Belt Conveyor 3

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Belt Conveyor

The belt conveyor is an endless belt moving over two end pulleys at fixed positions

and used for transporting material horizontally or at an incline up or down. The main

components of a belt conveyor are:

1. The belt that forms the moving and supporting surface on which the

conveyed material rides. It is the tractive element. The belt should be

selected considering the material to be transported.

2. The idlers, which form the supports for the carrying and return stands of the

belt.

. The pulleys that support and move the belt and controls its tension.

!. The drive that imparts power to one or more pulleys to move the belt and its

loads.

". The structure that supports and maintains the alignments of the idlers and pulleys and support the driving machinery.

#ther components include:

1. Loading chute or feeder chute that organises the flow of material and directs it on

the belt conveyor.

2. Take-up-device which is used to maintain the proper tension of the belt for

effective power transmission.

. Belt cleaner that $eeps the belt free from materials stic$ing to the belt.

!. Tramp removal device, which is optionally used in case the conveyed material

bears the chance of having tramp iron mixed with it and subse%uent handling of thematerial, demands its removal.

". Continuous weighing device for constantly measuring the load being carried by

the conveyor belt.

&. Discharge chutes to guide the discharged pro'ectile to subse%uent conveyor or

other receiving point.

(. Surge hopper and feeder , which is essential for supplying material to the conveyor

at uniform rate when the supply of material is intermittent.

). Tripper arrangement to discharge material at different point or to other device.

Application

*onveyor belts are widely used in mineral industry. +nderground mine transport,

opencast mine transport and processing plants deploy conveyor belts of different

$inds to adopt the specific 'ob re%uirements. The main advantages of conveyor belt

system are:

1. wider range of material can be handled which pause problems in other

transportation means. -elt conveyor can be used for abrasive, wet, dry, stic$y or

dirty material. The lump size of the transported material is limited by the width of

the belt. -elts up to 2" mm wide are used in mining industry.

1



2. /igher capacity can be handled than any other form of conveyor at a considerably

lower cost per tonne $ilometre. *onveyor belts with capacity of 11t0h and even

higher can be deployed to match with higher capacity mining machinery.

. onger distances can be covered more economically than any other transportation

system. single belt conveyor or a series of belt conveyors can do this. -elt

conveyors can be adopted for crosscountry laying.

!. -y the use of many forms of ancillary e%uipment such as mobile trippers or

spreaders bul$ material can be distributed and deposited whenever re%uired.

". 3any other functions can be performed with the basic conveying li$e weighing,

sorting, pic$ing, sampling, blending, spraying, cooling, drying etc.

&. 4tructurally it is one of the lightest forms of conveying machine. It is

comparatively cheaper and supporting structures can be used for many otherwise

impossible structures such as crossing rivers, streets and valleys.

(. The belt conveyor can be adopted for special purposes 5fire resistant, wear

resistant, corrosion resistant, high angle negotiation etc.6 and can be integrated

with other e%uipment.

). It can be horizontal, incline or decline or combination of all.

7. 3inimum labour is re%uired for the operation and maintenance of belt conveyor

system.

1. In underground mine transport, belt conveyor can be used in thin seams as it

eliminates the roc$ wor$s that might otherwise be re%uired to gain haulage height.

3oreover, belt conveyor can provide continuous haulage service from pit bottom

to the surface.

The limitations of conveyor belt are:

1. The loading and transfer points need to be properly designed.

2. 8umbers of protective devices have to be incorporated to save the belt from getting

damaged by operational problems.

. The belt needs higher initial tension 5!29 of useful pull6.

!. The use of belt is restricted by the lump size. If the maximum diagonal of a

irregular lump is X then the belt width 5-6 is approximately given by:

2..+≥ Xa B

where, -: -elt width, mm

: ongest diagonal of irregular lump, mm

a: ;actor to account for grading. a is ta$en as 2." for graded

material and for ungraded material. /owever, for particular

material these values must be properly estimated.

". *onveying of stic$y material is associated with problems of cleaning and discharge

causing poor productivity.

&. /igher elongation of the belt 5!9 elongation may ta$e place at the wor$ing load6.4ome of the applications of belt conveyors are shown in ;igures below:

2



evel or inclined *onveyor receiving material at tail end and discharging at head end.

evel *onveyor receiving material at any point through travelling /opper and

discharging at head end.

evel and inclined *onveyor receiving material at and near tail end, having vertical

curve to incline, and discharging at head end.



evel and inclined *onveyor with chute. 3aterial received from bins too close to

elevated head end to permit use of vertical curve.

Inclined and level *onveyor receiving material at tail end and discharging from level

section through a movable Tripper.

evel *onveyor on raised structure with doublewing Tripper forming storage piles

on both sides of *onveyor.

!



Inclined *onveyor receiving material at tail end and discharging at several points

through a series of fixed Trippers.

evel *onveyor with 4tac$er or -oom *onveyor mounted on revolving turntable soas to discharge to both sides of *onveyor.

INFORMATION REQUIRED TO DESIGN A BELT CONVEYOR

1. ength of conveyor from centre to centre of end pulleys.

2. Inclinationlevel or inclined. <ither degree of inclination, or distance to be lifted or

lowered.

. verage capacity per hour.

!. 3aximum capacity per hour.

". 3aterial to be conveyed, and weight per cubic foot. &. verage size of material.

(. 4ize of largest pieces and percentage in feed.

). 5a ) 8ature of material dry or wet 5moisture content6.

5b6 brasive or corrosive=

7. /ow material is to be fed to the belt and particulars of feed point or points.

1. /ow material is to be discharged from the belt i.e. overhead pulley or by trippers,

and particulars of discharge points.

11. >eneral indication of supporting structure.

"



12. ?ower available for driving. If by .*. electric motor, state voltage, phase and

fre%uency. If @.*. motor state voltage.

Items 1 and 2 determine the suitability of belt conveyors, since inclination is a

limiting factor. Items 1( determine the speed and width of the conveyor belt, the

power needed for the drive, the type of drive, the number of belt plies, size of pulleys,

shafts and spacing of idlers. Items )1 determine the %uality and thic$ness of the

rubber cover on the belt.

Suitability o a B!lt Con"!yo#

Table I shows the maximum safe inclination for troughed belt conveyors handling

various bul$ materials and for convenience, chart shows the rise in feet

corresponding to the horizontal distances at various angles of inclination.

3aterial ngle Aise in

m per

1 m

3aterial ngle Aise in

m per

1 m

*ementoose 22B !.! *oal-it 4lac$ 2B !2.!

*lay;ine @ry 2B !2.! *oalnthracite 1&B 2).&

*layCet 1)B 2." *o$e oven run 1)B 2."

*oal3ine Aun 1&B 2).& *o$e4ized 1&B 2).&

*oal4ized 1&B 2).& *o$e-reeze 1)B 2."

*oncreteCet 1"B 2&.) #re4ized 1)B 2."

<arthoose 2B &.! ?ac$ages?aper

Crap.

1&B 2).&

>lass-atch 21B ).! Aoc$;ine

*rushed

22B !.!

>rain 1&B 2).& Aoc$3ixed 1)B 2."

>ravel-an$ Aun 1)B 2." Aoc$4ized 1)B 2."

>ravel4creened 1"B 2&.) 4alt 2B &.!

>ypsum?owdered 2B !2.! 4and@ry 1"B 2&.)

lime?owdered. 2B !2.! 4and@amp 2B &.!

limestone 1)B 2." 4andTempered

;oundry

2!B !!."

#re;ine 2B &.! 4ulphur

?owdered

2B !2.!

&



#re*rushed 1)B 2." Cood*hips 2r ".7 >

4hould the horizontal distance be more than sufficient for the re%uired rise, it may be

more economical to run the first section of the conveyor horizontally, and incline it

upwards at the discharge end, rather than use a smaller angle of inclination for the

entire length.

In such a case, the transition from the horizontal to the inclined sections must be made

by a vertical curve, to ensure that the belt does not lift off the idlers.

B!lt Con"!yo# Typ!$

Permanent: This type of conveyors is installed for the life of the

mine. They are used in main line, slope, long overland installation,

preparation plants and stoc$piles.

Portable: These are characterised by relative ease of assembling and

disassembling to facilitate advances and recovery in development and

retreat operations in underground mining. ?ortable conveyors mounted

on crawler or wheels are also used in mechanised %uarries and surface

mines.

Shiftable: +sed in continuous surface mining this type of conveyor is

mounted on s$id or supporting structures aligned together and the

whole can be shifted transversely to follow the advancing wor$ing face.

High Angle Conveyor: These are special type of conveyor belt

arrangement used for negotiating steeper angle of inclination. 4uch

belts can wor$ in slope up to (). 4andwich belt conveyor is a type

of such belt conveyor.

Cable Belt Conveyor: Chere the belt is carried on moving wire ropes and

the tractive force is applied through the rope to the belt is $nown as

cable belt conveyor. 8*# 5in collaboration with ;rance6 is using

such system for long distance conveying of bauxite in their mines in

#rissa.

D!$c#iption o Co%pon!nt$

Belt

The belt consists of a carcass covered from all sides with a filler material li$e ?D*

and neoprene as shown in ;igure 1.

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Top *over

-ottom *over

5*arrying 4ide6

58on*arrying 4ide6

<nd *over <nd *over

*arcass

;igure 1 *onstruction of conveyor belt.

Essential Properties

The belt wor$s as a tractive element as well as loadcarrying element. It may be used

for different $ind of material transportation at a higher speed 5 &) m0s6. ;or this purpose the belt need to have the following essential properties:

1. ;lexibility

2. Transverse rigidity

. ow mass per unit length

!. /igh strength

". 4implicity and inexpensive

&. onger life

(. 4hould not stretch under normal wor$ing stresses ,i.e., low relative elongation.

). Cear resistant

7. ;ire resistant

Aecommended maximum belt speeds are given as shown in Table 1

4peed

5m0sec6

4peed

5fpm6

Cidth 5mm6 Cidth

5inches6

*oal, damp clay, soft ore,

fine crushed stone, #ver

burden and earth

2.2

.!)

!.&!

".)

!

&

)

1

!"(.2

&7.&71!.!

1&&.)1"2!

1)2).)2!1

1)

2!&

!2&

(27"

/eavy, hard, sharp edged

ore. *oarse crushed stone

1.(()

2."!

.!)

"

"

&

!"(.2

&7.&71!.!

over 71!.!

1)

2!&

over &

The carcass can absorb the longitudinal tensile stresses and ma$e the belt rigid

transversely. ;iller protects carcass against moisture, mechanical damage, abrasion

and combine the carcass into an integral body forming top cover and bottom cover.The filler can be synthetic rubber or polymer li$e ?D* with ade%uate additives for

)



getting particular expected characteristics. The carcass can be a fabric type with plies

of fabric or steel chord type.

fabric ply has a longitudinal thread called warp and a transverse thread called weft.

The fabric plies are made of capron, nylon or lavsan etc. The longitudinal member of

the carcass transfers the tension. -oth the warp and weft carry the load via the cover.

The cover while protecting the carcass from external damage bear the impact and

abrasion at the feeding points and wear at the cleaning points. ;igure 2 shows the

cross section of the types of conveyor belt.

Aubber Interply

Figure 2 *ross section of a multi ply conveyor belt.

The belt ends are 'oined together by mechanical means or by vulcanising. The belt

needs to be protected from damage of its sides that may occur due to sway of the belt.

In case of belt carrying wet stic$y material fixtures for cleaning the belt should be

properly selected. 3aterials coming on to the return side of the belt needs to be

arrested from coming under the end pulley by ade%uate scrapers. s shown in the

;igure ! belt cleaners are used to clean the return side of the conveyor belt. These

cleaning belt can be of D shape as well.

Figure 3 -elt scrapers

s shown in the ;igure 5a6, the pow bladeEs 2B leading edge FspiralsF debris off the

returnside belt surface. There are specially designed belt cleaners for the tail pulley,

they are engineered to clean the inside of the belt so roc$s, lumps and other debris

never get the chance to damage the pulley, belt, splices or lagging. 8ormally plows

are easy to install on virtually any conveyor structure, and come with universal

mounting brac$ets. Though there are suppliers of such scrapers, these can be

fabricated at the mineGs wor$shop.

The diagonal deflector plow 5;igure a6 is installed on a !"B angle across the belt to

discharge debris to one side of the belt. In such cleaners the blade is installed in a

fixed position, eliminating bouncing problems associated with some floating style

plows.

7



Twinbladed plow 5 ;igure b6 is designed to clean belt in both directions of travel.

This cleaner discharges material to either side of the belt. It is installed securely to

conveyor structure and can wor$ on conveyors with severe belt vibration.

CONVEYOR BELT FASTENERS

#ne of the important components that re%uire attention in maintaining services of beltconveyor is the conveyor belt fasteners. 4election of fasteners should consider

re%uired performance, expected life and ease of installation and maintenance so that

higher availability of the belt conveyor is ensured.

There are different types of fasteners. 3echanical fasteners are commonly used in

underground coal mining. The re%uired rating of the mechanincal fasteners is

calculated based on the re%uired belt tension and it may be upto 2& $80m of belt

width.

#ne such fastener is ;lexcoH 4A 4calloped <dge AA) belt fastener, designed

for use on mainline and panel belts with mechanical fastener ratings up to 1," ?IC

52&$80m6. The )rivet pattern, along with the scalloped edge design, ensures %uality performance in hightension applications.

Figure ! 3echanical -elt 'oint

;asteners are available with selfsetting rivets which allow to install %uic$ly from the

topside of the belt. 3ost important in belt fastening is to ta$e care that the plates must

be accurately positioned to get perfect edges and stress distribution should be uniform

along the 'oints.

<ffectiveness of maintenance will be enhanced by provision of ade%uate and

improved tools for carrying out the 'ob. 3anagement should encourage innovation of

wor$ers for ma$ing wor$ tools or improvement of wor$ environment and safety.

Idlers

In a conveyor belt installation different types of idlers or roller supports are used. The

idlers are re%uired for proper support and protection of the belt and proper support of

the load being conveyed.Idlers are designed with different diameters and are provided

with antifriction bearings and seals, and are mounted on shafts. ;rictional resistanceof idlers influences the belt tension and conse%uently the power re%uirement.

1



Idlers are mounted on a support frame, which can be shiftable or permanent. The

carrying side of the belt is supported on the carrier rollers sets. set of three rollers

are arranged to form a trough for the troughed belt conveyor. The return side of the

belt is supported on straight return idlers. The spacing of the idlers is determined

based on the belt sag between the idlers. The sag depends on the belt tension, belt

width, belt properties and the payload per meter of the belt. The idlers are specified by its length and diameter. These parameters are selected based on the re%uired belt

speed for the particular width of the belt.

Figure 5 @ifferent types of roller supports

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Figure 6 4elf aligning idler

Idlers are classified as shown in Table 2

Table 2 Idler *lassification.

*lassification @iameter 5inches6 -elt Cidth 5Inch6 @escription

-!

-"

!

"

1) J !)

1) J !)

ight duty

ight @uty

*!

*"

*&

!

"

&

1) J &

1) J &

2! J &

3edium @uty

3edium @uty

3edium @uty

@"

@&

"

&

2! J (2

2! J (2

3edium @uty

3edium @uty

<& & & J 7& /eavy @uty

12



<( ( & J 7& /eavy @uty

*losely spaced impact idlers with rubber cushions are used the support the belt at the

loading point, below the s$irt board. ;igure (.

<8@ ?+<K

<8@ ?+<K

48+- ?+<K

-<8@ ?+<K

A<T+A8 I@<A4*AAKI8> I@<A4

>ADITK TL<+?

TAI??<A

4LIAT -#A@

I3?*T I@<A4

@I4*/A>< /##@

4*A?<A

-<T *<8<A

<8@ ?+<K

<8@ ?+<K

48+- ?+<K

-<8@ ?+<K

A<T+A8 I@<A4*AAKI8> I@<A4

>ADITK TL<+?

TAI??<A

4LIAT -#A@

I3?*T I@<A4

@I4*/A>< /##@

4*A?<A

-<T *<8<A

Figure 7 *omponents of belt conveyor

4elf aligning idler set is used infront of the loading point. This set of idlers can rotate

on a horizontal plan depending on the belt sway and restores true running of the belt.

-elt training idlers should be spaced 1 to 1" feet apart and at least one such idlersshould be used on conveyors less th%an 1 feet long. 4uch idlers are not used in the

areas of belt transition.

;ixed guide rolls placed perpendicular to the edge of the conveyor belt are not

generally recommended as they cause edge wear and reduce belt life.

#ffcentre running of the belt occurs when the belt loading is not proper. >arland type

idlers assist true running of the belt under difficult loading conditions. In this type of

idlers the idlers are connected to form a string. The connections are through universal

type coupling that allows each idlers to rotate about its own axis independently.

>arland idlers are available as two roll, three roll or five roll units. 8ormally tworoll

units are used as return idlers and threerolls or fiverolls units are used in carryingidlers.

-elt weight, material weight, idler load rating, belt sag, idler life, belt rating, belt

tension and radius in vertical curves determine the spacing of idlers. 4ome suggested

normal spacing are shown in Table .

Table 3 Idler spacing

-elt

Cidth

5inches6

Troughed Idler 4pacing

Ceigh of 3aterial /andled 5lbs0cu ft6

Aeturn

Idler

" (" 1 1" 2

1



1)

2!

"."

".

".

".

!."

!."

".

!."

!."

".

!.

!.

!."

!.

!.

!."

!.

!.

1.

1.

1.

&!2

!)

".!."

!."

!."!."

!.

!.!.

!.

!.."

."

.".

.

.".

.

1.1.

1.

"!

&

(2

!."

!.

!.

!.

!.

."

."

."

."

."

.

.

.

.

2."

.

.

2."

1.

1.

).

)!

7&

."

."

."

."

.

.

2."

2."

2."

2.

2.

2.

).

).

Pulley

conveyor belt system uses different types of pulleys li$e end pulley, snub pulley,

bend pulley etc. as shown in the ;igure . The end pulleys are used for driving and

sometimes for ma$ing tensioning arrangements. 4nub pulleys increase the angle of

wrap thereby increasing the effective tension in the belt. The pulley diameter depends

on the belt width and belt speed.

?ulleys are used for providing the drive to the belt as well as for maintaining the

proper tension to the belt.

3inimum transition distance as shown in Table ! should be followed while placing

idlers in front of pulleys.

Table Aecommended minimum transition distance

Troughing angle ! "ate#Ten$ion

Fabri% Belt

&for half

trough

#e'th()

Fabri% Belt

&for full

trough

#e'th(

SteelCor# Belt

&for half

trough

#e'th()

SteelCor# Belt

&for ful

trough

#e'th(

2 M7

& J 7

N&

.7b

.)b

.&b

1.&b

1.2b

2.b

1.&b

1.ob

.2b

2.)

" M7

& J 7

1.&b

1.b

.2b

2.!b

.!b

2.&b

&.)b

".2b

1!



N& 1.b 1.)b 1.)b .&b

!" M7

& J 7

N&

2.b

1.&b

1.b

!.b

.2b

2.!b

!.b

.2b

2.b

).b

&.!b

!.!b

4nub pulleys may be fitted in as shown in the following figures:

oose 4nub Tight 4nub

Figure *

The angle of wrap is increased by using tandem drive as shown in ;igure below:

Figure + Tandem drive

Drive

-elt drive is provided normally at the discharge ends, however, it may be provided

through the head end or through intermediate pulley by coupling the pulley shaft tothe reducing gearGs output shaft. The coupling is selected based on the load

characteristics and applications. ;lexible coupling or fluid couplings are often used.

Darious drive arrangements are shown in the ;igures below:

Take-up

The purposes of ta$eup are:

1. To allow for stretch and shrin$age of the belt.

2. To ensure that the minimum tension in the belt is sufficient to prevent unduesag between idlers.

1"



. To ensure that the tension in the belt in the rear of the drive pulley is sufficient

to permit such pulley to transmit the load.

There are different types of ta$eup systems as shown in the ;igures below:

Figure ,- 4crew ta$eup

1&



1(



Figure ,, >ravity Ta$e up

Conveyor Support

The support of conveyor is normally a structural frame. @epending on the situationthe structure can be mounted on floor or on s$id. The main 'ob of the support is to let

the belt run without getting s$ewed. @epending on situations the support can be made

moving type. In such cases idler a wheel mounted or crawler mounted platform $eeps

the necessary provision to support the idlers on which the conveyor runs.

BELT CONVEYOR MAINTENANCE

-elt conveyor system can serve economically provided it is maintained well.

3aintenance of this system involves number of routine wor$s. Inspection of the

various components and initiating timely repair or servicing of these components incase any default is noticed is of premier importance. To maintain a belt conveyor

system following items must be carefully loo$ed into:

Belt cleaners,

-elt cleaners are re%uired for both the carrying side and the non carrying side of the

belt. 3aterial falling on the noncarrying side of the belt needs to be arrested before it

get traped in the tail pulley to cause damage to the lagging and sway of the belt. The

carrying side needs cleaning when carried material is stic$y in nature.

To deflect the material coming on the noncarrying side deflector belt plows are used.

4uch plows can be selected from number of available sources or can be locally madeconsidering that the rubber used in it should be softer than the surface of the belt

conveyor. It must be easy to install and maintain.

Belt trainers

-elt trainer is a device that helps true running of belt conveyor. It prevents offcenter

loading and belt mistrac$ing. The belt trainers are also called self aligning idlers

designed with a pivot and tilt action. They can immediately centre and control the

misalignment problems of a running belt.

1)



Skirt clamps,

Skirt clamps are used for eliminatin loadin point spillae at t!e con"e#or loadin andtransfer points$ T!e skirt ru%%er used for t!is s!ould %e selected considerin its !ardness &it!respect to t!e top co"er of t!e %elt$ As it &ill %e re'uirin ad(ustments after &ear so t!e fi)inarranement s!ould %e simple* easil# accessi%le and less time consumin$

Pulley lagging

Pulle# lains are necessar# for %etter traction and to eliminate %elt slippae$

CONVEYOR BELT MAINTENANCE TOOLS

To sa"e time and mone#* and to simplif# routine %elt maintenance procedures* proper ser"iceand maintenance tools s!ould %e procured$ Some e)amples are+

,-LT.PLE R.VET /R.V.N0 TOOLS

This tool is used for mechanical belt fastening. 5 ;lexco produces 34AT 8@34AT) 6.This easytouse, portable tool ma$es multiple rivet driving simple and fast.

4ome tools have drive rods that can drive five rivets simultaneously.

BELT C-TTER

-elt cutters are designed to enhance operator safety. 4ome belt cutters are chain

driven, doubleedged safety blade and are shielded from operator contact. 4uch blade

can be driven from either end of the cutter and cuts in both directions.

B!lt &#ot!ction Cont#ol$

There are number of devices provided for protecting conveyor belt system. These are:

1. -elt alignement control: -elt should be aligned with the drive pulleys and the

carrying and return idlers. -elt alignment sensors are typically positioned

along the edges of the conveyor fabric. They are usually at the discharge and

at the loading zones, however can be distributed over the length of the

conveyor. 4witches consists of "oller S.it%he$/ 0imit S.it%he$/ Pro1imity

S.it%he$/ Photoele%tri% S.it%he$/ et%) Chen the edge of the belt trips the

alignement switch for a timed period, the conveyor is halted. In steel cord

belts edge trac$ing is done by using alignment sensors. This helps to get

signature of tension distribution within the carcass which in turn does thecondition monitoring.

2. -elt #verload: The electric drive motor has overload protection. The motor

overload can be a simple bimetallic or melting eutectic alloy or a complex

computer based motorthermal model. 4ometimes belt weigh scales are also

used for overload protection.

. -elt 4lip: -elt slip is the loss in traction of the drive pulley5s6 to the belt cover.

-elt slip can destroy a belt or drive pulley. -elt slip protection provides a belt

drive speed sensor that compares the present belt speed with the belt intended

speed. ;or constant speed belts belt slip monitoring is done by a slip switch

with a setpoint that trips the conveyor drive when the belt speed is below )9of full speed. The belt slip switch is bypassed during starting and stopping.

17



;or variable speed conveyor belt slip monitoring consists of a speed sensor

that measures the belt speed and compares with the speed reference sent to the

drive system. Chen the belt speed is below )9 of the intended speed the

conveyor drive is tripped. method to ad'ust and test belt slip is normally

provided in the belt control system.

!. Ta$eup #vertravel : #vertravel limit switches can be placed at the far

extremes of the counterweight or ta$e up device travel. In a gravity

counterweight ta$eup, the top overtravel switch trip may suggest a 'ammed

conveyor belt condition. bottom overtravel switch may indicate belt stretch,

or a bro$en belt fabric flight. <xcessive ta$eup motion during starting and

stopping indicate that the type of drive control is either inade%uate or that is

not wor$ing properly.

". Transfer *hute ?lug: If the conveyor transfers material through a transfer

chute, the transfer chute plug monitors bloc$ed flow as bloc$ed flow may

damage the conveyor belt. +nder bloc$ed condition the transfer chute plug

switch trips the conveyor drive.

&. -in evel *ontrol: If the conveyor belt is used to fill bins or stoc$ piles over

dumping may damage the belt. -in level sensors protect the belt from

probable beltdamage. 4imple hanging tilt switch or analogue devices li$e

ultrasonic, radar or laser devices may be used.

(. ?ullchord 4top 4witches: These are emergency switches that can be actuated

by pulling a chord provided along the belt conveyor.

). Aip @etectors: Aip detectors provide belt protection in case of a rip or tear of

the belt. 4imple rip detector is spill switch located below the conveyor near the

loading point. There are complex rip switches available, which re%uire periodic maintenance.

7. ;ire @etection: Thermal trip switches are provided with smo$e sensors, *#

sensors or fibre optic temperature sensors.

1. @ust 4prays: Cater or chemical based dust suppressing system can eliminate

or reduce dust problems in certain special conveyor belt installations

B!lt Cont#ol$

The belt control involves the following:

4top0start: t single or multiple stations.4tart warning: udible or visual signal for prestart warning

Interloc$: The se%uence control between the master and slave conveyors.

Telemetry: @istribution of belt control and information over significant distance.

oc$out: ?hysical loc$out of the all motive power sources.

Regulatory Provisions

;or use of belt conveyors in special applications li$e under ground coal mining state

imposed regulations must be followed. @>34 circulars and *3A should be

considered during installation, running and maintenance of belt conveyor inunderground coal mines.

2



B!lt Con"!yo# T#oubl! S'ootin(

5The number refers to the list below the table.6

Com'laint Cau$e

n or#er of 'robable

o%%urren%e$

Com'laint Cau$e

n or#er of 'robable

o%%urren%e$

-elt runs off at tail pulley

( 1" 1! 1( 21 <xcessive wear, includingrips, gouges, ruptures, andtears

12, 2", 1(, 21, ), "

<ntire belt runs off at all points of the line

2&, 1(, 1", 21, !, 1& <xcessive bottom cover wear

21, 1!, ", 17, 2, 22

#ne belt section runs off at all points of the line

2, 11, 1 <xcessive edge wear, bro$en edges

2&, !, 1(, ), 1, 21

-elt runs off at head pulley

1", 22, 21, 1& -elt hardens or crac$ ), 2, 22, 1)

-elt slip 17, (, 21, 1!, 22 *overs become chec$ed or

brittle

), 1)

-elt slip on starting 17, (, 22, 1 ongitudinal grooving or

crac$ing of top cover

1!, 21, 22

<xcessive belt stretch 1, 1, 21, &, 7 ongitudinal grooving or crac$ing of bottom cover

1!, 21, 22

-elt brea$s at or behindfastenersO fasteners tear loose

2, 2, 1, 22, 2, 1 ;abric decay, carcasscrac$s, ruptures, soft spotsin belt5gouges6

12, 2, ", 1, ), 2!

Dulcanised spliceseparation

1, 2, 1, 2, 2, 7 ?ly separation 1, 2, 11, ),

1. -elt bowed: void telescoping belt rolls or storing them in damp locations.

2. -elt improperly spliced or wrong fasteners: +se correct fasteners. Aetighten

after running for a short while. If temporarily spliced remove belt splice and

ma$e new splice. 4et up regular inspetion schedule.. -elt speed too fast: Aeduce belt speed

!. -elt strained on one side: llow time for new belt to Pbrea$ inQ. If belt does

not brea$ in properly or is not new, remove strained section and splice in a

new piece.

". -rea$er strip missing or inade%uate: Chen service is lost, install proper

brea$er strip 5 -rea$ers are woven fabric of nylon R0or polyster placed above

the carcass to dissipate impact energy and to prevent belt puncture6

&. *ounterweight too heavy: Aecalculate weight re%uired and ad'ust

counterweight accordingly. Aeduce ta$eup tension to point of slip thenlighten slightly.

21



(. *ounterweight too light: Aecalculate and ad'ust or screw ta$eup accordingly.

). @amage by abrasive, acid, chemicals, heat etc: +se belt designed for specific

purpose. Aepair cuts. +se enclosure where needed.

7. @ifferential speed on dual pulleys: 3a$e necessary ad'ustments

1. @rive underbelted: Aecalculate maximum belt tensions and select correcxt belt. @etermine if extension is feasible or another belt to be installed. *hec$

the carcass is rigid enough for load, replace if service is lost.

11. <dge worn or bro$en: Aepair edge. If the edge is out of s%uare or badly

damage replace the worn portion of the belt.

12. <xcessive impact of material on belt or fasteners: +se correctly designed

chutes and baffles. 3a$e vulcanised splices. Instal impact idlers. Chere

possible load fines first. Chere material is trapped under s$irts , ad'ust

s$irtboards to minimum clearance or install cushioning idlers to hold belt

against s$irts.

1. <xcessive tension: Aecalculate and ad'ust tension. +se vulcanised splice

within recommended limits.

1!. ;rozen Idlers: ;ree idlers. ubricate. Improve maintenance. @onGt over

lubricate.

1". Idlers or pulleys out of s%uare with centre line of the conveyor: Aealign. Install

limit switches for greater safety.

1&. Idlers improperly placed: Aelocate idlers or insert insert additional idlers

spaced to support belts.

1(. Improper loading, spillage: ;eed should be in direction of belt travel and at belt speed, centred on the belt. *ontrol flow with feeders, chutes and

s$irtboard.

1). Improper storage or handling: Aefer to the manufacturerGs instructions for

storage and handling.

17. Insufficient traction between belt and pulley: Increase wrap angle with snub

pulley. ag drive pulley. In wet condition use grooved lagging. Install correct

cleaning devices for safety.

2. 3aterial between belt and pulley: +se s$irtboard properly. Aemove

accumulation. 3aintain properly.

21. 3aterial buildup: Aemove accumulation. Install cleaning devices, scrapers

and inverted D dec$ing. Improve house$eeping.

22. ?ulley lagging worn: Aeplace worn pulley lagging. +se grooved lagging for

wet conditions. Tighten loose and protruding bolts.

2. ?ulleys too small: +se large diameter pulleys.

2!. Aadius of convex vertical curve too small: Increase radius by vertical

realignment of idlers to reduce excessive edge tension.

2". Aelative loading velocity too high or too low: d'ust chute or correct belt

velocities. +se impact idlers.2&. 4ide loading: oad in the direction of belt run and at the centre of the belt.

22



2(. 4$irts improperly ?laced: +se ad'ustable s$irtboards and chec$ that it does not

rub the belt.

A#%ou#!) Fac! Con"!y!#$ o# Un)!#(#oun) Coal T#an$po#tation

+nderground coal conveyers widely employed in collieries relate to the group of

conveyers with low flights, but differ substantially from the conveyers used in other industries. They perform many various operations in collieries and accordingly have alarge number of design versions.

Figure ,2 rmoured face conveyor

n underground coal conveyer has one 5two or three6 hauling chain with low flights

attached to it. The chain along the bottom of an open trough draws the flights. The

chain bends around terminal 5drive and ta$eup6 sproc$ets at the ends of the conveyer

and is moved by a drive. The conveyer is mounted directly on the ground of a mine

drift. #ne of the principal re%uirements to underground coal conveyers is that their

height, and especially that of the carrying run, must be as low as possible in order to minimizethe loading height.

@epending on the scheme of arrangement of the tractive element 5of the carrying and

return run6, it is distinguished between vertically closed conveyers 5 a to d in the

above figure6 , horizontally closed 5e6 , and those with a combined path. In the last

type, the terminal sproc$ets are arranged at an angle of !" to the horizontal. The

flights are attached to the chain at an angle of !" and are oriented in the horizontal

plane in the carrying run and in the vertical plane, in the return run.

Dertically closed conveyers are made 5with one, two or three parallel hauling chains

5a , b, and c respectively6. threechain conveyer may have a greater length and

higher reliability, since brea$age of. a chain does not disturb the stability of flightsand the operating capability of the conveyer. Their application is however limited by

2



their higher cost and large mass. In singlechain conveyers, the flights may have

symmetrical 5the chain at the centre of flight6 or unsymmetrical and rigidly fixed or

hinged attachment to the hauling chain.

The path of a vertically closed conveyer for coal transportation in curved drifts may

be either straight 5horizontal, inclined or horizontalinclined6 or bending in the

horizontal plane 5spatial6.

The tra%tive element is in the form of one, two or three detachable chains of elevated

strength with the pitch ) mm or roundlin$ chains with the chain pitch of " or &! mm and

rod lin$s. of a diametet of 1! or 1) mm. The chains are made of steel of specified grade and

heattreated.

The flight$ are made of steel and have a height roughly e%ual to the height of chain.

The pitch of flights is !),&! or 12! mm, and the linear mass of a chain with flights

is 1 1) $g0m on the average.

The trough is stamped from steel sheets 5steel grades " or f6 in sections of a

length of 22." mO the wor$ing portion 5bottom6 is hardened.The #rive is electrical, pneumatic or electrohydraulic in an explosionsafe

embodiment. @rives with one or two motors at the front end and one motor at the rear

end of a conveyer have found wide application. The transmission mechanism is of the

reducer typeO the electric motor is connected with the reducer gear through a hydraulic

coupling.

To'i%$ for #i$%u$$ion in the %la$$room

1. 4teep ngle conveying and their applicability in underground use.

2. -elt tension and power calculation

. *onveyor accessories

!. ?ractical problems and innovative solutions

". Information 4ystem for -ul$ 4olid /andling

2!



Con"!yo# Calculation

Initial @ata:

1. *haracteristic of material li$e lumpiness, density, moistue content, angle of repose, particle flowability, abrasiveness, particle strength, slumping 5losing of

mobility on long storage, e.g. lime, cement etc.6, stic$yness etc.

2. The average and maximum load carrying capacity

. @iagram of the designed conveyor with its principal dimensions

!. @ata on the exceptional wor$ing conditions

". rrangements of the operation of the conveyors.

etermining Belt 4i#th

The belt width depends on maximum rated capacity and lump size. The cross

sectional profile of the bul$ material on the conveyor belt is determined by the profile

of the load carried on the belt. #n straight roller this area is :

bh A2

1=

φ tanb.h ".=

φ tanb. A 22".=

where, b: width of the base of material on the belth:height of material on the belt

φ: ngle of repose

: area of cross section of the material

#n an inclined conveyor this area will be reduced depending on the angle of

inclination of the belt, mobility or particles and angle of repose.

;or a belt running over the troughed idler the cross sectional area of the material is the

sum of the trapezium and the circular sector as shown in ;igure:

2"



The area is given as:

β sinm

l l

Ab2

1 +

=

2

2

&.

2 2

2α α π sin

r r

A s

−=

where, the symbols are as illustrated in the figure.

Total area is the sum of b and s.

*apacity of *onveyor in te0hr

ρ .v. A.Q &..= 56

If belt width is - and area of cross section of material is , it is often ta$en that:

1.

2 B

A = 5-6

Thus from e%uation 56 and 5-6 the belt width can be calculated.

To test the calculated belt width for suitability with lump size the following relation is

used:

2..+> Xa B

where S coefficient of lump sizeS ." for graded material

2&



S2." for ungraded material

aS maximum linear size of the represntative lump

- is selected from the available width as: !, ",&", ), 1,12", 1!, 1&,

2, 2", mm.

Idler 4pacing

The spacing of idlers depends on belt width and bul$ density of material. This is

calculated from :

T

W S

)

2

=

where,

/: sag, in feet

4: 4pacing in feet

T: Tension in pound

C: Ceight of the loaded belt in lb0ft.

Idler spacing in the mid portion of the conveyor in meter for different material is

given in the following table.

-elt Cidth

mm

@ensity t0m

N.)

@ensity t0m

.)11.&

@ensity t0m

1.&12

@ensity t0m

2.1 2."

@ensity t0m

M2."

! 1." 1.! 1.! 1. 1.2

" 1." 1.! 1.! 1. 1.2

&" 1.! 1. 1. 1.2 1.2

) 1.! 1. 1. 1.2 1.1

1 1. 1.2 1.2 1.1 1.1

12 1. 1.2 1.2 1.1 1.1

1! 1. 1.2 1.2 1.1 1.1

1& 1. 1.2 1.2 1.1 1.1

2 1. 1.2 1.1 1.1 1.

The return idlers are spaced at 2 to 2." times the spacing of carryng idler sub'ect to the

condition that it is not more than ." m.

Documents

Belt Conveyor 3