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Sealing Technology Analysis of Hydraulic Support Hydraulic Valve
Abstract: The hydraulic valve in hydraulic supports often suffers from short service life due to poor sealing performance. Although foreign countries have tried to improve the filtration system and emulsion quality, these efforts have yielded limited results. This paper analyzes the development of the seal pair in the holder valve and discusses the relationship between the material properties of the sealing components and their sealing effectiveness. It emphasizes that advanced sealing technology is crucial for extending the service life of hydraulic valves in hydraulic supports.
Hydraulic supports are essential supporting devices in coal mining machinery, typically designed to last up to five years after overhaul. However, the service life of various hydraulic valves within these systems is often very short—sometimes only a few weeks or a few months. Foreign solutions have primarily focused on improving filtration systems and emulsion quality, but with limited success. For example, a British hydraulic valve, despite having high processing accuracy and a well-filtrated hydraulic system, has been phased out due to its low durability.
One of the main causes of sealing failure is contamination in the working fluid. Impurities in the emulsion can grind against sealing surfaces, leading to leaks. To address this, foreign manufacturers recommend using filters with appropriate precision. They suggest that 5μm seals require 3μm filtration, which can increase filter life by ten times compared to 10μm filtration. However, in the harsh environment of coal mining, where pipelines can exceed 1,000 meters and contain thousands of connectors, achieving clean emulsion is extremely challenging. Emulsions often contain floating impurities, coal dust, rock particles, and iron filings, especially in the cylinder and valve cavities.
The intake valve plug and seat experience frequent opening and closing, along with high liquid flow rates, which accelerate seal degradation. Despite attempts to install high-pressure filters at the emulsion pumping station and small filters at each support inlet, blockage frequently occurs, causing operational interruptions. As hydraulic support technology advances, the demand for more durable and reliable valves increases. Current valve life tests use total emulsion flow and the number of valve operations, with a 120-mesh filter and magnetic filtration. However, there is a significant discrepancy between laboratory testing and real-world underground conditions.
Many countries have now introduced stricter anti-pollution testing standards, including adding pulverized coal and mechanical impurities to the emulsion. Therefore, it is necessary to develop new sealing materials with enhanced pollution resistance, suitable for the demanding underground environment. Historically, early hydraulic supports used metal-to-metal contact seals, requiring high precision and strong bonding forces to ensure tightness. Over time, the use of elastic sealing materials has improved performance, but challenges remain in maintaining long-term reliability under extreme conditions.