Pnuematic diaphragm valves convert the energy of compressed air in order to engage an elastomeric membrane thereby maintaining and regulating the flow of a given process stream. While manual, hydraulic and electric diaphragm valves are common alternatives, the use of a pneumatic actuator is preferred when quick valve adjustments are needed.
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Pneumatic diaphragm valves are air powered devices that provide significant returns on input force allowing for easy use, even in high pressure or high flow pipelines. Liquid, gaseous and semi-solid process streams are all frequently maintained through the use of these effective and economic actuation devices. Industries including biopharmaceutical, agriculture, irrigation, plumbing, medical, water treatment, chemical and food processing, pulp and paper, mining and energy production employ these valves in daily operations to monitor and control the flow of materials such as silicones, adhesives, oils, chemicals, water, cleaners, sanitizers, coatings, fuel and more. It is important to consider the chemical composition and abrasive qualities of a given process flow as valve component construction must be compatible. Often the valve body and actuating mechanisms are made of metals such as copper, brass and stainless steel or durable plastics such as PVC or polypropylene. The diaphragm itself is composed of elastomers such as polyethylene, polycarbonate, polystyrene and PVC which are wound, cast, molded or extruded to the desired thickness. In addition to material and media choice, manufactures should consider compressed air supplies, fixed or adjustable flow, operating pressures, maximum operating temperature, flow compensation features and valve type.
Each pneumatic diaphragm valve has three main components. The body is the housing unit which holds all other components and is installed to the pipeline or cistern depending upon the application. Air valves can be attached perpendicular to piping or inline, seat and weir valves respectively. The diaphragm itself is the elastomeric membrane which stretches to fully or partially impede the flow of process materials through the pipeline. The actuator, in this case a pneumatic actuator or cylinder, is the device that directs the actions of the diaphragm. There are two designs or methods in which this activation is accomplished. In one configuration the compressed air acts on an intermediary piston which acts as the valve stem by stretching or contracting the diaphragm as needed while the other model allows the air to act directly upon the diaphragm. Despite this minor variation the overall function is similar. The introduction of compressed air into the cylinder or vessel is sent to the piston of diaphragm. Increases in pressure cause the material to stretch, effectively reducing the cross-section of the pipeline. If shut off is desired, the diaphragm is stretched to completely block the conduit. When pressure is released, the diaphragm retracts to its original position and allows free flow of materials.
