“Cryogenic valve: A valve used in applications with fluid temperatures below -50° F (-45° C).
A cryogenic valve is provided with an extended stem contained in an extension tube so that the valve packing and operator remain at ambient temperature when the cryogenic fluid is in the valve body. The valve is oriented so that the packing is at a higher elevation than the valve body. It allows a vapor-gas pocket to form inside the extension tube, thereby making the extension tube more effective at insulating the packing from cryogenic fluid cold temperature.”
Ref.: Piping Handbook, Published by: McGraw Hill.