Full definition
Impact idlers are critical components in conveyor systems, specifically designed to mitigate the effects of falling material on the conveyor belt. When material is discharged from transfer chutes or hopper outlets, it generates significant kinetic energy that can lead to damage if not properly absorbed. Impact idlers are constructed from a steel tube core that is fitted with rubber or polyurethane disc rings, which typically have an outer diameter (OD) that is 50-75 mm larger than the core tube. This design allows the rings to act as shock absorbers, cushioning the belt and its carcass from puncture and impact damage. The ring material, often a natural rubber or polyurethane, has a hardness rating of 40-55 Shore A, which provides the necessary elasticity and durability to withstand repeated impacts.
These idlers are strategically installed in the loading zone, replacing standard carrying idlers to deliver superior support where the belt experiences the highest stress. The spacing between impact idlers is reduced to 300-500 mm compared to the standard 1,000-1,500 mm, ensuring maximum support and stability for the belt under the weight of falling materials. In scenarios involving very heavy impacts—such as large lump sizes or significant drop heights—impact cradle or bed systems equipped with continuous rubber bars may be used instead of individual idlers. This setup helps to support the belt across its entire width, further distributing the impact forces.
The design and selection of impact idlers must adhere to established guidelines, such as those provided by the Conveyor Equipment Manufacturers Association (CEMA) in their loading zone design recommendations. According to these guidelines, impact energy increases in proportion to both the drop height and the mass of the material being conveyed. Therefore, accurate calculations and careful planning are essential to ensure that the impact idlers can handle the anticipated loads effectively. Compliance with relevant standards, such as DIN 22112 and CEMA 7th Edition, is crucial for ensuring that the conveyor system operates safely and efficiently.