the role of the weight limiter in lifting the tower crane, and what is its structure and working principle

30-07-2019

The tower crane has a variety of safety devices such as limiters, which can effectively reduce the occurrence of tower crane accidents. In this paper, the function, structure and working principle of the weight limiter around the tower will be explained and analyzed.

1. Act as a weight limiter:
When the lifting load exceeds the rated load, the lifting weight limiter can output the electrical signal, cut off the lifting control loop, and can issue an alarm to prevent the tower from overloading.

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The existing national standard "Safety Regulations for Tower Cranes" stipulates that tower cranes should be equipped with weight limiters.

If a weight display device is installed, the numerical error should not exceed 5 % of the actual value.

 When the maximum rating of the starting weight is greater than the corresponding block and is less than 110 % of the rated value, the power supply in the ascending direction of the lifting mechanism shall be cut off, but it may be used as a motion in the descending direction.
2. Construction and operation of the lifting weight limiter:
At present, the most commonly used weight limiter is a force measuring ring type. It consists of a force measuring ring, a guide pulley, and a limit switch. It is characterized by compact size, good performance and easy adjustment.

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Working principle: tower lifting heavy lifting, pulley by the joint action of steel wire rope, the force passed to the measuring ring, measuring the deformation of the ring and load into a certain proportion.

 Depending on the lifting load, the pulley will also have different force sizes. The shell of the measuring ring is deformed with the force, and the metal plate in the measuring ring is fixed with the shell of the measuring ring, and it extends with the deformation of the shell.

 At this time, according to the load situation, the adjustment bolt fixed on the metal strip is adjusted. And the limit switch distance, When the load exceeds the rated lifting weight, the limited-position switch is moved so as to cut off the power supply of the lifting mechanism and achieve the purpose of limiting the lifting weight overload.

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