Wear and repair parts

The following parts of a conveyor belt scale are subject to a need for service due to wear and tear and, possibly, repair or replacement: integrator, weigh bridge, load cells, and speed sensor proximity switch.

The integrator is prone to potential failure due to issues with seasonal lightning if not properly grounded during electrical installation of the belt scale. Additionally, with a long cable run (i.e., between a conveyor and a control room) there is the opportunity for noise from wire interference (from anything that uses or produces power) to be introduced into the signal wires and affect the accuracy/operation of the scale.

This weigh bridge shows one (of two) load cells. The rigid weigh bridge allows the pressure (weight) of the material being conveyed to be sent to the integrator for processing.

The weigh bridge has additional electronics including junction cards, load cells, and failure potential for frayed wiring due to neglect. Additionally, the belt scale installation can suffer from problems as a result of a need for shimming/alignment of the scale weigh bridge and/or the idlers both before and after the scale. Some conveyor belt scale manufacturers require the idlers before and after the scale idlers to be shimmed.

Load cells are the devices which receive the force transferred by the conveyor idler supported by the weigh bridge. The force is then converted to an electrical signal that can be received by the integrator, which processes the signal as a load on the conveyor belt scale. Typical load cell designs for conveyor belt scales include both “shear-beam” and “S-type” load cells similar to beam and platform scales. The capacity of the conveyor in tons per hour will determine the load rating of the load cells commonly in 100-pound, 250-pound, 750-pound, and 1-kilogram capacities. A weigh bridge will use either one or two load cells. A multiple idler scale system consisting of multiple weigh bridges can use up to a total of eight load cells.

Speed sensors utilize electronic proximity switches and wiring in addition to mechanical wheels and greaseable bearing sets. Due to the mechanical nature of the speed sensor design, a catastrophic failure of a proximity switch may also require the replacement of a cog or counting wheel, in addition to a new proximity switch, to complete a repair of the speed sensor.

It is best to contact a manufacturer or local scale service company with your specific issues and further questions for their review and expert recommendation. AM

Austin W. Amos has 16 years of experience in the weighing industry and currently holds the position of general manager at ConveyWeigh, LLC., a West Virginia-based manufacturer of conveyor belt scales, and is an appointed member of the West Virginia District Export Council.