A valve is a device used in fluid systems to control the direction, pressure, and flow rate of a fluid. It allows the media (liquid, gas, powder) within piping and equipment to flow or stop and controls their flow rate.
Valves are control components in pipeline fluid transport systems, used to change the cross-sectional area of the passage and the direction of media flow. They have functions such as guiding, stopping, throttling, check valves, diverting flow, or overflow pressure relief. Valves used for fluid control range from the simplest shut-off valves to various valves used in extremely complex automatic control systems. Their types and specifications are numerous, with nominal diameters ranging from extremely small instrument valves to industrial pipeline valves with diameters up to 10 meters. They can be used to control the flow of various types of fluids, including water, steam, oil, gas, slurry, various corrosive media, liquid metals, and radioactive fluids. Valve operating pressures can range from 0.0013 MPa to ultra-high pressures of 1000 MPa, and operating temperatures can range from ultra-low temperatures of -270°C to high temperatures of 1430°C.
Valves can be controlled by various transmission methods, such as manual, electric, hydraulic, pneumatic, turbine, electromagnetic, electromagnetic-hydraulic, electro-hydraulic, pneumatic-hydraulic, spur gear, bevel gear drive, etc. They can operate according to predetermined requirements under the action of pressure, temperature or other forms of sensor signals, or simply open or close without relying on sensor signals. Valves rely on drive or automatic mechanisms to make the opening and closing parts move up and down, slide, swing or rotate, thereby changing the size of their flow channel area to achieve their control function.
