Design and manufacture: API 6D
Face to face: ANSI B 16.10
Flange: ANSI B 16.5a
Butt welding end dimension: ANSI B 16.25
Pressure test: API 6D or API 598

API check valve is applied to petroleum, chemical, water power, thermal power station and other pipelines. It is used to cut off or turn-on the medium, for example water, oil, steam, etc.