Sour service (NACE MR0175/ISO 15156) compliance is mandatory for HH-class valves. Elastomers must resist hydrogen sulfide embrittlement and cracking, while metallic seal components must have hardness ≤22 HRC (or ≤34 HRC with documented environmental limits). Inconel 718 seat springs and stem components are solution-annealed and aged to meet both corrosion and strength requirements sim... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-gate-valve-seals/