Several problems that should be paid attention to

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Several problems that should be paid attention to in the use of tower crane

in recent years, with the rapid development of urban construction travel of 600-800mm, the application of tower crane is also more and more widely. Some neglected problems often occur in the use of tower crane, which leads to mechanical accidents and safety accidents from time to time. This requires that the tower crane operators should pay attention to the following problems during the use of the tower crane

first, do not use the tower crane rotation positioning as the rotation brake, and it is strictly prohibited to turn the reverse direction to realize the rotation and stop

The slewing system of the tower crane mostly adopts the combination of slewing bearing and hydraulic coupling, which increases the slewing inertia of the slewing system. When stopping in operation, although the slewing motor loses power and stops running, the front and rear arms of the tower crane still continue to slow down under the action of huge slewing inertia, causing the hoisted object to slide over the destination in a short time and cannot fall accurately, which requires the tower crane operator to stop by jogging continuously a certain distance in advance according to experience. If the wind is relatively strong and the forearm can be rotated and shifted, the rotation positioning system can be used to stabilize the forearm for a short time, so that the lifted object can fall accurately. In the actual operation process, someone understood the rotary positioning as the rotary brake. When the lifted object is about to have a closer look, it suddenly presses the lower switch when it passes the landing point, in order to force the rotary system to stop running, which is absolutely not allowed. Because, although the rotation positioning stops the operation at the root of the forearm, the far end of the forearm still continues to operate for a short time under the action of the rotation inertia. This kind of asynchronous operation between the far end and the near end will produce a large torque on the tower body, which is not conducive to the overall stability of the tower crane. The most direct manifestation is that the rotary motor shaft cannot withstand a huge reverse torque and disconnect, so, During operation, it is strictly forbidden to realize rotary parking by reversing the steering

II. If the winch releases the holding brake and the empty hook falls quickly, it will seriously damage the motor

during the installation, disassembly or maintenance of the tower crane, sometimes in order to speed up the speed, loosen the electromagnetic brake of the winch and let the hook fall freely in many cases, which is absolutely not allowed. Because under the acceleration of free fall, the falling speed of the hook is faster and faster, which may make the falling speed greater than or even far greater than the rated lifting speed, so that the gearbox drives the motor to accelerate passively, so that the speed of the motor exceeds the rated value. Although the motor is only idling, the mechanical strength of the motor is designed according to the rated speed. Exceeding the design rated speed, especially exceeding its limit allowable speed, will destroy the mechanical characteristics of the motor, make the rotor disperse under the action of large centrifugal force, and thus damage the motor

III. the lifting torque limiter and the lifting weight limiter have their own division of labor and can never be replaced

the lifting torque limiter is the most important one in the tower crane limit protection system. It is a comprehensive limit on the interaction between the force arm and the crane weight. It not only strictly limits the lifting weight at different distances, but also limits the maximum travel allowed by the lifting object with the same lifting weight. When the lifting torque limiter acts, the lifted object is only allowed to fall, not allowed to rise; The luffing trolley is only allowed to recover, not to advance, so as to prevent the tower crane from overturning and protect the tower crane foundation, tower body and other structural components from damage; The lifting limiter plays the role of limiting the maximum lifting capacity of the tower crane and protecting the lifting mechanism of the tower crane from damage. The two concepts are completely different. If the lifting torque limiter is canceled and only the lifting torque limiter is used, the maximum lifting weight can be lifted at any distance from the forearm, and the torque limit protection at different distances cannot be realized; If the lifting moment limiter is only used, even if the lifting weight at the arm root near the tower exceeds the rated maximum lifting weight, the lifting limit protection cannot be achieved. Therefore, the functions of lifting torque limiter and lifting weight limiter are different. In terms of the overall protection of the tower crane, both are indispensable and cannot be replaced by each other

there are many factors that affect the safety during the use of the tower crane. Here, a simple analysis is made from the above three aspects. To ensure the safe use of the tower crane, we must strictly follow a series of norms and standards for the use and management of the tower crane, so that the tower crane operators can master the basic performance and operation methods of the tower crane, and reduce the occurrence of tower safety accidents to the lowest point

(sunchunlei, zhuchongfeng)

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