The difference between cryogenic valves and normal temperature valves

Overview of Cryogenic Valves

As the name implies, cryogenic valves are valves that can work in deep cold conditions. The working temperature is usually defined as valves with working temperatures below -40°C. They are mainly used in equipment for gas liquefaction, separation, transportation, and storage, and the use temperature can reach below -270°C. Currently, there are gate valves, stop valves, check valves, ball valves, butterfly valves, and throttle valves.

Application of Ultra-low Temperature Valves

In recent years, the use of ultra-low temperature valves has become more and more extensive. They are indispensable pieces of equipment in industries such as petrochemicals, air separation, and natural gas. Their working media are not only low in temperature, but also mostly toxic, flammable, and explosive, and have strong permeability. Therefore, many special requirements are determined for valve materials and designs. Not only are they required to work normally at the set temperature, but they must also ensure working performance at room temperature.

The difference between cryogenic valves and normal temperature valves

Compared with normal temperature valves, the packing parts of cryogenic valves are all elevated, and extended valve stems are used. Its purpose is to reduce the heat transmitted from the outside to the device; to ensure that the temperature of the stuffing box is above 0℃ so that the stuffing can work normally; to prevent the valve stem in the stuffing box and the parts on the upper part of the valve cover from frosting or freezing due to the overcooling of the stuffing box.

The design of the long-necked valve cover is mainly the design of the neck length L. L refers to the distance from the bottom of the stuffing box to the upper surface of the upper sealing seat. It is related to the thermal conductivity, thermal conductivity area, surface heat dissipation coefficient, heat dissipation area, and other factors of the material. The calculation is relatively cumbersome and is generally obtained by experimental method. Ferritic stainless steel can be used when the temperature is higher than -100℃, and austenitic stainless steel can be used when the temperature is lower than -100℃. Copper alloy or aluminum alloy can be used for low-pressure and small-diameter valves. The valve body should be able to fully withstand the expansion and contraction caused by temperature changes, and the structure of the valve seat part will not be permanently deformed due to temperature changes.