How does the single seat regulating valve achieve sealing？

In industrial automation control systems, the regulating valve, as an important part of the actuating mechanism, has a direct impact on the control accuracy, safety, and economy of the system. Among them, the single seat regulating valve is widely used in various process flows due to its simple structure and high control accuracy. However, due to its structural characteristics, the single seat regulating valve also faces certain challenges in terms of sealing. This article will discuss in detail the sealing principle, sealing structure, factors affecting the sealing performance, and measures to improve the sealing properties of the single seat regulating valve.

一、单座调节阀的密封原理

1. Sealing principle of single seat regulating valve

A single seat regulating valve consists of a valve body, valve seat, valve core, and actuator, etc. In the closed state, a sealing pair is formed between the valve core and seat, and the fluid is cut off through the close contact between the two. The main sealing principle relies on the contact pressure between the valve core and seat, which is usually transmitted to the valve core through the valve rod by the thrust provided by the actuator, making the valve core tightly fit the seat, thus preventing medium leakage.

2. Sealing structure design

The common sealing structures of single seat regulating valves mainly include two forms: soft sealing and hard sealing.
1. Soft sealing: Usually made of polytetrafluoroethylene (PTFE), rubber, or other high polymer materials, the valve seat has good sealing performance and is suitable for normal temperature or medium and low temperature working conditions. It can achieve nearly zero leakage.

2. Hard sealing: The valve seat and valve core surfaces are made of metal materials (such as stainless steel, hard alloy) to achieve sealing through precision processing and grinding. It is suitable for high temperature, high pressure, or media containing particles. Although the sealing performance is slightly inferior to soft sealing, it has higher wear resistance and temperature resistance.

In addition, some high-performance single seat regulating valves also adopt a double sealing structure, that is, an auxiliary sealing ring is added on the basis of the main seal to further improve the sealing reliability.

3. Factors affecting the sealing performance
1. Machining accuracy: The surface roughness, roundness, and coaxiality of the valve core and seat directly affect the sealing effect, and the higher the machining accuracy, the more reliable the sealing.
2. Material selection: Choosing the appropriate sealing material according to the characteristics of the medium is the key to ensuring the sealing performance. For example, corrosion-resistant materials should be selected in strongly corrosive media.
3. Installation and maintenance: Improper installation (such as misalignment) or wear of the sealing surface after long-term operation will lead to leakage.

4. Operating conditions: High temperature, high pressure, frequent opening and closing, and other working conditions will accelerate the wear of the sealing surface and reduce the service life of the seal.

To improve the sealing performance of the single seat regulating valve, the following measures can be taken:

- Optimization of the sealing surface design: Adopting conical sealing, spherical sealing, and other methods to increase the contact area and sealing pressure ratio.
- Selection of high-performance sealing materials: Such as graphite composite sealing, ceramic sealing, etc., to adapt to more complex working conditions.
- Regular maintenance and inspection: Replace worn parts in time, clean the seal surface impurities, and keep the seal surface clean.
- Use of intelligent locator: Improve the positioning accuracy of the valve through intelligent control to ensure that the valve core and seat are tightly fitted when closed.

Conclusion

In summary, the sealing performance of a single seat regulating valve is not only related to the control accuracy of the system, but also to the safety and economy of the production process. Through reasonable design, high-quality materials, proper installation, and regular maintenance, the sealing capacity of the valve can be effectively improved to meet the requirements of different working conditions. With the continuous improvement of industrial automation levels, the requirements for the sealing performance of regulating valves will also become increasingly strict, and the future sealing technology of regulating valves will develop towards high precision, long life, and intelligence.