Many bulk materials can be carried on flat belts. Flat belts are particularly common for materials with a steep angle of repose, the angle that a freely formed pile of material will make. Materials with angles of repose above 30 degrees are materials suitable for flat belts and range from irregular, stringy, fibrous, and interlocking, such as wood chips and bark. When maintaining the same edge distance with materials with a low angle of repose, the volume of material conveyed is reduced; therefore, materials with a low angle of repose generally require the belt to be troughed.
Flat belt are especially effective when the load, or a portion of the load, is to be discharged from the belt at intermediate points by plows or deflector plats.
Belt feeders use flat belts almost exclusively. This is because feeders are generally very short and they must fit into operations where there is little room to form the belt into a trough. Feeders typically operate with very high loads and use heavy-duty idlers. Many feeder belts can reverse direction, to move a large material load, feeder belts often run at high tension making it difficult to tough a belt. In addition, the high head load of belt feeders makes sealing difficult. This difficulty can be overcome by leaving generous edge distances and operating at slower speeds; then spillage from these belt feeders can be controlled. In many cases, these belts are equipped with a skirtboard and a sealing system along their full length. Other feeder belts incorporate dual chutewall design, where a space is left between the interior chutewall installed with a wear liner and an outside chutewall that includes the belt’s edge seal. Flat belts do not require the transition areas or suffer the transition problems encountered by troughed conveyors. However, most of the other conveyor components and problems discussed in this book will apply to flat belt conveyors
For most materials and most conveyors, the forming of the belt into a trough provides the benefit of a generous increase in the belt’s carrying capacity.
See Also: Conveyor Belts Flat and Troughed Part 2.