API 6D allows two seat designs for LNG: self-relieving (SPE) and double isolation bleed (DIB-1). LNG operators prefer DIB-1 for transfer lines requiring positive isolation. The upstream seat maintains sealing when cavity pressure exceeds line pressure. LNG seals use bidirectional lip design with dual spring energization. Valves include cavity pressure gauges with low-temperature bourd... https://globalsealstech.com/product-category/oil-gas-seals/api-6d-ball-valve-and-lng-seals/