Section 2
DESCRIPTION
16
pressures.
START MODE - TO 160 PSIG (11 BAR)
When the compressor start button is depressed, the
sump pressure will rise from 0 to 160 psig (0 to 11
bar). During this period, the control pressure regu-
lator is closed at this time. The inlet poppet valve
opens allowing full air flow to the compressor inlet
and the sump pressure builds to approximately 160
psig (11 bar). No air is supplied to the system serv-
ice line during this phase by the minimum pressure
valve. When the sump pressure exceeds approxi-
mately 160 psig (11 bar), the minimum pressure
valve starts to open and allows air to flow to the sys-
tem service line.
NORMAL OPERATION MODE - 160 TO 350 PSIG
(11 TO 24.1 BAR)
When the sump pressure rises above 160 psig (11
bar), the minimum pressure valve opens and deliv-
ers compressed air to the system service line.
From this point on, a line air pressure transducer
continually monitors the air pressure. The modulat-
ing control regulator valve remains closed during
this phase, keeping the inlet poppet valve wide
open. The blowdown solenoid valve also remains
closed during this phase. Flow will occur when the
discharge pressure is higher than the line pressure.
The check valve, which is built into the minimum
pressure valve, will prevent back flow into the com-
pressor.
MODULATING MODE - 350 TO 360 PSIG (24.1 TO
24.8 BAR)
If less than the rated capacity of compressed air is
being used, the system service line pressure will
rise above 350 psig (24.1 bar). The modulating
control regulator valve gradually opens applying air
pressure to the control side of the inlet poppet
valve, which modulates the position of the inlet pop-
pet valve. This reduces the amount of air entering
the compressor until it matches the amount of air
being utilized. The control system functions contin-
ually in this manner, between the limits of 350 to
360 psig (24.1 to 24.8 bar) in response to varying
demands from system service line. The control
pressure regulator valve has an orifice, which vents
a small amount of air to the atmosphere when the
control pressure regulator valve modulates the inlet
poppet valve.
UNLOAD MODE - EXCESS OF 360 PSIG (24.8
BAR)
As the required air is reduce, the discharge pres-
sure and line pressure rise above the 360 psig (24.8
bar), the Supervisor II activates the unload solenoid
valve which in turn pressurizes the blowdown valve.
This opens the blowdown valve, which allows dis-
charge air to flow back to the compressor inlet.
Since the inlet poppet valve is closed, the air pres-
sure from the sump tank will be relieved through the
blowdown valve, which will reduce the sump pres-
sure. Some of the outgoing air will flow directly into
the compressor inlet to avoid cavitation during this
time of blowdown. As the sump pressure drops,
motor power consumption is also reduced. The
unload control regulator is set to maintain the
unload pressure at a designated value of approxi-
mately 150 psig (10.3 bar). At this time, the com-
pressor is in the unload mode.
When the line pressure drops back to the load point
(cut-in pressure) of the Supervisor II, usually 350
psig (24.1 bar), the compressor will change state
back to the modulating mode as discussed earlier.
This cycle will repeat itself, maintaining the demand
required on the system line supply.
SHUTDOWN MODE
When the compressor is shut down based on a
manual shutdown, a safety shutdown or an auto-
matic shutdown from the Supervisor II touch pad,
the unload solenoid valve is de-energized allowing
air to flow through the check valve and into the pop-
pet valve keeping the inlet poppet valve closed.
This also opens the blowdown valve to vent com-
pressed air through the inlet filter. The control lines
are properly sized and routed to allow the com-
pressed air to relieve to atmosphere rather than
below the inlet poppet valve.
If the compressor Supervisor II controller is in the
automatic mode, the compressor will shut down
after running unloaded for a specific amount of
time. The reverse also holds true, if the system
requires additional compressed air, the compressor
will start automatically to satisfy this demand.
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