Cryogenic valve characteristics and material requirements

Low temperature valve has the following performance characteristics: 1, bonnet design for the long neck structure, can isolate the effect of low temperature medium on the packing, to prevent the performance of the lid seal to reduce, but also allows the valve opening and closing flexibility; 2, filler using flexible graphite or Teflon composite structure, with good low temperature performance; 3, the valve used in the low-pressure valve hole opened the structure. Gasket with stainless steel wallet PTFE or flexible graphite winding structure; 4, the valve is closed, in order to prevent the valve cavity temperature rise due to temperature, resulting in abnormal gasification step-up in the gate or valve body high pressure side With pressure relief structure; 5, the valve sealing surface surfacing cobalt-based hard alloy, carbide deformation at low temperatures, wear-resistant, can maintain good sealing performance. Due to the output of liquid cryogenic medium such as ethylene, liquid oxygen, liquid hydrogen, liquefied natural gas, liquefied petroleum gas and other products not only flammable and explosive, but also in the gasification when gasification, gasification, volume expansion hundreds of times. The material of the cryogenic valve is very important, the material is unqualified, it will cause the leakage and leakage of the shell and the sealing surface. The mechanical properties, strength and hardness of the parts can not meet the requirements of use or even rupture; resulting in the explosion caused by the leakage of the liquefied natural gas medium . Therefore, in the development, design, development of low-temperature valve in the process, material handling is the primary key issue.