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Investigation Skills Of Excavator Turning Inability


Fault case: There is an existing excavator, whether it is rotary single action or rotary compound action, the rotary action is weak and slow, and other actions are normal.

1. Check the electrical reasons first. The feedback voltage value of the rotary low voltage sensor was measured. The voltage value was 0.5V(within the normal range of 0.4V to 0.5V) when the operating handle was neutral, and there was no abnormality. The operating handle is 4.3V throughout the operation (within the normal range of 4.5V). If there is no exception, go to the next step.

2. During the whole rotation operation, the electromagnetic current of the front pump was measured, and the current value was 540mA(within the standard range of 350mA to 750mA), and no abnormality was found.

3. There is no abnormality in the electrical side, so check the hydraulic side again. Measure the secondary pressure of rotary operation, the measurement result is 39kg(normal pilot pressure is greater than 35kg), no abnormality, go to the next step.

4. The rotary overflow pressure was measured, and the measured pressure value was 195kg(seriously lower than the normal overflow pressure of 280kg), which was abnormal. There is no change in pressure of the adjustment relief valve. The main relief valve was measured and the pressure value was 348kg, no abnormality was found. Therefore, the hydraulic main pump and the main relief valve were determined to be normal.

5. Disassemble the relief valve of rotary motor. No internal damage is found, so the relief valve is judged to work normally.

6. Disassemble the rotary spool on the main valve. The spool can move freely, and the return spring does not break, so the spool is judged to be normal.

7. Disassembling the rotary motor, it was found that the contact surface between the valve plate and the piston pump was seriously worn, and the rotary motor had a leakage phenomenon, which caused the pressure of the rotary hydraulic system to be too low, thus causing the weak rotary action

8. For the valve plate with more serious wear and tear, reassemble the rotary motor and start the machine again for rotary work. There is no abnormality and the fault is removed.


The reasons for slow and weak rotary action of hydraulic excavators mainly come from two aspects: electrical and hydraulic. First check the electrical rotary low-pressure sensor, the front pump electromagnetic proportional valve current value, and then detect the hydraulic reasons, according to the "pressure depends on the load, flow determines the speed" principle, from simple to complex, from outside to inside the way to deal with and analyze the fault. After troubleshooting, it was found that the internal wear of the rotary motor caused the leakage of hydraulic oil with loose sealing, resulting in slow rotation.


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