Excavator loader main gun relief valve 708-1W-04850

As a unloading valve as a remote pressure regulator:

A high and low pressure multistage control valve is used as a sequence valve to generate back pressure (string on the return oil circuit).

The pilot relief valve consists of two parts: the main valve and the pilot valve. Pilot valves are similar to direct-acting relief valves, but they are generally cone valve (or ball valve) shaped seat structures. The main valve can be divided into one concentric structure, two concentric structure and three concentric structure.

After a PC200-6 fully hydraulic excavator is started, the working device can realize various actions, but the main pump sends out abnormal noise.

According to the preliminary analysis, it is believed that the pump is vacuumed or the oil circuit is mixed with air. Therefore, first adjust the working device to the oil level detection position, and check that the oil level of the hydraulic tank is below the low level of the oil target, which is the position of oil shortage. After asking the driver, the sealing ring of the high-pressure oil pipe leading to the rodless chamber of the bucket rod cylinder was replaced due to oil leakage during work, but the oil level was not checked in time after replacement. Therefore, firstly, the hydraulic oil tank is refueled to the standard oil level, and the test shows that the abnormal noise is reduced, but it still exists; Then, through the main pump exhaust valve to the main pump after the re-test, it is found that the abnormal noise is still there, indicating that the noise can not be completely caused by the pump suction.

Next, the oil suction filter and the oil return filter of the hydraulic tank are checked, and it is found that the oil suction filter is black and there is oil mud, and the brown metal particles are stuck on the oil return filter. Considering that there are brown metal particles stuck on the return oil filter, the oil of the main pump is released and inspected, and it is found that there are also brown metal particles; At the same time, when the main pump was disassembled and inspected, it was found that the piston, valve plate and swash plate were not damaged, and the slipper shoe was worn. After its replacement, the assembly was carried out in strict accordance with the requirements, the hydraulic system was cleaned and the oil was changed, and when the test machine was started again, the abnormal noise disappeared and the fault was eliminated.

Under normal circumstances, the possible causes of abnormal noise around the main pump are as follows:

Insufficient hydraulic oil causes the main pump to empty; Air is mixed in the suction line; Suction filter block leads to the main pump suction; The internal wear of the main pump causes abnormal noise in the operation of the main pump.

In this case, the abnormal noise is caused by insufficient hydraulic oil and the wear of the slipper inside the main pump. The reason is that the oil level is not checked in time after the replacement of the seal, resulting in insufficient hydraulic oil, so that the main pump produces suction phenomenon; When the oil mixed with air flows through the main pump, the slipper can not float or float insufficiently in some moments, resulting in the formation of a good lubricating oil film between the slipper and the swash plate, which makes the slipper wear and eventually causes abnormal noise in the operation of the main pump