~A swing check valve consists of a flap or disc which hangs down in the flow path. With flow in the forwards direction, the pressure of the fluid forces the disc to swing upwards, allowing flow through the valve. Reverse flow will cause the disc to shut against the seat and stop the fluid going back down the pipe. In the absence of flow, the weight of the flap is responsible for the closure of the valve.

 Normative reference
 API 6D Pipeline Valves
 BS 1868 Specification for Steel Check Valves (Flanged and Butt-Welding Ends) For The Petroleum, Petrochemical and Allied Industries
 ASME B16.34 Valves Flanged, Threaded and Welding Ends
 ASME B16.5 Pipe Flanges and Flanged Fittings: NPS 1/2 through 24
 ASME B16.47 Series A Large Diameter Steel Flanges: NPS 26 Through NPS 60 Metric/Inch Standard

 ASME B16.25 Buttwelding Ends
 ASME B16.10 Face to Face and End to End Dimensions of Valves
 MSS SP-25 Standard Marking System for Valves, Fittings, Flanges and Unions

 Size available
 NPS 2 to NPS 24 (DN50 to DN600)
 Pressure rating available
 Class 150 to Class 2500