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FIGURE 4–5 – SHUTTLE VALVE
Solenoid Valves IVC and IVO – These valves control
position of the inlet valve in response to signals from
the “Auto Sentry
” Controller. With both valves de–en-
ergized, the normally open IVC valve allows control
pressure to the inlet piston to close the valve. If IVC
only is energized, the inlet valve is held in its current
position. If both valves are energized, control pressure
is relieved from the inlet piston to allow the valve to
open.
Pressure Regulator – The pressure regulator is used
to supply a constant and low control pressure to pre-
vent damage to the inlet valve from “slamming.” The
regulator should be set for 25–30 psig.
Shuttle Valve (FIGURE 4–5) – Also known as a
double check valve, the shuttle valve is a device which
will take two (2) supply signals and allow the one with
the highest pressure to pass through. The shuttle valve
is used to provide control air pressure from either the
reservoir or plant air system, as required during differ-
ent operating conditions.
Purge Air Valve – The purge valve is a normally closed
two–way air actuated valve that admits purge air from
the final discharge manifold to the compressor to coun-
teract the oil knock that occurs in oil–flooded rotary
screw compressors when they are completely un-
loaded with pressure in the oil reservoir. This valve is
controlled by the same control pressure which controls
the inlet valve.
Turn Valve (Electra–Saver only) (FIGURE 4–6)– The
turn valve is a helical valve which, when rotated, opens
and closes a series of ports cast into the compressor
cylinder. When these ports are open, they direct some
of the air which would otherwise be compressed back
to the inlet, reducing both capacity and power con-
sumption.
Turn Valve Actuator (Electra–Saver only) – The turn
valve actuator is a rotary rack and pinion device which
positions the turn valve according to system demand.
Filtered oil from the compressor sump is directed to the
outboard end of the two actuating cylinders to move the
FIGURE 4–6 – TURN VALVE – ELECTRA–SAVER ONLY
213ECM797
(Ref. Drawing)
