This kind of valve is used to prevent medium backflow. It opens by itself using the kinetic energy of the fluid and closes automatically when it flows backwards. Permanent at pump outlet, trap outlet and other places where reverse flow of fluid is not allowed. Check valves are divided into three types: swing-open, lifting and clamping. For swing check valves, fluids can only flow from left to right, and automatically close when flowing backwards. For lift check valves, when the fluid flows from left to right, the spool rises to form a path, and when the reverse flow occurs, the spool is pressed to the seat and closed. For the clamp check valve, when the fluid flows from left to right, the valve core is opened to form a path, and when the reverse flow, the valve core is pressed to the seat and closed. For the clamp check valve, it can be installed in many places, with small volume, light weight and compact structure.
When the pressure difference between front and back of the valve is constant, the flow rate of the ordinary valve changes little when the opening of the valve varies in a large range, but when a certain opening, the flow rate changes sharply, that is, the regulating performance is not good. The regulating valve can change the resistance number of the valve by changing the core stroke according to the direction and size of the signal, so as to achieve the purpose of regulating the flow rate of the valve. Regulating valves are divided into manual control valves and automatic control valves, while manual or automatic control valves are divided into many types, and their regulating performance is also different. Automatic control valves include self-operated flow control valves and self-operated differential pressure control valves.