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

The valve is a control component in the fluid conveying system, which has the functions of cut-off, regulation, diversion, prevention of backflow, stabilization, diversion or overflow, and pressure relief. Valves used in fluid control systems, ranging from the simplest shut-off valves to extremely complex valves used in automatic control systems, have a wide variety 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, chromium-molybdenum steel valves, chromium-molybdenum vanadium steel valves, duplex steel valves, plastic valves, non-standard customized valves, etc. according to their materials.