6
ANGI OPERATION AND SERVICE MANUAL
Rev
2006/06
After cooling, the gas is past through a filter to
remove any condensed liquids and to reduce the
amount of oil introduced into the gas stream by the
compressor.
At the discharge of each stage of compression, the
gas temperature and pressure is monitored
against shutdown limits and the compressor will
shutdown should any inter-stage pressure or
temperature trend outside of the operational limits.
Exiting the final stage of compression, the gas is
passed through an air-cooled, fin and tube heat
exchanger for after-cooling. The after-cooler and
cooling fan have been sized to meet the
application.
The gas is then passed through a pre-coalescing
filter and a coalescing filter to remove oil from the
gas stream prior to delivery to the storage system
or dispenser.
After the final stage filtration, the discharge
pressure is monitored by the control system
against START and STOP limits to determine if the
compressor should resume, continue or stop
compressing gas.
Safety relief valves are provided on each stage of
the compressor discharge piping to prevent
dangerous over-pressurization due to compressor
valve failure, flow blockage or control system
failure.
2.2.3 Re-circulation System
Tubing lines and valves are installed between the
inter-stage and discharge filter bowls and the
captive receiver tank. At pre-determined intervals
of operation and during warm-up and cool-down
sequences, the gas is allowed to flow from the
discharge of the compressor stages, through the
filter bowls and into the receiver tank. During this
time, the compressor is effectively operating
unloaded and, consequently, allows for smooth
compressor starts and stops. This system also
allows for automatic purging of the filter bowls of
accumulated liquids.
2.3. COMPRESSOR AND FAN DRIVER
An electric motor rated for the application is used
to drive the compressor. The motor has been
sized for this application and has adequate power
to drive the compressor with ample reserve power
to maintain a continuous duty rating. A smaller
secondary motor is provided to drive the cooler
fan.
A
motor starter starts the compressor motor.
Inside the motor starter enclosure is a motor
contractor for starting the fan motor. The motors
are started and stopped automatically based on
control signals sent to the motor starters from
the control system.
2.4 CONTROLS AND INSTRUMENTATION
2.4.1 Control System
This compressor station is delivered with a PLC
based control system. The control system
provides all the compressor controls and
monitoring function required to allow fully
automatic, unattended operation and to provide
fault code annunciation for quick fault recovery.
For additional technical information on the
control system refer to the control system
operations manual and the electrical drawing
package included in this manual.
2.4.1.1 Modes of Operation
With power supplied to the station and the
ON/OFF keyswitch placed in the ON position,
the control system is capable of supporting five
modes of operation. These modes of operation
are;
1) STAND-BY
In this mode the storage is considered to be full
and the compressor is stopped. The control
system monitors the discharge pressure against
a START pressure limit. The compressor will
remain in this mode until the storage is depleted
below this START pressure limit.
2) WARM-UP
Once the control system detects that the gas
storage has been emptied below the START
pressure limit, the pre-lube pump runs for a
period of time, the inlet valve opens, the fan
motor is started and runs and then the
compressor drive motor is started and runs.
During this warm-up period the load/recirculation
valve is open so that gas is simply re-circulated
through the captive receiver tank.
3) COMPRESSION
After the completion of the warm-up cycle, the
control system switches to loaded compressor
operation. During the transition from warm-up
mode, the fan and compressor motors remain
on and the load/recirculation valve is closed so
that gas flows into to the discharge piping.
During longer, uninterrupted operation in this
mode, the load/recirculation valve will open
during pre-determined intervals to drain the filter
bowls of accumulated fluids. The control system
