Gardner Denver EnviroAire 15, Original Operating Manual

Page: 22 / 56

5. Design and functioning
20
5.3 Water circuit
The water flows from the pressure tank (-6- Fig. 3)
through the water cooler (-13- Fig. 3) and water filter
(-12- Fig. 3) and is then injected into the screw
compressor (-4- Fig. 3).
The entire water circuit is based on a differential
pressure in the system. At a vessel pressure of, for
example, 145 PSI, the water is injected into the screw
compressor at around 116 PSI.
The intake controller is closed when the screw
compressor is idling. An idling pressure (residual
pressure) of approx. 50 PSI is maintained in the vessel
by means of a bypass bore in the intake controller.
There is thus always sufficient pressure at the injection
point to assure supply of the necessary quantity of
water for injection.
5.4 Air circulation
The air drawn in passes via intake filter (-1- Fig. 3) into
the screw compressor (-4- Fig. 3). The air is cooled by
the injected water during the compression process and
the compressed-air/water mixture flows into the vessel
(-6- Fig. 3). The water is largely separated from the
compressed air in this process and passes via the
pressure maintenance and non-return valve (-7- Fig. 3)
into the supply system.
5.5 Control
(Please also see the operating instructions for the
compressor control GD Pilot TS)
(see Fig. 3)
System downtime
•
Solenoid valve (- 25 -(Y4)) is de-energized (open)
when the system is shut down, solenoid valve
(-26- (Y11)) is also de-energized (closed).
•
The pressure reservoir (- 6 -) is depressurized to
atmospheric pressure via the solenoid valve
(-25-(Y4)) and the orifice (-17-).
Starting up the system
•
The drive motor (- 3 -) starts up.
•
The compressor draws air in via the air filter; a
certain quantity is blown off again into the intake
zone via the solenoid valves (-25-(Y4)) and
(-26-(Y11)).
•
This way, constant pressure of approx. 58 to 65 PSI
is maintained in the pressure tank (- 6 -), as the
pressure holding non-return valve (-7-) still remains
closed at this pressure level.
•
The water supply of the screw compressor (- 4 -) is
provided by the drop in pressure between the
pressure tank (-6-) and the injection site in the
screw compressor.
•
If pressure in the load system falls below the
minimum pressure programmed on the control
system, the solenoid valve (-25-(Y4)) is energized
(closed). Pressure then continues to build up in the
pressure reservoir (-6-).
•
At a tank pressure of ca. 65 PSI, the pressure
holding non-return valve (-7-) opens.
•
The compressed air transportation into the mains
has begun.
Stopping the system:
•
After pressing the OFF button on the control panel
of the compressor control system GD Pilot TS, the
magnet valve (- 25 - (Y4) is de-energized (opened)
and the solenoid valve (-26-(Y11)) is energized
(opened) when the drive motor is running.
•
The pressure reservoir (-6-) is depressurized to a
constant pressure of 58 to 65 PSI.
•
The drive motor (-3-) reduces its number of revs to
the set minimum value and comes to a standstill
after 30 seconds have passed.
•
Once the drive motor has stopped, solenoid valve
(-26-(Y11)) is de-energized (closed) and the
remaining pressure in the reservoir is discharged via
the orifice (-17-).
Speed control operation
Speed is controlled using a software-implemented PI
regulator that adapts the RPMs according to the need
for compressed air.
The controller attempts to maintain the mains pressure
between the values set in the control for max. and min.
mains pressure (target pressure).
Automatic operation
•
If the mains pressure achieves the preset maximum
value, then the electric motor (-3-) will have its
speed lowered in order to allow for the delivery
amount to adapt to the actual need for compressed
air.
•
If the motor has reached minimum speed and the
load-system pressure continues to rise, solenoid
valve (-25-(Y4)) is de-energized (opened) and
solenoid valve (-26-(Y11)) continues energized
(open). Reservoir pressure is reduced to approx. 58
to 65 PSI and the pressure-maintenance valve (-7-)
closes.