Control System, Functional Description - Sullair 12 Series Operator's Manual

panel, shows red if abnormal pressure drop through
the separator develops. At this time, separator ele-
ment replacement is necessary.
The receiver is ASME code rated at 175 PSIG
(1206kPa) working pressure. A minimum pressure/
check valve, located downstream from the separa-
tor, assures a minimum receiver pressure of 55
PSIG (379kPa) during all conditions. This pressure
is necessary for proper air/fluid separation and
proper fluid circulation.
A terminal check valve is incorporated into the mini-
mum pressure/check valve to prevent compressed
air in the service line form bleeding back into the re-
ceiver on shutdown and during operation of the
compressor in an unloaded condition.
A pressure relief valve (located on the wet side of
the separator) is set to open if the sump pressure ex-
ceeds 175 PSIG (1206kPa). A temperature switch
will shut down the compressor if the discharge tem-
perature reaches 240ºF (115ºC).
All compressor models are equipped with a high
pressure shutdown switch to shut down the com-
pressor at 135 PSIG (931kPa). This prevents the
pressure relief valve from opening under routine
conditions, thereby preventing fluid loss through the
pressure relief valve.
!
DO NOT remove caps, plugs, or other compo-
nents when compressor is running or pressur-
ized.
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 tank to prevent overfilling
of the sump. A sight glass enables the operator to
visually monitor the sump fluid level.
2.6 CONTROL SYSTEM, FUNCTIONAL DESCRIP-
TION
Refer to Figure 2-5. 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 Sullicon
Control, a butterfly valve (located on the compres-
sor air inlet), a pressure switch, a pilot valve and
pressure regulator. The functional description of the
control system is described below in four distinct
phases of compressor operation.The following de-
scriptive text applies to all 12 and 16 Series com-
pressors. For explanation purpose this description
will apply to a compressor with an operating pres-
sure range of 100 to 110 PSIG (689 to 758kPa). A
compressor with any other pressure range would
operate in the same manner except for the stated
pressures.
WARNING
DESCRIPTION
START MODE - 0 TO 55 PSIG (0 TO 379kPa)
When the compressor START button is depressed,
the pressure will quickly rise from 0 to 55 PSIG (0 to
379kPa). During this period both the pressure regu-
lator and the pilot valve are closed and the Sullicon
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 compres-
sor air pressure is isolated from the service line in
this phase by the minimum pressure valve, set ap-
proximately at 55 PSI (379kPa).
NORMAL OPERATION MODE - 55 TO 100 PSIG
(379 TO 689kPa)
When the compressor air pressure rises above 55
PSIG (379kPa), the minimum pressure valve opens
and delivers compressed air to the service line.
From 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.
MODULATING MODE - 100 TO 110 PSIG (689 TO
758kPa)
If less than the rated 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 which 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 the 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 - IN EXCESS OF 110 PSIG (758kPa)
LINE PRESSURE
When no air is being used, the service line pres-
sures rises to the setting (cut-out pressure) of the
pressure switch. The pressure switch opens, inter-
rupting the electrical power to the solenoid-type pilot
valve. At this time, the pilot valve allows dry sump
tank air pressure to be applied directly to the control
diaphragm, keeping the butterfly valve closed. Si-
multaneously, the pilot valve sends a pneumatic sig-
nal to the blowdown valve. The blowdown valve
opens the sump to the atmosphere, reducing the
sump pressure to approximately 40 to 50 PSIG (276
to 379kPa). The check valve in the air service line
prevents line pressure from returning to the sump.
When the line pressure drops to the low setting (cut-
in pressure) of the pressure switch (usually 100
PSIG [689kPa] on low pressure compressors and
115 PSIG [793kPa] on high pressure compressors),
the pressure switch closes, re-energizing the three-
Section 2
9