The rotary bearing or bearing inside the power head of rotary drilling rig is damaged, resulting in abnormal rotation of the power head. This situation is often accompanied by unknown noise inside the power head box. At this point, the slewing bearing or bearing should be replaced. Due to the long service time of the rotary excavator, the main pump is excessively worn, and the high and low pressure cavities of the main pump leak oil, resulting in low system pressure. In this case, all the actions of the whole machine will show weakness, and only the main pump can be repaired or replaced at this time.

The proportional pressure reducing valve of the handle is seriously worn, and excessive leakage leads to abnormal rotation of the power head. Because the leakage of proportional pressure reducing valve is too large, the main valve core can not be completely opened, and the oil supply of power head motor is insufficient, which will also lead to the slow speed of power head. At this time, the proportional pressure reducing valve needs to be replaced.

The gear in the reducer is damaged or the transmission shaft is broken. The judgment method of this situation is similar to the serious wear or fracture of spline sleeve. When this kind of fault occurs, it is necessary to replace the reducer gear or transmission shaft.

The overflow valve on the oil seat of the power head is stuck or damaged, resulting in too low overflow pressure.