Full definition
A backstop, also known as an anti-runback device, is a critical component in inclined conveyor systems, designed to prevent the unintended reversal of the conveyor belt when the driving motor ceases operation. This failure mode can occur due to power loss or motor malfunction, leading to potential hazards and material loss. The backstop functions by locking the drive mechanism, ensuring that the loaded belt remains stationary and prevents the material from sliding backward down the incline. This is especially vital in applications where bulk materials are loaded onto inclined conveyors, as uncontrolled movement can result in spills, equipment damage, or safety risks to personnel.
There are several types of backstops, including ratchet backstops, sprag clutches, and centrifugal backstops. Ratchet backstops engage when the belt attempts to run backward, utilizing a pawl and ratchet mechanism to lock the drive. Sprag clutches, equipped with rollers or sprags, allow rotation in one direction while preventing movement in the opposite direction. Centrifugal backstops use centrifugal force to engage the locking mechanism as the speed decreases, thus providing a reliable solution for various operational conditions.
The selection of a backstop is a critical task that involves calculating the holdback torque necessary to counteract the weight of the material being conveyed, the conveyor's length, and the angle of inclination. The backstop must be capable of withstanding these forces without failure. Accurate calculations are essential to ensure the backstop can handle the maximum expected load, which can be determined using the formula for torque: Torque (T) = Force (F) × Distance (d), where force is the weight of the material and distance is the radius of the pulley. Reference standard ISO 9588 provides guidelines for the design and performance of such devices, ensuring they meet industry safety requirements.