What are the reasons for elevator wire rope slipping? [answered]

When the elevator is in normal operation, such as sudden power failure, safety protection device action and other dangerous events, the brake will make emergency braking to slow down the elevator and keep it stopped. Elevator emergency braking usually depends on the sliding friction between the brake wheel and the brake shoe to slow down the elevator until it stops. However, if the deceleration generated by the brake during elevator emergency braking exceeds the maximum deceleration provided by the traction force (friction), there will be slip between the traction wheel and the steel wire rope, and the deceleration provided by the traction force will slow down the elevator until it stops.

The following is a brief analysis of the slip of emergency braking when the elevator runs to the same horizontal position as the counterweight with a simplified elevator model. Although the steel wire rope, compensation chain and traveling cable may also produce unbalanced torque when the car is at the same horizontal position as the counterweight, considering the role of the compensation chain and the small unbalanced torque, the unbalanced torque generated by the steel wire rope, compensation chain and traveling cable is ignored, and its weight is included in the self weight of the car and counterweight for analysis.

2 Summary

During elevator inspection, there is often slip between traction wheel and steel wire rope during no-load up emergency braking or heavy load down emergency braking. And it is often easier to slip between the traction wheel and the steel wire rope during no-load up emergency braking than during heavy load down emergency braking. During emergency braking, the traction wheel and the steel wire rope slip, indicating that the traction force between the traction wheel and the steel wire rope is less than the traction force required to support the braking deceleration generated by the brake. In turn, the traction force can only provide a smaller deceleration, that is, the deceleration after starting sliding, which is also the deceleration measured by us.

During the elevator inspection, if the elevator operation record shows that the traction wheel and the steel wire rope slip during the no-load up emergency braking of an elevator or a certain type of elevator, but there is no slip between the traction wheel and the steel wire rope during the no-load up emergency braking, it indicates that the braking force of the elevator decreases or the traction force has changed significantly. It is recommended to conduct a braking test to verify whether the braking force meets the requirements, On this basis, it is selected whether to further check whether the steel wire rope, traction wheel groove and lubrication have changed significantly affecting the traction force.