d conveyors th e w e ig h t-o f th e b e l t
on th e s lo p e cau ses te n s io n a t th e to p of th e s lo p e . The
slope b e l t te n s io n , Ts , depends on th e w eight o f th e b e l t
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 co
e 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 s lo p e b e l t
te n s io n can be determ ined by th e fo llo w in g fo rm ula
Ts = C x L x (0 -1 /1 5 ) . ___________ (22)
Where: G = g ra d ie n t o f th e s lo p e ex p ressed as af 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 i n e a r f t .( s e e below f o r th e d e te rm in a tio n of
; b e l t w e ig h t)
Should th e v a lu e of s lo p e te n s io n , Ts , as c a lc u la te d
by th e above fo rm u la exceed th e v a lu e of s la c k s id e te n s io n ,
Tg, th e n th e maximum b e l t t e n s io n , T^, w i l l be eq u a l to
(Te / Ts ) and th e b e l t shou ld be designed a c c o rd in g ly . The
v a lu e of Ts r a r e ly exceeds Tg even fo r conveyors on s te e p
s lo p e s u n le s s a th ree -d ru m d r iv e i s u sed .
D ete rm in a tio n o f B e lt W eight: -
The v a lu e o f b e l t w e ig h t, C, v a r ie s w ith th e ty p e
of b e l t c o n s tru c t io n and m an u fac tu re r* s s p e c i f i c a t i o n s .
1 5 / N. Brook, o p. c l t . « p . 1*90
I f no In fo rm a tio n a s to th e w eight o f b e l t I s a v a i la b le an
approxim ate v a lu e may be determ ined by th e fo llo w in g
fo rm 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 id th in in ch es
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 l t
q * w eigh t o f th e to p and bottom cover of th e b e l t ( in lb s ) per f t . long and p e r in c h wide of b e l t . U su a lly th e v a lu e of q = 0.030 l b s . when to p and bottom cover th ic k n e s s = 1 /32 In ch .
NOTE: The above fo rm u la must be used only to determ ine th e
w eight o f p ly type b e l t s . For s t e e l ca b le r e in fo rc e d b e l t s ,
th e e x tra w eight of th e s t e e l members must be co n s id e red .
DETERMINATION OF MAXIMUM AND MINIMUM NUMBER OF PLIES OF
BELTS FOR PROPER TROUGHINO AND STIFFNESS
The ch o ice o f number o f p l i e s in a norm al m u lti
p ly b e l t I s governed n o t on ly by th e s t r e s s bu t 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 o f 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 i e n t s t r e n g th In
te n s io n bu t owing to s iz e and w eight of m a te r ia l i t may be
too f l im s y . C on v erse ly , a b e l t may be so heavy or th ic k
th a t i t w i l l n o t be tro u g h a b le in th e r e q u ire d w id th . In
16/ i& ia
TABLE X II
- 'MINIMUM PLIES TO SUPPORT LOAD OF R.O.M. COAL UP TO 2 0 -INCH MAXIMUM .LUMP-SIZE AND MAXIMUM PLIES FOR PROPER TROUGHING
Duck w eight and p ly qual . i t y
B e lt w id th
( in in ch es)Minimum p l ie s to su p p o rt load Maximum p l i e s f o r p ro p er tro u g h in g
28 o z ._ c o tto n -
32 02. c o tto n -
36 02. c o tto n -
42 02. U stex
Heavy 28 o z . c o tto n -
32 oz . c o t to n -
36 02. c o t to n -
42 02. U stex -
Heavy
nylon nylon nylon nylon rayon nylon n y lo n n y lo n n y lo n< . . '' ' . ;
ray o n
2k 4 4 4 4 5 6 5 ■ 4 6
30 5 5 4 4 6 7 ; V : 6 ■ 5 5 7
36 6 5 5 4 6 9 6 5 8
42 6 6 5 5 6 10 8 8 ;■ 7 9 .
48 7 6 6 6 7 12 12 U 8 10
54 7 7 6 6 7 _ , 12 : 12 8 11
60 7 7 7 6 8 13 13 9 12 .
NOTE: 1 . Campass cord and s t e e l ca b le b e l t s 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 id th
of th e s e I s d es ig n ed w ith s u f f i c i e 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 l l 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 s ig n o f a
c a rc a s s f o r s u f f i c i e n t s t r e n g th to su p p o rt th e lo ad p rov ided 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 ssa ry to check th e b e l t f o r minimum or maximum p ly re q u ire m e n ts .
t h is case an a lte r n a t iv e i s to use a Campass cord or s t e e l
cab le 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 l ie s may be used i f i t i s w ith in th e
minimum and maximum p ly l im it a t io n s . • '
53
The ta b le X II g iv e s the minimum and maximum p ly
l im ita t io n s of ty p ic a l rubber covered b e lt s to carry ru n -o f-
mine c o a l. For p . v . c . covered b e lt s 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 l ie s
Minimum number o f p l ie s
7-5Ww •
3-5Ww
__(2W
— (25)
Where: W = b e lt w idth in inches
w r duck weight in ounces
DETERMINATION OF SIZE OF DRIVING DRUMS AND PULLEYS,
The s iz e o f drums and p u lley s required depends on
th e number of p l ie s and duck w eight used in th e b e lt con
s tr u c t io n . These s iz e s must be such th a t i t should not cause
the outer p ly o f the b e lt to exceed i t s e l a s t i c l im 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 l ie s ) req u ire la rg e diameter p u lley s
and th inner ca rca sses ( i . e . fewer p l ie s ) need sm aller and
l e s s expensive p u lle y s . . The thinner carcass of rayon w i l l
1 2 / Ik M -
$ 4
have the same maximum p erm iss ib le ten s io n per inch per p ly
as the th ick er carcass of co tto n . Sometimes i t i s d e s ir
ab le to use th in carcass b e lt s fo r u t i l i z in g older p u lley s
of sm aller s i z e , i f a v a ila b le a t no extra c o s t . Otherwise
th e th inner carcass o f 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 l t . The fo llo w in g formulae
serve th e gen era l gu ides fo r determ ining the s iz e of drums
and p u l l e y s : ^ /
, •
f' ::v
Diameter o f d riv in g ,drums
( in in ch es) = y . — . . R' 6
(2 6 )
.(27)
( 28)
( i i ) Diameter of driven drums
( in in ch es) r v x ? _ _______- -■ - . . : 8
( i l l ) Diameter o f snub p u lley s
( in in ch es) = ________\ ■ ' . . . - ■ 1° ' ■
. Where: w = duck, weight in ounces
. u ; p = number o f p l ie s in a b e lt
SELECTION g F PROPER BELT CONSTRUCTION MATERIAL
Of the many t ie lt s a v a ila b le , se v e r a l of th ese may
s u it the predetermined ten s io n requirem ents. The conveyor
b e lt s are made o f co tton fa b r ic , rayon, nylon and other
1 8 / I b i d . , pp. 486-92 , p assim .
s y n th e t ic f i b e r m a te r ia l s , s t e e l cab le r e in fo rc e d members,
f i r e - r e s i s t a n t b e l t s u s in g p . v . c . , te ry le n e and neop rene , -
e t c . In th e s e le c t io 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 s id e red and i t does n o t n e c e s s a r i ly con
f irm th e u l t im a te s t r e n g h t o f b e l t . In o rd er t h a t some
knowledge may be had o f some o f 1th e o th e r f a c to r s in vo lved
in th e s e le c t io n of a s u i t a b le b e l t , th e fo llo w in g c o n d itio n s
t h a t a f fe c t 'w o rk in g te n s io n s a re b r i e f l y d is c u sse d :
1 . F a tig u e o f 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 asse s from h ig h er to a low er
or low er to a h ig h er te n s io n r e g io n somewhere in i t s hau l
d is ta n c e . Thus th e re w i l l be c y c l ic te n s io n changes de
pending upon th e b e l t speed and le n g th . When th e f a b r ic
i s s t r e s s e d to more th an 50^ o f i t s u l t im a te s t r e n g th
f a i l u r e from f a t ig u e occu rs r a p id ly .
2 . S tr e tc h : The more h ig h ly th e b e l t i s s t r e s s e d th e more
i t w i l l s t r e t c h . The e x tra s t r e s s causes more f re q u e n t ta k e -: ■ • ' • . ' : VV ' . . . . . . . ... . ; ,. - t , . ;up ad ju s tm en ts 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 t io n s : Conveyor b e l t s may be s p lic e d
11 e n d le s s u by means of m e ta l 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 ta l f a s te n e r s has p u l l - o u t s t r e n g th t h a t i s
l e s s th a n th e s t r e n g th o f 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 t io n by th e te n s io n r a t in g s g iv en in
Table X I.
5 5
The b e l t s o f campass cord or s t e e l cab le r e in fo rc e d
c o n s t ru c t io n .a r e made " e n d le s s " by v u lc a n iz e d s p l ic in g ONLY.
The s t r e n g th i n th e s p l i c e cannot be as g r e a t as th e sum of
th e s t r e n g th s o f th e in d iv id u a l co rds or c a b le s . The f a b r i c
p ly b e l t s 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 l i c e . W hile t h i s method does n o t p ro v id e a
s p l i c e as s tro n g as an u n d is tu rb e d b e l t s e c t io n s , however, i t
i s very s tro n g and f r e e from th e l o c a l s t r e s s e s found in a
m e ta l 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 t in g as compared to a m e ta l fa s te n e d
j o i n t . The t a b l e XI g iv e s th e te n s io n r a t in g s f o r th e v u l
can ized s p l i c e b e l t s .
P u lle y Bending F o rc e s : The fo rm ulae 26 th ro u g h 28 on
page 54 a re e s ta b l i s h e d in o rd e r 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 o f th e b e l t th ic k n e s s . No
m a tte r what th e p u lle y d iam ete r may b e , th e o u te r p l i e s ofv - '
th e b e l t 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 t ra s t r e s s in th e o u te r p l i e s induced by
bending i s dependent on th e d iam eter o f th e p u l le 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 o f th e b e l t
te rm in a l . Hence th e p e rm is s ib le working s t r e s s must be l e s s
th a n th e u l t im a te s t r e n g th o f th e duck to a llow fo r th e se
bending s t r e s s e s . The campass cord and s t e e l cab le b e l t s
a re so c o n s tru c te d th a t th e p u lle y bending s t r e s s e s a re
r e l a t i v e l y i n s i g n i f i c a n t .
5 6
57
5. A c c id e n ta l Damage to B e l t : In underground c o a l h au lag e ,
b e l t s a re su b je c te d to many h aza rd 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 a s an a d d i t io n a l a id to b e t t e r s e le c t io n
of b e l t s to guard a g a in s t p o s s ib le dam ages. .
(a ) P ieces o f tram p i ro n and o th e r hard m a te r ia ls
may p ie rc e th e b e l t , b reak 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
s to p and r e p a i r a b e l t th e i n 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 conven ien t s to 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 i t a b le
f a c to r o f s a f e ty in c lu d ed in th e a llo w ab le s t r 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 r e s e rv e f o r ..tempo
r a r y o p e ra t io n under such c o n d i t io n s .
(b) D e te r io ra t io n o f 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 e lts w orking ’ in m o is t and humid con-
d i t io n s in m ines. . I t i s a breakdown of th e c e l lu 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 con
s t r u c t io 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 e lp
f u l to guard a g a in s t such d e t e r io r a t io n . W ith th e advent o f
th e u se of rayon in th e b e l t c a rc a s s , th e d i r e c t e f f e c t of
th e p resen ce of m o is tu 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 resen ce of m o is tu re does n o t lo s e i t s
s t r e n g th bu t a c tu a l ly 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 t i o n . C onversely , depending upon th e
5 8
p e rce n tag e o f m o is tu 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 e rce n tag e of i t s dry s t r 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 ex
trem e ly wet c o n d i t io n s . Hence rayon b e l t s shou ld n o t be used
under such, c o n d i t io n s .
In s t e e l c a b le r e in fo rc e d b e l t s , a d i f f e r e n t ty p e of
d e t e r io r a t io n may o c c u r , namely c o r ro s io n . M echanical
damage o f th e ru b b er cover by gouging or open s p l i c in g , i f
n e g le c te d , can become a s e r io u s f a c to r because of th e r e
s u l t in g c o r ro s io n of c a b le s encased in th e b e l t .
(c ) F i r 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 ,cau sed by b e l t , conveyors.
As a m a tte r o f f a c t conveyor f i r e s a re exceeded in number
on ly by spon taneous com bustion o f c o a l or carbonaceous ma-
t e r i a l . Hence a l l underground b e l t s shou ld be f i r e - r e s i s t a n t .
The U. S. Bureau of Mines has recommended th e u se o f .n e o
p rene and po ly 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 o tw ith stand ing a l l th e s e con
s id e r a t io n s f o r s a fe ty re q u ire m e n ts , th e b e l t s 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 r e c e n t y e a rs .
One of th e p r o p e r t ie s of p .v .c . used in f i r e - r e s i s t a n t b e l t s
i s i t s h ig h e l e c t r i c a l in s u la t io n q u a l i t i e s or i t s h ig h r e
s i s t i v i t y . On some conveyors, m ostly o p e ra tin g in d ry
c o n d it io 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 .
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 develop ing a n t i - e l e c t r o s t a t i c m a te r ia l f o r
b e l t c o n s tru c tio n i s being r e a l iz 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 cau ses conveyor f i r e s . A lso , w ith th e
h igher b e l t speeds th e chance of dangerous sp a rk in g s i s more
l i k e l y to o cc u r. The b e l t s 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 a rk s w i l l no t be
produced when th e b e l t s 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 l t depends, to a g r e a te r e x te n t ,
upon th e s e le c t io n o f c o r r e c t to p and bottom cover q u a l i ty
and th ic k n e s s . The to p cover must be of s u i t a b le com position
and s u f f i c i e n t th ic k n e s s . I d e a l ly , i t i s d e s i r a b le to f u r
n is h a cover q u a l i ty 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 i l l 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 on ly from th e s ta n d p o in t of
w ear, bu t a ls o as a cush ion to absorb th e lo a d in g im pact
of m a te r ia l to be conveyed. A la y e r o f f a b r i c having a
s p e c ia l weave c a l le d “b reak e r p ly “ i s o f te n imbedded in th e
co v e r. The b reak e r p ly ab so rb s im pact and p r o te c ts th e
c a rc a s s and cover a g a in s t gouging . The s e le c t io n of p ro p er
cover q u a l i ty 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 t io n s of working c o n d it io n s . E xperience w ith
p rev io u s b e l t s w i l l h e lp i n th e s e le c t io n o f th e p ro p er b e l t
co v e r. T h is e x p e r ie n c e ' shou ld in d ic a te many, c lu e s f o r f u tu r e
s e le c t io n . Loss o f cover by a b ra s io n w h ile th e c a rc a s s i s
r e l a t i v e l y i n t a c t would in d ic a te t h a t succeed ing b e l t s could
p r o f i t a b ly c a r ry a h e a v ie r or a b e t t e r q u a l i ty c o v e r . Severe
c u t t in g o f th e cover w ith o u t s e r io u s a b ra s io n lo s s would in
d ic a te e i th 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 i ly , be more econom ical to im
prove lo a d in g c o n d i t io n s . F a i lu 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 i th 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 .
6 0
.. The bottom cover th ic k n e s s of a b e l t depends m ainly
on th e l ik e l ih o o d of damage caused by th e m a te r ia l con
veyed g e t t in g betw een th e b e l t and i d l e r s and p u l le y s .
A b rasiv e m a te r ia ls r e q u ir e a h ea v ie r cover th a n n o n -a b ra s iv e
m a te r ia l s . The g e n e ra l c le a n l in 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 s id e re d . Where th e b e l t i s kep t c le a n and
s p i l l a g e or p i le -u p s a re u n l ik e ly , i t i s l e 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 i te s a t i s f a c to r y f o r h and ling r .o .m . c o a l
w ith b e l t o p e ra t io n under good c o n d it io n s . However, b e l t s
w ith a h ig h ly s t r e s s e d c a rc a s s such as ray o n , campass cord
or s t e e l c a b le shou ld have th e e x tra p r o te c t io n of 1 /16
in c h a d d i t io n a l th ic k n e s s of bottom co v e r.
61
To a s s i s t i n th e s e le c t io n o f p ro p er th ic k n e s s of
to p cover f o r b e l t s c a rry in g c o a l , t a b le X II I has been p re
p ared based on b e l t s p e c i f ic a t io n s o f Goodyear T ire and
Conveyor B e lt M anufacturing Company.
v: In conclud ing t h i s c h a p te r , i t should ag a in be no ted
th a t b e s id e s d e te rm in in g p roper b e l t w id th , speed , motor • "
s i z e s , and. maximum o p e ra tin g te n s io n o f th e b e l t , o th e r r e
qu irem en ts such as b e l t t r o u g h a b l l i ty and s t i f f n e s s , s iz e of
d r iv in g drums and p u l le y s , q u a l i ty o f b e l t c o n s tru c tio n .
m a te r ia l , b e l t cover th ic k n e s s , and p h y s ic a l working con-
d i t io n s in th e mine must a ls o be co n s id e red s im u ltan eo u sly
th ro u g h o u t b e l t s e le c t io n p ro ced u re . A ll of th e s e f a c to r s
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 .
6 2
TABLE X III
RECOMMENDED CONVEYOR TOP COVER THICKNESS FOR CARRYING COAL
Example 1 . S e le c t io n o f s u i t a b le b e l t in 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 .
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 cub ic f t .
4 . S ize of. lumps: up to 1 2".
5 . G rad ien t o f road-w ay: 1 in 50 a g a in s t th eloaded 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 4-50f .p .m .
7* Two lo a d in g p o in ts on th e b e l t w ith peak lo ad in g o f 3°0 tp h and 350 tp h r e s p e c t iv e ly . Ho t r ip p e r i s n e c e s s a ry .
S tep 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 a llo w ab le lu m p -s iz e .
The Peak c a p a c ity of b e l t » 300 / 350 s 750 tp h or
1 2 .5 to n s /m in u te . 15
Assuming a b e l t speed o f 4-50 f . p .m . , th e b e l t w id th
in in ch es - j ;
=1 10,000P .f s x U * 5 (fo rm ula 1)
= 1 3 - 6 aAl0 ,000 x 12 .5 ,
J 4-50 x 50
- 30.4- / 5 = 35.4- o r 36 in ch es
1 ' ; ■ W - 6 'A llow able lu m p -size * — r — (form ula 2)
36 - 615 in ch es
2
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 it io n s .
C x Q x (L / L0 ) x S( i ) he =
(11) hm ~
33,000
_ 0 .03 % 36 x (3000 / 150) x 4503 3 ,0 0 0
= 4 6 .5 0 hp.
- 0 X (L / Lp) x T
(form ula 6)
® 990
_ 0 .03 x (3000 / 150) x 750
(form ula 7)
990
( i i i ) hp
= 71*50 hp.
- y x H990
(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 ) h t = ze ro (S ince no t r ip p e r i s co n s id e red ).2
(v) ha -_ (Q / M) x (L/100) x (S /100)'
6 3 .8 x t
(36 / 55*5) x (3000/ 100) x (450/100)
(form ula 10)
2
63 .80 x 3
29 hp.
Because t h i s a c c e le ra tio n , horsepower i s l e 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 e re fo re , t o t a l b e l t motor horsepower a t 80% motor
e f f ic ie n c y : ' * ,
_ 4 6 .5 0 / 7 1 .5 0 / 4 5 .5 0 _QOfto " 200 hp*
Step I I I D eterm ine th e p roper, b e l t s p e c i f i c a t io n s .
U sing a th ree -d ru m d r iv e (an g le of wrap = 660 d eg .)
w ith p la in drums and p .v . c . b e l t in g , F = 1 .1 1 (from
i : v.
t a b le X ). ;
- S in c e , TV = 1 .1 1 x ^ 3 ^ ° x 33,000 ■ - .. -450
= 13,200 lb s .
(N ote: The s lo p e te n s io n Ts of th e b e l t i s n o t con
s id e re d h ere as i t does n o t exceed th e s la c k s id e
te n s io n T2 )
Now ' f x p = JL (fo rm ula 21)
= M i f -0.0 = 367 lb s p er in c h o f b e l t •5 • 3d , w id th
Taking v a lu e s o f p (number o f p l i e s in th e b e l t ) -
5, 6 , 7, ...... . . . . . . . ..... ;
The p .w .s . /p ly / in c h - w id th = .........5 6 7
= 7 3 .3 , 6 1 .1 , 5 2 .4 , . . . .
f
66
R e fe rr in 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) 7 -P ly , *+8 oz. c o tto n or heavy rayon b e l t in g
(b) No. 100 campass cord b e l t in g
(c) No. 150 s t e e l c a b le b e l t in g
The a c tu a l s e le c t io n o f b e l t to be used i s
p o s s ib le on ly a f t e r c o n s id e r in 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 t in 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 t e s t le n g th o f conveyor p e rm is s ib le
u s in g 6 -p ly , b2 o z. c o t to n f a b r ic c a rc a ss b e l t in g of 36
in ch es in w id th w ith ru b b e r covering and conveying 400 tp h
a t a speed of 350 f .p .m . up an in c l in e 1 in 50. The system
u ses m e ta l l ic hook jo in t s 'a n d au to m atic co u n te rw e ig h t takeup
d ev ice w ith no t r i p p e r .
S tep I D eterm ine th e t o t a l b e l t horsepow er.
H ere,
( i )
C = 0 .0 3 ; .Q = 36; L ~ ?; L0 I 150; S = 350;
T = 400; H =. Jr,-..; 5 0 ' :: -
hQ z 0 .03 x 36 x (L / 150) x 350 3 3 ,0 0 0
; ( W 150) x hP- 100
( l i ) hm = 0-03 X (L / 150) X 400k . ... l.,- - . - - • ..............
(L / 1^0) x1.21100
( i l l ) hr400 x L _ 0.82L 990 X 50 *■ 100“
The t r i p p e r and a c c e le r a t io n horsepow ers a re n o t con
s i d e r e d . ' ’ ' ' '
T h e re fo 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 t r 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 t e n s io n f o r a 42 o z .
c o t to n b e l t 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 r iv e (an g le of wrap z 440 d e g .)
w ith p la in drums, F = 1 .1 7 (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
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 3503 3 ,0 0 0 3 3 ,0 0 0
T h e re fo re , 3 _ - /. 353 = Zj . 92. x....3i £ (from p rev io u s100 33,000 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 . ' : ' * '
CHAPTER VI
DISCUSSION ON BELT HAULAGE ECONOMICS AND COST ESTIMATION
........ The' f in a l d e c is io 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 s ts o f a l l methods of
tra n sp o r ta tio n . When used under the proper co n d itio n s , b e lt
conveyors can move m a ter ia l more econom ically than most
other methods. They consume l e s s power per u n it o f 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 l im ita t io n s ,
and th e ir use i s not th e so lu t io n to every haulage problem;
they have the a b i l i t y to handle la rg e tonnages a t low u n it
c o s t s . S ince they have a high c a p ita l co st they are not
e f f i c i e 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 i f y the in s t a l la t io n o f b e lt
conveyors and, secon d ly , to determine the approximate break
even p o in ts between conveyors and other types o f 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 s ts can then be compared w ith other
system s of mine haulage to . determine which .system or:
69 .. • ' ,.
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
70
u n i t co s t: f o r - t h e t r a n s p o r ta t io n o f c o a l under th e con
d i t io n s being in v e s t ig a te d . No a ttem p t has been made in
t h i s s tudy to compare th e u n i t c o s ts o f o th e r hau lage sy s
tems w ith th o se of conveyors; such a com parison i s beyond
th e scope o f th e p re s e n t s tu d y .
B efo re an a ly z in g ow nership and o p e ra tin g c o s ts of
b e l t hau lage system , c e r t a 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 o f th e con
veyor equipm ent depends on ( i ) th e r a t e a t which th e equip
ment i s am o rtized and ( i i ) th e r a t e a t which th e m ain ten
ance and r e p a i r c o s ts in c re a s e w ith th e age o f th e equipm ent.
These f a c t o r s a r e d isc u sse d below .
The d e p re c ia t io 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 i t a l in v e s t
ment must be determ ined on ly a f t e r c o n s id e ra t io 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 t ly used
a d e p re c ia t io n p e r io d of 10 y e a rs f o r conveyor fram e-w ork
and a l l m echan ical and e l e c t r i c a l equipm ent. The ru b b er
b e l t in g i s d e p re c ia te d on a 5 y ea r b a s i s . The b e l t manu
f a c t u r e r s c o n s id e r th e above f iv e - y e a r l i f e o f b e l t in g to
be to o s h o r t , b u t ex p e rien ce has shown th a t i t i s a f a i r
71
average l i f e ' f o r b e l t in g used In th e main and In te rm e d ia te
hau lage s e rv ic e . A number of d e p re c ia t io n methods a re •
a v a i la b le to d e te rm in e y e a r ly d e p re c ia t io n c o s t of th e equ ip
m ent. The most im p o rtan t o f th e s e a re th e s t r a i g h t - l i n e ,
s in k in g fu n d , p ro d u c tio n u n i t s and d e c lin in g b a lan ce m ethods.
I t i s ex trem 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 p roper 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 o f th e equipm ent. The
annua l r e p a i r 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 i r c o s ts do r i s e each year - th ey r i s e
on ly 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 o f cy c le s of
heavy r e p a i r s in c r e 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 e lap se d tim e may le s s e n . E v en tu a lly o v e r a l l
m ain tenance c o s ts w i l l l e v e l o f f . Hence a uniform r a t e of
o p e ra tin g m ain tenance c o s t may be co n s id 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 c lu d ed in th e an n u a l ow nership c o s ts .
The an n u a l c o s t o f ta x e s and in su ran c e may be tak en a s eq u a l
to bfo o f th e A v erag e Investm ent* c a lc u la te d as fo llo w s :
A verage Investm en t = n / 1 (29)2 x n
Where:n%= th e l i f e o f th e conveyor equipm ent (10 y e a rs f o r
conveyor fram e, m echan ica l 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 o f a com plete
conveyor system i n s t a l l e d i s ab o u t S 1 5 0 .0 0 p er f o o t o f le n g th
f o r a c o n v e n tio n a l b e lt '.co n v ey o r .u sing 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 t in g ow nership c o s ts i s
g iv en below:
(a) Cost o f Equipm ent: T h is .in c lu d e s th e c o s t of
p u l le y s , speed re d u c t io n tr a n s m is s io n , m o to r s ,c o n t r 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 a ls ted S t r e e t , Chicago 9 , I l l i n o i s :
Up to 6o hp.. = $220.00 per hp.$ " ..
61 to 75 hp. = • $160.00 per hp.$I ______ (30)
76 to 200 hp. z $145.00 p er h p .I
over 200 hp. ' :Z $140.00 p er hp.$
(b) Cost o f S t ru c tu r e s , I d l e r s , and o th e r S upporting
Equipment: •
72
For c o n v e n tio n a l b e l t hau lage s t r u c tu r e s ( r ig id - f r a m e ) , th e
c o s t in d o l la 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 t r u c tu r e in f t . ) - - ______________ (31)
For ro p e-fram e b e l t conveyor s t r u c tu r e s , th e c o s t in d o l la r s
,Z (0 .50 x b e l t w id th in in ch es x le n g th of
s t r u c tu r e in f t . ) ______________ (32 )
(c) Cost of B e lt in g : The c o s t of b e l t in g v a r ie s
w ith th e duck w eig h t, number o f p l i e s , ty p e of b e l t con
s t r u c t io 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 o f a b e l t f o r any p a r t
i c u la r du ty 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 u sed . However,
a f a i r e s tim a te o f th e c o s t o f b e l t in g can be found as
fo llo w s : • : ) ‘ '
The c o s t of b e l t in g (p ly ty p e ) p er f t . in d o l la r s
= (0 .0006 x T-l / 0 .2 0 ) x W ___________ (33)
Where: T j z maximum o p e ra tin g te n s io n of b e l t in
lb s / in c h -w id th .
W Z b e l t w id th in in ch es
(d) E re c tio n c o s ts : .U vvr:; .. i
( i ) C leaning o ld mine openings and e la b o ra te
73
7 4
s i t e p re p a ra t io n s a re excluded c o s t s . When th e b e l t con
veyor can be extended as th e working fa c e advances, th e
e r e c t io n c o s ts may be ta k en a t l i $ to 2$ of th e c a p i t a l to
be in v e s te d f o r e x te n s io n under id e a l c o n d itio n s .
(11) I f w ir in 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 done.
(e) C o n tin g en c ie s : The c o n tin g e n c ie s a re in c lu d ed
to cover th e u n fo re see n c o s ts . These c o s ts may be tak en as
eq u a l to 2$ o f th e sum of th e equipm ent, b e l t , and e re c t io n
c o s ts . .
T h ere fo re th e t o t a l Ownership C osts
= (a ) / (b) / (d) / (e) p lu s (c ) ;
Using th e s t r a i g h t l i n e method, th e y e a r ly de
p r e c ia t io n c o s t :
- (a) / (b) / (d) / (e ) _ (c)- ------------ ----------------------- p lu s -----------
10 y e a rs 5 y e a rs
Y early f ix e d c o s ts z y e a r ly d e p re c ia t io 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 r ly d e p re c ia t io n c o s t / 10/5 of
“Average Investm ent"
7 5
WOTS: There a re many more c o s ts o f owning a com
p le te b e l t conveyor system . These in c lu d e t r a n s f e r s t a t i o n s ,
supp ly t r a c k , c a r s , and lo co m o tiv e s , and, i f needed , su rge
b in s , f e e d e r s , and l in in g s in them, power s t a t io n s f o r b e l t
d r iv e s , in te rcom m unication and r e l a t e d f a c i l i t i e s , and equip
ment c a r r i e r s . The c o s ts o f a l l th e se item s a re n o t con
s id 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 , excep t
f o r power c o s t , a re n o t p ro p o r t io 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 s t
f a c to r s of conveyor hau lage a re g iv en below.
(a) Power C ost: G en e ra lly a l l th e roadway con
veyors a re e l e c t r i c a l l y d r iv e n . There a re v e ry few con
veyors 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 o f power proved u n s u c c e s s fu l .
T h e re fo re , th e energy req u irem e n ts must be d e riv e d on a
t h e o r e t i c a l b a s is assuming a known runn ing 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 dete rm in ed a s fo llo w s :
Y early power c o s t in d o l la 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
x 0 .008 ..■v;:: __________OH)
7 6
■ . (b) O p era tin g ;L ab o r C o sts i For a l l ty p e s of con
veyo rs th e o p e ra tin g la b o r c o n s is ts o f one man a t each t r a n s
f e r p o in t f o r every s h i f t th e conveyor i s in o p e ra t io 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
o f $ 2 .5 0 per hour i s assum ed. T his r a t e in c lu d e s a l l
f r in g e b e n e f i t s .
; (c) M aintenance and R ep a irs C ost:
( i ) M aintenance la b o r c o s t : Only ro u t in e
la b o r on conveyors may be c o n s id e re d . N on-rou tine 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 con
s id e re d s e p a r a te ly . This r o u t in e la b o r f o r d a i ly m aintenance
i s o f two k in d s . F i r s t , u n s k i l le d la b o r i s used fo r
p a t r o l l in g and c lean in g th e s p i l la g e ; f o r t h i s purpose one
or two men per m ile o f conveyor p e r s h i f t i s a f a i r av e ra g e .
Secondly , s k i l l e d la b o r i s used f o r th e m aintenance of th e
m echan ical and e l e c t r i c a l p a r t s o f th e conveyor equipm ent.
One m echan ical 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 ain tenance
fo rc e o f 3 to 4 men per m ile p e r s h i f t i s a ls o expected to
do some o th e r odd jo b s , such a s s m a ll-b e l t 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 $2 .50 p er hour as s t a te d .
( i i ) M a te r ia l c o s t f o r m ain tenance: From th e r e
cords o f components and b e l t s re p la c e d in th e p a s t an
a ttem p t i s made to dete rm in e th e l i v e s of th e m ajor components
77
of th e conveyor system ; b u t t h i s v e n tu re i s f u r th e r com
p l ic a te d , in some c a s e s , by th e ever changing d es ig n of
c e r t a in p a r ts of th e conveyor equipm ent. Hence an average
m aintenance c o s t may be u sed . . '
The main c o s t o f m aintenance i s , of c o u rse , th e r e
placem ent o f th e b e l t in g . The b e l t i s co n s id e red to have a
l i f e of 5 y e a r s , w hereas th e l i f e of th e o th e r elem ents of
th e e n t i r e i n s t a l l a t i o n i s 10 y e a r s . This means th e re w i l l
be one rep lacem en t o f th e whole b e l t in g in 10 y e a rs . Using
th e c o s t of th e o r ig in a l b e l t in g (item *c? in ow nership
c o s t s ) , th e y e a r ly b e l t rep lacem en t c o s t can be c a lc u la te d .
I t w i l l be eq u a l to o n e - te n th o f o r ig in a l b e l t c o s t .
B esides y e a r ly b e l t rep lacem en t c o s t , th e re w i l l be
sm all c o s t f o r sp a re p a r ts on th e conveyor s t r u c tu r e , lu b
r i c a t i o n s , e t c . This c o s t may be tak en to be eq u a l to 2$
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 r ly 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 tst o t a l to n s moved p er y ea r
PROBLEM ON TgE COST ESTIMATION ££ & BELT HAULAGE SYSTEM
Example: C a lc u la te th e u n i t c o s t of conveying c o a l f o r
example ( l ) on page 62 . :
I Ownership c o s ts :
7 8
(a) Cost o f equipm ent @ $1^5*00 per hp. =
200 x Ik? = $29,000
( b ) " Cost o f s t r u c tu r e = (0 .80 x b e l t w id th x le n g th
o f s t r u c tu r e )
= (0 .8 0 x 36 x 3 ,000) = $86,500
(c ) Cost o f b e l t in g * (0 .0006 x / 0 .2 0 ) x 36 x
(3000/ 3000/ 1 5 0 )
, - r (0.0006 x 367 / 0 .2 0 ). 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 l t )
c o s t
r 20^ of (29,000 / 93,000)
z $24,400
(e) C o n tin g en c ies z 2% o f (equipm ent / b e l t /
i n s t a l l a t i o n )
= 2% o f (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 t io n based on s t r a i g h t l i n e method
. ( a ) / ( b ) / ( d ) / ( e ) , (c)5 y e a rs10 y e a rs
7 9
_ 144,828 , 93,000 10 5
= 133,083
Average Investm en t (ex c lu d in g b e l t c o s t) = 144,828 x I P - / —.. ... .. 2 x 5
(form ula 29)
•= $ 79,500
Average in v estm en t f o r b e l t in g 93,000 x dJ—2 x 5
:: - - = #55i75o
T o ta l average in v estm en t - 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 ave
rage investm ent- • - - ' .• ;■ . 1
= 10;S of 135,250 =
■ - ®13,525
Yearly f ix e d c o s ts = yea r ly d ep rec ia tio n / y ear ly in t e 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 year)
= $(200 x 0.746 x 2000 x 0 . 008)
* -$ 2 ,4 9 0 : ' : : " .
8 0
(b ) Y ea r ly o p e r a tin g la b o r c o s t
= S ( 2 .5 0 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 2 .5 0 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
p lacem 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 ( i i ) 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 nersh ip 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 year @ 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
81
Or c o s t /to n /m ile = 0 .053 x 28° . e.e t .3 ,0 0 0 (len g th of haul)
Z $0.093 per to n per m ile .
NOTE: A ctu a lly the c o s t /to n -m ile w i l l be l e s s than
th e above f ig u r e s in c e maintenance labor co st i s not
d ir e c t ly p rop ortion a l to len g th of haul.
COST CHARACTERISTICS OF BELT HAULAGE SYSTEM
Based on the above c o s t estim ation procedure, a
range o f “hypothetical*1 d u tie s rep r ese n ta tiv e o f co n d ition s
under which the conveyors w i l l run are in v e s t ig a te d to de
term ine the b e lt haulage co st c h a r a c te r is t ic s . The use of
th e term “h ypothetica l" should be c le a r ly understood th a t i t
i s the conveyor in s t a l la t io n s which are h y p o th e tica 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 c tu a l conveyor in s t a l la 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 t ic 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 . ,
rig id -fram e supporting s tru c tu res) w ith 20 deg. troughing
id le r s .
(2) S tra ig h t l in e d ep rec ia tio n method i s u sed .
(3) No sa lvage or r e s a le va lu e of the equipment i s
82
co n s id e red .
(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 s tm 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 echan ica l f i t t e r
. : ! one man f o r p a t r o l l in g and c le a n in g s p i l la g e
(6) Labor r a t e f o r a l l c a te g o r ie 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 i t s .
(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 if ie 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 t r e s s e d th a t f o r co n tinuous
o p e ra t io n , h ig h p ro d u c tio n , and low u n i t c o s t th e b e l t
haulage system i s th e b e s t s o lu t io n f o r t r a n s p o r ta t io n of
c o a l in m in es. But h ig h e r u n i t c o s t may r e s u l t because of
im proper d e s ig n and i n s t a l l a t i o n or poor m aintenance and
o p e ra t io n . W ith c a r e f u l d e s ig n o f th e b e l t hau lage system
and p ro p er m ain tenance , most o f th e b e l t hau lage c o s ts can
be kep t 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 c in g th e b e l t hau lage u n i t c o s t w herever
p r a c t ic a b le and p o s s ib le .
( l ) Use o f narrow b e l t w id ths and in c re a se d sp eed s.
A c tu a l lo a d in g t r 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 o f th e m a te r ia l
HnXlZTS EECAIT' T -
- L i _ 1.
r 1 - - r
„ u!
Ifkisai T i-r-ri t ig a a r ii icOUTPUT:Tons p er Hour
rrrT
i LLi
OUTPUT* TONS Per HOUR
may p la c e some r e s t r i c t i o n s on th e ch o ice of b e l t speed . To
f in d ou t w hether h ig h e r speeds r e a l l y red u ce th e conveyor
c o s ts , a h y p o th e tic a l case can be s e t up as fo llo w s by assum
ing a s e t o f norm al conveyor c o n d i tio n s :
( a ) ib e l t le n g th : 2000 f t .
(b) 1000 tp h w ith maximum lum psize r .o .m . c o a l of
12 in ch es
(c) l e v e l g rad e w ith no l i f t s or d e c l in e .
(d) s ta n d a rd 20 deg . tro u g h in g id l e r s on r i g i d -
fram e s t r u c t u r e s .
8 5
Now r e f e r r in g to F ig . 5 , th e fo llo w in g co n c lu s io n s can be
drawn:
h2" b e l t conveys |iood]j@5l*0 "1 w ith u n i t c o s t of $ 0 ,0 2 6 /|_ tp tu |f .p .m j to n
48“ " |io o o ] |4 o o 1 " ".p .m j
" " $ 0 ,0 2 9 /to n
" " $0 , 031/to n
Ltphjf.i54" " " E006I I 320 "I » »
[ tph] (C.p.mj
The n e t sav ing o f having a n arrow -w id th b e l t o f 42" a t th e
h ig h er speed o f 540 f .p .m . i s 11^ and 20% over t h a t o f a
48" b e l t a t 400 f .p .m . and a 54" b e l t a t 320 f .p .m .
r e s p e c t iv e ly .
(2) Use o f deep tro u g h id l e r s -
For some y e a rs th e Germans in t h e i r s t r i p m ining
o p e ra tio n s have made use o f i d l e r s w ith a 30 deg. tro u g h in g
an g le in p la c e o f commonly used 20 d e g . tro u g h in g i d l e r s in
th e U nited S ta te s . The d es ig n of deep tro u g h in g i d l e r s
8 6
r e q u ir e s b e l t in g th a t w i l l be a b le to w ith s ta n d sev e re t r a n s
v e rse f le x in g .
A 48 m b e l t a t 400 f .p .m . can hand le 1000 tp h w ith
20 deg . tro u g h in g i d l e r s . The same o u tp u t can be handled
by a 42" b e l t a t th e same speed o f 4-00 f .p .m . bu t w ith 35
deg. tro u g h in g i d l e r s . The n e t sav ing in c o s t w i l l be , in
t h i s c a se , about 10%.
(3) M u ltip le s h i f t o p e ra t io n in s te a d o f one s h i f t
per day -
O pera ting th e b e l t a t two s h i f t s per day in s te a d of
one s h i f t , a n e t sav ing of 5% to 8% in u n i t c o s t can be
accom plished . This i s because th e o u tp u t i s d i r e c t l y p ro
p o r t io n a l to number o f hours worked, whereas th e d e p re c ia t io n
p e r io d or th e l i f e o f th e equipm ent i s n o t .
(4) I n s t a l l i n g long s in g le conveyors -
W herever p o s s ib le and n ec e ssa ry th e f e a s i b i l i t y of
u sing one long conveyor u n i t as compared to s e v e ra l s h o r te r
f l i g h t s should be s tu d ie d . For in s ta n c e , a 4 0 0 0 - f t . long
s in g le conveyor u n i t w i l l r e q u ir e an expensive and h igher
s t r e n g th b e l t in g o f s y n th e t ic f ib e r o r s t e e l cab le con
s t r u c t io n . However, th e i n i t i a l c o s t o f t h i s long b e l t in g
as a whole w i l l be app ro x im ate ly 6% l e s s th a n th e t o t a l c o s t
of 4 s h o r te r u n i t s o f 1000 f t . each . A lso th e i n i t i a l
c a p i t a l in v estm en t (w ith o u t b e l t in g ) f o r a 4000 f t . long
8 7
s in g le u n i t w i l l be about 20^ l e s s th a n f o r fo u r s h o r te r
u n i t s . T his sav ing i s due to th e e l im in a tio n o f th r e e t r a n s
f e r p o in ts w ith t h e i r i n s t a l l a t i o n s o f m o to rs, t r a n s f e r
g e a rs , takeup d e v ic e s , e t c . , as compared to on ly one t r a n s
f e r p o in t o f th e lo n g e r u n i t . , A lso t h e r e .w i l l be reduced
breakage and d e g ra d a tio n o f c o a l c a r r ie d on a: longer, s in g le
u n i t . . : - : : ; v .; - : . . : - ■ :■
(5) Use of m u lti-m o to rs in s te a d of s in g le motor
f o r la r g e r u n i t s -
On long h o r iz o n ta l conveyors a tw o -p u lley ty p e of
d r iv e o f te n p e rm its low er b e l t o p e ra tin g te n s io n and th e re
fo re low er b e l t c o s t . A m u lti-m o to r d e s ig n w i l l a llo w a
w ider cho ice in th e s e le c t io n o f th e low er horsepower
m oto rs. A lso th e c o s t o f sp a re motor u n i t s i s much lo w er.
(6) S h if t .f ro m r i g i d to ro p e -su p p o rted equipment -
The ro p e -su p p o rte d conveyor hau lage can be in
s t a l l e d , ex tended and r e lo c a te d f a s t e r th an th e co n v e n tio n a l
ty p e of conveyor system . Hence th e re w i l l be a n e t sav ing
in th e u n i t c o s t o f h au lin g c o a l when compared to r i g i d -
fram e b e l t h au lag e . However, th e s h i f t from r i g i d to ro p e -
supported s t r u c tu r e s f o r main l i n e b e l t hau lage i s v e ry slow
owing to i t s somewhat n o n - r ig id i ty f o r perm anent hau lage and
to random breakdow ns.
8 8
S im ila r to ro p e -su p p o rte d conveyor h au lag e , th e
c a b le - b e l t conveyors (see page 7) a ls o do n o t compare fa v o r
ab ly w ith co n v e n tio n a l co n v ey o rs . The e f f e c t iv e rope l i f e
i s one of th e im p o rtan t f a c to r s in de te rm in in g th e o p e ra tin g
c o s ts of c a b le - b e l t co n v ey o rs . These u n i t s may be expected
to be removed from s e rv ic e sooner th an co n v e n tio n a l b e l t s
f o r two main re a s o n s : (a) a c c id e n ta l damage may occur w ith
g r e a te r freq u en cy or (b) w earing down of b e l t and ca b le may •
ta k e p la c e a t a g r e a te r r a t e : '
W ith a l l th e s e s h o r t comings of ro p e-fram e ( i . e . rope
su p p o rted i d l e r s t r u c tu r e s ) and c a b l e - b e l t . ( i . e . c a b le or
ro p e -su p p o rte d b e l t s t r u c tu r e s ) u n i t s , i t i s d o u b tfu l w hether
th e s e conveyor system s w i l l be. more co m p e titiv e f o r a w ider
ran g e of d u t ie s in c o a l t r a n s p o r ta t io n . A d d itio n a l r e - .
s e a rc h work must be u n d ertak en by en g in eerin g e s ta b lish m e n ts
to de term ine b reak -ev en p o in ts f o r d i f f e r e n t k in d s of b e l t
hau lage sy stem s. ..... : . . .
CHAPTER V II
INSTALLATION AND MAINTENANCE OF CONVEYOR BELTS FOR EFFICIENT OPERATION
A v/ell designed conveyor, which, has been properly in s ta lled and maintained, w ill lower subsequent maintenance, repair and replacement costs. The benefits of good maintenance, regular inspection and proper housekeeping of the belt conveyor w ill re su lt in increased production, efficiency and ease of operation. Like a l l machinery, however, they can be an endless source of trouble when neglected . Lack of periodic checking and maintenance of alignment, leveling , cleaning, correct loading, lubricating of the moving p a rts , e t c . , may cause severe damage or may ru in a be lt th a t frequently has a dollar value greater than any piece of equipment in the mine. By following simple ru les and procedures, smooth running of the conveyor can be expected with few or no breakdowns.
INSTALLATION PROCEDURE ' ' : ' : v
Success with the be lt haulage system comes from proper in s ta lla tio n according to the recommendations of belt manufacturers. The services of competent consultants
89 ::: ' .
90
a re u s u a lly j u s t i f i e d on Im p o rtan t i n s t a l l a t i o n s .
.... , F i r s t l y , th e d e te rm in a tio n of re q u ire d b e l t le n g th
i s made a f t e r ta k in g in to c o n s id e ra t io n th e 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 and-number and le n g th of b e l t
s p l i c e s . . Then an o rd e r i s s e n t to th e m anufactu rer f o r i t s
p u rch ase . ... .......
...........Secondly , some p re c a u tio n s in hand ling and s to r in g
of conveyor b e l t r o l l s must be ta k en when th e y a re re c e iv e d
from th e m a n u fac tu re r . The b e l t r o l l s must be s to re d in a
co o l d ark p la c e where o i l s , g a s o lin e and p a in t in g m a te r ia ls
a re n o t p r e s e n t . The p la c e s where ozone i s produced: by
e l e c t r i c a l equipm ent or w elding must be avoided f o r b e l t
s to ra g e . 'New as w e ll as o ld b e l t s must be handled c a r e f u l ly
w ith o u t d ro p p in g . I f r o l l s a r e handled w ith s l i n g s , a bar
th ro u g h th e c e n te r f o r l i f t i n g i s used and th e b e l t edges
a re p ro te c te d w ith p la n k s . In hand ling and i n s t a l l a t i o n th e
b e l t must n o t be b en t more sh a rp ly th a n minimum p u lle y d ia
m e te r ....P roper equipm ent and methods must be used in moving
a b e l t in to '-th e m ine, such a s w inding i t on a h o r iz o n ta l
sp ind le" 'and moving i t u p r ig h t in to th e m ine.
T h ird ly , th e fo llo w in g p re c a u tio n s must be ta k en
d u r in g , i n s t a l l a t i o n of b e l t conveyors: , ... , _ 1
(1) S ince th e a lignm en t i s c r i t i c a l w ith under
ground b e l t s , p ro p er a lignm en t i s n e c e s s a ry .
91
(2) Keep b e l t l e v e l t r a n s v e r s e ly .
(3) P rov ide p ro p er c le a ra n c e . T his f a c i l i t a t e s
in s p e c tio n and m aintenance as w e ll as avo id ing damage or
f a u l ty o p e ra t io n .
0+) A lign i d l e r s p ro p e r ly . P rov ide added in
surance by ju d ic io u s use of s e l f a l ig n in g i d l e r s a t in
t e r v a l s of 200 f e e t on r e tu r n and 400 f e e t on c a rry in g
s id e , and c lo s e to head and t a i l p u lle y s f o r c e n te r in g .
(5) Make su re t h a t lo a d in g and d isc h a rg e ch u tes a re
p ro p e r ly c o n s tru c te d and a lig n e d and th a t p ro v is io n i s made
to e l im in a te or red u ce th e im pact to a minimum.
(6) S e le c t c o n t ro l equipm ent f o r s t a r t i n g th e
m otors and f o r a u x i l ia r y c o n t ro ls on th e b a s is o f th e type
and s iz e of m otor u sed , th e to rq u e re q u ire d to a c c e le r a te
th e conveyor, and v a r io u s p ro te c t io n s a g a in s t overflow of
m a te r ia l , a c c id e n ta l r e v e r s a l and o v ersp eed in g , ro o f f a l l s ,
m isa lig n m en t, e x c e ss iv e b e l t s l ip p a g e , ch u te c logg ing and
p i l in g o f m a te r ia l a t d isc h a rg e p o in ts , conveyor f i r e s , e t c .
A ll th e s e c o n tro ls a re n e c e ssa ry on b e l t conveyor in
s t a l l a t i o n from th e s tan d p o in t o f s a fe and e f f i c i e n t
o p e ra t io n .
(7) Do n o t use o ld b e l t in g f o r s k i r t i n g . The in
g ra in e d c o a l p a r t i c l e s make i t a c t l i k e sand p ap e r. Use
s p e c ia l s k i r t in g m a te r ia l a v a i la b le from b e l t m an u fac tu re rs .
(8) Check conveyor p a r ts th o ro u g h ly b e fo re b e l t
i n s t a l l a t i o n . These in c lu d e : s t r u c t u r e , p u l le y s , i d l e r s ,
92
lo ad in g equipm ent and s k i r t b o ard s. '■ . / : r-
■ •": (9) P o s i t io n b e l t in g r o l l p ro p e r ly , w hether on a
h o r iz o n ta l or v e r t i c a l s p in d le . ' v »
(10) Unwind b e l t r o l l by power i f p o s s ib le - - from
to p of r o l l i f fe d in to c a rry in g r o l l s , or from th e bottom
i f onto th e r e t u r n ' i d l e r s A w ire -ro p e and p u l l in g p la te
may be used or -the new b e l t may be a tta c h e d to th e o ld in
re p la c e m e n t. - ' ; - . ' .i- ' - : ' ; "
:(11);...-Keep:';t e i t t i g h t a s i t i s u n ro lle d to p rev en t
tw is t in g or te le s c o p in g . Avoid sharp tw i s t s , bends and hard
p u l l in g . - Unwind s lo w ly . • -•-- • - ' :
• (12) P u l l b e l t ' i n t o p o s i t io n by-'w inch;or s im ila r
equipm ent. P u l l even ly a c ro s s e n t i r e w id th of b e l t .
(13) -Exert s u f f i c i e n t te n s io n • in pul-ling th e b e l t
to g e th e r so t h a t th e screw ty p e takeup i s in p roper p o s i t io n
when s p l ic e s a re made. W ith coun terw eigh t g ra v i ty - ty p e
ta k e u p , app ly s u f f i c i e n t f o rc e to move takeup p u lle y from
maximum p o s i t io n to c o r r e c t p o s i t io n . ' .
( I1*) - Check t r a in in g o f b e l t , in c lu d in g r e tu r n ru n
and t a i l p u l le y . : on .
- - (15) Check f o r a lignm en t and ru b b in g -a g a in s t .
lo ad in g and d isc h a rg e ch u te s and s k i r t i n g .
PROTECTION OF BELTS
A fte r p ro p er i n s t a l l a t i o n o f a b e l t conveyor- system ,
i t i s "necessary to ta k e c a re o f a b e l t from p o s s ib le damage
during i t s norm al o p e r a t io n . - The fo llo w in g " p o in ts a re .w orth
n o tin g :"
' (1) P rovide p ro p er ro o f and r ib - s u p p o r ts .
’• • (2) K eep -b e lt head ings f r e e o f w ater and p r o te c t
th e b e l t from dir ip s . ;;
(3 ) V e n t i la te b e ltw a y s"p ro p e r ly .
(4) Reduce f i r e hazards by u sin g approved f i r e -.................................... ...... ' - ' ' - - - " - ' ' - ' - ' - " : X . . . u i
r e s i s t a n t .b e l t s and f i r e - r e s i s t a n t m a te r ia l f o r p u lle y
la g g in g , im pact i d l e r s , s k i r t i n g , e t c . Guard a g a in s t
" fro zen " or hot runn ing r o l l e r s by re g u la r in s p e c t io n .
E s ta b l i s h c o r r e c t te n s io n in th e b e l t . - E lim in a te s p i l la g e
and over lo a d in g . P rev en t p i le u p s a t lo ad in g and t r a n s f e r
p o in t s . ■
(5) P ro v id e p ro p er lu b r ic a t io n , p e r io d ic in s p e c tio n
and prompt r e p a i r to th e damaged b e l t .
BELT MAINTENANCE GUIDES
The beg inn ing and a ls o end of p ro p er b e l t m ain tenance
i s good housekeep ing . T h is does n o t mean c lean in g u p .a
conveyor roadway m onthly or every two m onths. But i t means .
m a in ta in in g a c le a n conveyor system a t a l l t im e s ; th a t i s ,
d a i ly and w eekly in s p e c tio n sch ed u les must be a rran g ed . The
patro lm en on th e conveyor system must be made re s p o n s ib le f o r
making qu ick d a i ly exam inations" to d e te c t dangerous c o n d it io n s .
A ll em ergencies shou ld be re p o r te d im m ediately so t h a t th e
conveyor can be sh u t down and r e p a i r e d . Im proper m aintenance
93
may r e s u l t in conveyor f i r e s . Good m aintenance i s n e c e ssa ry
n o t only from th e s tan d p o in t o f red u c in g breakdow ns, bu t
a ls o from th e s ta n d p o in t o f s a fe ty and c o n t in u i ty of opera
t i o n . The fo llo w in g check l i s t can be used as a gu ide to
d a i ly and weekly in s p e c t io n s . A d d itio n a l ch eck p o in ts may be
needed to f i t p a r t i c u l a r s i t u a t i o n . .
9 4
(1) TROUBLE: B e lt ru n s o f f
clim bs side-w ays on some id le
Cause
(a) Off c e n te r lo a d in g
(b) Conveyor fram e n o t
• s t r a i g h t J
(c) I d le r s ta n d s n o t
cen te red . . , - v
(d) I d le r s s t i c k -
(e ) Loose i d l e r s
( f ) One s id e o f conveyor
i s low
(g) M a te r ia l b u ild s on
i d l e r s a t te rm in a l
p u l le y s .
c e n te r a t a s p e c i f ic p o in t or
\. ; . v ' .y/ vi
Remedy
A d ju st ch u tes and o th e r lo a d
ing d ev ices to p u t lo a d in th e
c e n te r and in th e d i r e c t io n of
b e l t movement.
S tra ig h te n acco rd in g to need .
Same c o r r e c t io n as above.
L u b ric a te p ro p e r ly .o r r e p la c e .
R e p o s itio n and f a s te n s e c u re ly .
L evel up and s e c u re . , •: v
Improve m a in te n an ce ;and r i n s t a l l
b e l t c le a n in g equipm ent r.v.”
95(2) TROUBLE:: B e lt ru n s o f f a t t e rm ln a l..
Cause Remedy,
■ P u lle y or approach ing : v . .
i d l e r s n o t in l i n e . A lig n p ro p e r ly . •. , , .
(3) TROUBLE: B e lt w anders a t random.
(a) Too s t i f f because of Use b e l t w ith more t r a n s v e rs e
d es ig n f l e x i b i l i t y o r add e x tra
a l ig n in g a id s and t i l t tro u g h -
ing id l e r s ahead n o t over 2
v : v;: ;: ; , d e g re e s . -
(b) Too s t i f f because o f Allow; p roper .b reak -in tim e ,
new ness. Reduce b re a k - in tim e by l e t t i n g
b e l t s tan d loaded over n ig h t .
(4) TROUBLE: B e lt s t r e t c h e s e x c e s s iv e ly . S p lic e s weaken
p rem a tu re ly . Cuts or b reak s e n la rg e q u ic k ly . .
E xcess s t a r t i n g te n s io n In c re a s e speed . Keep tonnage
or excess b e l t te n s io n th e same or red u ce tonnage a t
th e same speed . Even up fe e d -
in g r a t e . D ecrease drag by p ro
p er i d l e r lu b r i c a t io n , r e p la c e
ment of worn ou t i d l e r s and
rem oval of s p i l l a g e m a te r ia l .
Use minimum w eight o f co u n te r
b a lan c in g w e ig h ts . R ep lace w ith
low er e lo n g a tio n b e l t .
96(5) TROUBLE: B e lt edges worn or gouged. .
Cause
(a) Rubbing.
(b) O ff-c e n te r lo a d in g .
M isalignm ent, d e f e c t -
(: ) i v e .s e l f - a l i g n i n g
• ■ i d l e r s . . '
(6) TROUBLE: E x cess iv e to p
(a) Poor- cover., q u a l i ty .
(b) Slow ru nn ing or s tu c k
m isa lig n ed r e tu r n
r o l l s .
(c) Poor lo a d in g .
/ '• \ . , . —\ ! i ti ■■ . . ' . » - . • ‘ •, -
(d) P i l in g up a t head
■ ) and t a i l p u l le y s .
Remedy
R e a lig n b e l t i f n e c e ssa ry .
Remove a l l o b s t r u c t io n s .
R e p o s itio n lo a d in g and
t r a n s f e r c h u te s . A lign
b e l t s ; R epair or r e p la c e ;
f a u l t y ; i d l e r s .
cover w ear.
R eplace b e l t w ith one
having a*, h ea v ie r cover
o r h igh q u a l i ty cover
m a te r ia l . : , .
C le a n ;up b e l t w i th .b e l t •
c le an in g d e v ic e s .: R ea lig n
r e tu r n r o l l e r s . Use ru b b er
d is c r e tu r n r o l l s , i f ;•
n e c e s s a ry .
Feed c o a l onto b e l t in th e i
s a m e .d ire c tio n and a t th e
same speed o f th e b e l t .
Keep c lean in g and lo ad
p ro p e r ly .
9 7
(7) TROUBLE: E x cess iv e bottom cover w ear.
Cause
(a) B e lt s l ip p in g o f f
d r iv e p u l le y .
(b) S tic k in g r o l l e r s . -
(c) Excess tro u g h in g
i d l e r s .
(d) B o lt heads pro-,
tru d in g above
lag g ed d r iv in g
drum s.
(e) M a te r ia l b u ild s up
due to s p i l l a g e or; ‘ ’ r 1" " • ‘ "V - k-' ‘.j. '
o th e r re a s o n s .
Remedy
A djust takeup d ev ices to in
c re a se te n s io n . In c re a s e a rc
of c o n ta c t w ith snub p u lle y
o r tandem d r iv e .
' S e rv ice and lu b r i c a t e p ro p e r ly .
T i l t n o t over 2 d eg rees from
u p r ig h t .
T ig h ten b o l t s , r e p la c e worn
o u t la g g in g .
Do n o t lo ad b e l t to o h e a v ily .
Use good ch u te lo ad in g
f a c i l i t i e s . Use s c ra p e rs ( to
c le a n b e l t ) ahead of t a i l
p u lle y on r e tu r n ru n . Use
p la te or v u lc a n iz e d s p l ic e s to
check le a k a g e . In sp e c t and
c le a n r e g u la r ly .
(8) TROUBLE: The c a rc a s s b re a k s .
(a) -Im pact. ~ < Load a t f l a t an g le a t b e l t
speed and In l i n e w ith b e l t .
Use cush ion i d l e r s .
98
Cause
(b) M a te r ia l trap p e d
betw een ;b e l t a n d ,
p u lle y ..
(c ) M a te r ia l b u ild in g up
on p u l le y s .
(9) TROUBLE: C rescen t b:
Mildew
Remedy
P lace s c ra p e rs ahead of t a i l
p u lle y on r e tu r n s id e .
Use p roper b e l t c le a n e rs .
:s , o r mushy s p o t s .
Use mildew in h ib i te d b e l t s .
(10) TROUBLE: C rossw ise
(a) B e lt edges fo ld in g
up.
(b) Poor p o s i t io n in g of
i d l e r s n ex t to head
p u lle y - to o c lo se
or to o h ig h .
(c) Too sharp v e r t i c a l
cu rv e . 11
(11) TROUBLE: Lengthw ise
to p co v ers i n t a c t .
ak a t edge.
Use l im i t sw itch es to s to p
ex c ess iv e s h i f t in g of b e l t .
Remove o b s tru c t io n s and p ro
v id e ample s id e c le a ra n c e .
R e lo ca te or r e a d ju s t i d l e r s
or p u lle y p o s i t io n .
In c re a s e curve r a d iu s to r e
duce s t r e s s e s on i d l e r s and
b e l t .
c a rc a s s b reak bu t bottom and
99
Cause Remedy
(a) B e lt ru n n in g o f f
and fo ld in g back . Use l i m i t sw ith c e s .
(b) Im pact. . : Reduce im pact.
(12) TROUBLE: S hrinkage of b e l t .
M o is tu re . ... ;' S p l ic e - in e x tra p ie c e w ith -
- v .1 tak eu p d e v ic e . h a l f down. -
(13) Bowing up th e E lim in a te o i l sou rce or use
c e n te r o r sp o t an o i l r e s i s t a n t b e l t . To
s w e l l in g . r e l i e v e c o n d itio n in th e
e x is t in g b e l t , groove le n g th -
- - l v . - w ise w ith t i r e -g ro o v in g to o l .
(14) TROUBLE: B l i s t e r in th e c o v e r .
F in e m a te r ia l working
U n to c u ts or p u n c - . ; Spot r e p a i r and v u lc a n iz e
• 1 t u r e s . . ' .. th e p a r t .
(II?) TROUBLE: C rossw ise b reak s of m e ta l f a s te n e r b e l t
jo in t s . ... 1 v... ■
B e lt f a s te n e r Use s h o r te r f a s te n e r s or
p la te s to o lo n g . in c re a s e p u lle y s iz e , or b o th .
_ i - ; CHAPTER V II I - - : : .
CONCLUSIONS; AND SUGGESTIONS FOR FUTURE STUDY ' ‘
CONCLUSIONS
: : ; (1) ;.¥ h en f i r s t c o n s id e r in g th e i n s t a l l a t i o n o f b e l t
conveyors, one shou ld c a r e f u l ly e s tim a te th e c o a l r e s e rv e s
a v a i la b le in o rd er to a s s u re t h a t d e p re c ia t io n c o s ts w i l l
h o t be e x o rb i ta n t and to d ec id e w hether to i n s t a l l com plete
b e l t conveyor hau lage or a com bination of b e l t s and o th e r
hau lage system s.
(2) G reat c a re must be ta k en w ith th e i n s t a l l a t i o n
of a l l m a in - lin e and o th e r im p o rtan t conveyor s t r u c t u r e s .
These should be equipped w ith p ro p er e l e c t r i c a l o verload
d ev ices and sequence and s lip p a g e c o n tro ls to p re v e n t “p i l e -
ups'* of c o a l a t t r a n s f e r p o in ts . The o p e ra tin g c o s ts of th e
b e l t hau lage system w i l l be h ig h e r w ith f a u l ty i n s t a l l a t i o n
and m ain tenance . v. ■ •
(3) For econom ical o p e ra tio n o f conveyor h au lag e ,
th e b e l t w id th shou ld n o t be w ider th a n n e c e ssa ry and I t
should be ru n as f a s t as p o s s ib le w ith in th e ran g e of r e - c - n r : r .
commended b e l t sp eed s .
100
-U (h) A ll th e b e l t hau lage c o s t components v a ry w ith
th e b e l t le n g th ; some v ary d ir e c t ly ^ -T o r example th e owner
sh ip and energy c o s ts ; some v a r y : p a r t i a l l y and in s te p s , as
w ith o p e ra tin g ex p en ses . T h ere fo re ,' th e c o s t per to n w i l l
be somewhate p ro p o r t io n a l to th e le n g th , and th e c o s t p e r
to n -m ile w i l l be re a so n a b ly c o n s ta n t , ten d in g to d ec rease
s l i g h t l y - i f a t a l l - w ith in c re a s e in le n g th .
(5) The ow nership and energy c o s ts a re d i r e c t l y
p ro p o r t io n a l to th e tonnage c a r r ie d ; however, th e o p e ra tin g
and m ain tenance c o s ts rem ain f a i r l y s te a d y . Hence w ith in
c re a s in g tonnage c a r r ie d , th e c o s t per to n w i l l f a l l
s t e a d i ly .
(6) The e f f e c t o f in c re a s in g g ra d ie n t a g a in s t th e
lo ad w i l l be to in c re a s e c a p i t a l and energy ch a rg es as in
i t i a l c o s t o f equipm ent r i s e s because of th e more c o s t ly
b e l t r e q u ire d to w ith s ta n d th e h ig h er s t r e s s e s and e x tra
horsepower needed to e le v a te th e m a te r ia l .
(7) The o p e ra tin g c o s ts f o r o p e ra tin g la b o r and
m ain tenance la b o r w i l l rem ain f a i r l y c o n s ta n t up to a
hau lage d is ta n c e o f abou t one m ile ; beyond t h i s , th e la b o r
c o s t may in c re a s e in s te p s f o r each a d d i t io n a l m ile or
f r a c t i o n th e r e o f .
The o p e ra tin g and m ain tenance la b o r c o s ts depend,
a l s o , upon th e d eg ree o f au tom ation a t th e lo a d in g and
101
d isc h a rg e p o in ts and on th e number of s e p a ra te conveyor u n i t s
o p e ra tin g in th e same v i c i n i t y . This i s because more u n i t s
can be o p e ra ted ' and m a in ta in ed by th e sam e.crew of men and
i f th e s e u n i t s a r e c o n c e n tra te d a t one p la c e , th e r e s u l t in g
o p e ra tin g and m aintenance c o s ts can be d i s t r ib u t e d among a l l
u n i t s . I f th e d is ta n c e between s e p a ra te u n i t s in c re a s e s ,
s e p a ra te m ain tenance crews must be employed as i t w i l l n o t be
p o s s ib le f o r th e same crew to lo o k a f t e r a l l th e u n i t s .
FUTURE TRENDS ./ • ’
(1) As la rg e r c o a l m ining m achines a re used and
p ro d u c tio n becomes more c o n c e n tra te d , more a t t e n t io n must be
p a id to hau lage problem s to red u ce u n i t c o s ts .
(2) New p o ly e s te r s y n th e t ic f i b e r m a te r ia ls w i l l be
developed in th e f u tu r e to w ith s ta n d h ea v ie r s t r e s s e s , whence
i t w i l l be p o s s ib le to use lo n g e r s in g le conveyor u n i t s .
A lso , th e in v e n tio n of.som e kind o f m a te r ia l to be used in
b e l t s must be made to guard a g a in s t e l e c t r o s t a t i c sp a rk s
produced when th e b e l t s a re o p e ra ted a t h igh speeds and
th e reb y overcoming one cause o f conveyor f i r e s .
(3) I t w i l l become a s ta n d a rd p ro ced u re in th e
f u tu r e to use on ly f i r e - r e s i s t a n t b e l t in g f o r a l l under
ground conveyor hau lage i n s t a l l a t i o n s .
(^ ) Use of deeper tro u g h in g i d l e r s f o r underground
t r a n s p o r ta t io n o f c o a l w i l l be in tro d u c e d in th e n ea r f u tu r e .
102
(5) Improvements and. m o d if ic a tio n s in th e e x te n s ib le
b e l t s , a r t i c u l a t e d and cascade ty p e conveyor equipm ent; and
s in g le b e l t conveyor u n i t s -which can c lim b , tu rn and have an
alm ost u n lim ite d number of d isc h a rg e p o in ts w i l l be used f o r
co a l t r a n s p o r ta t io n in m ines.
(6) The rope-fram e conveyor hau lage (n o t c a b le - b e l t )
system may become alm ost s ta n d a rd fo r many underground s e r
v ic e s and may f in d growing use in o th e r in d u s t r i e s f o r t r a n s
p o r ta t io n o f b u lk m a te r ia l s .
(7) . . . . I t i s expected th a t c a b le - b e l t conveyors w i l l
be used in th e U. S. c o a l m ining in d u s try .
SUGGESTIONS FOR FUTURE STUDY
The fo llo w in g s tu d y shou ld be made re g a rd in g con
veyor hau lage in m ines:
(1) P re c is e in fo rm a tio n must be o b ta in ed f o r es
ta b l i s h in g s ta n d a rd c o s t e s tim a tio n p ro ced u res f o r o th e r
ty p e s of conveyor hau lage system s such as ro p e -fram e , c a b le -
b e l t , pan or p l a t e , sh a k e r , b r id g e , c h a in , a r t i c u l a t e d and
cascade conveyors. The l im i ta t io n s o f th e s e ty p e s o f con
veyor hau lage system s f o r e f f i c i e n t and economic o p e ra t io n
must a ls o be a s c e r ta in e d .
(2) A com parison o f owning and o p e ra tin g c o s ts of
d i f f e r e n t k in d s of conveyor and o th e r hau lage methods should
103
be made f o r v a r io u s le n g th s , c a p a c i t i e s , g r a d ie n ts and o th e r
■working c o n d itio n s ; and economic l im i ta t io n s f o r each type
of hau lage shou ld be d e te rm in ed .
(3) The modern e le c t r o n ic com puters shou ld be in
v e s t ig a te d f o r p o s s ib le a p p l ic a t io n s in th e s o lu t io n of con
veyor hau lage p rob lem s, e s p e c ia l ly th o se th a t a re r e p e t i t i v e
or i t e r a t i v e in n a tu r e . These in c lu d e d e te rm in a tio n of
b reak -even p o in ts f o r owning and o p e ra tin g conveyor haulage
system s f o r d i f f e r e n t com binations of g ra d e s , le n g th s , w id th s ,
sp eed s, e t c . , and th e s e must be compared w ith o th e r haulage
system s. A ll th e s e r e s u l t s shou ld enable management to make
b e t te r d e c is io n s in th e s e le c t io n and d e s ig n o f d i f f e r e n t
haulage system s. .
104
BIBLIOGRAPHY AND SELECTED REFERENCES
PERIODICALS
1 . “New p ro d u c ts d ig e s t - .C lim b in g and tu rn in g con
v e y o rs ," E n g in eerin g and Mining J o u r n a l . Vol 163 ,
No h, A p r i l 1962, p . 53.2. E. R . T r a x l e r , "Conveyor b e l t horsepow er and o p e ra tin g
d is ta n c e s co n tin u e to In c re a se in f u tu r e . "
E n g in ee rin g and Mining J o u r n a l . V ol 162, No 8 ,
August 1961 , pp . 86- 7 .
3 . A. W. Asman, "B e lt hau lage econom ics," Coal Age.
Vol 65 , No 10, O ct. I9 6 0 , pp. 112-14 , 116.
•4 . D. C. Jo n es , "H andling lump co a l on b e l t s , "
M echan iza tion . Vol 24, No 9, S ep t. I9 6 0 , pp. 73 -5 .
5. H. W. Meador, "New developm ent in b e l t h au lag e ,"
: : . Mining Congress J o u r n a l . Vol 4 6 , No 9 , S ep t, i 960 ,
p p . 86-9. .. . , . ■•6 . W. A. McCurdy, "Track fo r long h a u l ," M echan iza tion ,
Vol 2 4 , No 8 , August i 960 , pp . 69- 7 2 . . ;
7* W. A. McCurdy, "Problem s o f new mine d e s ig n ,"
M ech an iza tio n . V ol 25, No 6 , June i 960 , pp. 43-53*
8. W. G. H allam , "L ab o ra to ry assessm en t o f conveyor b e l t
p erfo rm ance." C o l l ie ry G uard ian . Vol 200, No 5 l6 4 ,
A p r i l 7 , I9 6 0 , pp. 391-4 .
105
“C ontinuous t r a n s p o r ta t io n in s p e c ia l mine la y o u t
paces high, p r o d u c t iv i ty ,” Coal /lee . Vol 65 , No 4 ,
A p r i l I9 6 0 , pp . 72 -8 .
J . R. Brandon, “T ips on b e l t conveyor m a in te n an ce ,”
G oai Age. Vol 65, No 3 , March I9 6 0 , pp. 100-2 , 104.
D. S,. Kedick and T. Furman, "Review of b e l t conveyors
w ith s t e e l hau lage m embers,” C o l l ie ry E n g in e e rin g ,
Vol 37, No 431 , J a n . I9 6 0 , pp. 17-24 .
N. Brook, “E s tim a tio n of conveyor s p e c i f i c a t i o n s ,”
C o l l ie ry E n g in e e rin g . Vol 36, No 429 , Nov. 1959,
pp. 480-92 .
G. H. V ulcan , “Changes in conveyor,b e l t p r o p e r t ie s
w ith s e r v i c e ,” C o l l ie ry E n g in ee rin g . Vol 36,
No> 2 4 , June 1959, pp . 2 4 l-6 .
D.. B; Shupe, "E xperience w ith flam e r e s i s t a n t b e l t in g
Mining Congress J o u r n a l . Vol 45 , No 4 , A p r i l 1959,
-PP* 59-62.
“Low. speed and low c o s t b e l t s f o r h o is t in g m en,"
Coal Age, Vol 63 , No 7A, M id-July 1958, p . 79-
"Three y e a rs of h o is t in g w ith P r in c e s s C a b le -b e l t ,"
Coal Age, Vol 6 3 , No 9 , S ep t. 1958, pp. 106-8 .
" E le c tro n ic conveyor c o n t r o l s , ” Coal Age. Vol 63 ,
No 8 , August 1958, pp . 106-7 .
H. J . A tk in so n , J . F . C arr and E. H oyle, "Development
and use of f i r e - r e s i s t a n t b e l t i n g ," C o l l ie ry
G uard ian , Vol 196 , No 5072, May 8 , 1958, pp . 567-73
107
19. T. D. E l l i o t , “Development of c a b le - b e l t co n v e y o rs ,”
I ro n and Coal T rades Review. V ol 176, No 4689,
A p ri l 4 , 1958, pp. 809-13.
20. "B e ltm an 's g u id e ,” Coal Age, Vol 6 ^ T No 3 , March 1958,
pp. 122-27.
21. A. E. F lo w ers , "Rope b e l t s b o o stin g e f f ic ie n c y a t
Peabody," Coal Age, V ol 62 , No 2 , Feb. 1958,
pp. 124-34.
22. E. F . H ew ett, " C a b le -b e lt conveyor and i t s a p p l i
c a t io n s ,"
P ro c eed in g s . No l8 4 . Dec. 1957, PP. 4 4 -8 .
23. R. F . Knobloch, "How to g e t more and b e t t e r s e rv ic e
from b e l t co n v ey o rs ," Coa^ ^ g e . Vol 62 , No 8 ,
August 1957, pp . 76-9•
24. "B e lt t h a t goes around c o rn e r s ," M echan iza tion .
Vol 20, No 10, O ct. 1956, pp. 72-3•
25. R. U. Jackson , "Conveyors V s. t r a c k h a u la g e ,"
Mining E n g in e e rin g . V ol 4 , No 9 , S ep t. 1952,
pp. 866-9 . .
BOOKS AND MISCELLANEOUS ARTICLES
1 . E. R. D revdah l, P r o f i ta b le use of ex cav a tio n eq u ip - >
d e n t , Tucson, A r iz . , D ese rt L a b o ra to r ie s , T ec h n ica l
P u b l ic a t io n s , 1961 .
2 . J . J . S h ie ld s and J . J . Dowd, "M echanical m ining in
bitum inous c o a l m in e s ." P ro g re ss r e p o r t No 9 -
Face h a u la g e , USBM I n f e r . C irc . No 7978, I9 6 0 .
108
3. J . ¥ . Hardy, B e lt conveyor co m p u ta tio n s . H a ls ted
S t r e e t , C h icago-9> Goodman M anufacturing Co . , I9 6 0 .
U-. ,,RopexH - Goodman*s e x te n s ib le b e l t conveyor and
R o p e-b e lt conveyorT Goodman*s c a ta lo g No G-123
and G-150.
5. M a te r ia ls h and ling handbook, New York, Ronald P re ss
Co. , 1958.
6 . C. E. B u l l in g e r , E n g in ee rin g economy. New York,
McGraw-Hill Book Co. , 1958.
7 . R e la tin g roadway conveyors to i t s d u ty . N.C.B. I n f o r .
B u l le t in No 58 /197 , Grosvenor P la c e , London, S.W. 1 ,
N a tio n a l Coal B oard, 1958.
8 . L in k -b e lt C atalog No 1000. 233, Broadway, New York 7 ,
L in k -B e lt Co. , 1958. /:...
9 . H. E. P ru n e r , AH about b e l t in g r Handbook M, 63lH—B -l
and 17 , R o c k fe lle r C e n te r , New York 20, U nited
S ta te s Rubber Co. , 1957.
10. N a tio n a l E l e c t r i c a l M anufactu rers A sso c ia tio n
s ta n d a rd s f o r m ining b e l t conveyors, C irc. No MB-1,
1956.
11. P e rm iss ib le mine equipm ent approved du ring th e
ca len d e r y e a rs 1955-56. USBM I n f o r . C i r c . No 7840.
12. R/M E n g in eerin g gu ide f o r conveyor b e l t i n g T P a s s a ic ,
' New J e r s e y , R aybestos-M anhattan , I n c . , 1956.
1 3 . W. G. Hudson, Conveyors and r e l a t e d equipm ent. New