The Categories of Check Valves
1. Swing check valve
The flap of the swing check valve is disc-shaped. It rotates around the shaft of the valve seat. Since the channel inside the valve is streamlined, the flow resistance is smaller than that of the lift check valve. It is suitable for use in large-caliber occasions where the flow speed is low and the flow doesn’t constantly change. But it’s not suitable for pulsating flow. Its sealing performance is not as good as that of the lift check valve. Swing check valve can be divided into single-valve, double-valve and multi-valve. These three types are defined mainly according to the valve caliber so as to weaken the hydraulic shock when the medium stops flowing or backflows.
2. Lift check valve
The flap slides alongside the vertical central line of the valve body. It can only be installed on horizontal pipelines. Round balls can be used as valve flaps on high pressure small caliber sanitary check valve. The shape of the valve body of lift check valve is the same as that of the sanitary shut-off valve, so the fluid resistance coefficient is large. Its structure is similar to that of the shut-off valve. Its valve body and valve flap are the same as those of the shut-off valve. There’s an orientation sleeve at the upper part of the valve flap and lower part of the valve cover. The valve flap orientation sleeve can move freely up and down. When the medium flows downstream, the valve flap is opened by the medium thrust. When the medium stops flowing, the valve flap drops on the valve seat to prevent medium backflow. The inlet and outlet channel direction of straight lift check valve is vertical to the direction of valve seat channel. The media inlet and outlet channel direction of vertical lift check valve is the same as that of the valve seat channel. And its flow resistance is smaller than that of straight lift check valve.
3. Disc check valve
The valve flap rotates around a pin inside the valve seat. Its structure is simple and can only be installed on horizontal pipelines. It has a relatively poor sealing performance.
4. Pipeline check valve
The valve flap slides alongside the central line of the valve body. Pipeline check valve is a relatively new type of valve. Its size is small, weight is light, processing technology is good. But the fluid resistance coefficient is slightly larger than that of the swing check valve.
5. Pressed check valve
This type of valve is used to supply water to boilers and shut off steam. It has an integrated function of lift check valve, shut-off valve and angle valve.