Check valves are one of the most basic but important valves in a water or steam system. The most common check valves are Ball Check Valves, Swing Check Valves, and Lift Check Valves.
Although different in design these valves are generally designed to allow fluid flow in only one direction.
The Ball Check design closes off fluid flow via a spherical ball that can be spring loaded or non-spring loaded. Fluid Flow through the valve will move the ball off the seat allowing continuous flow. When flow stops a spring (if spring loaded) will push the ball to a closed position not allowing back flow through the check valve. In the case of a non-spring loaded ball check valve the fluid back pressure will push the ball back against the seat to a closed position.
The Swing Check valve design features a gate that is attached to a pivot lever that allows the opening of the valve with flow present. Any back flow from the downstream side of the check valve will force the closure of the gate.
The Lift Check design incorporates the use of a disc that allows the disc to lift upward when positive pressure from the inlet flow is present. When inlet pressure is removed or if downstream pressure is higher than the inlet flow pressure the disc via a disc guide is lowered down to the valve’s seat stopping a reverse flow situation.
Because of varying media characteristics, including type of media like steam, air, water, and oil along with media temperatures and pressures, care must be taken in selecting the proper check valve that best meets service conditions.
Look for upcoming videos on other types of mechanical valves and I would like to thank Process Technology for their excellant videos on this subject.
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