There is a fault case in the construction site: an existing excavator, whether it is a single action of rotation or a compound action of rotation, the rotation action is weak and slow, and other actions are not abnormal. This paper will analyze the troubleshooting steps to find the reasons for the weak rotation of the excavator.

Analyze troubleshooting steps:

1. Check electrical reasons first. The feedback voltage value of the rotary low-voltage sensor was measured, and the voltage value was 0.5V(normal range 0.4V to 0.5V) when the operating handle was neutral, and there was no abnormality. 4.3V(normal range not more than 4.5V) during the whole operation of the operating handle, no abnormality, go to the next step.

2. During the whole operation of the rotation, the electromagnetic current of the front pump was measured, and the current value was 540mA(which belongs to the standard range of 350mA to 750mA) without abnormality.

3. Because there is no abnormality in the electrical aspect, check the hydraulic aspect again. Measure the secondary pressure of the rotary operation, the measurement result is 39kg(normal pilot pressure is greater than 35kg), no abnormality, and 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), indicating that there was an abnormality. Adjustment relief valve pressure does not change. The main relief valve was measured, and the pressure value was 348kg, which was not abnormal. Therefore, it was determined that the hydraulic main pump and the main relief valve were not abnormal.

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

6. Remove the rotary spool on the main valve, the spool can move freely, and the return spring does not break, so the spool is not abnormal.

7. Disassembly of the rotary motor, it is found that the contact surface between the valve plate and the plunger pump is seriously worn, and the rotary motor has a partial leakage phenomenon, resulting in low pressure of the rotary hydraulic system, resulting in weak rotary action

8. For the more severely worn flow plate, reassemble the rotary motor and start the machine again for rotary work. There is no abnormality and troubleshooting.

Take corresponding measures:

After the steps,we will know the causes of slow and weak rotary action of hydraulic excavator mainly come from two aspects of 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 principle of "pressure depends on the load, flow determines the speed", from simple to complex, from outside to inside to deal with the analysis of the fault. After the fault is found that the internal wear of the rotary motor, resulting in lax sealing hydraulic oil leakage, resulting in slow rotary weakness.