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Section 2
DESCRIPTION
filter. There will be no problem in gaining access to
any components in the event they require service.
2.3 SULLAIR COMPRESSOR UNIT, FUNCTIONAL
DESCRIPTION
The compressor unit supplied with your compressor
is a 2--stage, positive displacement, flood lubri-
cated--type rotary screw air compressor.
As the rotors turn, air is drawn into the compressor
unit at the first stage inlet. At the outlet of the first
stage the air is compressed and discharged into the
second stage where it is recompressed to obtain a
higher pressure.
Lubricating fluid is injected into the compressor unit
at each stage and mixes directly with the air as the
rotors turn, compressing the air. The fluid flow has
three basic functions:
1. As coolant, it controls the rise of air temperature
normally associated with the heat of compres-
sion.
2. It seals the leakage paths between the rotors as
well as between the rotors and stators.
3. It acts as a lubricating film between the rotors al-
lowing the male rotors to directly drive the female
rotors (which are idlers).
After the air has been compressed in both stages of
the compressor unit, it is discharged in the form of
an air/fluid mixture. This mixture is routed through
the discharge system where the fluid is separated
from the air. At this time, the air flows to your service
line and the fluid is directed through the cooling and
lubrication system in preparation for reinjection.
2.4 COMPRESSOR COOLING AND LUBRICATION
SYSTEM, FUNCTIONAL DESCRIPTION
Ref er t o F igur es
2 -- 2
ing and lubrication system is designed to provide ad-
equate lubrication as well as maintain the proper op-
erating temperature of the compressor. The system
is comprised of a finned tube exchanger, main line
filter, extra--fine bearing lube filter, thermal valve,
fluid stop valve and interconnecting piping.
Fluid is used in the system as a coolant and lubricant
and is housed in the receiver/sump (from this time
forward, the receiver sump will be referred to as the
sump). Fluid circulation is achieved by forcing the
fluid from the higher pressure area of the sump to
lower pressure regions at the compressor unit.
Fluid flows from the bottom of the receiver/sump to
the thermal valve. The thermal valve is fully open
when the fluid temperature is below 220_F (155_C).
The fluid passes through the thermal valve, the main
filter and directly to the compressor unit where it lu-
bricates, cools and seals the rotors and the com-
pression chamber.
After the fluid passes through the thermal valve, it is
then directed through the fluid filter. There the fluid is
6
and
2 --
3. T he c om pr es s or c ool-
filtered in preparation for injection into the compres-
sion chambers. This filter has a cleanable element
and built--in bypass which allow some fluid to flow
even when the filter becomes plugged and requires
changing, or when the viscosity of the fluid is too
high for adequate flow. After the fluid is properly fil-
tered, it then flows to the fluid stop valve and on to
the bearing filter.
The fluid stop valve prevents the fluid from filling the
compressor unit when it is shut down. When the
compressor is in operation, the fluid stop valve is
held open by air pressure from the compressor unit
allowing a free flow of fluid from the sump back to the
compressor unit. On shutdown, the compressor unit
pressure is reduced causing the fluid stop valve to
close and isolate the unit from the cooling system.
The fluid stop valve pilot valve also opens to assist in
relieving the stop valve pilot signal pressure and
shutdown.
A portion of the fluid flowing to the compressor is
routed to the anti--friction bearings which support
the rotors inside the compressor unit. Prior to enter-
ing the compressor unit, this fluid is taken through
an extra--fine bearing filter, thus assuring properly
filtered fluid for bearing supply.
The bearing filter has a replacement element and an
integral pressure bypass valve. An associated ser-
vice indicator shows red when the filter needs ser-
vicing. This indicator has a pressure setting lower
than that of the bypass valve. After the initial 50 hour
filter change, the indicator will rarely show red under
normal operating conditions.
2.5 COMPRESSOR DISCHARGE SYSTEM, FUNC-
TIONAL DESCRIPTION
Ref er t o F igur e
2 -- 3
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 sump from returning to the compres-
sion chamber after the compressor has been shut
down. The receiver has three basic functions:
1. It acts as a primary fluid separator.
2. It serves as the compressor fluid sump.
3. It houses the final fluid separator element.
The compressed air/fluid mixture enters the receiv-
er and is directed against the wall of the tank. By
change of direction and impingement action, the
larger droplets of fluid fall to the bottom of the sump.
The fractional percentage of fluid remaining in the
compressed air collects on the surface of the final
separator element as the air flows through the sepa-
rator. As more and more fluid collects on the surface
of the element, the fluid descends to the bottom of
the separator, where the return line (scavenge tube)
leads from the bottom of the separator element to
the compressor unit. Fluid collected at the bottom of
the element is returned to the compressor unit by a
pressure difference between the area surrounding
the separator element and the compressor. An ori-
and
2 --
4. T he S ullair c om pr es -
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