API 598
API 598 – Valve Inspection and Testing This standard covers inspection, examination, supplemetary examinations, and pressure test requirements for resilient-seated, nonmetallic-seated (e.g. ceramic), and metal-to-metal-seated valves of the gate, globe, plug, ball, check, and butterfly types, Resilient seats are considered to be: a) soft seats, both silid and semi-solid grease type(e.g. lubricated plug) b) cmbination…