Belt Conveyor

Introduction Belt conveyor is an endless belt operating

between two or more pulleys with its load supported on idlers.

Classification

According to design & application

General purpose conveyor

Special purpose conveyor

Parts of belt conveyor1. Belt2. Drive mechanism3. Pulleys4. Idlers5. Loading and discharging device

1.Belt Materials :A. Rubber• used for bulk material• Made up of carcassB. Woven cloth• Light weight materialC. Steel • For metal industries

Belt

High strengthLow massLow relative elongationHigh elasticity longitudinally and crosswiseLow hygroscopicityHigh wear resistance

Characteristics

2. Drive mechanism For single pulley drive up to 30-50 kW is

required. We can provide up to 250 kW. Depends on pulley drive.

Pulleys• Head Pulley - turns belt back around

to return - may be coupled to drive• Tail Pulley - turns empty belt around

for loading - occasionally coupled to drive

• Drive Pulley - Coupled to motor pulls belt - usually special grip surface

• Snub Pulley - usually used to change direction of belt and increase the contact angle with the drive pulley (more surface area to transfer power)

• Take Up Pulley - Used to maintain tension on a belt left loose enough for some flexibility

5. Idlers • Supports Belt and Material Load• Built with

– Shaft surrounded by bearings– Then roll of steel or rubber

• Two main types– Carrying for material and belt– return supports belt on return trip

• Efficiency of conveyor largely dependent on this.• Its diameter ranges from 4 to 7 inches.

Idler type1. Flat belt idler Used for granular materials of

angle of repose not less than 35º. Preferred for low capacity where

inexpensive conveying is required.2. Toughing idlers with 20º trough Used for conveying all kinds of

bulk material3. Toughing idlers with 35º and 45º

trough Mainly used for transportation of

small particle light weight materials like grains, cotton seed etc.

used for carrying heavier, medium size lumps like crushed stones.

6. Loading device

6. Unloading device

o More than one point dischargeo Generally used in flat and

horizontal conveyoro Scrappers or ploughs are

diagonally mounted usually at 30º across the direction of travel

o May damage the belt if speed is higher than 60m/min.

Plough scrapper

Unloading device

o Used to discharge the material at a number of fixed points

o Made of two pulley which may be fixed or movable

Tripper

Design of belt conveyor

Design of belt conveyor system is based on:Available spaceHorizontal conveying lengthCharacteristics of material to be conveyedCapacity requirement

Design parameters1. Speed and width of belt- Speed should not increase 3.5 m/s.- For grain conveying: 2.5 to 2.8 m/s.- Belt width in meter;

where is coefficient of cross sectional area of load on belt is coefficient of load reduction of load layer cross

section on an inclined portion of conveyor

2. Thickness of belt3. Diameter of pulleys and idlers - for rubber-fabric belt

Where is coefficient depending on strength of ply fabric

is coefficient depending on type of pulley I is number of plies- For rubber-cable belt

i

4. Required horsepower - It depends on the capacity of belt conveyor.- The capacity of belt conveyor in m³/hr is given by:

5. Belt tensionEffective tension,

kW is power in kilowatt S is the belt speed, m/s

T = kW / S

(area of cross-section of belt, m²) * (belt speed, m/min) * 60

6. Trough angle and surcharge angle in idlers

7. Torque of driving pulley

Where K =1.1 or 1.2 W= circumferential force on driving pulley

8. Strength of belt Rubber-fabric and

rubber-cable belts can be employed if the required strength ranges from 1.5-4 kN/mm.

9. Idler spacing Approximately equal to

width of belt Should not exceed 1.2

meters.

Advantages High load carrying capacity (up to 30000t/h) Large length of conveying path (up to 3-4 km in

single conveyor)Simple designEasy maintenanceHigh reliability for operationMore flexible

Disadvantages Vertical transportation can not be done.A separate arrangement for material

handling is required.Hot materials can not be transported .High initial cost for short distances.

Applications • Many other functions can be performed

with the basic conveying like weighing, sorting, picking, grading, spraying, cooling, drying, sampling etc.

• Major role in mining.• It can be used for special purposes like fire

resistance, wear resistance, corrosion resistance and can be integrated with other equipment.

Reference Sahay, K.M. and Singh, K.K. (2009). “Unit

Operations of Agricultural Processing”. Vikas publication: 287-315.

Spivakovsky, A. and Dyachkov, V. (1985). “ Conveying machines”. Mir publishers, moscow: 99-165.