Troubleshooting tips for excavator failure to rotate

What are the troubleshooting tips for excavator failure to rotate? Let us analyze it in detail through a fault case.

Fault case: There is an existing excavator. Whether it is a single rotation action or a combined rotation action, the rotation action is weak and slow, and other actions are normal.

Analyze troubleshooting steps:

1. First check the electrical reasons. Measure the feedback voltage value of the rotary low-voltage sensor. When the operating handle is neutral, the measured voltage value is 0.5V (normal range 0.4V to 0.5V), no abnormality; when the operating handle is fully operated, 4.3V (normal range no more than 4.5V), no abnormality Exception, go to next step.
2. During the full rotation operation, measure the electromagnetic current of the front pump and the measured current value is 540mA (within the standard range of 350mA to 750mA), and there is no abnormality.
3. Since there is no abnormality in the electrical aspects, check the hydraulic issues again. Measure the secondary pressure of the rotation operation. The measurement result is 39kg (the normal pilot pressure is greater than 35kg). There is no abnormality. Go to the next step.
4. Measure the rotary overflow pressure, and the measured pressure value is 195kg (severely lower than the normal overflow pressure of 280kg), which indicates an abnormality. There is no change in the pressure of the relief valve. The main relief valve was measured and the measured pressure value was 348kg. There was no abnormality. Therefore, it was determined that there were no abnormalities in the hydraulic main pump and the main relief valve.
5. Disassembled the rotary motor relief valve and found no internal damage, so it was determined that the relief valve was working normally.
6. Disassemble the rotary valve core on the main valve. The valve core can move freely and the return spring does not break. Therefore, it is determined that the valve core is normal.
7. Dismantling the rotary motor, it was found that the contact surface between the valve plate and the plunger pump was seriously worn, and there was partial leakage in the rotary motor, causing the pressure of the rotary hydraulic system to be too low, resulting in weak and weak rotary action.
8. For the severely worn valve plate, reassemble the rotary motor and restart the rotary operation. No abnormality is found, and the fault is eliminated.

Reflection:
The reasons for the slow and weak rotation of hydraulic excavators mainly come from two aspects: electrical and hydraulic. First check the electrical aspects of the rotary low-pressure sensor and the current value of the front pump electromagnetic proportional valve, and then detect the hydraulic reasons. Based on the principle of “pressure depends on the load, and flow determines the speed”, perform processing and analysis from simple to complex, and from outside to inside. Fault. After troubleshooting, it was found that the internal wear of the rotary motor caused leakage of hydraulic oil due to loose sealing, resulting in weak and slow rotation.

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