Views: 0 Author: J-VALVES Publish Time: 2024-03-05 Origin: Site
Low-temperature ball valves are valves designed specifically for operation at extremely low temperatures and are widely used in the handling of low-temperature media such as liquefied natural gas (LNG), liquid nitrogen, and liquid oxygen. Due to the particularity of their working environment, low-temperature ball valves have strict requirements in design and material selection.
Special requirements for low-temperature ball valves
Low-temperature sealing performance:
Low-temperature ball valves must maintain sealing performance at extremely low temperatures to prevent medium leakage. This requires sealing materials to still maintain flexibility and elasticity at low temperatures.
Resistance to low-temperature brittleness:
Metal materials are prone to becoming brittle at low temperatures. Therefore, the main body material of low-temperature ball valves needs to have good low-temperature toughness and impact resistance.
Low-temperature ball valves usually adopt a long-necked bonnet design to protect packings and seals from the influence of low temperatures. At the same time, the structure of the valve body and bonnet needs to be able to withstand expansion and contraction caused by temperature changes.
Material selection for cryogenic ball valves
Main materials
Body and bonnet: When the temperature is higher than -100°C, ferritic steel can be selected; when the temperature is lower than -100°C, austenitic steel should be selected. Commonly used austenitic stainless steels include 304L, 316L, etc.
Stem and fasteners: The stem material needs to be treated with hard chrome plating, nitriding or nickel-phosphorus plating to increase the surface hardness and prevent scratching with the packing.
Sealing materials
O-rings: Materials such as silicone rubber, fluororubber and hydrogenated nitrile rubber are suitable for low-temperature environments. The specific choice needs to be based on the working temperature and medium characteristics.
Packing: Usually asbestos packing impregnated with polytetrafluoroethylene or flexible graphite is used. These materials can still maintain good sealing performance at low temperatures.
Gasket materials
Gaskets need to maintain reliable sealing and resilience at normal temperature, low temperature and temperature changes. Commonly used gasket materials include asbestos rubber sheets, wound gaskets and flexible graphite.
The design and material selection of low-temperature ball valves must meet the requirements of sealing, brittleness resistance and structural stability in extremely low temperature environments. Through reasonable material selection and optimized structural design, cryogenic ball valves can operate safely and reliably in the handling of low-temperature media such as liquefied natural gas and liquid nitrogen.
