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Section 5
COMPRESSOR SYSTEMS
5.3 SULLAIR COMPRESSOR UNIT, FUNCTIONAL
DESCRIPTION
Sullair air compressors feature the Sullair compres-
sor unit, a single--stage, positive displacement, lu-
bricated--type compressor. This unit provides con-
tinuous pulse--free air compression to meet your
needs. With a Sullair compressor, there is no main-
tenance or inspection of the internal parts of the
compressor unit permitted in accordance with the
terms of the warranty.
Sullair 24KT compressors are filled with a fluid
which rarely needs to be changed. In the event a
change or make--up fluid is required, use only Sullair
24KT fluid.
Mixing of other lubricants within the compressor
unit will void all warranties!
Sullair recommends that a 24KT sample be taken at
the first filter change and sent to the factory for anal-
ysis. This is a free service. The sample kit with in-
struction and self--addressed container is to be sup-
plied by your Sullair representative at start--up. The
user will receive an analysis report with recommen-
dations.
Fluid is injected into the compressor unit in large
quantities and mixes directly with the air as the ro-
tors turn, compressing the air. The fluid flow has
three primary functions:
S Controls the rise of air temperature normally asso-
ciated with the heat of compression.
S Seals the leakage paths between the rotors and
the stator and also between the rotors themselves.
S Acts as a lubricating film between the rotors allow-
ing one rotor to directly drive the other, which is an
idler.
After the air/fluid mixture is discharged from the
compressor unit, the fluid is separated from the air.
At this time, the air flows to the service line and the
fluid is cooled in preparation for re--injection.
The fluid also serves as lubricant for the anti--friction
bearings and the drive gear sets.
5.4 COMPRESSOR COOLING AND LUBRICATION
SYSTEM, FUNCTIONAL DESCRIPTION
Refer to Figures 5--2 and 5--3. The cooling and lu-
brication system (air--cooled version) consists of a
fan, radiator- -type cooler/aftercooler assembly,
full- -flow main line filter, thermal valve and inter-
connecting piping.
For the water--cooled models, a shell and tube fluid
cooler, aftercooler and water--flow regulating valve
are substituted for the radiator--type cooler on air--
cooled compressors.
The pressure in the receiver/sump causes fluid flow
by forcing the fluid from the high pressure area of the
sump to an area of lower pressure in the compres-
sor unit.
14
WARNING
!
Fluid flows from the bottom of the receiver/sump to
the thermal valve. The thermal valve is fully open to
the compressor unit when the fluid temperature is
below 170_F (77_C). The fluid passes through the
thermal valve, the main filter and directly to the com-
pressor unit where it lubricates, cools and seals the
rotors and the compression chamber.
As the discharge temperature rises above 170_F
(77_C), due to the heat of compression, the thermal
valve begins to close and a portion of the fluid then
flows through the cooler. From the cooler, the fluid
flows to the main filter and on to the compressor unit.
The filter has a replacement element and an integral
pressure bypass valve. When the element pressure
drop exceeds 20 psid (1.4 bar), an internal switch
contact opens and the Supervisor II module dis-
plays a maintenance requirement message.
Water--cooled versions of the compressor have a
water--flow regulating valve. This valve automatical-
ly shuts off the water supply when the compressor is
shut down. In addition, water--cooled models have a
water pressure switch to prevent operation with in-
adequate water pressure.
5.5 COMPRESSOR DISCHARGE SYSTEM, FUNC-
TIONAL DESCRIPTION
Refer to Figure 5--3. The compressor unit dis-
charges the compressed air/fluid moisture into the
combination receiver/sump. The receiver has three
functions:
S It acts as a primary fluid separator.
S Serves as the compressor fluid sump.
S Houses the final fluid separator elements.
The compressed air/fluid mixture enters the receiv-
er and is directed against a curved shroud. Its direc-
tion of movement is changed and its velocity signifi-
cantly reduced, thus causing large droplets of fluid
to form and fall to the bottom of the receiver/sump.
The fractional percentage of fluid remaining in the
compressed air collects on the surface of the dual
separator elements as the compressed air flows
through them. Two return lines (or scavenge tubes)
lead from the bottom of each separator element to
the inlet region of the compressor unit. Fluid collect-
ing on the bottom of each separator is returned to
the compressor by a pressure difference between
the receiver and the compressor inlet. Sight glasses
are located in the return lines to observe this fluid
flow. There are also orifices in these return lines
(protected by strainers) to assure proper flow. When
the total pressure drop across the elements ex-
ceeds 10 psid (0.7 bar), the Supervisor II module
displays a maintenance requirement message.
The receiver is an ASME pressure vessel. A com-
bination minimum pressure/check valve, located
downstream from the separator, assures a mini-
mum receiver pressure of 50 psig (3.5 bar) during all
conditions. This pressure is necessary for proper
air/fluid separation and proper fluid circulation while
supplying air to the system. This valve also acts as a
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