Belt conveyors have long been recognized as the simplest, most reliable, and most economical means of handling materials in large or small volumes.
A belt conveyor consists of a moving, endless belt, which supports material and, by its motion, carries the material from one place to another. The belt is driven by a pulley and is supported through all its length, going and coming, by rollers or by a runway. The wheat is usually put on the belt by a chute and is removed from the belt by discharge over the end pulley or by deflection at some point along the run of the conveyor with a special mechanism . The elements of the belt conveyor are 1) a belt to carry the material and transmit the pull, 2) a means to support the belt, usually rollers or pulleys, 3) a means to drive the belt, usually a pulley or a pair of pulleys, and 4) accessories for maintaining belt tension, such as take-ups; for loading the belt, such as a chute; for discharging the material, such as a chute, tripper, or scraper; and for cleaning and protecting the belt, such as housing, decks, covers, and cleaning brushes.
The belt is a flexible, endless, and usually joint less, flat strip of material that runs quietly at any speed. With good aspiration at the wheat loading and unloading points, no dust should be generated to cover the belt structure or moving parts. In addition, the wheat does not come into contact with moving parts such as pulleys, rollers, or shafts, which ensures low friction losses and reduced power consumption. The belts themselves are made from a wide range of materials. They must be flexible to wrap around the pulleys, must withstand the tension between the pulleys, and must convey the pull between them. Their width and strength are calculated based on the amount of material they convey. During construction of the belt conveyor, a support system can be installed to reduce loading zone impact stress and control fugitive materials. Thissystem can be installed below the conveyor loading point to cushion blows of heavy loading and reduce impact damage to the belt, idlers, and conveyor structure.
Some of the advantages of properly designed belt conveyors are 1) handling bulk at the lowest cost per ton—in large and small volumes, 2) carrying material up slopes of up to 27°, 3) being low in cost, 4) having large capacity at low power consumption—up to 6,000 tons per hour, 5) delivering uniform volumes at high or low speed, 6) having few parts subject to wear, 7) being simple, quiet, and reliable, and 8) with good care, handling up to 100 million tons. A general expression of horsepower for belt conveyors depends on two elements: the empty conveyor and the material requirements. It can be expressed as follows:
where F = a friction factor of the belt, B = weight of the belt and moving parts, L = length of the conveyor in feet, G = friction factor of the load on the belt, and T = tons of material per hour. A weighing segment can be installed on the conveyor belt. Such devices are fitted as one segment of the roller support system in the belt. They are available at up to 182 cm (72 in.) in width and with a capacity of up to 6,000 t/hr. Heavy-duty plate magnets suspended from a support frame can be installed over the conveyor belt. Plate magnets for conveyor belts are available up to about 120 cm (48 in.). A recent development eliminates the supporting rollers along the conveyor belt. The belt moves on a 1-mm (0.04-in.) thick film of air generated by a fan located between the belt and the trough supporting it from below. The thin film of air supports loads up to 976 kg/m2 (200 lb/ft2) at high speed with no mechanical friction. The benefits of the air-supported belt conveyor are the reduced maintenance of rollers and up to 30% reduction in power requirements. The smooth movement of the belt on the air layer in an enclosed structure eliminates material segregation and dusting and reduces noise level.