Aircel AHLD E-Series Installation And Operation Manual page 16

Aircel AHLD E-Series - Models 70 - 750
Sequence of Operation (cont'd)
Step 4: Extended Drying Vessel 1
A few seconds before the end of repressurization the AHLD
E-SERIES Controller's integrated Energy Management Purge
Reduction System looks at the moisture sensor, if the moisture
load is low enough, vessel 1 (T1) will continue to dry for an
extended drying period until the moisture load has reached a
set high level, the controller will then advance to step 5 and
the vessels will switch. This feature reduces the overall purge
consumption saving energy and money.
Step 5: Vessel 1 Depressurizing (0-5 secs)
Vessel 1 (T1) purge exhaust pilot solenoid valve is energized which
supplies control air to the purge exhaust valve (V3) which opens
slowly, depressurizing vessel 1 (T1). Simultaneously the inlet and
outlet APV (Automatic Piston Valve V1 & V2) shift positions directing
the inlet air to vessel 2 (T2) to be drying the air. The air flows up
through the desiccant bed and exits to the outlet APV valve (V2) to
the outlet particulate filter then to the customer dry process
air system.
Step 6: Vessel 1 Regenerating (6-240 secs)
Step 6 is a continuation of step 5 except vessel 1 (T1) will be
regenerating, vessel 1 (T1) purge exhaust valve (V3) is still open,
vessel 2 (T2) is drying the inlet air. A small portion of dry outlet air
from vessel 2 (15% average based on standard design capacity
of 100 psig, 100°F inlet air, 100°F ambient air and PDP of -40°F)
is taken through a small orifice in the outlet APV valve (V2) and
used to regenerate the desiccant bed in vessel 1 (T1)
until 240 seconds has been reached.
Step 7: Vessel 1 Repressurizing (241-300 secs)
Vessel 1 (T1) purge exhaust pilot solenoid valve will de-energize
causing vessel 1 purge exhaust valve (V3) to close, this allows
vessel 1 (T1) to repressurize to line pressure, since air continues
flowing though the small orifice in the outlet APV valve (V2)
pressurizing vessel 1 (T1).
Step 8: Extended Drying Vessel 2
A few seconds before the end of repressurization the AHLD
E-SERIES Controller's integrated Energy Management Purge
Reduction System looks at the moisture sensor, if the moisture
load is low enough, vessel 2 (T2) will continue to dry for an
extended drying period until the moisture load has reached a
set high level, the controller will then advance to step 1 and
the vessels will switch. This feature reduces the overall purge
consumption saving energy and money.
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