Check valve: It is a typical seat valve, Check Valve, also known as check valve or check valve. One-way open-close valve used in hydraulic system to prevent reverse flow of oil flow and prevent back flow of fluid medium on various pipelines or equipment. It can be said that the one-way valve is a kind of check valve.
    There are two types of check valves: straight-through and right-angle. The straight-through check valve is installed on the pipeline with a threaded connection. Right-angle check valves have three forms: threaded connection, plate connection and flange connection.
The difference between "valve" check valve and check valve
    Check valves have a wide range of uses, and there are many types. The following are the check valves commonly used in water supply and heating:

    1. Spring type: the liquid is from bottom to top, relying on the pressure to push up the valve flap controlled by the spring. After the pressure disappears, the spring force pushes down the valve flap to seal the liquid back flow. Often used for check valves with small diameters.
    2. Gravity type: Similar to the spring type, it relies on the self-gravity of the valve flap to close it to prevent backflow.
    3. Swing type: The liquid flows through the valve body directly, and the rotary valve flap on one side is opened by the pressure. After the pressure is lost, the valve flap returns to position by its own weight, and the reverse liquid pressure closes the valve flap.
    Other check valves (check valves), such as sewage check valves, are only available for one-way open and close valves that prevent backflow of fluid media on various pipelines or equipment. To summarize the above, check valves or one-way valves are mainly used to prevent backflow, and they are all fully open or fully closed.