Valve (famen) is the control part of the fluid conveying system, which has the functions of cut-off, regulating, diversion, preventing countercurrent, stabilizing, shunt or overflow pressure.
Valves for fluid control systems, ranging from the simplest cut-off valves to a variety of valves used in an extremely complex self-control system, are quite diverse. Valves can be used to control the flow of fluids such as air, water, steam, various corrosive mediums, mud, oil, liquid metals and radioactive media. Valve According to material also divided into cast iron valves, cast steel valves, stainless steel valves (201, 304, 316, etc.), chromium-molybdenum steel valves, chromium-molybdenum vanadium steel valves, dual-phase steel valves, plastic valves, non-standard custom-made valves such as material.