ValvesDOE-HDBK-1018/2-93VALVE ACTUATORSHammerHandwheelFigure 31 Hammer HandwheelAs illustrated in Figure 31, thehammer handwheel moves freelythrough a portion of its turn andthen hits against a lug on asecondary wheel. The secondarywheel is attached to the valvestem. With this arrangement, thevalve can be pounded shut fortight closure or pounded open if itis stuck shut.GearsFigure 32 Manual Gear HeadIf additional mechanical advantage isnecessary for a manually-operatedvalve, the valve bonnet is fitted withmanually-operated gear heads asillustrated in Figure 32. A specialwrench or handwheel attached to thepinion shaft permits one individual tooperate the valve when twoindividuals might be needed withoutthe gear advantage. Because severalturns of the pinion are necessary toproduce one turn of the valve stem,the operating time of large valves isexceptionally long. The use ofportable air motors connected to thepinion shaft decreases the valveoperating time.Rev. 0ME-04Page 45
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