User manual

Industrial Air Division
2920 1163 04
14
cools the air to close to the evaporating temperature of the
refrigerant. More water and oil in the air condense. The cold air
then flows through moisture trap (MT) where all the condensate is
separated from the air. The condensate is automatically drained
through outlet (Da). The cold dried air then flows through heat
exchanger (5), where it is warmed up by the incoming air.
Condensation in the air net cannot occur unless the air is cooled to
below the pressure dewpoint. The pressure dewpoint can be called
up. See section 2.4.1.
1.6.2 Refrigerant circuit
Compressor (M1) delivers hot, high-pressure refrigerant gas which
flows via liquid separator (7) through air-cooled condensor (9)
where most of the refrigerant condenses. The cooled refrigerant
then collects in receiver (10).
The liquid flows through heat exchanger (8) 1) and filter (12) to
expansion valve (11) where it expands to evaporating pressure.
The refrigerant enters evaporator (6) where it withdraws heat from
the compressed air by further evaporation. Dependent on the
compressed air load, all, or almost all, refrigerant evaporates at
constant pressure and temperature. The vapour refrigerant leaving
evaporator (6) flows through heat exchanger (8) 1) into liquid
separator (7). The liquid separator prevents any droplets from
entering compressor (M1) because warm refrigerant, leaving the
compressor, flows through the liquid separator evaporating the
surrounding liquid. The refrigerant gas is sucked in by compressor
(M1).
1.6.3 Automatic regulation system
Expansion valve (11) maintains the evaporating temperature
between 1 and -1°C (34 and 30°F); these are the approximate
temperatures at zero and maximum air load respectively.
1.6.4 Dryer control and safety devices
Fan control switch (S3)
The condensor pressure must be kept as constant as possible to
obtain stable operation of expansion valve (11). Therefore, fan
control switch (S3) starts motor (M2) of the condensor fan as soon
as the condensor pressure reaches the upper set point and will
stop the motor when the condensor pressure reaches the lower set
point.
Overload switch (S6-Fig. 6b) 1)
The motor of the refrigerant compressor (M1) is protected by a
thermal overload switch (S6), built into the motor. The motor will
automatically be restarted when it has cooled down.
Pressure shut-down switch (S7) 2)
The switch breaks the circuit to motor (M1) of the refrigerant
compressor if the refrigerant pressure becomes too high. If this
occurs, the switch must be reset by pressing its reset button.
AV. Air outlet valve
Dm. Manual condensate drain valve
1. Condensate drain flexible for automatic drain
2. Condensate drain flexible for manual drain
3. Connection between flexible (2) and valve (Dm)
4. Bottle containing Atlas Copco Roto-injectfluid
Fig. 8. Components delivered with the compressor (typical
examples)
1) Not on dryers of type ID120
2) Only TÜV-approved compressors
123Dm4 AV
F022