Section 2
DESCRIPTION
9
pressure is necessary for proper air/fluid separation
and t o assure proper fluid circulation while supply-
ing air to the system. Also, a check valve is provided
to prevent compressed air in the service line from
bleeding back into the receiver during shutdown, as
well as in the unload operation mode.
An ASME pressure relief valve, located on the wet
side of the sump, is set to open at 140 PSIG
(965kPa). The compressor is also equipped with a
high pressure shutdown switch to shut down the
compressor at 135 PSIG (931kPa). This prevents
the relief valve from opening and dumping fluid un-
der normal conditions. Also, a thermistor type high
discharge temperature switch is provided to shut
down the compressor if the discharge temperature
reaches 240_ (116_C).
WARNING
!
DO NOT remove caps, plugs, or other components
when compressor is running or pressurized.
Stop compressor and relieve all internal pressure
before doing so.
Fluid is added to the sump via a capped fluid filler
opening, placed low on the sump tank to prevent
overfilling of the sump. A sight glass enables the op-
erator to visually monitor the sump fluid level.
2.6 CONTROL SYSTEM, FUNCTIONAL DESCRIP-
TION
Refer t o Figure 2 --- 5. The purpose of the compres -
sor control system is to regulate the amount of air
being compressed to match the a mount of com-
pressed air being used. At a 0 to 100 percent air out -
put, the control system will automatically blowdown
the compressor and greatly reduce the unload pow-
er consumption. The control system consists of a
Sullicon Control, a butterfly valve located on the
compressor air inlet, a pressure regulator, pressure
switch, pilot valve and blowdown valve. The func-
tional description of the control system is described
below in four distinct phases of compressor opera-
tion. The following descriptive text applies to all Se-
ries 32 compressors. For explanation purposes, this
description will apply to a compressor with an oper-
ating pressure range of 100 to 110 PSI (689 to
758kPa). A compressor with any other pressure
range would operate in the same manner excepting
stated pressures.
START MODE -- 0 TO 50 PSIG (0 TO 345kPa)
When the compressor START button is depressed,
the pressure will quickly rise from 0 to 50 PSIG (0 to
3454kPa). During this period, both the pressure
regulator and the pilot valve are closed and the Sulli-
con Control is inoperative. The spring on the control
holds the butterfly valve fully open and the compres-
sor pumps at full rated capacity. The rising air pres-
sure is isolated from the service line in this phase by
the minimum pressure valve, set at approximately
50 PSI (345kPa).
NORMAL OPERATION -- 50 TO 100 PSIG (345
TO 689kPa)
When the compressed air pressure rises above 50
PSI (345k Pa), the minimum pressure valve opens
and delivers compressed air to the service line.
F rom this point on, the line air pressure is continually
monitored by a line pressure gauge. The pressure
regulator and the pilot valve remain closed during
this phase, keeping the Sullicon Control inactive.
MODULATION MODE -- 100 to 110 PSIG (689 TO
758kPa)
If less than t h e ra ted capacity of compressed air is
being used, the service line pressure will rise above
100 PSIG (689kPa). The pressure regulator valve
gradually opens, applying air pressure to the dia -
phragm chamber of the Sullicon Control w h ich par-
tially closes the butterfly valve on the compressor air
inlet, reducing the amount of air entering the com-
pressor until it matches the amount of air being
used. The control system functions continually in
this manner, between the limits of 100 to 110 PSIG
(689 to 758kPa), in response to varying demands
from th e service line.
The pressure regulator has an orifice which vents a
small amount of air to the atmosphere when the
pressure regulator controls the butterfly valve. The
orifice also bleeds any accumulated moisture from
the Sullicon Control.
UNLOAD MODE -- IN EXCESS OF 110 PSIG
(758kPa)
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
pressure switch opens, interrupting the electrical
power to the solenoid---type pilot valve. At this time,
the pilot valve allows dry separator tank air pressure
to be applied directly to the control diaphragm,
keeping the butterfly valve closed. Simultaneously,
the pilot valve sends a pneumatic signal to the blow-
down valve. The blowdown valve opens the sump to
the atmosphere, reducing the sump pressure to ap -
proximately 40 to 55 PSIG (276 to 379kPa). The
check valve in the air service line prevents line pres-
sure from returning to the separator tank.
When the line pressure drops to the low setting
(cut---in pressure) of the pressure sw itch (usually
100 PSIG [689kPa]) due to an increase in air de-
mand, the pressure switch closes, re---energizing
the three---way pilot valve and allowing the blow-
down valve to close. The re---energized pilot valve
again prevents line pressure from reaching the Sulli-
con Control. Should the pressure begin to rise, the
pressure regulator will resume its normal function
as previously described.
F or a compressor with varied periods of time when
there a re no air requirements, a “Dual Control” op-
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