Product Manual

3
2920 1339 02
Instruction book
M1. Refrigerant compressor
M2. Condenser fan motor
1. Control panel
2. Condenser
3. Fan
Fig. 1. General view of FD7
1 LEADING PARTICULARS
1.1 General description
The FD air dryers remove moisture from compressed air by
cooling the air to near freezing point. This causes water to
condense. The condensate is automatically drained. The air is
warmed up before leaving the dryer.
1.2 Air circuit (Figs. 2)
Compressed air enters heat exchanger (13) and is cooled by
the outgoing, cold, dried air. Water in the incoming air starts
to condense. The air then flows through heat exchanger/
evaporator (11) 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 separator (3) where all the condensate is
separated from the air. The condensate collects in condensate
trap (4) and is automatically drained. The cold, dried air flows
through heat exchanger (13), where it is warmed up by the
incoming air to approx. 10°C (18°F) below the incoming air
temperature. Condensation in the air net cannot occur unless
the air is cooled to below the pressure dewpoint indicated by
gauge (1).
1.3 Refrigeration circuit (Figs. 2)
Compressor (M1) delivers hot, high-pressure refrigerant gas
which flows through condenser (9) where most of the refrigerant
condenses.
The liquid flows through liquid refrigerant dryer/filter (12) to
capillary tube (7). The refrigerant leaves the capillary tube at
evaporating pressure.
The refrigerant enters evaporator (11) 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.
1.4 Automatic regulation system
(Figs. 2)
The condenser pressure must be kept as constant as possible to
obtain stable operation, therefore, fan control switch (S3) stops
and starts the cooling fan.
When, at partial or no load, the evaporator pressure drops to
2.25 bar(e), the by-pass regulator opens and hot, high pressure
gas is fed to the evaporator circuit to prevent the evaporator
pressure from dropping any further.
F6832