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Belt conveyors consist of two powered pulleys with a continuous loop of belting material used to convey products. Belt conveyors are the most economical powered conveyor and are typically used for conveying products over long distances, at high speeds, or for incline/decline applications. This is done with endless

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CONTENTS

1 INTRODUCTION

2 BELT CHARACTERISTICS

3 BELT CONVEYORS BASIC CALCULATIONS

4 CEMA BELT TENSION THEORY

5 TROUGHED BELT CONVEYOR CAPACITIES

6 BELT CARRYING IDLERS OR BELT TROUGHED ROLLERS

7 CEMA TROUGHED IDLERS

8 STANDARD BELT CONVEYOR PULLEYS

9 BELT CONVEYORS ACCESSORIES

10 BASIC DESIGN CRITERIA

11 LOADING OF BELT AND IMPACT ROLLERS

12 BELT CONVEYOR COVERS

13 BELT FABRICATION TYPES

14 INTERNATIONAL ISO STANDARDS

15 EASY SPREADSHEET CALCULATION TABLE

References

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BELT CONVEYORS FOR BULK MATERIALS

1 INTRODUCTION

Belt conveyors consist of two powered pulleys with a continuous loop of belting material used to convey

products Belt conveyors are the most economical powered conveyor and are typically used for conveying

products over long distances at high speeds or for incline decline applications This is done with endless

procession of hooks gears buckets and a wide rubber belt The belt is then supported by a series of

rollers along the path

Belt conveyors are an excellent choice for an inexpensive and simple method of moving products from

one point to another Because of the simplicity of the flat moving belt they can be used to move a variety

of product sizes shapes and weights effectively for long lengths with a single drive Belt Conveyors are

also a great option to move products through elevations Incline Belt Conveyors from low to high and

Decline Belt Conveyors from high to low

This manual is short with quick and easy reading paragraphs very practical for calculations of belt chain

conveyors and mechanical miscellaneous in the metric and imperial system The main function however

is to give more informative methods for both experienced professionals and beginners interested in

knowing the dynamics of Material Handling

Material handling equipment is mechanical equipment used for the movement storage control and

protection of materials goods and products throughout the process of manufacturing distribution

consumption and disposal

Material handling equipment include belt conveyors of several models and patterns horizontal vertical

inclined declined with chains or rollers tube type etc Works in warehousing distribution

manufacturing order fulfillment aerospace government military agency automotive parcel Handling

appliances cabinetry furniture food beverage

Note In recent years CEMA Conveyor Equipment Manufacturers Association and many member

companies have developed computer programs capable of engineering analysis of the most complex and

extensive process for belt and other material conveyor types These programs are more comprehensive

and include more extensive analysis and calculations not included in this short manual

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2 BELT CHARACTERISTICS

There are a great range of belt conveyors specially manufactured to perform any carrying application and

to surpass since a simple unit loading to tough conveying industrial conditions See below some of the belt

characteristics and special applications

a Standard Rubber Belts

Standard belts incorporate covers suitable for the handling of most abrasive materials

having a blend of natural and synthetic rubber

b Cut Resistant Belts

Cut resistant belts have a high content of natural rubber recommended for belts operating

under extremely difficult conditions where cutting and gouging of covers may occur

c Heat Resistant Belts

Heat Resistant belts incorporate covers with styrene butadiene recommended for belts

handling materials with temperatures up to 1200 C

d Super Heat Resistant Belts

Super Heat Resistant belts have Chlorobutyl covers recommended for belts handling

materials with temperatures of up to 1700 C

e Fire Resistant Belts

Fire resistant belts are manufactured with covers containing neoprene with multi ply

carcass constructions to meet the maximum standards of safety in underground mines

f Wood Handling Belts

These belts were especially developed non staining for the timber industry compounded to

provide resistance to oil and resin

g Concentrator Belts

Concentrator belts are uniquely applied at gold mine concentrators

h PVC Solid Woven Belts

PVC solid woven belts also known as Vinyplast are manufactured with polyester and

nylon with cotton soaked in armor of PVC and PVC coatings developed to withstand the

impact tear and abrasion as the requirements to meet the most stringent flame resistant

standards

i Food Quality Belts

Food quality belts are manufactured from non toxic materials resistant to oils fats and

staining to meet the hygiene requirements of the food processing industry

j Nitrile Covered PVC Belts

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Nitrile covered PVC belts were developed for application in mines where the danger of fire

exists and also have properties of flame retardant oil abrasion and heat resistance

k Steel cord Belts

Steel cord belts are generally manufactured for application in long distances conveyors

stiffened with a steel wire inserted within a high quality rubber in order to get exceptional

traction load and material high impact

l Fire Resistant Steel cord Belts

Fire resistant steel cords belts were developed with properties of self extinguishing fire to

offer advantages in free maintenance operations and long life for conveyors situated in fiery

mines

m Oil Resistant Belts

Oil resistant belts are manufactured to provide easily washable linings in nitrile neoprene

or synthetic rubber in all layers allowing ease application in handling of materials

containing vegetable oils and minerals

n Chevron Standard Belts

Chevron standard belts are manufactured with steel tyre cords in a V shape at intervals

over the belt length These belts are generally recommended for standard belting where

difficult conditions are applied i e slag transportation

o Corrugated Sidewall Belts

Corrugated sidewall belts are the most effective ways of elevating materials in a confined

space and less space requirements no transfer point low maintenance and big capacity

commonly used in cement plants coal fired power plants ports and chemical industry

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3 BELT CONVEYORS BASIC CALCULATIONS

1 Mass of the Load per Unit Length

Load per unit length Given the production capacity Qt tph the weight of the load per unit length

kg m lbs per ft is calculated by

Wm 2000 Qt or Wm 33 333 Qt lb ft

60 x v v

Q 0 278 Qt or Q Qt Kg m

v 3 600 x v

2 Belt Tensions

In order to find the maximum tension is necessary to calculate the effective tension that is the force

required to move the conveyor and the load at a constant speed The calculation of the total tension is

based on a constant speed of the belt including the necessary basic conditions to overcome the frictional

resistance and tension forces In a basic way the effective tension is composed of

The tension to move with an empty belt Tx

The tension of move the load horizontally Ty

The tension to increase or decrease the load Tz

The tension to overcome the resistance of accessories Tus

The tension to overcome the resistance of scrapers Tuc

a The total tension is

Te T x Ty Tz Tus Tuc

b The tension to move the empty belt is

Tx G x fx x Lc

c The tension to move the load horizontally is

Ty Q Wm x fy x LC

d The tension to lift the load is

Tz Q Wm x H

e The tension needed to overcome the resistance of the skirtboards Tus

T us fs x Q Wm x Ls Kg or T us fs Ls hs lb

vxb

f The tension to overcome the resistance of scrapers Tuc

T uc A x x fc

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g Moving trippers require additional pulleys in the system and therefore add a new tension Tut

T ut 0 01 do x T 1

Dt

3 Belt Length Correction Lc

Short belt conveyors require relatively more power to overcome the resistance to friction than long ones

and therefore an adjustment is made to calculate the effective tension

LC L 70 m metric

LC L 230 ft imperial

Therefore the belt length correction is

C Lc

L

All conveyors require an additional belt tension in order to allow the pulley to drive forward an effective

tension without slipping In a case of a simple horizontal conveyor T1 is the sum of the effective tension Te

and the slack side the tension T2

T1 T e T2

For the inclined conveyor additional tensions are induced due

to the mass of the belt on the slope

T 1 T e T 2 Th

Minimum tension to prevent slipping Tm

The relations between T 1 and T 2 are

T1 e

T2

So

T2 1 T e

e 1

The fundamental equation is given by

The Euler s equation T1 T2 e

where

T1 and T2 tight side and slack side tensions at the driving pulley

wrap angle of the belt in radiation

e natural logarithmic Naperian base 2 718

Friction factor

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Considering the factor K to prevent slipping T m is

T m k x Te

The minimum tension to prevent belt sag between two rolls T s is

Ts Sf x B Q x ld

The slope tension T h is

Th B x H

Table 1 Coefficient of friction between driving pulley and belt of pulley lag

Table 2 Wrap factor k

The final driving power P is calculated with the following formulas

P T e x v metric and P Te x v imperial

75 33 000

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Table 3 Symbols

Symbol Description Unit Symbol Description Unit

A Contact area of scraper m ft Sf Sag factor See Table

kg m lb ft

B Belt mass per unit length T Unit tension kg m lb ft

See Table

Maximum belt tension

b Width between skirt plates m ft T1 kg lbs

across full belt width

Bc Edge Distance mm in T2 Slack side tension kg lbs

Length correction

C Te Effective tension kg lbs

coefficient

D Material Density kg m lb ft Th Slope tension kg lbs

Minimum tension to

Dt Diameter of pulley mm in Tm kg lbs

prevent slipping

Minimum tension to

do Diameter of pulley bearings mm in Ts kg lbs

limit sag

Tension to overcome

Friction coefficient for

fc See Table Tu resistance of kg lbs

scrapers

accessories

Friction coefficient for Tension to overcome

fs See Table T uc kg lbs

skirtboards resistance of scrapers

Tension to overcome

Friction coefficient for

fx See Table T us resistance of kg lbs

empty belt

skirtboards

Friction coefficient for Tension to move the

fy See Table Tx kg lbs

loaded belt empty belt

G Mass of moving parts kg m lb ft Ty Tension to move the kg lbs

See Table load horizontally

Change in elevation along Tension to lift or lower

H m ft Tz kg lbs

conveyor length the load

depth of the material Wm Mass of load per unit kg m lb ft

hs in

touching the skirt board length

ld Idler spacing carry idlers m ft W Belt width mm in

Belt mass per unit kg m lb ft

k Drive factor See Table Wb

length

Horizontal length of Angle of wrap on the

L m ft radians

conveyor drive radians

Corrected length of Pressure of scraper on

Lc m ft kg m2 lb ft

conveyor the belt

Belt capacity in ton per

Ls Length of skirt board m ft t hr tph

hour

P Absorbed power kW HP Trough angle degree

Material surcharge

Q Mass of load per unit length kg m lb ft degree

angle

Qt Belt Capacity tph v Belt Speed m s fpm

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Table 4 Material Characteristics

Max

Angle of

Suggested Bulk Density Bulk Density Conveyor

Material Type Surcharge

Grade t m lb ft Slope

degrees

degrees

Aluminium sulphate NA N 0 90 56 20 17

Ammonium sulphate MA N 0 80 50 10 10

Asbestos ore or rock VA N M 1 30 81 20 18

Ashes coal dry MA N 0 60 37 25 23

Ashes coal wet MA N 0 75 47 25 25

75

Ashes gas producer MA N 1 20 30 28

Bark wood NA N 0 24 15 30 27

Bauxite ground dry VA N M 1 10 68 20 18

Bauxite mine run VA N M 1 36 85 20 17

Brick VA N M 1 76 110 30 27

Calcium carbide MA N 1 20 75 20 18

Carbon black pelletized MA N 0 35 22 5 5

Cement Portland NA N PHR 1 50 94 25 20

Cement clinker MA N DHR 1 36 85 25 18

Chalk lumpy MA N 1 30 81 10 15

Chalk 100 mesh and 68

MA N 1 10 25 28

under

Charcoal MA N 0 35 22 25 22

Clay calcined MA N 1 44 90 25 22

Clay fines MA N 1 76 110 20 22

Coal anthracite sized NA N PVC 0 90 56 10 16

Coal bituminous sized NA N PVC 0 80 50 20 16

Coke petroleum calcined VA N M 0 64 40 20 20

Concrete wet VA N M 2 20 137 24 18

Copper ore VA N M 2 17 135 20 20

Copper sulphate VA N M 1 30 81 20 17

Dolomite VA N M 1 60 100 18 20

Earth as dug dry VA N M 1 20 75 20 20

Earth wet with clay MA N 1 70 106 30 23

Feldspar VA N M 1 44 90 25 17

Foundry sand old sand VA M PHR 1 36 85 25 20

cores

Granite broken 75mm

VA N M 1 44 90 10 18

lumps

Graphite NA N 0 65 40 10 15

Gravel pebbles VA N M 1 52 95 10 12

Gypsum dust MA N 1 50 94 20 20

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Iron ore coarse crushed VA N M 3 00 187 20 18

Iron ore crushed fine VA N M 3 50 218 20 18

Kaolin clay 75mm and

MA N 1 00 62 20 19

under

Lead ores MA N 3 80 237 10 15

Lime hydrated NA N 0 60 37 25 21

Lime pebble MA N 0 90 56 10 17

Limestone agricultural

MA N 1 10 68 10 20

3mm and under

Magnesium sulphate MA N 1 10 68 10 15

Manganese ore VA N M 2 15 134 25 20

Mica ground MA N 0 22 14 20 23

Phosphate ground 50

MA N OR PVC 0 80 20 18

fertilizer

Phosphate rock broken 125

VA N M 2 00 20 18

dry

Phosphate rock 131

VA N M 2 10 25 18

pulverized

Phosphate triple super MA N OR PVC 0 80 50 20 18

Pyrites pellets VA N M 2 00 125 10 15

Potash ore MA N 1 30 81 10 15

Quartz HA S N M 1 36 85 10 15

Rock crushed HA S N M 2 15 134 20 18

Rubber pellets MA N 0 80 50 20 22

Sand bank dry VA N M 1 60 100 20 18

Sand foundry prepared VA N M 1 36 85 30 24

Sawdust NA N OR PVC W 0 20 12 25 22

Sinter VA N M PHR 1 80 112 10 15

Slag blast furnace 85

VA M PHR DHR 1 36 10 10

crushed

Sodium phosphate MA N 0 90 56 10 16

Sugar granulated NA GF 0 83 52 10 15

Sugar raw cane MA N 0 96 60 20 22

Talc powdered NA N 0 90 56 10 12

Titanium ore VA N M 2 40 150 10 18

Vermiculite ore MA N 1 20 75 20 20

Woodchips NA OR W 0 32 20 30 27

Zinc ore crushed HA S M 2 60 162 25 22

Obs Consider point where is the comma Example 0 20 consider 0 20

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Table 5 Standard Trough Angle and Surcharge Angle Characteristics

Belt Cover Types Typical Flowability

N NH Polyisoprene

Std Surcharge

M Higher natural rubber content Material

Trough or Repose

Characteristics

OR Oil resistant Angle Angle

GF Grey Food 5 0 19 Uniform size

PHR Heat Resistant Round dry medium

10 20 29

weight

SPHR Super heat resistant

Granular lumpy Coal

W Wood master 20 30 34

Clay

DHR Delta Hete heat resistant 25 35 39 Coal stone ores

PVC Polyvinylchloride 30 40 45 Irregular wood chips

FR Fire resistant

Material

abrasiveness

HA S Highly

abrasive sharp

MA Mildly

abrasive

NA Non abrasive

VA Very abrasive

4 CEMA BELT TENSION THEORY

The CEMA procedure can be applied to any conventional troughed conveyor belt However it is advised

that this analysis must be verified by a competent and experienced conveyor designer The general

factors and terms can be used by the following formula

Q 2000 x Qt Kg m or Wm 33 333 x Qt lb ft

V m s v fpm

Wb Belt mass measured in kg m lb ft

Q Wm Material mass on the belt also measured in kg m lb ft

Qt Capacity of conveyor in tons hour t h

Obs The metric formula gives difference in lb ft direct conversion

The tension or force required to move the load horizontally over the conveyor length will depend on the

length of the conveyor the rate of loading and the calculation selection of the factors listed above

a Tension required to carry the load horizontally T hor

T hor L Kt Kx Ky Wb Wm 0 015 Wb

Where

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L Conveyor length m ft

Kt Factor Normally this factor is set at 1 0 however a note of caution is required at extreme low

temperatures below freezing because the lubrication selection of the idler bearing becomes critical and

has resulted in failure of some installations

Table 6 Kx Factor Idler resistance and the belt sliding resistance over the idler

Kx 0 00068 Wb Wm Ai lb ft belt length

Si

Ai 1 5 for 6 diameter idler rolls CEMA C6 D6

Ai 1 8 for 5 diameter idler rolls CEMA B5 C5 D5

Ai 2 3 for 4 diameter idler rolls CEMA B4 C4

Ai 2 4 for 7 diameter idler rolls CEMA E7

Ai 2 8 for 6 diameter idler rolls CEMA E6

Ky Factor Is considered to vary between 0 016 and 0 035 The normal selection is 0 022 For the return

belt use a Ky factor of 0 015 throughout Ky factor is a function of belt tension material characteristic

and load shape

b Tension required to lift or lower the load T lift

The tension or force necessary to raise or lower the load through the vertical distance required This

component can be positive or negative according to whether the load is raised or lowered

T lift H x Wm

Where

H Top height or down height of belt conveyor vertical distance m ft

Wm Mass of load per unit length Kg m lb ft

CEMA empirical factors Some of these factors include Idler roller friction Kx belt and load flexure

resistance Ky and skirtboard friction Tsb

c Required HP

To determine the required HP first calculate the belt tension or belt effective pull at specified belt

speed Belt tension Te required to overcome gravity friction momentum and conveyor components

Calculate the using the following formula

Te L Kt Kx Ky Wb 0 015Wb Wm L Ky H Tx Ty T z T us

The final formula components indicated above are

T X Tension to move the empty belt

Ty Tension to move the load horizontally

Tz Tension to lift the load

T us Tension to overcome friction

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Calculate the power required to drive the belt using

HP Te lb x v fpm imperial or CV Te Kg x v m s metric

33 000 75

Table 7 Sag Factor

Percentage Sag Factor

Sag Sf

3 4 2

2 6 3

1 5 8 4

Table 8 Recommended Sag Percent

Lumps up to

Trough Angle Fine Max Lump

max lump

degree Material Size

size

20 3 3 3

35 3 2 2

45 3 2 1 5

Table 9 Friction Factors

Value of the friction factor

Very well

Normal Normal

aligned

operating operating

structure

conditions conditions

Symbol

No

Description tilted idlers

Horizontal Horizontal

Horizontal

length length

length

up to more than

more than

250 m 250 m

500 m

820 ft 820 ft

1640 ft

Friction coefficient for

fC 0 600 0 600 0 600

scrapers

Friction coefficient for

fS 0 650 0 650 0 650

skirtboards

Friction coefficient for empty

fX 0 022 0 020 0 020

belt

Friction coefficient for loaded

fY 0 027 0 022 0 020

belt

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Table 10 Estimated Belt Mass B Wb kg m lb ft

Operating Conditions

Belt Width

Belt Width Light Duty Medium Duty Heavy Duty

mm

in kg m kg m kg m

lb ft lb ft lb ft

500 20 4 1 2 75 6 2 4 16 10 3 6 92

600 24 5 0 3 36 7 4 4 97 12 3 8 26

750 30 6 2 4 16 9 3 6 25 15 5 10 41

900 36 7 4 4 97 11 1 7 46 18 5 12 43

1050 42 8 6 5 78 13 0 8 73 21 6 14 51

1200 48 9 8 6 58 14 8 9 94 24 7 16 60

1350 54 11 0 7 39 16 7 11 22 27 8 18 68

1500 60 12 3 8 26 18 6 12 50 30 9 20 76

1650 66 13 5 9 07 20 5 13 77 33 9 22 78

1800 72 14 7 9 88 22 3 14 98 37 0 24 86

Table 11 Mass of Moving Parts G

Mass of Moving Parts kg m lb ft

Medium Extra Heavy

Light Duty Duty Heavy Duty Duty

Belt Width Belt Width 4 Idlers 5 Idlers 6 Idlers 6 Idlers

mm in Light Belt Moderate Heavy Belt Steel Cord

Belt Belt

450 18 23 15 4 25 16 8 33 22 2

600 20 29 19 5 36 24 2 45 30 2 49 33 0

750 24 37 25 0 46 31 0 57 38 3 63 42 3

900 30 45 30 0 55 37 0 70 47 0 79 53 0

1050 36 52 35 0 64 43 0 82 55 0 94 63 2

1200 42 63 42 3 71 47 7 95 63 8 110 74 0

1350 48 70 47 0 82 55 0 107 72 0 127 85 3

1500 54 91 61 2 121 81 3 143 96 0

1650 60 100 67 2 132 88 7 160 107 5

1800 66 144 96 7 178 119 6

2100 72 168 112 8 205 137 7

2200 84 177 119 0 219 147 2

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