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As the name implies, low-temperature valves are valves capable of operating in extremely cold conditions. The threshold for such operating temperatures is generally set at below -40°C; valves that operate at temperatures lower than this are considered low-temperature valves. They are primarily used in equipment for the liquefaction, separation, transportation, and storage of gases, and can operate at temperatures as low as -270°C. Currently, there are various types of these valves, including gate valves, globe valves, check valves, ball valves, butterfly valves, and throttle valves. In recent years, ultra-low temperature valves have seen an increasing range of applications; they are one of the essential devices in industries such as petrochemicals, air separation, and natural gas. The working media involved not only have low temperatures but are also often toxic, flammable, or explosive, in addition to having high permeability. This leads to various special requirements regarding the materials used for these valves as well as their design. It is required not only to function properly at the set temperature, but also to maintain its performance at normal temperatures. Compared to valves for normal temperatures, low-temperature valves have elevated packing areas, and longer valve stems are used. Its purpose is to reduce the heat entering the device from the outside ； Ensure that the temperature in the packing box area remains above 0°C, so that the packing can function properly ； Prevent frosting or freezing of the valve stem located in the stuffing box area, as well as the components above the valve cover, due to over-cooling in that area. The design of a long-neck valve cover primarily involves determining the length L of the neck, where L refers to the distance from the bottom of the packing box to the upper surface of the upper sealing seat. This value is related to factors such as the material’s thermal conductivity, thermal transfer area, as well as the surface heat dissipation coefficient and heat dissipation area; calculating it is rather complicated, and it is usually determined through experimental methods. Ferritic stainless steel can be used when the temperature is above -100°C, while austenitic stainless steel is suitable for temperatures below -100°C. Copper alloys or aluminum alloys can be used for low-pressure and small-diameter valves. The valve body must be able to withstand the expansion and contraction caused by temperature changes, and the structure of the valve seat must not suffer from permanent deformation as a result of such temperature changes.