Bridge Crane Maintenance Tips

Bridge Crane Maintenance Tips
 

In the operation and use of general-purpose bridge cranes, there are often some simple phenomena that are not faults and cannot be operated.

(1) Safety door
 

For a 10 ton double-beam bridge crane in a certain unit, its power indicator light is on, and the indicator light of the control linkage platform is on, but it cannot start.
 

After the maintenance personnel went to the scene to check, it was found that the safety door from the driver's cab to the walking platform was not closed. When the maintenance personnel close the safety door, all the operation of the crane is normal, which is a false fault.
 

In the safety protection of the crane, there is a door switch on the hatch door, cab door and inspection door. When the crane driver or maintenance personnel go to the crane for inspection and maintenance, they must open the hatch door to the crane walking platform, or Open the inspection door to the crane track beam, at this time the normally closed contact of the electrical switch on the opened door is disconnected, the main contactor of the electrical box is released, and then the crane power is cut off, making the crane unable to start.
 

At the same time, this protection protects the maintenance personnel from the threat of electrification of the trolley sliding wire on the bridge frame, and also prevents others from starting and driving to injure the maintenance personnel. It can be seen that the protective function of the safety door switch is very necessary.

(2) Controller
 

The power supply of a 10 ton double girder bridge crane is normal, and the safety doors are closed intact, but it cannot be started.
 

After on-site inspection by the 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.
 

This is a crane that has been used for many years, and its contact elasticity has weakened, causing false faults that sometimes cannot be contacted. Replaced the contacts with new ones, and the non-start problem was resolved.
 

From the structure of the cam controller, it can be seen that the zero contact of the lifting, trolley and cart controllers is closed only when the handles of each controller are placed in the zero position. And in any other working position (that is, non-zero position), it is in the disconnected position.
 

Therefore, when any controller handle is not at 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 dangerous accident that the mechanism suddenly moves when the handle does not return to the zero position for some reason and is restarted when it is placed in the working position. This is the zero position protection function of the crane.

(3) Button
 

A 10t double-girder bridge crane has a normal power supply, safety door and control handle, but it cannot be started by pressing the start button.
 

The maintenance personnel went to the scene to check and forcibly started the main contactor, and it was running normally. However, the contactor cannot be disconnected when the stop button is pressed, and 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 stop button are reversed.
 

This is the false fault caused by the failure of the maintenance personnel to explain clearly.

(4) Wire rope, pulley
 

A 10t double-girder bridge crane has a reduced lifting capacity and can only lift more than 5 tons of heavy objects.
 

After several repairs, it is considered to be caused by the aging of the electrical part. However, in the electrical part of the inspection, from the power supply to the controller, the wire diameter meets the standard; the contacts of each contactor are in good condition; the main contact of the cam controller is also in good condition; the wiring of the main hook resistor is correct and the wiring is good; The wiring of the motor is correct, the rotor brushes are in good condition, and the sound of the motor rotating is normal, indicating that the fault is not in the electrical part.
 

When checking the mechanical part, it was found that the wire rope of the main hook was greatly worn. Open the fixed pulley cover on the trolley frame, and saw that the wire rope was not on the pulley, but had fallen on the pulley shaft, and found that there was a gap in the rim of the pulley. A new pulley was changed, and a new steel wire rope was replaced at the same time. As a result, the 10t heavy object of the test run was normal.

For these fault phenomena, the general maintenance experience is mostly in the electrical part, such as insufficient wire diameter, poor contact of the main contact, wrong wiring of the resistor, etc. will cause the lifting capacity to decrease, so many maintenances are carried out in the electrical part, but this fake The fault is blocked by the fixed pulley protective cover, which makes the maintenance take a detour.