Thread Content
After the PC200-6 fully hydraulic excavator is started, its working equipment can perform various movements, but the main pump emits abnormal noises. Preliminary analysis suggests that it is caused by pump cavitation or air entering the oil circuit. Therefore, the working device was first adjusted to the oil level detection position, and it was found that the oil level in the hydraulic oil tank was below the lower mark on the gauge, indicating a low oil level. Upon inquiry with the driver, it was learned that the seal ring of the high-pressure oil pipe leading to the rod-side chamber of the boom cylinder had been replaced due to oil leakage during operation, but the oil level was not checked promptly after the replacement. Therefore, first, the hydraulic oil tank was filled to the standard level. Testing the machine showed that although the abnormal noise had decreased, it was still present. Next, the main pump was vented through its exhaust valve and the machine was tested again; the abnormal noise was still there, indicating that this noise could not be entirely caused by pump cavitation. Next, the suction filter and return filter of the hydraulic oil tank were inspected. It was found that the suction filter had turned black and was covered with sludge, while the return filter had brown metal particles stuck to it; therefore, these filters were replaced. Given the presence of brown metal particles on the return filter, the oil in the main pump was drained and inspected, and brown metal particles were also found there. Meanwhile, upon disassembling and inspecting the main pump, it was determined that the piston, valve plate, swash plate, etc., were not damaged, but the slip rings were worn out. After replacing it, assembly was carried out strictly in accordance with the requirements; the hydraulic system was cleaned and the oil was changed. When the machine was started again for testing, the abnormal noise disappeared, and the fault was resolved. Generally, the possible reasons for abnormal noise around the main pump are as follows: insufficient hydraulic oil causing the main pump to draw in air; air entering the oil suction pipeline; a clogged oil suction filter leading to air being drawn into the main pump; internal wear within the main pump, resulting in abnormal noise during its operation. In this case, the abnormal noise is caused by both insufficient hydraulic oil and wear of the sliding shoes in the main pump. The reason is that the oil level was not checked in a timely manner after replacing the seal, resulting in insufficient hydraulic oil and causing cavitation in the main pump. When oil mixed with air flows through the main pump, the slip rings fail to rise or rise inadequately at certain moments, preventing the formation of a proper lubricating film between the slip rings and the swash plate; this leads to wear of the slip rings and ultimately causes abnormal noises during the operation of the main pump. For more information, please visit the China Pump Industry Network.