Liquefied gases — LNG at −162 °C, liquid nitrogen at −196 °C, liquid oxygen, ethylene — are among the least forgiving services a valve can see. A standard ball valve installed on a cryogenic line will leak, seize, or worse. Here is what actually changes at cryogenic temperatures, and what to look for when you specify.<\/p>\n
Cryogenic valves per BS 6364<\/strong> (and ISO 28921) carry an extended bonnet, installed vertically, so a vapor column forms between the cold fluid and the stem packing. The standard defines minimum extension lengths — this keeps the packing near ambient temperature, where it can actually seal.<\/p>\n A prototype is tested at<\/em> cryogenic temperature (typically immersed in liquid nitrogen at −196 °C) for seat leakage with helium, external tightness, and operability. When you buy, ask for: the type-test certificate covering your size\/class, materials with low-temperature impact certs, degreasing for oxygen service if applicable, and cavity relief direction clearly marked.<\/p>\n LNG terminals and bunkering, air separation units (LIN\/LOX\/LAR), CO2 capture, hydrogen and ethylene plants, and cryogenic tank truck loading. Ball, globe, gate, check and triple-offset butterfly designs all exist in cryogenic execution — see our cryogenic & LNG valve range<\/a> et triple-offset butterfly valves<\/a>.<\/p>\n The extended bonnet must point upward (within the angle allowed by the manufacturer, commonly ±45° from vertical) so the vapor column is maintained. Horizontal stem orientation defeats the design.<\/p>\n Austenitic stainless is the default. Bronze and Monel appear in oxygen service; 9% nickel steel and aluminum appear in LNG static equipment more than in valves.<\/p>\n Specify the BS 6364 \/ ISO 28921 type-test acceptance with helium at design temperature — not just an ambient API 598 test. Ambient tightness says little about −162 °C behavior.<\/p>\nWhat BS 6364 Type Testing Covers<\/h2>\n
Applications typiques<\/h2>\n
Foire aux questions<\/h2>\n
Can a cryogenic valve be installed horizontally?<\/h3>\n
Is 316 stainless always required?<\/h3>\n
What seat leakage class should I specify?<\/h3>\n