Cryogenic Treatment Process           

Cryogenic treatment process in the valve industry mainly used in the working temperature is below -100 degree ultra-low temperature valve components, in this temperature section of timber mainly F304, F304L, F316 and F316L such as Cr-Ni austenitic stainless steel mainly. These materials belong to the sub-stabilized stainless steel at low temperature will occur to the microstructure of martensite transformation, due to body-centered cubic lattice of martensite in austenite than the face-centered lattice with a larger specific volume, low-temperature. After the phase transition would cause volume expansion which led to part distortion.

Cryogenic treatment can make phase change and deformation fully transformation, and then maintain the relative stability about the organization and size by finishing a part. Specific method were: part-dip on the liquid nitrogen, when the temperature reaches-196 degree heat one to two hours, then removed, naturally return to room temperature, repeated cycles 2 times.

Low-temperature Test

At present, the valve performed by low-temperature test criteria are: JB/T7794, ANSI B 16.34 and so on. Before the test, at low temperature, the valve should be carried out to the oil and dried, as oil and water at low temperatures into the environment will become to be of solid material, causing structural damage valve. Valves and test equipment will be connected later, at room temperature and the maximum working pressure, using helium to do the initial detection cooling valve to maintain the valve there is always helium flow cooling process in order to remove moisture that may form. The entire testing process to be completed at low temperature test tank, the valve immersed in liquid nitrogen as a whole and alcohol mixture, liquid height should reach the neck position of valve cover. When the temperature reaches all parts of the requirements, they can begin testing.