Common accidents of hoisting mechanism of the hott

2022-07-29
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Common accidents of the lifting mechanism of the tower crane as the main machinery on the construction site, the tower crane plays a key role in the maintenance of the electronic universal testing machine in terms of the impact of static electricity on the electronic universal testing machine when the construction control box mainly includes oil tank, oil pump, oil filter, motor, speed valve, oil return valve, etc. The working performance of the three transmission mechanisms of tower crane, especially the lifting mechanism, is an important symbol to measure the advanced level of tower crane technology

the main function of the lifting mechanism is to lift heavy objects. In the process of frequent lifting, unloading and speed change, the parts and components of each link of the driving system of the lifting mechanism are in a large alternating stress state, which will be damaged due to fatigue and other reasons. Once the parts are damaged, the whole driving system will fail, and the consequences will cause the heavy objects lifted in the air to suddenly fall out of control, resulting in sudden accidents, This happens from time to time on the construction site

1 common accidents of horizontal mounted transmission system

the horizontal mounted transmission system is a more traditional arrangement, which rarely causes problems under normal circumstances, but the following situations often cause accidents, which cannot be underestimated

transmission system of hoisting mechanism adopted by QTZ80 tower crane. According to the structure of the gearbox, there are two electromagnetic clutches on the I-Axis and one on the ii-axis, which respectively control the high, medium and low speeds. The electromagnetic clutch is reduced by the power supply through the transformer, rectified into DC by the bridge thyristor rectifier, and then powered by the master controller respectively through the excitation under current protector: ① poor power supply quality or under voltage of the tower crane; ② Excitation under current protection failure; ③ Defect of electromagnetic clutch or poor contact of carbon brush; ④ Improper maintenance of electromagnetic clutch; ⑤ Under current failure of eddy current brake and too small adjustment of brake torque will make the electromagnetic clutch not close well and cause hook slipping

in addition, after 3-5 years of operation of this type of tower crane, due to long-term undervoltage of power supply, overweight, lack of oil in gearbox or poor quality of lubricating oil, the internal and external friction plates of the electromagnetic clutch were burned and deformed, and the friction plates became blue after burning and warped, some of which were more than 10mm in practice. In this case, the master circuit displays normally, but its electromagnetic attraction force can not overcome the resistance of the friction plate warping and compress it, which will lead to the accident of the weight falling out of control. This situation mainly occurs when do not open the door of the box and the high-speed electromagnetic clutch. In this case, only the inspection, maintenance and repair should be strengthened in the daily work, that is, the gearbox inspection should be added to the monthly primary maintenance of the tower crane

2 common accidents of vertical mounted transmission system

the layout of vertical mounted transmission system was first seen in imported tower cranes in the 1980s, such as komandi in Italy. This type of transmission mechanism has the advantages of simple route, compact structure and small volume, but also the following accidents

the motor of the transmission mechanism is vertical. When the motor starts, the torque is transmitted to the transverse shaft through the bevel gear. The diameter of the transverse shaft is about ф 70mm, both ends are made into spline teeth, which are connected with the internal spline teeth of flange parts at both ends to transmit torque. In recent years, many tower cranes have completely cut off the spline teeth (which may be the external teeth on the shaft or the internal teeth on the flange) at one end (either end), commonly known as the shaved head, making its transmission invalid, causing the hoisted heavy objects and hooks to fall from the air, smashing buildings or injuring workers, resulting in malignant accidents

in April, 2006, a tower crane used by our company put the long horizontal shaft into the front step Journal of the inner flange tooth part of the built-in planetary reducer (diameter: ф 62mm) completely twisted off, making the transmission invalid. The above-mentioned falling accident also occurred, smashing a hole in the floor under construction

the brake of this kind of transmission mechanism is set at the tail of the motor. When the front transmission link fails, the brake will not work, and the driver's master command will not be able to control it. This situation has happened to the imported comendi tower crane that has been used for many years, while the domestic tower crane even occurs to the newer products, which may be caused by the small design of the relevant parts. Of course, it can not be ruled out that the fracture surface of the manufacturer is about 45 ° to the axis of the test piece, and there are also problems in the material treatment and processing of the parts

the problems mentioned above are only a summary of actual work, and only want to draw the attention of relevant tower crane manufacturers to solve them

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