Overview of cryogenic valves

The main reason for the internal leakage of the valve is the deformation of the sealing pair in the low temperature state. When the temperature of the medium drops to a phase change of the material, the volume changes, and the sealing surface with high grinding accuracy is warped and deformed, resulting in poor low-temperature sealing.

Valve leakage: First, when the valve and the pipeline are connected by flanges, leakage occurs due to the unsynchronized contraction of gaskets, connecting bolts, and connecting parts at low temperatures. Therefore, the connection method between the valve body and the pipeline can be changed from flange connection to welding structure to avoid low temperature leakage. The second is leakage at the valve stem and packing.

This is because the plasticity and sealing of the low temperature valve packing will become worse as the temperature drops, leakage and icing will occur at the packing, which will affect the low cooling capacity loss, and the valve cover must adopt a long neck structure. The cross-sectional area of the long neck portion should be small, generally cylindrical, and the gap between the inner wall and the valve stem should also be small. In order to reduce the cold transfer upwards. The length of the neck is related to temperature and caliber. The lower the temperature and the larger the caliber, the longer the length.

It must be on the high pressure side. The purpose is to maintain the pressure balance between the upstream and the valve ball flow passage cavity when the ball valve is closed, to prevent the cryogenic liquid in the ball valve cavity from instantaneous vaporization and expansion, causing the valve body to burst.