Motor Operated Shutoff ValvesThe purpose of the shutoff valve, shown infigure 7-26, is to shut off the flow of hydraulic fluid tothe engine in case of an engine fire. The valve mayalso be used to great advantage during replacement ofline quick-disconnects and other maintenancefunctions.There are usually other shutoff valves,identical in appearance, installed within the same areathat prevent oil and fuel from reaching the engine incase of an engine fire.When the shutoff valve is energized, an electricalimpulse is applied to the electrical connector on themotor, which converts the electrical energy into rotarymotion of the actuator output shaft by the means of agear train. his rotary motion is then transmitted tothe shaft, which couples the actuator output shaft tothe crank assembly.The crank assembly thentransmits the rotary motion of the shaft to the linearmotion of the slide. The amount of rotation of thevalve output shaft is controlled by means of limitswitches in the motor and gear assembly, whichinterrupt current to the motor. When the valve is inthe open position, the slide is retracted into the valvebody, thus permitting the flow of hydraulic fluidthrough the valve. When the valve is in the closedposition, the slide is positioned between the inlet andoutlet ports, thus shutting off the fluid flow.The valve incorporates a visual position indicator(on the valve itself). The indicator is mechanically con-nected to the operating parts of the valve and provides apositive indication of the position of the valve.CAUTIONOperating an engine with the fire wallshutoff valve closed could cause severedamage to the engine-driven pump.Electric Solenoid Shutoff ValveThe shutoff valve, shown in figure 7-27, is used toshut off the fluid flow to selected subsystems of a7-26Figure 7-26.—Motor operated shutoff valvue.
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