API6D Standard Cryogenic Valve

 Low-temperature parts into liquid nitrogen tank insulation a certain length of time, to reduce its due to temperature differences andmetallographic changes resulting from the deformation,which increases when the low-temperature valve sealing performance of a processing method.

Austenitic stainless steel in Martensitic transition temperature, part of austenite into martensite changes causing the resulting volume parts deformation is an important reason for the valve sealing surface leakage. Moreover, as the temperature decreases parts produces shrink and thermal stress caused by the valve irregular parts of deformation caused by low leakage is also one of the reasons. To this end, before finishing of parts (e.g. sealing surface grinding) on main parts such as: the valve body, valve covers, plate (disc), the valve stem fasteners such as below the operating temperature of cryogenic treatment.

As a general rule, use of the valve below 101C, before finishing the main part for cryogenic. But if the user requires, above-101.C working temperature valve parts for cryogenic.

Cryogenic method: soak the parts to be processed into liquid nitrogen tank for cooling, when parts of 196 degrees centigrade temperature reaches-, start insulation 1 ~ 2 hours, then remove the carton natural treatment to room temperature, repeat cycle twice.