Cooling And Condensate Drain Systems; Unloading/Loading System; Unloading; Loading - Atlas Copco GA55 Instruction Book

Instruction book
1.1.3 Cooling and condensate drain systems (Fig. 1.6)
The cooling system comprises air cooler (Ca) and oil cooler
(Co). On air-cooled compressors, the cooling air is generated
by fan (FN). Water-cooled compressors have a cooling water
system (Fig. 3.7). The water flows through the inlet pipe, the
tubestacks of the air cooler and oil cooler, and the outlet pipe.
A condensate trap (MTa) is provided in the air outlet system.
The trap is equipped with a valve for automatic condensate
draining during operation (Daa-Fig. 1.5) and a manually
operated valve for draining after stopping the compressor (Dma-
Fig. 1.5).
1.2 Unloading/loading system (Fig. 1.6)

1.2.1 Unloading

If the air consumption is less than the air output of the
compressor, the net pressure increases. When the net pressure
reaches the unloading pressure, solenoid valve (Y1) is de-
energized. The plunger of the valve returns by spring force:
1. The control pressure present in the chambers of loading
plunger (LP) and unloading valve (UV) is vented to
atmosphere via solenoid valve (Y1).
2. Loading plunger (LP) moves upwards and causes inlet valve
(IV) to close the air inlet opening.
3. Unloading valve (UV) is opened by receiver pressure. The
pressure from air receiver (AR) is released towards unloader
(UA).
4. The pressure is stabilized at a low value. A small amount
of air is kept drawn in and is blown to the unloader.
Air output is stopped (0 %), the compressor runs unloaded.

1.2.2 Loading

When the net pressure decreases to the loading pressure,
solenoid valve (Y1) is energized. The plunger of solenoid valve
(Y1) moves upwards against spring force:
1. Control pressure is fed from air receiver (AR) via solenoid
valve (Y1) to loading plunger (LP) and unloading valve
(UV).
2. Unloading valve (UV) closes the air blow-off opening.
Loading plunger (LP) moves downwards and causes inlet
valve (IV) to open fully.
Air output is resumed (100 %), the compressor runs loaded.
2920 1381 02

1.3 Elektronikon regulator

The control system consists of an electronic regulator and a
control panel.
1.3.1 Regulator (CM-Fig. 1.1)
The regulator has following functions:
1.3.1.1 Automatic control of the compressor
The regulator maintains the net pressure between programmable
limits by automatically loading and unloading the compressor.
A number of programmable settings, e.g. the unloading and
loading pressures, the minimum stop time and the maximum
number of motor starts are taken into account.
The regulator stops the compressor whenever possible to reduce
the power consumption and restarts it automatically when the
net pressure decreases. In case the expected unloading period
is too short, the compressor is kept running to prevent too-
short standstill periods.
Warning: A number of time-based automatic start/stop
commands may be programmed. 2) Take into
account that a start command will be executed (if
programmed and activated), even after manually
stopping the compressor.
1.3.1.2 Protecting the compressor
Shut-down
If the compressor element outlet temperature exceeds the
programmed shut-down level, the compressor will be stopped.
This will be indicated on display (4-Fig. 1.9). The compressor
will also be stopped in case of overload of drive motor (M1-
Fig. 1.3) or fan motor (M2-Fig. 1.3). 3)
Shut-down warning
If the compressor element outlet temperature exceeds a
programmed value below the shut-down level, this will also be
indicated to warn the operator before the shut-down level is
reached.
Service warning
The regulator continuously monitors the oil, oil filters, oil
separator and air filter. Each input is compared to programmed
limits (temperatures, pressures and/or running hours). If these
limits are exceeded, a message will appear on display (4-Fig.
1.9) to warn the operator to replace the indicated component.
Warning
A warning message also appears if:
On water-cooled compressors the cooling water outlet
temperature exceeds the warning level.
On Full-feature compressors the dewpoint temperature exceeds
the warning level.
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