Water Valves Are Designed to Handle and Control Hot Water, Cold Water or Wastewater

Water valves are designed to handle and control hot water, cold water, ground water, potable water, salt water and/or wastewater. They are made from metal or plastic. Metal water valves are made of aluminum, brass, bronze, cast iron, ductile iron, copper, steel, or stainless steel. Plastic water valves are made of acetal polymers, polyvinyl chloride (PVC), chlorinated PVC (CPVC), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). Acetal polymers offer excellent lubricity, fatigue resistance, and chemical resistance. PVC provides good flexibility, smooth surfaces, and nontoxic qualities. CPVC is suitable for high temperature applications and is used in hot water distribution. PTFE exhibits a high degree of chemical resistance and a low coefficient of friction. PE is a soft, flexible and tough plastic with outstanding electrical properties but poor temperature resistance. It is prone to stress cracking and has poor resistance to ultraviolet (UV) light. PP is similar to PVC, but can be used in exposed applications because of its resistance to UV, weathering and ozone. PVDF has good wear resistance and excellent chemical resistance, but does not perform well at elevated temperatures. There are many types of water valves. Ball valves provide tight shut-offs, but are not suitable for sanitary applications. Butterfly valves permit flow in only one direction. Check valves are self-actuating and prevent the reversal of process flow. Diaphragm valves separate the flow of water from the closure element. Directional valves steer flow through selected passages. Diverter valves redirect process flow. Drain valves reduce surplus media. Float valves open or close automatically as the level of a fluid changes. Foot valves are check valves with a built-in strainer. Gate or knife valves are linear motion valves in which a closure element slides into the flow to shut off the stream. Globe and pinch valves are other types of linear motion devices. Needle valves have a slender, tapered point at the end of a valve stem. Poppet valves open and close ports with a sealing device and spring. Plug or stop-cock valves are designed for both on/off and throttling functions. Other types of water valves include sanitary or hygienic valves, sampling or dispensing valves, shut off valves, solenoid valves, and toggle valves. Selecting water valves requires an analysis of performance specifications, actuation methods, and connection types. Performance specifications include valve size, pressure rating, number of ports or ways, media temperature, and valve flow coefficient. Suppliers specify valves according to metric or English (imperial) measurements. Some water valves are actuated manually, by a hand wheel or crank, or with mechanical devices such floats and cams. Others are actuated by electric, pneumatic, electro-hydraulic, or electro-hydraulic methods. There are many connection types for water valves. Examples include compression fittings, bolt flanges, clamp flanges, union connections, tube fittings, butt welds, and socket welds. Water valves with internal or external threads for inlet or outlet connections are also available. AWWA certified valves meet the requirements of the American Water Works Association (AWWA). Source: globalspec.com