Stem seals in LNG valves use live-loaded graphite packing with PTFE chevrons for -196°C to 200°C. Belleville washers maintain 1,500 psi packing stress. Valbart’s cryogenic valves achieve ISO 15848-1 Class AH, https://globalsealstech.com/product-category/oil-gas-seals/api-6d-ball-valve-and-lng-seals/