Flange Check Valve
What ischeck valve?
Acheck valve,clack valve,non-return valve,reflux valve,retention valveorone-way valveis a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.
aretwo-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are varioustypes of check valvesused in a wide variety of applications.Check valvesare oftenpart of common household items. Although they are available in a wide range of sizes and costs,check valvesgenerally are very small, simple, or inexpensive.Check valveswork automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. The bodies (external shells) of mostcheck valvesare made of plastic or metal.
ball check valveis acheck valvein which the closing member, the movable part to block the flow, is a ball. In someball check valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the mainseats of ball check valvesare more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Wafer check valveshave asolid thermoplastic bodywith a very thin "wafer" profile that makes them anideal check valvefor applications that require valves with short takeout lengths.Wafer check valvesare used in applications where it is essential to ensure fluid flow passes in only one direction.
Adiaphragm check valveuses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, forthe check valveto open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
Aswing check valveor tilting disc check valve is a check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow.
stop-check valve
stop-check valveis acheck valvewith override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
lift-check valveis acheck valvein which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
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