Technical data

Oil is injected into the compressor by differential
pressure to lubricate the bearings, seal the rotors and
remove the heat of compression. The injected oil mixes
with the compressed gas and is separated from the
refrigerant gas in the oil separator.
The compressor has an oil reservoir located at the rotor
bearings to provide lubrication during start-up and
during coast-down even in the event of a power failure.
A check valve is installed in the compressor discharge
housing (suction housing for S4 and S5 compressors) to
prevent reverse running of the rotors due to system
refrigerant pressure gradients during shutdown.
The open-drive compressor shaft seal consists of a
spring-loaded, precision carbon ring, high temperature
elastomer "0" ring static seal, and stress-relieved,
precision lapped collars.The entire shaft seal cavity is at
low pressure, being vented to the oil drain from the
compressor, combining low pressure with direct oil
cooling for long seal life.
Capacity control is achieved by use of a slide valve
providing fully modulating capacity control from 10% to
100% of full load. The slide valve is positioned between
the male and female rotors and moves axially to match
the compressor capacity to that of the evaporator
refrigeration load. As the slide valve moves toward the
unloaded position, less suction gas is pumped through
the compressor.
The slide valve is actuated by oil pressure controlled by
external solenoid valves via the control panel. When the
compressor is shut off, a spring returns the slide valve to
unloaded position to ensure that the compressor starts
with the slide valve in the unloaded position.
2.3 Motor
The compressor motor is a 2-pole, continuous-duty,
cage induction type with suction gas cooling
(semi-hermetic design).
2.4 Lubrication
An oil pressure transducer is located on the compressor
oil manifold. The differential pressure is measured as
the difference between the oil pressure transducer and
the filter pressure transducer located in the oil separator.
This value is compared to the limits in the control panel
logic. If the oil filter differential reaches 138 kPa
(20 PSID), a warning message is displayed on the
control panel, at 172.5 kPa (25 PSID), a safety shutdown
is initiated.
The oil leaving the oil eductor manifold block flows into
the compressor to lubricate the compressor bearings
and shaft seal. The oil injected into the compressor
mixes with refrigerant gas during compression. The oil
and refrigerant gas is discharged into the oil separator,
where it is separated and returned to the oil sump. A high
discharge temperature safety is located in the discharge
line, between the compressor and oil separator. This
safety will initiate a safety shutdown.
Oil cooling is accomplished by liquid injection into the
suction of the compressor
2.5 Oil Separator
The oil separator removes the oil that was injected into
the compressor. The separator is a vertical two stage
design without moving parts.
2-2 160.81-ICOM-GB0 (01/02)
Figure 2.2 Oil Separator