Compared to room temperature valves, low-temperature valve valves have higher packing positions and adopt extended valve stems. Its purpose is to reduce the heat input from the outside into the device; Ensure that the temperature of the stuffing box is above 0 ℃, so that the stuffing can work normally; To prevent the valve stem and upper parts of the valve cover located in the packing box from frosting or freezing due to the cold part of the packing box.

The design of a long neck valve cover mainly involves the design of the neck length L, which refers to the distance from the bottom of the packing box to the upper surface of the upper sealing seat. It is related to factors such as the thermal conductivity, thermal conductivity area, surface heat dissipation coefficient, and heat dissipation area of the material, and the calculation is relatively complicated, usually obtained by experimental methods.

When the temperature is above -100 ℃, ferritic stainless steel can be used. When the temperature is below -100 ℃, austenitic stainless steel can be used. Low pressure and small diameter valves can be made of copper or aluminum alloy. The valve body should be able to fully withstand the expansion and contraction caused by temperature changes, and the structure of the valve seat will not be permanently deformed due to temperature changes.