PCTFE (Kel-F) lip seals are used as primary low-temperature barriers in small-bore LNG ball valves. With a -196°C to +80°C operating range, PCTFE offers superior dimensional stability and lower permeation than PTFE, reducing LNG boil-off losses through stem seals in cryogenic transfer lines. https://globalsealstech.com/product-category/oil-gas-seals/api-6d-ball-valve-and-lng-seals/