api 5000API Specification 6A covers wellhead and tree equipment as follows: API Specification 6A Wellhead Equipment Valves, Chokes, and Actuators Plugs, Connectors, and Gaskets OtherAPI 6A TYPE 6B 5000 PSI Blind pipe flanges are used to seal the end of a piping system or pressure vessel openings to prevent flow.API 6A TYPE 6B 5000 PSI Blind flanges are mainly used for pressure testing the flow of liquid or