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MISCELLANEOUS CONTROL DEVICES - Refer to Figure 4-15 for the schematic diagram of the control system.
Intake [Air] Filter (1) - Captures solid impurities in the air stream entering compressor inlet. It also attenuates
noise emitted by the compressor inlet.
Inlet-Valve Assembly (2) - This device controls the intake of atmospheric air entering the compressor during the
Load/Unload phases of operation.
During the loaded state: The inlet poppet (2.2) remains open and enables atmospheric air to enter the
compressor inlet.
During the unloaded state: The 2-way solenoid valve (Y) feeds pressurized air underneath the piston
(2.1), forcing it and the inlet poppet (2.2) upward and blocking-off the compressor intake. A small purge
orifice (18), located below the poppet, allows a stream of air to reach (e.g., purge) the rotors and keep them
from unstable, noisy operation and producing sufficient pressure to maintain cooling/lubricating oil flow. See
Section 9 for maintenance information.
Electric Motor (3) – Drives the compressor (4) via a belt drive assembly (5), and drives the package
ventilation fan from a secondary rear shaft. It is energized by the full voltage-type starter (variable speed drive in
1 phase models), which in turn is controlled by the GD Pilot controller.
Oil Sump (6) – Separates by inertial effects the bulk of the compressed air and injection oil streams and serves
as a sump for the latter.
Air/oil separator (7) - Intercepts and coalesces the aerosol oil stream in the compressed air exiting the inertial
separation process within the oil sump.
Oil Filler Cap (8) – Oil fill port on the oil sump.
Oil drain (9, 28) – Ball valve (9) drains the oil from the sump and cap (28) drains the oil trapped in the oil cooler
and associated hoses.
Oil Level Indicator (10) - This gauge is located on the oil sump and indicates the oil level. See "Oil Level Gauge"
on Section 5 for more details.
Oil Filter (11) - Captures solid impurities in the oil entering the compressor injection port.
Oil Cooler (12) – The air-cooled heat exchanger removes heat from the oil stream prior to injection.
Pressure Relief Valve (13) – This device protects the pressure containing components of the compressor
package against high pressure exceeding 217 psig. See Section 9 for maintenance information.
Minimum Discharge Pressure/Check Valve (14) - This device maintains minimum pressure (70 psig) within the
air/oil sump, thus ensuring adequate lubricating oil injection flow to the compressor even when no air delivery into
the system is taking place. It also functions as a check valve to prevent reversed air flow from the system line
during compressor stoppage. See Section 9 for maintenance information.
Air cooler (15) – The air-cooled heat exchanger removes heat from the air stream prior to exit from the package.
Scavenge line orifice and orifice (16) – This annular orifice, built into the air/oil separator element adaptor pipe,
controls the amount of oil and compressed air that is returned from the air/oil separator back into the compressor.
A separate check valve (19) prevents the backflow of oil into the air/oil separator element upon unit stoppage.
13-25-629 v03
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