Motor Operated Shutoff Valves
The purpose of the shutoff valve, shown in
figure 7-26, is to shut off the flow of hydraulic fluid to
the engine in case of an engine fire. The valve may
also be used to great advantage during replacement of
line quick-disconnects and other maintenance
functions.
There are usually other shutoff valves,
identical in appearance, installed within the same area
that prevent oil and fuel from reaching the engine in
case of an engine fire.
When the shutoff valve is energized, an electrical
impulse is applied to the electrical connector on the
motor, which converts the electrical energy into rotary
motion of the actuator output shaft by the means of a
gear train. his rotary motion is then transmitted to
the shaft, which couples the actuator output shaft to
the crank assembly.
The crank assembly then
transmits the rotary motion of the shaft to the linear
motion of the slide. The amount of rotation of the
valve output shaft is controlled by means of limit
switches in the motor and gear assembly, which
interrupt current to the motor. When the valve is in
the open position, the slide is retracted into the valve
body, thus permitting the flow of hydraulic fluid
through the valve. When the valve is in the closed
position, the slide is positioned between the inlet and
outlet 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 a
positive indication of the position of the valve.
CAUTION
Operating an engine with the fire wall
shutoff valve closed could cause severe
damage to the engine-driven pump.
Electric Solenoid Shutoff Valve
The shutoff valve, shown in figure 7-27, is used to
shut off the fluid flow to selected subsystems of a
7-26
Figure 7-26.—Motor operated shutoff valvue.
