Piston check valves use a globe valve style body with a piston that works in the vertical direction, as flow goes through the valve the piston lifts and when back flow is experienced the piston drops onto the seat. These are sometimes used with a globe valve style top works to push the piston onto the seat when a shut off is needed in both directions.
A check valve, clack valve, non-return valve orone-way valve is a mechanical device, a valve, which normally allows fluid (liquid or gas) to flow through it in only one direction.
There are various types of check valves (wafer,piston, swing, SSIV) used in a wide variety of applications. Check valves are often part of common household items (flapper) up to major gas pipeline subsea check valves (SSIV), which maintain the safety and integrity of refineries and off shore platforms. There for they are available in a wide range of sizes and costs. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. They are often part of a safety system (SSIV) or pump protection to stop reverse flow (swing check).
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