CONVEYOR BELT

CONVEYOR BELT

what is conveyor belt?Aconveyor beltis the carrying medium of abelt conveyor system.A belt conveyor system consists of two or morepulleys with an endless loop of carrying mediumthe conveyor beltthat rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley is called the idler pulley.Conveyor speed control

HISTORY OF CONVEYOR BELT -In 1892,Thomas Robinsbegan a series of inventions which led to the development of a conveyor belt used for carrying coal, ores and other products.

-In 1901,Sandvikinvented and started the production ofsteel conveyor belts.

-In 1905Richard Sutcliffe invented the first conveyor belts for use in coal mines which revolutionized the mining industry. CONTD-In 1913,Henry Ford introduced conveyor-belt assembly lines atFord companys Highland Park, Michigan factory.

-In 1972, the French society REI created in New Caledonia the then longest straight-belt conveyor in the world, at a length of 13.8km.

-In 1957, the B. F. Goodrich Company patented a conveyor belt that it went on to produce as the Turnover Conveyor Belt System.

Major Components of ConveyorLong Continuous beltCarried on rolls - rollers held by frameBelt wrapped around pulleys at endsPulleys coupled to gears and motorsPeripheral Devices to drop on belt, direct around corner, clean, discharge etc.

Conveyor Parts

How Conveyors Function?Material Falls on moving belt that carries it alongA continuous haulage system that is not limited by cycles of batch movementRequires a continuous frame and structure before can transport material over route

Mechanism of conveyor beltMechanism involved is rotary motion is converted into linear motion.In pulley mechanism involved is Indexing mechanism.

CalculationDesign ParametersBelt tension: The belt of the conveyor always experience a tensile load due to the rotation of theelectric drive, weight of the conveyed materials, and due to the idlers. The belt tension at steadystate can be calculated as:

Tb = 1.37*f*L*g*[2*mi+ (2*mb + mm)*cos ()] + (H*g*mm)

ContdWhere,Tb is in Newton.f = Coefficient of frictionL = Conveyor length in meters. Conveyor length is approximately half of the total belt length.g = Acceleration due to gravity = 9.81 m/sec2mi = Load due to the idlers in Kg/m.mb = Load due to belt in Kg/m.mm = Load due to the conveyed materials in Kg/m. = Inclination angle of the conveyor in Degree.H = vertical height of the conveyor in meters.

Load due to idlers (mi): This can be calculated as below:mi = (mass of a set of idlers) / (idlers spacing)

Power at drive pulleyThe power required at the drive pulley can be calculated from the belttension value as below:Pp = (Tb*V)/1000)

Where,Pp is in KW.Tb = steady state belt tension in N.v = belt speed in m/sec.

Belt tension while starting the system

Initially during the start of the conveyor system, the tension in the belt will be much higher thanthe tension in steady state. The belt tension while starting can be calculated as

Tbs =Tb*KsWhere,Tbs is in N.Tb = the steady state belt tension in N.Ks = the startup factor

Sizing of the motor: The minimum motor power can be calculated as:Pm = Pp/Kd

Where,Pm is in Kw.Pp = the power at drive pulley in KwKd = Drive efficiency.

Acceleration The acceleration of the conveyor belt can be calculated as:A= (Tbs Tb)/ [L*(2*mi + 2*mb+mm)]

Where,A is in m/sec2Tbs = the belt tension while starting in N.Tb = the belt tension in steady state in N.L = the length of the conveyor in meters.mi = Load due to the idlers in Kg/m.mb = Load due to belt in Kg/m.mm = Load due to the conveyed materials in Kg/m.

Belt breaking strength This parameter decides the selection of the conveyor belt. The belt breaking strength can be calculated as:

Bs= (Cr*Pp)/ (Cv*V)Where,Bs is in Newton.Cr = friction factorCv = Breaking strength loss factorPp = Power at drive pulley in Newton.V = belt speed in m/sec.

Model calculationInput data:Conveyor capacity (Cc) = 1500 t/h = 416.67 Kg/secBelt speed (V) = 1.5 m/secConveyor height (H) = 20 mConveyor length (L) = 250 mMass of a set of idlers (mi) = 20 KgIdler spacing (l) = 1.2 mLoad due to belt (mb) = 25 Kg/mInclination angle of the conveyor () = 5 0Coefficient of friction (f) = 0.02Startup factor (Ks) = 1.5Drive efficiency (Kd) = 0.9Friction factor (Cr) = 15Breaking strength loss factor (Cv) = 0.75

load due to idlers:mi = (20/1.2) = 16.67 Kg/m

Tb = 1.37*0.02*250*9.81*[16.67+ {2*25+ (416.67/1.5)}*cos (5)] + (20*9.81* (416.67/1.5)) = 77556.88 N.

The belt tension while starting the system Tbs = 1.5 * 77556.88 = 116335.32 N

power at drive pulley, Pp = (77556.88*1.5)/ 1000 = 116.335 Kwsize of the motor:Pm = 116.35/0.9 = 129.261 Kw.

acceleration of the motor:A = (116335.32 77556.88)/ [250*{(2*16.67) + (2*25) + (416.67/1.5)}]= 0.429 m/sec2

the belt breaking strength:Bs = (15*116.35) / (0.75*1.5) = 1551.33 N/mm

This Bs value is used to select the conveyor belt from the manufacturers catalogue