The Classifications of Check Valves
1. Swing check valve
The valve flap of swing check valve is disc-shaped and rotates around the axis of valve seat channel. As the channel inside the valve is streamlined and the flow resistance is smaller than that of the lift check valve, it is suitable for low flow rate occasions or large caliber occasion where the flow doesn’t frequently change, but it’s not suitable for use in pulsating flow. Its sealing performance is not as good as that of the lift check valve. Swing check valve can be divided into single-flap, double-flap and multi-flap types. These three types are defined according to the caliber of the valve. The purpose is to weaken the hydraulic shock when the medium stops flowing or backflows.
2. Lift check valve
It is a kind of check valve whose valve flap slides along the vertical centerline of the valve body. Lift check valve can only be installed on horizontal pipelines. On high pressure small caliber check valve, the valve flap can use round balls. The shape of the valve body of lift check valve is the same with that of the shut-off valve, so it has a relatively large fluid resistance coefficient. Its structure is similar to that of the shut-off valve. Valve body and valve flap are the same with those of the shut-off valve. The upper part of the valve flap and the lower part of the valve cover are machined with a guide sleeve. The valve flap guide sleeve can be freely lifted inside the valve guide sleeve. When the medium flows downstream, he valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap drops onto the valve seat by its own weight, preventing medium backflow. The channel direction of medium inlet and outlet of straight-through lift check valve is vertical to the channel direction of the valve seat. The channel direction of medium inlet and outlet of vertical lift check valve is the same with the channel direction of the valve seat. Its fluid resistance is smaller than that of the straight-through lift check valve.
3. Disc check valve
Its valve flap rotates around the axis inside the valve seat. Disc check valve has a simple structure, can only be installed on horizontal pipelines. Its sealing performance is poor.
4. Pipeline check valve
Its valve flap slides along the centerline of the valve body. It is a new type of valve. Its size is small, weight is light, processing technique is good. It is one of the development directions of sanitary check valve. But its fluid resistance coefficient is slightly larger than that of the swing check valve.
5. Pressed check valve
This kind of valve is used to feed water for boilers and cut off the steam. It has combined functions of lift check valve, shut-off valve and angle valve.
Besides, there are other types of check valves that are not suitable for pump outlet installation, such as bottom valves, spring-type and Y-type check valves.