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; DN 65; DN 80; DN 100; DN 125; DN 150; DN 200; DN 250; DN 300; DN 350; DN 400; DN 450; DN 500; DN 600; DN 700; DN 750; DN 800; DN 900; DN 1000. DN 750 is used for Class designated valves only. DN 8 and DN 12 are not used for PN designated flanged end connections. DN 8, DN 10 and DN 12 are not used for Class designated flanged end connections. Socket welding end valves and threaded end valves are limited to the range DN 8 to DN 65. The range of pressure designations covered is: a) for flanged end, wafer type and butt welding end valves: PN 10; PN 16; PN 25; PN 40; PN 63; PN 100; Class 150; Class 300; Class 600. b) for socket welding end valves and threaded end valves: PN 40; PN 63; PN 100; Class 600; Class 800. NOTE Class 800 is a Class designation widely used for socket welding and threaded end valves.