Product Manual

SHOPTEK
™
USER MANUAL SECTION 2
14
02250180-090 R00
2.3 COMPRESSOR COOLING
AND LUBRICATION SYSTEM
— FUNCTIONAL
DESCRIPTION
Refer to Figure 2-3 and Figure 2-4. The cooling and
lubrication system consists of a fan, fan motor,
aftercooler (ST1100/ST1500 15-20HP only) /fluid
cooler, full flow fluid filter, thermal valve,
interconnecting hoses and separator tube.
The pressure in the separator tube starts the fluid
flow by forcing the fluid from the high pressure area
of the tube to an area of lower pressure in the
compressor unit. Fluid flows from the bottom of the
separator/tube to the thermal valve that is fully open
when the fluid temperature is below 185°F (85°C)
[195°F (91°C) for pressures rated above 150 psig].
The fluid passes through the thermal valve, the fluid
filter, and directly to the compressor 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 adjust and a portion of the fluid then
flows through the cooler. From the cooler the fluid
flows to the fluid filter and on to the compressor. A
portion of the fluid flow to the compressor is routed to
the anti-friction bearings which support the
compressor rotors.
The fluid filter must be replaced. Refer to Section 3.5:
Lubrication Change Recommendations and
Maintenance, Fluid Filter And Separator on page 23.
2.4 COMPRESSOR DISCHARGE
SYSTEM—FUNCTIONAL
DESCRIPTION
Refer to Figure 2-3 and Figure 2-4. The compressor
discharges the compressed air/fluid mixture into the
separator/tube. The separator/tube 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
separator/tube and flows through an internal baffle
system that changes the flow’s direction and velocity,
which causes most of the fluid to fall to the bottom of
the separator tube. A small amount of fluid remaining
in the compressed air collects on the surface of the
separator element as the air flows through the
separator.
A return line (or scavenge tube) leads from the dry
side of the separator tube to the medium pressure
region. Scavanged fluid is returned by a pressure
differential between the separator tube and
compressor.
The separator system reduces the fluid carry-over to
less than 2 ppm at nominal rated pressures.
The Controller will shut down the compressor if the
discharge temperature reaches 235°F (113°C).
A minimum pressure/check valve located
downstream from the separator maintains the
separator tube pressure at 50 psig (3.4 bar) during
load conditions. This pressure level is necessary for
proper air/fluid separation and sufficient fluid
circulation.
A terminal check valve is a sub-component of the
minimum pressure/check valve that prevents
compressed air in the service line from back-flowing
into the separator tube on shutdown or when the
compressor is operating in an unload condition. Also,
a pressure relief valve on the compressor’s wet side
opens if the separator tube pressure exceeds its
rating.
Add fluid to the separator tube through the capped
fluid fill port. There is also a sight glass that enables
the user to check the separator tube fluid level. See
Fluid Level Check on page 52.
2.5 CONTROL SYSTEM —
FUNCTIONAL DESCRIPTION
Refer to Figure 2-5 and Figure 2-6. The compressor
control system regulates its output to match the
demand. This system consists of a solenoid valve
and an inlet valve that control the compressor’s
operational modes. The following descriptions of
operational modes apply to a compressor whose
operating range is 112 to 127 psig (7.7 to 8.8 bar)
WARNING
Stop the compressor and relieve all internal
pressure before removing caps, plugs, and/
or other components when the compressor
is running or pressurized.