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Sealing Technology of Hydraulic Valve and Its Analysis
Hydraulic support valves suffer from short service life, and despite efforts to improve filtration systems and emulsion quality, foreign solutions have not yielded significant results. This article explores the development of the seal pair in the holder valve, examining the relationship between the material used for the seal and its overall sealing performance. It highlights that sealing technology is a critical factor in extending the life of hydraulic valves within hydraulic supports.
Hydraulic supports are essential components in coal mining equipment, designed to last up to five years underground after maintenance. However, the service life of individual hydraulic valves remains extremely limited—often only a few weeks or a few months. Although some foreign countries have attempted to enhance filtration accuracy and emulsion quality, success has been minimal. For example, British hydraulic valves, despite high processing precision and filtration standards, have struggled with durability and are being phased out in some markets.
A major cause of seal failure is contamination in the working fluid. Impurities in the hydraulic system act like abrasives, wearing down the sealing surfaces and leading to leaks. To address this, foreign manufacturers recommend using filters with appropriate accuracy levels. For instance, 5-micron seals require 3-micron filtration, which can increase filter life by up to ten times compared to 10-micron filtration. However, in the harsh environment of a coal mine, where pipelines can exceed 1,000 meters and contain over 4,000 connection points, maintaining cleanliness is extremely challenging. Dust, coal dust, rock particles, and metal shavings often accumulate in the emulsion tank and inside the valve chambers, making it difficult to maintain clean hydraulic fluid.
The intake valve plug and seat, due to frequent opening and closing, experience 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, these systems often clogged quickly, causing operational downtime. As hydraulic support technology advances, the demand for more durable valves increases. Current testing methods measure valve life based on total emulsion flow and the number of opening/closing cycles, using 120-mesh filters and magnetic filtration devices. However, there is a significant gap between laboratory test results and real-world performance underground.
In many countries, anti-pollution requirements in formal tests have been strengthened. Some tests now include pulverized coal or mechanical impurities in the emulsion to simulate real conditions. This underscores the need for new sealing materials that are more resistant to contamination and better suited for the challenging underground environment. The evolution of seal materials has also played a key role in improving valve performance. Early hydraulic supports relied on direct metal-to-metal contact seals, requiring high machining accuracy or additional bonding forces to ensure tightness. Plastic deformation of the contact surface was sometimes used to block leakage paths. Today, advanced seal materials offer better resilience and adaptability, contributing to longer-lasting and more reliable hydraulic systems.