Sullair Compressor Unit - Sullair LS-20S Operator's Manual And Parts List

Section 2
DESCRIPTION
2.3 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
analysis. This is a free service. The sample kit with
instruction and self--addressed container is to be
supplied by your Sullair representative at start--up.
The user will receive an analysis report with recom-
mendations.
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 As coolant, it controls the rise of air temperature
normally associated 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.
2.4 COMPRESSOR COOLING AND LUBRICATION
SYSTEM, FUNCTIONAL DESCRIPTION
Ref er t o F igur es 2 -- 2
brication system (air--cooled version) consists of a
fan, radiator- -type cooler/aftercooler assembly,
full- -flow main line filter, thermal valve, fluid
stop valve and interconnecting piping.
For the water--cooled models, a shell and tube fluid
cooler, and aftercooler are substituted for the radia-
tor--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.
6
WARNING
!
and 2 -- 3. T he cooling and lu -
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 180_F (82_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 180_F
(82_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.
The fluid stop valve prevents fluid from filling the
compressor unit when the compressor is shut down.
When the compressor is operating, the fluid stop
valve is held open by air pressure from the compres-
sor unit allowing a free flow of fluid from the receiver/
sump back to the compressor unit. On shutdown,
the compressor unit pressure is reduced, causing
the fluid stop valve to close and isolate the compres-
sor unit from the cooling system.
Water-cooled models have a water pressure switch
to prevent operation with inadequate water pres-
sure.
2.5 COMPRESSOR DISCHARGE SYSTEM, FUNC-
TIONAL DESCRIPTION
Ref er t o F igur es 2- 2,
sor unit discharges the compressed air/fluid mixture
through a discharge check valve into the combina-
tion receiver/sump. The discharge check valve pre-
vents air in the receiver from returning to the com-
pression chamber after the compressor has been
shut down. 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 re-
ceiver and is directed against a curved shroud. Its
direction of movement is changed and its velocity
significantly 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 ele-
ment to the inlet region of the compressor unit. Fluid
collecting on the bottom of each separator is re-
turned to the compressor by a pressure difference
between the receiver and the compressor inlet.
Sight glasses are located in the return lines to ob-
serve 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 ele-
2- 4A and 2- 4B . T he c om pr es -