Definition, function, and classification of check valve
definition
Check valve is the valve relies on media flow to automatically open and close the disc, is used to prevent the media backflow, also known as check valve, one-way valve, reflux valve, and back pressure valve.
function
Check Valve is an automatic valve, its main function is to prevent the media backflow, prevent pump and drive motor reverse, and discharge the container medium. Check valve can also be used in pipelines that its pressure which may rise to exceed the system pressure auxiliary supply.
classification
according to its structure and installed methods Check valve can be divided into
1.Swing Check Valve: Swing check valve disc is cylindrical disk-shape, around the seat channel axis to do rotational movement, due to inner channel is the streamline, the flow resistance is smaller than the lift check valve, apply to the low flow rate and seldom flow changes large-caliber occasions, but it should not be used for pulsatile flow, its sealing performance is less than lift type. Swing Check Valve is devided into single disc, double disc, multi disc. These three types are mainly according to valve diameter, for the purpose to prevent the media stopping flow or reflux, reducing the hydraulic compact.
2.Lift Check Valve: disc slides along the body vertical axis, lift check valve can only be installed in horizontal pipelines, the high-pressure small-diameter check valve upper disc uses ball. Lift-type check valve body shape is the same with globe valve (commonly used to the globe valve), so its flow resistant coefficient is larger. its structure is similar to globe valves, body and disc are the same with globe valve. upper disc and lower bonnet have guided sleeve, the disc guided sleeve can freely lift, when the medium downstream, the disc opens by media thrust, when the media stopped-flow, the disc relies on self-vertical landing on the seat, affected as preventing media backwash. Straight-through lift check valve inlet and outlet media channel direction is perpendicular to seat channels; vertical lift-type check valve, its media inlet and outlet channel direction is the same with the valve seat passage, its flow resistance is smaller than the straight-through type.
3. butterfly Check Valve: the check valve that disc rotates around the seat pin. Its structure is simple, can only be installed in horizontal pipelines, with poor sealing.
4.Pipeline Check Valve: disc slides along the centerline of the valve body. Pipe-type check valve is a new valve, and its small size, light weight, processing technology is good, is one of valve development. But the fluid resistant coefficient is slightly larger than the swing Check Valve.
5.Clamp-in valve: This valve is used for boiler feed water and steam off, it has the integrated function of lift check valve and stop valve or angle valve.
