SECTION 2
®SULLAIR®
10
3700 Operator’s Manual and Parts List
2.4 COMPRESSOR COOLING AND
LUBRICATION SYSTEM,
FUNCTIONAL DESCRIPTION
Refer to Figure 2-2. The Cooling and Lubrication
System (air-cooled version) consists of a fan, fan
motor, radiator-type aftercooler/fluid cooler, full flow
fluid filter, thermal valve, and interconnecting hoses.
For water-cooled models, two shell and tube heat
exchangers and a water-flow regulating valve are
substituted for the radiator-type cooler listed above. 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 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 185°F (85°C) [200°F (93°C)
for 24KT] and pressures are rated at or above 150 psig.
The fluid passes through the thermal valve, the main
filter and directly to the compressor unit where it
lubricates, cools and seals the rotors and the
compression chamber.
As the discharge temperature rises above 185°F (85°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 fluid filter
and then on to the compressor unit.
A portion of the fluid flowing to the compressor is routed
to the anti-friction bearings which support the rotors
inside the compressor unit.
The fluid filter has a replacement element and an
integral pressure bypass valve. A message on the
controller indicates when the fluid filter needs to be
changed.
Water-cooled models have a water pressure switch to
prevent operation with inadequate water pressure.
2.5 COMPRESSOR DISCHARGE
SYSTEM, FUNCTIONAL
DESCRIPTION
Refer to Figure 2-2. The compressor unit discharges the
compressed air/fluid mixture into the combination
receiver/sump.
The receiver has three basic functions:
1. It acts as a primary fluid separator.
2. Serves as the compressor fluid sump.
3. Houses the final fluid separator.
The compressed air/fluid mixture enters the receiver and
flows through an internal baffle system. The 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 separator element as the
compressed air flows through the separator. A return line
(or scavenge tube) leads from the bottom of the
separator element to a medium pressure region of the
compressor unit. Fluid collecting on the bottom of the
separator is returned to the compressor by a pressure
differential between the receiver and the compressor. A
visual sight glass is located on the return line to observe
this fluid flow. There is also an orifice in this return line
(protected by a strainer) to assure proper flow. The
separator system reduces the fluid carry-over to less
than 1 ppm (parts per million) or 2 ppm for 24KT. A
message on the controller indicates if abnormal
pressure drop through the separator develops. At this
time, separator element replacement is necessary.
A minimum pressure/check valve, located downstream
from the separator, assures a minimum receiver
pressure of 50 psig (3.4 bar) during loaded conditions.
This pressure is necessary for proper air/fluid separation
and proper fluid circulation.
A terminal check valve is incorporated into the minimum
pressure/check valve to prevent compressed air in the
service line from bleeding back into the receiver 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 exceeds
the sump tank rating. A temperature switch will shut
down the compressor if the discharge temperature
reaches 235°F (113°C).
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.
A WARNINGA WARNINGA WARNING
DO NOT remove caps, plugs, and/or other
components when compressor is running
or pressurized.
Stop compressor and relieve all internal
pressure before doing so.
SU_0000023
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