The standard is a purchase specification for flanged steel pressure relief valves. … Pertains to inspection by the purchaser and to any supplementary examinations the purchaser may require at the valve manufacturer’s plant. ANSI/API 599. Metal PlugValves – Flanged, Threaded and Welding Ends.

API Valve Standards. The American Petroleum Institute (API), publishes over 600 standards for the design, manufacture, and testing of equipment in the oil & natural gas industry.

API also defines the industry standard for the energy conservation of motor oil. APISN is the latest specification to which motor oils intended for spark-ignited engines should adhere since 2010. API also defines and drafts standards for measurement for manufactured products such as: Precision thread gauges.