Views: 0 Author: J-VALVES Publish Time: 2024-04-25 Origin: Site
In a low-temperature environment, the performance and reliability of gate valves face severe challenges. Low-temperature media such as liquefied natural gas (LNG), liquid oxygen, and liquid nitrogen have extremely low temperatures and pose special requirements for the materials and structure of valves. To ensure the normal operation of gate valves under low-temperature conditions, optimization must be carried out in both material selection and structural design.
Material Selection for Gate Valves in Low-Temperature Environments
In low-temperature environments,many metallic materials become more brittle and less ductile as the temperature decreases. Therefore, selecting appropriate metallic materials is crucial. Austenitic stainless steels (such as 304L, 316L, and 310L) are among the commonly used metallic materials for low temperature valves. These materials have a face-centered cubic structure, which allows them to maintain good ductility and impact resistance even at low temperatures. In addition, nickel-based alloys (such as the Inconel series) and titanium alloys are also ideal choices for low temperature valves, as they can retain high strength and good corrosion resistance at extremely low temperatures.
Non-metallic materials are primarily used for seals and packing in low-temperature valves. Polychlorotrifluoroethylene (PCTFE) is an excellent low-temperature
non-metallic material that can be used for extended periods at -200°C. It has good chemical stability and low water vapor permeability. Flexible graphite is also a commonly used low temperature sealing material. It has good lubricity, corrosion resistance, and low temperature performance, and can maintain a stable sealing effect in
low temperature environments.
Structural Adaptability Design of Gate Valves in Low-Temperature Environments
Low temperature gate valves typically feature an extended bonnet design, which moves the packing gland away from the low-temperature medium. This prevents the packing from freezing at low temperatures, thereby ensuring sealing performance and extending the service life of the sealing components. This design effectively prevents the valve stem and components above the bonnet from freezing due to low temperatures, enhancing the valve's reliability and operational flexibility.
The stem is one of the critical components of a low temperature gate valve. Its material must possess excellent low temperature properties and sufficient strength. Stainless steel or alloy steel is commonly selected as the stem material, with surface treatments such as plating or coating applied to enhance its corrosion and wear resistance. The stem design must also consider the operating torque and impact strength at low temperatures to ensure the valve can operate normally in low temperature environments.
The performance of sealing materials is severely affected in low temperature environments, making it necessary to optimize the sealing structure design. Low temperature gate valves usually employ metal seals or flexible graphite seals, which can maintain good sealing performance even at low temperatures. Additionally, the sealing structure design must take into account the contraction and deformation characteristics at low temperatures to ensure that the sealing components can fit tightly and prevent fluid leakage under extreme temperatures.
