1. Slip hook during parking braking: the electrical control process stops, the motor stops, the brake brakes, and the goods slide more than 50 ~ 60 mm or fall out of control.
2. Slip hook during braking: the handle is pulled back to the zero position from the running gear. During the period from the motor starts to decelerate, the brake starts to brake to the end of the braking process, the goods slip down or stall and fall.
3. Slip hook during lifting operation: the handle is pulled from the zero position to the lifting working gear, the brake is opened, and the motor begins to accelerate until it operates stably, and the goods slip down or fall out of control.
4. Slip hook during lowering operation: the handle is pulled from the zero position to the lowering working gear, the brake is opened, the motor starts to accelerate until it runs stably, and the goods slip down or fall out of control.
5. Hook slipping caused by illegal operation.
Reasons for sliding hook of gantry crane
1. Causes of hook slipping during parking braking
With the change of climate, environment and equipment operating conditions, the positive pressure, friction coefficient and brake wheel diameter of the brake pad of the gantry crane will also change. When the actual braking torque of the brake is less than the static torque of the goods, the slip hook during parking braking will appear.
2. Causes of hook slipping during braking
(1) During the braking process of the gantry crane, the line voltage is too low, so that the working torque of the motor is lower than the load torque, or the motor suddenly loses power, and at this time, the brake has not been fully braked, which will cause the hook sliding fault.
(2) The control program of the electric control system of the gantry crane is wrong, and the brake action is delayed, that is, the brake starts to close after the electromagnetic torque of the motor is too small or completely disappears, causing hook sliding fault. This phenomenon often occurs in the hoisting mechanism that uses frequency converter, DC governor and stator voltage regulator to realize soft start and soft braking. In order to realize the soft start function, the adjustment of the accurate shutdown time is ignored, and this kind of hook slipping will occur.
(3) Failure of the electrical control system and protection system of the gantry crane, such as the adhesion of the contactor controlling the brake, which leads to the failure of the brake to close, or the wrong opening of the brake due to the influence of electromagnetic interference, or the premature loss of excitation of the motor during the braking process caused by the failure of the governor, will cause the occurrence of hook slipping failure.
3. Causes of hook slipping during lifting operation
(1) During the lifting operation of the gantry crane, the power supply voltage is too low or the motor suddenly loses power, which will reduce or disappear the starting torque of the motor, resulting in hook slipping.
(2) The control program of the electrical control system is wrong, and the brake is opened too early, that is, the brake is opened before the electromagnetic torque of the motor is established, causing hook slipping.
(3) If the electrical control system and protection system fail, such as the governor fails or the protection device acts, the motor loses excitation in advance before the brake is closed, resulting in the occurrence of hook slipping fault.
4. Causes of hook slipping during lowering operation
At the moment when the lifting mechanism descends and starts, the motor accelerates to start under the drag of the goods. With the increase of speed, the electromagnetic torque of the motor becomes larger and larger. If the electromagnetic torque of the motor decreases or becomes zero for some reason, the goods will stall and slide, resulting in hook slip failure.
5. Reasons for hook slipping caused by illegal operation
(1) Overload use, oblique pulling, excessive operation and strong wind operation lead to hook sliding failure.
(2) In case of accidental hook slipping fault, the driver operates in the reverse direction, resulting in the repeated starting process of the motor, and the electromagnetic torque of the motor cannot be established, resulting in the aggravation of hook slipping fault.
