Overloading of bridge cranes is absolutely not allowed. Overloading during lifting will cause pressure and damage to the equipment and pose a safety hazard to operators and workers. It is strictly prohibited to lift heavy objects exceeding the rated load on any equipment. Bridge cranes should always be used in accordance with the manufacturer's specifications and instructions. Do not attempt to lift loads exceeding the crane's rated lifting capacity.
Nowadays, most bridge cranes are equipped with safety devices to help prevent related accidents of the cranes. The following introduces what safety devices a bridge crane has and their functions.
The types of safety devices for bridge cranes mainly include electrical safety devices and mechanical safety devices.
The safety devices of the electrical types of bridge cranes include:
1. Lighting switch box: It can ensure the lighting at the work site and provide a better operating line of sight for the operators of electric bridge cranes.
2. Electric crane bell: Its main function is to remind the operator below the crane to take shelter when the large vehicle is in operation, or to alert the hoisting workers to start the crane operation.
3. Travel limit switch: Its function is to prevent the motor-driven machinery from overmoving and causing accidents when the crane reaches its limit or a specified location.
4. Emergency switch: Installed beside the driver's cab, it enables the driver to conveniently and quickly cut off the power supply of the control circuit in case of an accident or emergency.
5. Door cabin safety switch: Installed at the door and cabin opening, it is used to prevent accidents caused by the driver blindly powering on when someone is getting on or off the crane or working on the crane walkway.
6. Anemometer: Its main function is to cut off the power supply when the wind is strong, to prevent the electric crane from being blown away by the wind and unable to stop, which may cause safety accidents. (Mostly assembled on open-air bridge cranes and gantry cranes)
7. Fuse: Used to protect the control circuit from short circuits.
8. Phase sequence protector: It mainly protects the phase sequence of the main power supply. After the crane is debugged, the main power supply cannot be turned around at will; otherwise, it will cause the electric crane to operate in reverse and the limit device to malfunction.
9. Overcurrent relay: Protects the main circuit and motor from overload and short circuit.
10. Zero contact of the controller: Protects against zero start and prevents the controller handle from being powered on to start when it is in the working position. Causing the motor to run by itself leads to an accident.
11. Overload limiter: Its main function is to cut off the lifting circuit of the bridge crane when the lifted object exceeds the rated lifting capacity of the crane, to ensure the safety of the crane.
The safety devices of the mechanical types on the electric bridge crane include:
1. Railings at all parts: To protect the safety of the staff and prevent accidents caused by accidental falls. Railings of no less than 1 meter are installed on the outside of the walkway, end beams and trolleys.
2. Hook safety card: It prevents the steel wire rope from sliding out of the hook head when the crane is lifting objects due to a large distance between the two ends or a large force.
3. End guard plates of the track: The end guard plates on both sides of the trolley and the main trolley are designed to prevent the trolley and the main trolley from overstepping and causing accidents.
4. The sliding contact line baffle of the large vehicle is designed to prevent the hook from swinging out of position and causing electric shock accidents.
5. Buffer: It works in conjunction with the end plate (impact block) to reduce the impact force when the trolley collides with each other or with the end plate of the track (most buffers used in cranes are spring type).
6. Track sweeping plates: To prevent foreign objects from being on the track, track sweeping plates are used to push the foreign objects to both sides.
7. Protective covers: Rapid drive shaft covers, hook covers, pulley block covers, etc., are used to protect the safety of moving parts, ensure the safety of personnel, and prevent cast iron parts from being damaged by collision.
8. Cab fire extinguisher: Essential item to prevent electrical fires. Generally, powder fire extinguishers are used.
