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Sealing Technology Analysis of Hydraulic Support Hydraulic Valve
**Abstract:** The hydraulic valve in hydraulic supports often experiences a short service life, and although foreign solutions such as improving the filtration system and emulsion quality have been attempted, their effectiveness has been limited. This article examines the development of the sealing pair in the holder valve and explores the relationship between the material of the sealing components and their sealing performance. It emphasizes that sealing technology is crucial for extending the service life of hydraulic valves in hydraulic supports.
Hydraulic supports are essential support devices in coal mining machinery. After maintenance, they can typically be used underground for up to five years. However, the service life of individual hydraulic valves within the system is often very short—sometimes only a few weeks or a few months. Foreign approaches have focused on enhancing filtration systems and emulsion quality, but with limited success. For example, certain British hydraulic valves, despite having high processing accuracy and a well-filtered hydraulic system, have still faced elimination due to their low durability.
A major factor affecting the sealing performance of hydraulic valves is the presence of contaminants in the working fluid. These impurities can grind between the sealing surfaces, leading to leaks. As a result, foreign manufacturers recommend using filters with appropriate precision for hydraulic components. They argue that 5-μm oil seal components, when paired with a 3-μm filter, can extend the filter life by ten times compared to using a 10-μm filter. However, in the harsh environment of hydraulic support systems, where pipelines can exceed 1,000 meters in length and contain over 4,000 connectors, dust and impurities are unavoidable. Emulsions often contain floating debris, coal dust, rock particles, and metal shavings, which accumulate in the cylinder and valve cavity.
The intake valve plug and seat, due to frequent opening and closing and high liquid flow, tend to fail quickly. Reducing contamination in the system has proven extremely challenging. Some attempts included installing high-pressure filters at the emulsion pumping station and small filters at each support's inlet, but these were quickly clogged during operation, causing system downtime.
With the advancement of hydraulic support technology, the performance and lifespan of valves have come under greater scrutiny. Current testing methods measure valve life based on the total emulsion flow through the valve and the number of opening and closing cycles, using a 120-mesh filter and magnetic filtration. However, there is a significant gap between laboratory tests and real-world conditions. In many countries, formal testing now includes increased anti-pollution requirements, such as introducing pulverized coal or mechanical impurities into the emulsion. Therefore, new sealing materials with enhanced pollution resistance and better adaptability to underground conditions are urgently needed.
Historically, early hydraulic supports used direct metal-to-metal contact seals without additional sealing elements. This required precise surface matching and high machining accuracy, or the application of bonding forces to induce plastic deformation in the contact area, thereby blocking leakage paths. Over time, the development of more advanced sealing materials has aimed to improve reliability and reduce the impact of contaminants.