ASME B16.34 (pressure and temperature ratings).API 602 / BS 5351: forged steel (swing, ball, piston).BS 1868: standard type, in carbon and alloy steel.The key specifications that cover this type of valve are: gate or globe valves, that need an external force to work (level, wheel, gear or actuator).
Note that this type of valve accomplishes its scope without external forces or actuation. It is therefore critical that the valve is installed with a proper orientation! Also, the valve closes automatically when the pressure drops. The valve lets the fluid flow in the desired direction only (if there is enough pressure), and blocks any flow in the opposite direction. Briefly said, a check valve is a protection device that prevents the fluid from flowing in an unwanted direction within the piping system or the pipeline (as backflows may damage upstream equipment).
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