A valve is a device used to control the direction, pressure, and flow of a fluid in a fluid system. It is a device that allows the medium (liquid, gas, powder) in the piping and equipment to flow or stop and control its flow. The valve is a control component in the pipeline fluid conveying system. It is used to change the passage section and the flow direction of the medium. It has the functions of diversion, cut-off, throttling, non-return, shunt or overflow and pressure relief. Valves used for fluid control, from the simplest shut-off valve to various valves used in extremely complex automatic control systems, have a wide range of varieties and specifications. Valves for industrial pipelines. It can be used to control the flow of various types of fluids such as water, steam, oil, gas, mud, various corrosive media, liquid metals and radioactive fluids. Ultra-low temperature of c-270℃ to high temperature of 1430℃. The control of the valve can adopt a variety of transmission methods, such as manual, electric, hydraulic, pneumatic, turbine, electromagnetic, electromagnetic hydraulic, electro-hydraulic, gas-hydraulic, spur gear, bevel gear drive, etc.; Or other forms of sensing signals, act according to predetermined requirements, or simply open or close without relying on sensing signals, the valve relies on driving or automatic mechanisms to make the opening and closing parts lift, slide, swing or rotate Movement, thereby changing the size of its flow channel area to achieve its control function.