ValvesDOE-HDBK-1018/2-93TYPES OF VALVESPinchValveBodiesPinch valves have molded bodies reinforced with fabric. Pinch valves generally have amaximum operating temperature of 250oF. At 250oF, maximum operating pressure variesgenerally from 100 psig for a 1-inch diameter valve and decreases to 15 psig for a 12-inchdiameter valve. Special pinch valves are available for temperature ranges of -100oF to 550oFand operating pressures of 300 psig.Most pinch valves are supplied with the sleeve (valve body) exposed. Another style fullyencloses the sleeve within a metallic body. This type controls flow either with the conventionalwheel and screw pinching device, hydraulically, or pneumatically with the pressure of the liquidor gas within the metal case forcing the sleeve walls together to shut off flow.Most exposed sleeve valves have limited vacuum application because of the tendency of thesleeves to collapse when vacuum is applied. Some of the encased valves can be used on vacuumservice by applying a vacuum within the metal casing and thus preventing the collapse of thesleeve.Figure 19 Typical Butterfly ValveButterflyValvesA butterfly valve, illustrated inFigure 19, is a rotary motionvalve that is used to stop,regulate, and start fluid flow.Butterfly valves are easily andquickly operated because a 90orotation of the handle moves thedisk from a fully closed to fullyopened position. Larger butterflyvalves are actuated by handwheelsconnected to the stem throughgears that provide mechanicaladvantage at the expense of speed.Butterfly valves possess manyadvantages over gate, globe, plug,and ball valves, especially forlarge valve applications. Savingsin weight, space, and cost are themost obvious advantages. Themaintenance costs are usually lowbecause there are a minimalnumber of moving parts and thereare no pockets to trap fluids.Rev. 0ME-04Page 31
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