Abstract: The service life of various hydraulic valves in hydraulic supports is very short. Foreign solutions have focused on improving the filtration accuracy of the system and the quality of the emulsion, but with limited success. This article analyzes the development process of the sealing pairs of support valves and discusses the relationship between the materials and sealing performance of the sealing pairs. It points out that sealing technology is key to improving the service life of hydraulic valves in hydraulic supports. Hydraulic supports are support equipment in coal mining machinery. After major overhaul, they can generally be used underground for five years. However, the service life of various hydraulic valves in hydraulic supports is very short, ranging from three months to only a few weeks. Foreign solutions have focused on increasing the filtration accuracy of the system and improving the quality of the emulsion, but with limited success. Taking a certain British hydraulic valve as an example, although its machining accuracy and the filtration accuracy of the entire hydraulic system are relatively high, its short service life has led to its obsolescence in China. 1. Main Factors Affecting the Sealing Performance of Hydraulic Valves The main factor causing damage to sealing elements is impurities in the working fluid. These impurities grind between the sealing elements, causing leakage in the valve. Therefore, foreign countries have proposed that corresponding-grade hydraulic components should use filters of corresponding precision. They believe that the lifespan of a 5µM oil pump sealing element, if using a filter with a filtration accuracy of 3µM, can be increased tenfold compared to using a 10µM filter. However, the valves used in hydraulic supports operate in extremely harsh environments. In coal mining faces, the total length of the oil pipes exceeds 1000 meters, with over 4000 joints and ports, and the fluid tank lacks special dustproof facilities. The emulsion contains a large amount of floating impurities, leaving significant amounts of coal dust, rock particles, and iron filings at the bottom of the column cylinder and in the valve chamber. Due to frequent opening and closing and high fluid flow rates, the seals on the inlet valve core and seat quickly fail. Practice has proven that reducing contamination and impurities in the hydraulic fluid of the support system is extremely difficult. Some have considered using high-pressure filters in the emulsion pump station and adding small filters at the inlet of each support. However, these filters quickly become clogged during operation, causing flow interruptions. Furthermore, with the development of hydraulic support technology, higher requirements are being placed on the performance and lifespan of valves. Currently, under conditions of 120-mesh filters and magnetic filtration devices, valve life is measured by the total flow rate of the emulsion passing through the tested valve and the number of valve opening and closing cycles. However, in reality, indoor type testing results differ significantly from actual downhole working conditions. Many countries now require increased anti-contamination standards in type testing, sometimes by adding appropriate coal powder to the emulsion, and sometimes by adding mechanical impurities. Therefore, new types of sealing pairs with strong anti-contamination capabilities and suitable for downhole working conditions are needed. 2. History and Current Status of Hydraulic Valve Sealing Materials Leakage at the valve core and seat contact surface is the result of working fluid molecules being squeezed in. The main factors affecting sealing effectiveness are the contact specific pressure, unevenness, and pressure difference between the valve core and seat. When the valve core and seat mating surfaces are pressed together by force P, working fluid molecules are squeezed in by force F, causing elastic deformation of the sealing material. If the total resistance of the sealing pair is greater than the molecular repulsion force, the seal is effective; otherwise, leakage will occur. Early hydraulic supports had no other sealing measures between moving parts; they were sealed by direct metal-to-metal contact. This required the sealing surfaces to fit together perfectly and had high machining precision. Otherwise, the bonding force of the sealing surfaces had to be increased, causing plastic deformation of the contact surfaces and blocking the leakage channels.