It is well known that the main cause of damage to sealing elements is impurities in the working fluid. These impurities are ground between the sealing elements, causing the valve to leak. Therefore, foreign countries have proposed that the corresponding level of hydraulic components, should use the corresponding precision filter. They thought that the sealing element of 5μM oil pump, if the filter with a filtration accuracy of 3 / μM, the life can be improved by 10 times compared with the use of 10μM. However, the valve used in the hydraulic support has a harsh working environment. At the coal mining face, the total length of the oil pipe is more than 1,000 meters, and there are more than 4,000 joint sockets. There is no special dustproof measure for the liquid tank. There are a lot of floating impurities in the emulsion, and there are more coal powder, rock particles and iron filings in the cylinder bottom and valve cavity of the column. The inlet valve core and valve seat, because the opening and closing are relatively frequent, the liquid flow rate is high, and the seal will soon fail. Practice has proved that it is very difficult to reduce the contamination impurities of the liquid in the hydraulic system of the support. Some people once envisioned using high-pressure filters in the emulsion pumping station and adding small filters at the entrance of each support. However, it was quickly blocked at work and formed a cut-off.
On the other hand, with the development of hydraulic support technology. Higher requirements have been placed on the function of the valve and the service life of the valve. At present, under the premise of a 120 mesh filter and a magnetic filter device, the total flow of the emulsion through the valve under test and the number of times the valve is opened and closed are used to measure the life of the hydraulic valve. But in fact, the indoor type test is very different from the actual work results downhole. At present, the formal experiments in many countries have increased the requirements for anti-pollution. Some are mixed with appropriate coal powder in the emulsion, and some are added with mechanical impurities. For this reason, it is necessary to use a new type of sealing pair with strong anti-pollution ability and suitable for the premise of underground work.
The service life of various hydraulic valves in the hydraulic support is very low. The solution and methods abroad are to improve the filtration accuracy of the system and the quality of the emulsion, but the results are not great.
