The slewing bearing is a freely rotatable transmission on the tower crane. The device is generally composed of a motor with a brake, a planetary reducer, a pinion gear, a rotary limiter and the like. The slewing bearing is characterized by a large inertia impact, which requires accurate positioning when starting a smooth stop. If it is too fast, the impact of the whole machine will be large and the tower body will shake. In the case of parking brakes, too fast speed will result in inaccurate seating and the slewing ring turntable bearing
will be easily damaged. In addition, it has a certain relationship with the load capacity and the boom. The load capacity is greater, and the inertia of the boom when parking brakes is longer.
Common faults and their maintenance
1. The rotary motor has noise and jitter. At this time, check whether the three-phase voltage of the motor is balanced and whether there is a phase loss. First turn off the power and check if the motor connection is good. Secondly, power on, operate the crane console handle, use a multimeter to measure whether the three-phase input and output voltage of the thyristor are balanced, and whether there is a phase loss. When the three-phase input voltage is balanced, the three output line voltages do not differ by more than 20V. If it is exceeded, replace the rotary controller.
2. The slewing system has no eddy current brake. First, check whether the part of the line contact is good, check the transformer output voltage is low, and check the thyristor module. If it is damaged, replace the parts. All the above parts are normal, and please replace the rotary controller.