Improvements in Ball Valve Sealing Structures

Ball valves are widely used in fluid control systems, and the sealing performance directly affects the quality, performance, and lifespan of the valve. In the past, ball valves typically used O-ring rubber seals. Although this design is simple and easy to assemble, it often struggles to provide effective sealing in complex working conditions, especially under high pressure, large diameters, or media containing suspended particles. In these situations, traditional sealing designs are prone to failure. Therefore, improving the sealing structure of ball valves is crucial.

Drawbacks of Traditional O-Ring Seals

The working principle of traditional O-ring seals involves installing the O-ring at the contact area between the shaft and the hole, where the seal is formed through compression. The sealing effectiveness of this structure depends on several factors, mainly the compression of the O-ring and the precision of the shaft and hole machining. If the interference is too small, the seal will be ineffective, and if it's too large, the O-ring may be damaged during assembly, leading to seal failure. Although this design is simple and easy to assemble, it has several notable drawbacks:

High machining precision required: The precision of the shaft and hole machining needs to be very high, especially under large diameter or high-pressure conditions. If machining precision is poor, the sealing effect cannot be guaranteed.
Unstable sealing performance: When the valve operates under high pressure or in media with suspended particles, the O-ring is prone to wear, erosion, and other issues, leading to seal failure, frequent leakage, and affecting the long-term use of the valve.
Short lifespan: Particularly in harsh media, such as slag water, the lifespan of O-rings is relatively short, resulting in frequent maintenance and replacement, which increases maintenance costs.

Due to these issues, the traditional O-ring sealing structure fails to meet the high-performance and long-lifetime requirements in certain applications, necessitating technological improvements.

The Innovation of X-Shaped Seals

To overcome the shortcomings of traditional sealing structures, the X-shaped seal was introduced. Compared to the O-ring, the X-shaped seal offers significant advantages. Its main feature is that the sealing surface is distributed around the entire seal, with lubrication grooves on both the inside and outside. This structure not only reduces dependence on machining precision but also significantly improves sealing reliability. The improvements are evident in the following areas:

Lower installation precision requirements: The X-shaped seal design greatly reduces the precision required for installation. It can achieve reliable sealing even in situations where machining precision is difficult to improve, which helps reduce manufacturing costs.
Stable sealing performance: The sealing surface of the X-shaped seal is uniformly distributed, providing consistent sealing force under different pressure conditions. During operation, the seal is adjusted by the compression of the gasket to ensure effective contact of the sealing surfaces, reducing the likelihood of leakage.

Longer lifespan and lower maintenance costs: The X-shaped seal is made of wear-resistant materials such as polyurethane (CPU), which has excellent impact resistance, wear resistance, and improved hydrolysis and temperature resistance. This greatly extends its service life compared to traditional O-ring seals, reducing downtime and maintenance frequency, and lowering operational and maintenance costs.

The Application of Polyurethane Materials

The X-shaped seal uses polyurethane (CPU), one of the most widely used sealing materials today. Cast polyurethane offers several advantages.

High elasticity modulus: Polyurethane has a high elasticity modulus, allowing it to withstand large shock loads and adapt to high-pressure and large flow environments.
Excellent mechanical properties: Polyurethane has great wear resistance, corrosion resistance, and anti-aging properties, maintaining a good sealing effect over long-term use.
Hydrolysis resistance: Polyurethane's hydrolysis resistance has significantly improved, allowing it to withstand the corrosive effects of water-based media, making it suitable for a wide range of complex conditions.
Temperature resistance: Polyurethane's temperature resistance has been continuously enhanced, making it suitable for applications that require stable sealing performance in high-temperature environments.
Cost-effectiveness and process advantages: The manufacturing process for cast polyurethane seals is simple and cost-effective. Additionally, the hardness and elasticity of the seal can be adjusted through different processes to meet the needs of various working conditions.

Improved Sealing Performance

The sealing effect of the X-shaped seal mainly depends on the tightening force of the bolts during assembly, rather than the machining precision of the shaft and hole. This gives the X-shaped seal greater flexibility in practical applications. When the bolts are tightened, the packing gland compresses the gasket, and the V-shaped packing forces the internal and external lips of the X-shaped seal to tightly contact the shaft and hole sealing surfaces, ensuring reliable sealing.
In high-pressure, large-diameter applications, the X-shaped seal can also be used in combination with a pressure-transmitting ring. The pressure-transmitting ring, typically placed between two X-shaped seals, transfers the pressure from above, changing the force on the X-shaped seal, causing it to undergo radial deformation and thus improving sealing performance. This design is particularly important in high-pressure and large-diameter ball valves, as it effectively prevents seal failure and ensures stable operation under extreme conditions.

Conclusion

Through improvements to the sealing structure of ball valves, especially the introduction of the X-shaped seal, the sealing failures of traditional O-rings in high-pressure, large-diameter, and harsh media conditions have been addressed. The X-shaped seal not only requires lower installation precision but also significantly enhances sealing performance and lifespan, reduces leakage occurrences, and lowers maintenance costs. Made from polyurethane, the X-shaped seal offers excellent wear resistance, temperature resistance, and hydrolysis resistance, making it suitable for a broader range of applications. As this technology continues to evolve, the sealing reliability and lifespan of ball valves have greatly improved, making them an indispensable component in modern fluid control systems.