Valves are pipeline accessories used to open and close pipelines, control flow direction, adjust and control the parameters (temperature, pressure and flow) of the conveying medium. According to its function, it can be divided into shut-off valve, check valve, regulating valve and so on.

The valve is a control component in the fluid delivery system, which has functions such as cut-off, adjustment, flow diversion, reverse flow prevention, pressure stabilization, flow diversion or overflow pressure relief. Valves used in fluid control systems range from the simplest cut-off valves to various valves used in extremely complex automatic control systems, with a wide variety of varieties and specifications.

Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. Valves are also divided into cast iron valves, cast steel valves, stainless steel valves (201, 304, 316, etc.), chrome-molybdenum steel valves, chrome-molybdenum-vanadium steel valves, duplex steel valves, plastic valves, non-standard custom-made valves, etc. according to the material.