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Section 2
DESCRIPTION
pressure relief valve from opening under routine
conditions, thereby preventing fluid loss through the
pressure relief valve.
Fluid is added to the sump via a capped fluid filler
opening, placed low on the tank to prevent overfill-
ing. A sight glass enables the operator to visually
monitor the sump fluid level.
DO NOT open the fluid filler cap when the com-
pressor is pressurized. Shut down the compres-
sor and bleed the sump to 0 psig before removing
the cap.
A check valve is also provided to prevent air in the
service line from bleeding back into the sump at
shutdown or when the compressor is being run in
parallel with other compressors tied to a large sys-
tem. It is recommended that an optional gate-type
service valve be used downstream of the check
valve before the point at which service lines are con-
nected.
An indicator, located on the instrument panel, sig-
nals red if abnormal pressure drop through the
separator elements develops. At this time, separa-
tor element replacement is necessary.
2.6 CAPACITY CONTROL SYSTEM, FUNCTIONAL
DESCRIPTION
Refer to Figure 2-6. The purpose of the compressor
control system is to regulate the compressor air in-
take to match the amount of compressed air being
used.
The Control System consists of a pneumatic ac-
tuator cylinder, a butterfly valve (located on the
compressor air inlet), a pilot pressure regulator
valve, a solenoid pilot valve, closed inlet sole-
noid valve, Sullicon Control and a blowdown
valve.
The functional description of the Control System is
described below in five distinct phases of compres-
sor operation. For explanation purposes, this de-
scription will apply to compressors with an operating
pressure range of 340 to 360 psig (23.5 to 24.8 bar).
A compressor with any other pressure range would
operate in the same manner except for the stated
pressures.
START MODE - 0 TO 160 psig (0 TO 11 BAR)
When the compressor START button is depressed,
the sump pressure will quickly rise from 0 to 160 psig
(0 to 11 bar). During this period, both the pilot pres-
sure regulator and the solenoid pilot valve are
closed and the inlet cylinder is inoperative. Until the
closed inlet timer is satisfied, the inlet actuator cylin-
der remains withdrawn holding the inlet butterfly
valve closed (start Mode A). When the timer is satis-
fied, the closed inlet solenoid valve opens allowing
10
!
WARNING
the cylinder to extend, opening the butterfly valve
fully and the compressor then pumps at full rated ca-
pacity (start Mode B). The rising compressed air
pressure is isolated from the service line in this
phase by the minimum pressure valve, set at ap-
proximately 160 psig (11 bar).
NORMAL OPERATING MODE - 160 TO 340 PSIG
(11 TO 23.4 BAR)
When the sump pressure rises above 160 psig (11
bar), the minimum pressure valve opens and deliv-
ers compressed air to the service line. From this
point on, the line air pressure is continually moni-
tored by a line pressure gauge. The pilot pressure
regulator and the solenoid pilot valve remain closed
during this phase, keeping the Sullicon Control inac-
tive.
MODULATING MODE - 340 TO 360 PSIG (23.4
TO 24.8 BAR)
If less than the rated capacity of compressed air is
being used, the service line pressure will rise above
340 psig (23.4 bar). The pilot pressure regulator
valve gradually opens, applying air pressure to the
Sullicon Control which partially closes the butterfly
valve on the compressor air inlet reducing the
amount of air entering the compressor until it
matches the amount of air being used. The Control
System functions continually in this manner, be-
tween the limits of 340 to 360 psig (23.4 to 24.8 bar),
in response to varying demands from the service
line.
The pilot pressure regulator has an orifice which
vents a small amount of air to the atmosphere when
the pressure regulator controls the butterfly valve.
UNLOAD MODE - IN EXCESS OF 360 PSIG (24.8
BAR) LINE PRESSURE
When a relatively small amount or no air is being
used, the service line pressure rises to the setting
(cut-out pressure) of the pressure switch. The pres-
sure switch opens, interrupting the electrical power
to the solenoid-type pilot valve. At this time, this so-
lenoid valve allows dry sump tank air pressure to be
applied directly to the Sullicon Control keeping the
butterfly valve closed. Simultaneously, this solenoid
valve sends a pneumatic signal to the blowdown
valve. The blowdown valve opens the sump to the
atmosphere, reducing the sump pressure to ap-
proximately 160 to 180 psig (11 to 12.4 bar).
The check valve in the air service line prevents the
pressure from returning to the sump.
At a 0 to 10 percent air output, the control system
will automatically blow down the sump and greatly
reduce the unload power consumption.
When the line pressure drops back to the low setting
(cut-in pressure) of the pressure switch (usually 340
psig [23.4 bar]), the pressure switch closes, re-ener-
gizing the three-way solenoid pilot valve and allow-
ing the blowdown valve to close. The re-energized
solenoid valve again prevents line pressure from
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