API RP 591: 2019 [paper]
API Process Valve Qualification Procedure, 6th edition
This recommended practice (RP) provides recommendations for evaluation of a manufacturer’s valve construction and quality management system for the purpose of determining a manufacturer’s capability to provide new valves manufactured in accordance with the applicable standards listed in Section 2. Testing per this RP that does not have an established requirement in the applicable standard is for information only.
Qualification of valves under this RP is “manufacturing facility specific” and does not cover valves manufactured by other manufacturing facilities, whether owned by the same manufacturer or a third party.
API RP 591