A valve that is designed to allow the fluid to flow in a given direction but closes to prevent backflow. Types include swing check, tilting disc check and wafer check. Check valves (also called non-return valves) are usually self-acting.

The above attached product's specification is as follow:

Bolted, Cover, Swing Type Disc, Threaded of Welded Seat Ring
Standards Compliance:
Basic Design: BS1868
Face to Face Dimension: ANSI B16.10
End to End Dimension: ANSI B16.10
Flange End:
2"-24" to ANSI B16.5
>24": to MSS SP-44
to APS 605 on request
B.W.Ends to AMSI B16.25
Manufacturing to NACE MR-01-75 on request