What is Swing Check Valve ?
Swing check valve is a self actuated back flow preventer or uni-directional valve which allows full, unobstructed flow and automatically closes as pressure decreases. These check valves or non return valves (swing type check valve) are fully closed when the flow reaches zero and prevent back flow. Advantage of swing check valve is less turbulence and low pressure drop within the body of valve.
Swing Check Valve Types
Swing check valves are available in either Y-pattern or straight body design.In either style, the valve disk 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 for services where dirt or other particles may be present in the fluid, where noise is objectionable, or where positive shutoff is required.
Straight body swing check valves contain a disk that is hinged at the top. The disk seals against the seat, which is integral with the body. However seat rings may be replaceable.Replace-ability of seat rings eases the smooth,quite and leak-free operation of swing check valve.The seating surface of check valve is placed at a slight angle to permit easier opening at lower pressures, more positive sealing, and less shock when closing under higher pressures.
Check valve specification and check valve dimensions must match the application and location of valve .Care must be taken during the installation of check valve as these are NRVs or uni-directional valves.
Use of Swing Check Valves
A swing check valve is normally recommended for use in systems employing gate valves because of the low pressure drop across the valve. Application of swing check valves along with gate valve is because of relatively free flow in gate valve.They are recommended for lines having low velocity flow and should not be used on lines with pulsating flow when the continual flapping or pounding would be destructive to the seating elements. This condition can be partially corrected by using an external lever and weight.