How do cryogenic valves work?

How do cryogenic valves work?

The cryogenic valve refers to the valve can be used for low temperature condition, usually the valve will be considered as a cryogenic valve when the operating temperature will be lower than -40℃. Cryogenic valves are usually used for oil and gas, air separation, natural gas industry, etc., if it can work, the quality determines the safety, economy, sustainability. With the development of modern technology, the demand for cryogenic valves is increasing and the range of use is increasing.

Generally, do not use extended stem for temperatures above -50℃. For temperatures below -50℃, the length of the stem extension depends on the temperature. Cryogenic valves are mainly used for transmission of cryogenic medium such as ethylene, liquid oxygen and hydrogen, liquefied natural gas, liquefied petroleum, etc., which is not only easy to explode and flammable, but also becomes a gas at temperature. The volume will expand hundreds of times after the gasification.

Cryogenic valves material are very important, if not correct, it will lead to body shell and sealing surface inside and outside leakage, parts of the comprehensive mechanical capacity, strength and hardness of unqualified will cause fracture. If the liquefied natural gas leaks, it will explode. Therefore, in the design and manufacture of LNG valves, material is the most important. Body and bonnet are usually made of LCB (-46℃), LC3 (-101℃), CF8 (SS304) (-196℃).

Extended stem cryogenic valves are designed to reduce heat entering the valve from the outside; ensure that the packing gland temperature is above 0 degrees celsius, the packing is not affected; finally, it prevents freezing or frosting of stem and bonnet parts due to lowerpacking temperatures.

Cryogenic valves are designed primarily to prevent expansion design - L. L is the upper surface of the rear seat packaging from the bottom, it depends on the thermal conductivity of the material, thermal conductivity area and surface heat transfer coefficient, heat dissipation area, the calculation process is very complex, usually by the experiment.

Cryogenic valve working conditions are very bad, the medium is usually flammable, permeability, the lowest working temperature can reach -260 degrees celsius, the highest working temperature can reach 10mpa. In this case, there are generally differences in the design, manufacture, and inspection of cryogenic ball valves with forged ball valves, embedded ball valves, metal seat ball valves.