How to choose normal temperature valves and low temperature valves? What’s the difference?
There are many classifications of valves. Let’s learn about the difference between cryogenic valves and normal temperature valves today. Cryogenic valves are valves that can operate in low-temperature working systems. Usually, the operating temperature is lower than -40°C. They are mainly used in equipment such as liquefaction, separation, transportation and storage of gases. The operating temperature can be as low as -270°C. Currently there are gate valves, globe valves, check valves, ball valves, butterfly valves and throttle valves.
In recent years, ultra-low temperature valves have been used more and more widely. They are one of the indispensable important equipment in petrochemical, air separation, natural gas and other industries. The working medium is not only low in temperature, but most of them are either toxic or flammable and explosive. , and has strong permeability, so it determines many special requirements for valve materials and design. It is not only required to work normally at the set temperature, but also to ensure the working performance at room temperature.
Compared with normal temperature valves, low temperature valves have higher packing parts and longer valve stems. Its purpose is to reduce the heat introduced into the device from the outside; to ensure that the temperature of the stuffing box is above 0°C so that the stuffing can work normally; to prevent the valve stem at the stuffing box and the upper part of the valve cover from being overcooled due to the overcooling of the stuffing box. parts are frosted or frozen.
The design of the long-necked bonnet 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, which is related to the thermal conductivity of the material, the thermal conductivity area, the surface heat dissipation coefficient, and the heat dissipation area. , the calculation is rather cumbersome, and it is generally obtained by experimental methods.
Ferritic stainless steel can be used when the temperature is higher than -100°C, austenitic stainless steel can be used when the temperature is lower than -100°C, copper alloy or aluminum alloy can be used for low-pressure and small-diameter valves, and the valve body should be able to fully withstand temperature changes. The expansion and contraction of the valve seat part will not cause permanent deformation due to temperature changes.
After reading the above content, do you know how to choose normal temperature valves and low temperature valves? What’s the difference? Collect it now~