Views: 0 Author: J-VALVES Publish Time: 2024-04-25 Origin: Site
Structural design of top trunnion ball valve for LNG
Top trunnion ball valve is mainly composed of valve body, valve seat, ball, valve stem, packing box and operating mechanism and other components. Its core components are ball and valve seat. The ball is connected with the operating mechanism through the valve stem to realize 90-degree rotation to control the on-off of fluid. The valve seat adopts elastic sealing structure, which can closely fit with the ball to ensure sealing performance. The design of top entry structure makes the valve body and valve cover connected by bolts, which is convenient for disassembly and maintenance. At the same time, it reduces the welding parts and reduces the influence of welding stress in low temperature environment.
The design of LNG top trunnion ball valves needs to follow strict international and national standards. For example, API 6D standard stipulates the design, manufacture and testing requirements of pipeline valves; standards such as GB/T 12237 and GB/T 26480 put forward specific requirements for the structure, materials and inspection tests of valves. These standards ensure the reliability and safety of valves under complex working conditions such as low temperature and high pressure.
(I) Valve seat sealing structure
Valve seat sealing is one of the key technologies of LNG top trunnion ball valves. The design of the valve seat sealing structure needs to consider factors such as pressure distribution and sealing surface contact stress to ensure good sealing performance under different pressures. Common sealing structures include single sealing surface, double sealing surface and elastic sealing surface. Among them, the elastic sealing surface structure can automatically adjust the sealing state when the pressure changes and improve the sealing reliability.
The selection of sealing materials is crucial for the sealing performance of valves. PTFE and PCTFE are commonly used sealing materials, which have good low-temperature resistance and self-lubricating properties. In addition, new sealing technologies such as lip seals and bellows seals are gradually being applied to LNG valves. Lip seals can automatically adjust the sealing state when the pressure changes and have good elasticity and self-sealing properties; bellows seals can effectively prevent medium leakage and have good high-temperature resistance and corrosion resistance.
