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Valve is a fluid delivery system in the control of parts, with the cut-off, regulation, diversion, to prevent adverse current, voltage regulator, diversion or overflow relief and other functions. Valves for fluid control systems, from the most simple to the very complex control system used in a variety of valves, the variety and specifications of a considerable variety. Valves can be used to control air, water, steam, a variety of corrosive media, mud, oil, liquid metals and radioactive media and other types of fluid flow. Valve according to the material is divided into cast iron valve, cast steel valves, stainless steel valves (201, 304, 316, etc.), valves in chrome molybdenum steel, chrome molybdenum vanadium steel valve, dual phase steel valves, plastic valves, non-standard custom valve material.