Aircel AHLD E-Series Installation And Operation Manual page 29

Aircel Programmable Controller
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. The extended drying cycle
timer will count to 30 minutes unless the EMS relative humidity
sensor is higher than the set point. After 30 minutes, the unit will
switch and continue normal operation until the next extended
savings step. At the start of each extended savings step the PLC
checks for faults, EMS relative humidity sensor value and high outlet
dewpoint setting (optional) to ensure if the dryer needs to continue
drying and the dryer will go into extended drying. If the dryer needs
to continue to the next step to regenerate, the extended savings step
4 will be skipped.
Heatless Regenerative Desiccant Air Dryer
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