The valve is the control component in the fluid transportation system, which has the functions of cut-off, regulation, diversion, prevention of countercurrent, pressure stabilization, shunt or overflow pressure relief. The valve used in fluid control system, from the simplest stop valve to the most complex automatic control system, has a wide variety of varieties and specifications. The valve can be used to control the flow of air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive medium.

Valve is in the fluid system, used to control the direction of fluid, pressure, flow device. The valve is a device that makes the medium (liquid, gas, powder) flow or stop in piping and equipment and can control its flow. The valve is the control part in the pipeline fluid transportation system. It is used to change the channel section and medium flow direction. It has the functions of diversion, cut-off, throttling, check, shunt or overflow pressure relief. There are many kinds and specifications of valves for fluid control, from the simplest stop valve to the most complex automatic control system. The nominal diameter of the valve ranges from very small instrument valve to industrial pipeline valve with diameter up to 10m. The valve can be used to control the flow of water, steam, oil, gas, mud, corrosive media, liquid metal and radioactive fluid. The working pressure of the valve can be from 0.0013mpa to 1000MPa, and the working temperature is from - 269 ℃ to 1430 ℃. The valve can be controlled by a variety of transmission modes, such as manual, electric, hydraulic, pneumatic, turbine, electromagnetic, electromagnetic, electro-hydraulic, pneumatic, spur gear, bevel gear drive, etc, The valve operates according to the predetermined requirements, or simply opens or closes without relying on the sensing signal. The valve relies on the driving or automatic mechanism to make the opening and closing parts move up and down, slide, swing or rotate, so as to change the size of its flow channel area to realize its control function.