Instruction book
2920 1472 03
17
1.6 Air dryer on Full-Feature
Full-Feature compressors are provided with a dryer which removes moisture from compressed air.
Two dryer types are available: a refrigerant-type dryer (ID dryer) and an adsorption-type dryer (IMD
dryer).
1.6.1 Compressors with an ID dryer (Figs. 1.6)
Compressed air circuit of the dryer
Compressed air enters heat exchanger (6) and is cooled by the outgoing dried air. Water in the
incoming air starts to condense. The air then flows through heat exchanger/evaporator (7) where the
refrigerant evaporates, causing the air to be further cooled to close to the evaporating temperature of
the refrigerant. More water in the air condenses. The cold air then flows through condensate trap (5),
where all the condensate is separated from the air. The condensate collects in the condensate trap
and is automatically drained. The cold, dried air flows through heat exchanger (6), where it is warmed
up by the incoming air.
Refrigeration circuit of the dryer
Compressor (M3) delivers high-pressure refrigerant gas, which flows through condenser (10) where
most of the refrigerant condenses.
The liquid flows through liquid refrigerant dryer/filter (13) to capillary tube (8). The refrigerant leaves
the capillary tube at evaporating pressure.
The refrigerant enters evaporator (7) where it withdraws heat from the compressed air by further
evaporation at constant pressure. The heated refrigerant leaves the evaporator and is sucked in by
the compressor.
1.6.2 Compressors with an IMD dryer (Figs. 1.7)
Air drying circuit of the dryer
Wet air from the aftercooler (15) enters the dryer through inlet valve (26) and the nozzle of ejector
(14). The air leaving the aftercooler is normally saturated.
In the demister (18), water droplets are removed from the air. The air is then led through rotor (19),
which adsorbs the water vapour. The dried air leaves the dryer through outlet valve (28).
Regeneration air circuit of the dryer
Hot unsaturated regeneration air flows through shut-off valve (8) and throttle valve (7) through the wet
rotor channels (12). Since the hot air has a lower vapour pressure than the wet rotor channels, it will
dry the rotor.
The hot saturated air is then cooled down in regeneration air cooler (22) and led to the suction
chamber of ejector (14), where it is mixed with the wet compressed air from the compressor
aftercooler.
Drain system of the dryer
The condensate is collected in three EWD (Electronic Water Drains-Fig. 1.8). A sensor continuously
measures the liquid level. As soon as the collector is filled up to a certain level, the outlet opens,
discharging the condensate. When the collector has been emptied, the outlet closes quickly without
wasting compressed air.
If the controller registers a malfunction, the red alarm LED (Fig. 1.8) starts flashing and the electronic
drain valve will automatically change to the alarm mode, opening and closing the valve according to a
built-in sequence. This condition continues until the fault is remedied. If the fault is not remedied
automatically, maintenance is required. Consult your Atlas Copco Customer Centre.
