Check Valve

Check Valves permit fluid to flow through them in one direction only. Lift-type check valves are similarly constructed as globe valves and use a ball or piston, often backed by a spring that opens under a specified pressure but closes as the pressure decreases, thus preventing backflow. These valves are often suited for high-pressure applications. A variant is the stop check valve which doubles as a shut-off valve. Swing check valves employ hinged gates, disc wafers, or wafers that are often spring-actuated to close against ports as pressure diminishes. These devices can be effective in low-pressure applications. A tilting disc check valve varies the theme somewhat by hinging the gate slightly inward to reduce the pressure required for opening. Butterfly or double door check valves use two half-circle gates or wafers that are hinged at the centerline of the valve port and open downstream in the direction of flow.