Seat pocket elastomeric seals (typically O-rings or FS seals) prevent leakage between the seat ring and valve body cavity. These are often made from explosion-decompression-resistant HNBR or AFLAS. Incorrect groove design or excessive squeeze can cause spiral failure during rapid decompression. API 6A mandates groove dimensions per ASME B16.5 and squeeze between 12–30% depending on ma... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-gate-valve-seals/