The three main types of check valves are ball, piston, and stop check valves. The purpose of check valves is to prevent backflow within a piping system. Check valves are unidirectional valves that provide unobstructed flow in one direction as long as flow pressure remains constant and protect the piping system against reverse flow.
Ball check valves are lift check valves, and use a weighted ball rather than a disc to allow flow and inhibit backflow. Once the cracking pressure is attained, the ball lifts up from its seat, allowing flow to occur. When there is a reduction of flow pressure, it falls back into place to prevent backflow.
Applications of ball check valves include instances where high-pressure and high-velocity flows are critical and backflow may damage upstream components (Applications similar to piston check valves, but more suited to those for more viscous media).
Also part of the lift check valve family, piston check valves incorporate a weighted piston (or disc) to prevent backflow. These function in a manner similar to ball check valves, allowing for flow as long as flow pressure remains steady, but applying gravitational closure when flow pressure decreases to a point where it no longer has the force to lift the valve.
The valve bore maintains and guides piston alignment throughout its travel. Depending on flow conditions, piston check valves sometimes include spring assistance to aid in closure. Common cases employing piston check valves include:
ㆍFeed water control in the nuclear industry
ㆍDump lines
ㆍMake-up water
ㆍMiscellaneous process systems
ㆍN2 systems
ㆍMonitoring and sampling systems
Stop check valves combine the benefits of lift check valves with the positive closure functionality of globe valves. These features allow for the control of flow regardless of direction. The main purpose of stop check valves is to prevent damage to pump or boiler systems upstream of the valve in the piping system. Common case applications of stop check valves include:
ㆍHeat recovery steam
ㆍHigh-temperature service
ㆍGeothermal service
ㆍHigh-pressure safety service
ㆍUtilities
ㆍSafety systems
ㆍShutdown cooling
ㆍPetroleum production and refining
ㆍHydrocarbon processing
CNM VALVE is a leading global provider of check valves specifically designed to meet the unique needs of our customers. Contact us to learn more about the solutions we offer or request a quote to get started on your next project.
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