Crane protection devices and requirements

1. Overload limiter

Overload limiter

The overload limiter is a safety device that prevents the crane from overturning due to overload and prevents the parts of the crane from being damaged due to overload. Its function is: when the load reaches 90% of the rated lifting capacity, it can send out a revealing alarm signal. After the overload limiter is set, it should be adjusted or calibrated according to its performance and accuracy. When the rated lifting capacity is exceeded, the lifting power source can be automatically cut off and a prohibitive alarm signal will be generated. According to the requirements of GB6067-85 “Safety Regulations for Hoisting Machinery”, bridge cranes with a rated lifting capacity greater than 20t should be installed, and those with a rated lifting capacity of 3~20t should be installed; tower cranes with a lifting capacity of less than 25t.m should be installed.

2. Lifting moment limiter

Lifting moment limiter

The moment limiter of the crane is a very important safety device for the boom type and trolley luffing type crane because this kind of crane can only lift a certain weight within a certain range. Set the limiter brake. On some tower cranes, if the product of hoisting weight and amplitude is fixed, the lifting moment limiter can simultaneously control the two parameters of hoisting weight and amplitude to keep their product at a certain position. Its function is when the crane exceeds the rated lifting moment, first sends out an alarm signal, and then cut off the power source to ensure the stability of the crane. According to the requirements of the “Safety Regulations for Hoisting Machinery”, truck cranes with a lifting capacity of less than 16t should be installed, and those with a lifting capacity equal to or greater than 16t should be installed; tower cranes with a lifting capacity equal to or greater than 25t.m should be installed.

The moment limiter plays a protective role against the overload moment in the longitudinal and vertical plane of the crane jib, and cannot protect the crane from overturning accidents caused by oblique hanging, wind load, inclination or subsidence of the ground or track, and running wheel out of the wheel. Therefore, the relevant duties Personnel must not ignore the safety management and safe operation regulations of the crane because of the torque limiter.

3. Ascent limit position limiter

The function of this limiter is to automatically cut off the rising power supply when the pulley is lifted to 300mm from the limit of the winch, so as to prevent a major accident if the pulley continues to rise beyond the limit and breaks the wire rope. It can be extended; for the hydraulic lifting mechanism, a prohibitive alarm signal should be generated. According to the requirements of the “Safety Regulations for Hoisting Machinery”, the power-driven crane must be equipped with a limit position limiter.

4. Operating limit position limiter

The function of this limiter is to control the motor according to the process required by the mechanism. According to different purposes, it can be divided into two types: end switch and safety switch. The end switch is used to limit the operation of the working mechanism within a certain range and is installed at the end of the stroke of the working mechanism. The safety switch is used to protect personal safety to prevent sudden start electric shock, extrusion, twisting, misoperation, and other vicious accidents. According to the “Safety Regulations for Lifting Mechanisms”, for bridge and tower cranes, in order to control the travel range, an end limit switch must be installed so that the crane can automatically stop when it approaches the end of the track. A crane stop should also be set at the end of the crane track to prevent the crane from driving out of the track.

5. Buffer

buffer Crane protection devices

As an energy-absorbing device, the buffer can be used to reduce the collision force generated when the crane collides with the crane or the crane and the end stopper. The plant will not be damaged due to excessive impact, so as to prolong the life of the crane. Buffers are usually used in the crane’s trolley and trolley running mechanisms, and rubber, spring, and hydraulic buffers are commonly used. There are also wooden and plastic bumpers.