This European Standard specifies the requirements for steel check valves, which are forged, cast or fabricated in straight, angle or oblique pattern (see EN 736 2) with end connections flanged or wafer, butt welding, socket welding, or threaded.This standard is applicable to steel check valves mainly used for industrial and general purpose applications. However, they can be used for other applications provided the requirements of the relevant performance standards are met.Back flow prevention anti-pollution check valves are outside the scope of this standard.The range of nominal sizes covered is: DN 8; DN 10; DN 12; DN 15; DN 20; DN 25; DN 32; DN 40; DN 50;