Common false faults and solutions for general double-beam bridge cranes

In the process of using double girder bridge cranes in enterprises , there may be some problems that are not equipment but cannot be operated. For new operators and maintenance personnel with relatively little experience, it is necessary to understand some common false faults of general double girder bridge cranes, and they can be resolved in time to avoid affecting production. The editor uses a few examples to illustrate possible false faults and solutions for bridge cranes.

1.  A double-beam bridge crane in a certain unit has its power indicator light on and the control linkage platform indicator light on, but it cannot be started. After the maintenance personnel went to the site to check, it was found that the safety door from the driver's cab to the platform was not closed. When the maintenance personnel close the safety door, all the crane operations are normal, which is a false fault. In the safety protection of the crane, there is a door switch on the hatch door, the driver’s cab door and the inspection door. When the crane driver or maintenance personnel goes to the crane for inspection and repair, the hatch door must be opened to the crane platform, or Open the overhaul door to the voie de grue beam. At this time, the normally closed contact of the electrical switch on the opened door is disconnected, and the main contactor of the electrical box is released, thereby cutting off the crane power supply, making the crane unable to start. At the same time, this kind of protection protects the maintenance personnel from the threat of electrification of the trolley on the bridge frame, and can also prevent others from starting and driving to injure the maintenance personnel. It can be seen that the protective effect of the safety door switch is very necessary.
2.  The power supply of a double-beam bridge crane is normal, and the safety doors are closed intact, but it cannot be started. After inspection by maintenance personnel, it was found that the lifting control cam did not return to zero well, that is, although the zero mark of the cam was at the zero position, the zero protection contact was not in contact. Because this is a crane that has been used for many years, its contact elasticity is weakened, resulting in false faults that sometimes fail to reach. Replace the contacts with new ones, and the non-start problem is solved. It can be seen from the structure of the cam controller that only when the handles of the controllers are placed in the zero position, the zero position contacts of the hoisting, trolley and cart controllers are closed. In any other working position (that is, non-zero position), it is in the off position. Therefore, when any controller handle is not in the zero position (or the zero position contact is not closed), the main circuit of the crane cannot be connected and the crane cannot be started. This prevents the occurrence of dangerous accidents in which the mechanism suddenly moves when the handle is not returned to the zero position due to some reason, but is restarted in the working position. This is the zero protection function of the crane.
3.  A double-beam bridge crane has normal power supply, safety door and control handle, but it cannot be started by pressing the start button. The maintenance personnel went to the site to check and forcibly started the main contactor, which was operating normally. But the contactor cannot be disconnected when the stop button is pressed, but the contactor is disconnected when the start button is pressed. Press the stop button again, the main contactor starts normally, indicating that the start button and the stop button are connected reversely. This is the false fault caused by the maintenance personnel not explaining clearly.
4.  A 32/5-ton double-beam bridge crane has a reduced lifting capacity , and the main hook can only lift heavy objects of more than 20 tons. After several repairs, it is believed that the electrical part is aging. But in the inspection of the electrical part, from the power supply to the controller, the wire diameter meets the standard; the contacts of each contactor are intact; the main contacts of the cam controller are also intact; the wiring of the main hook resistor is correct and the wiring is good; the main hook The wiring of the motor is correct, the rotor brushes are good, and the motor rotating noise is normal, indicating that the fault is not in the electrical part. When inspecting the mechanical part, it was found that the wire rope of the main hook was worn out. Open the fixed pulley cover on the trolley frame. It was found that the wire rope was not on the pulley, but had fallen on the pulley shaft, and it was found that there was a gap in the rim of the pulley. A new pulley was replaced, and a new wire rope was replaced at the same time. As a result, the 10t weight of the test crane was normal.

For this failure phenomenon, the general maintenance experience is mostly in the electrical part. If the wire diameter is not enough, the main contact is not well connected, the resistor wiring is wrong, etc., the lifting capacity will be reduced. The fault was blocked by the protective cover of the fixed pulley, which caused a detour for the maintenance.

The staff and maintenance personnel who operate the bridge crane should abide by the crane’s safe operation regulations and have sufficient knowledge of the equipment when using the crane . When the double-beam bridge crane has an abnormal situation, the cause should be analyzed according to the problem. As long as careful inspection and comprehensive observation, some false faults can be identified.

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