Inspection methods for abnormal noises from the slewing mechanism of excavators

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When an imported excavator is rotating under heavy load, it makes three irregular clicking sounds. We used a sound wave detector to inspect the housing of the rotary motor, the housing of the rotary reducer, and the outer diameter of the rotary gear ring. The sound wave was the strongest at the rotary gear ring, but when measuring the rotary reducer, there was also a sound wave.

The pressure gauge we installed on the main pump shows the pointer swinging when the excavator rotates under heavy load. After each sound, the pressure value on the pressure gauge drops.

Our first step is to drive the excavator to an open area where there is space for it to rotate. Then, straighten the upper and lower arms, raise the bucket one meter above the ground, stop the engine and release the residual pressure.

Without disassembling the oil pipe of the rotary motor, remove the fixing bolts of the rotary motor, and pull the motor out of the reducer. It is required that the main shaft of the motor be separated from the center gear sleeve of the rotary reducer by a small distance and fixed. Start the engine and operate the motor to perform a rotary action. As the rotary motor has been disconnected from the rotary reducer, the motor is idling in both forward and reverse directions. If the motor operates smoothly without any abnormal noise, it indicates that the rotary motor is free of faults. Then, separate the motor from the excavator.

The second step is to have a person push the bucket (the bucket has been lifted off the ground) to make the excavator rotate left and right. The person on the machine then determines whether the abnormal sound comes from the rotary reducer or the rotary gear ring. The result was that both of them had abnormal sounds.

The reducer was removed from the excavator and disassembled. Upon inspection, it was found that the bearing at the end of the main shaft was damaged, and the abnormal noise was coming from the bearing area.

The third step is still to push the bucket by hand. There is still an abnormal noise from the rotating gear ring of the excavator. Before disassembling the rotating gear ring, seal the disassembled oil pipe, start the engine, and restore the excavator to the detachable position of the upper mechanism of the excavator. We separated the rotary gear ring from the excavator and took apart the inner and outer gear rings. We saw that the quenched layer on the rolling surface had peeled off.

The fourth step is to send the rotary gear ring to a professional bearing factory. After grinding the raceway according to the enlarged ball size, it is re-quenched. The repaired rotary gear ring is then reinstalled on the excavator, and everything is normal.