Troubleshooting Brake Failures in Chain-Drive Electric Hoists Chain-drive electric hoists are lightweight, compact specialized lifting devices. In large-scale lifting equipment, they are generally regarded as an essential component of the hoisting mechanism. If a chain-drive electric hoist experiences a brake failure, its performance will naturally be compromised.

The operating principle of the chain-type electric hoist is as follows: first, the lifting motor is started to raise the load to the desired height; then, the traveling motor is activated to transport the load to the designated location, with the trolley moving along the edge of a single I-beam below.

During travel, an electric motor drives the wheels on both sides of the trolley. Because the traveling speed is relatively low, traveling trolleys are typically not equipped with a braking mechanism. To prevent the load from descending, an electromagnetic brake is installed on the lifting mechanism when the trolley is in motion.

Braking is achieved by using spring pressure to tightly clamp the inner and outer discs together, operating on a principle similar to that of a friction clutch. To release the brake, an electromagnetic solenoid is energized to create a magnetic field that lifts the outer disc, thereby disengaging the inner and outer discs.

The circuit of the electromagnetic brake is connected in parallel with the circuit of the hoisting motor; therefore, once the hoisting motor is started, the electromagnetic brake releases, allowing the load to be raised and lowered freely.

When the electric motor is switched off, the electromagnetic brake is also de-energized, eliminating the electromagnetic holding force. Under the action of spring pressure, the inner and outer brake discs are pressed tightly together to engage the braking function. To prevent accidents caused by overtravel beyond the lifting position, a lift limiter is typically installed at the lower part of the drum. When the load reaches the designated position, the pressure plate contacts the switch, cutting off the power supply and preventing further upward movement of the load. Since the limiter is designed to prevent the hoist from rising above its intended position, it should not be used frequently.

When a chain-type electric hoist experiences a braking failure, the appropriate course of action is to disconnect the equipment’s power supply and forcibly bring the Chongqing chain-type electric hoist to a stop.

The next step is to identify the root cause of brake failure in chain hoists, starting with the braking motor and the braking mechanism itself. Generally, shaft breakage in the motor and improper assembly of the brake ring and other components are common causes of brake failure in chain hoists.

By inspecting the chain-type electric hoist, qualified personnel can readily identify the precise cause of the brake failure and then address it in a targeted manner—for example, by replacing defective components or correcting assembly errors. However, if the brake failure is attributable to improper assembly, it indicates that the brake ring of the chain-type electric hoist has entered a more severe stage of wear, making it necessary to replace the component outright.