ValvesDOE-HDBK-1018/2-93TYPES OF VALVESCheckValvesCheck valves are designed to prevent the reversal of flow in a piping system. These valves areactivated by the flowing material in the pipeline. The pressure of the fluid passing through thesystem opens the valve, while any reversal of flow will close the valve. Closure is accomplishedby the weight of the check mechanism, by back pressure, by a spring, or by a combination ofthese means. The general types of check valves are swing, tilting-disk, piston, butterfly, andstop.SwingCheckValvesA swing check valve is illustrated in Figure 22. The valve allows full, unobstructed flow andautomatically closes as pressure decreases. These valves are fully closed when the flow reacheszero and prevent back flow. Turbulence and pressure drop within the valve are very low.A swing check valve is normally recommended for use in systems employing gate valves becauseFigure 22 Swing Check Valveof the low pressure drop across the valve. Swing check valves are available in either Y-patternor straight body design. A straight check valve is illustrated in Figure 22. In either style, thedisk and hinge are suspended from the body by means of a hinge pin. Seating is either metal-to-metal or metal seat to composition disk. Composition disks are usually recommended forservices where dirt or other particles may be present in the fluid, where noise is objectionable,or where positive shutoff is required.Rev. 0ME-04Page 35
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