Step 1: Vessel 2 Depressurizing
Vessel 2 (T2) purge exhaust pilot solenoid valve is energized which
supplies control air to the purge exhaust valve (V4) which opens
slowly, depressurizing vessel 2 (T2). Simultaneously the inlet and
outlet APV (Automatic Piston Valve V1 & V2) shift positions
directing the inlet air to vessel 1 (T1) 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 2: Vessel 2 Regenerating
Step 2 is a continuation of step 1 except vessel 2 (T2) will be
regenerating, vessel 2 (T2) purge exhaust valve (V4) is still open,
vessel 1 (T1) is drying the inlet air. A small portion of dry outlet air
from vessel 1 (T1) (15% average based on standard design capacity
of 100 psig, 100°F inlet air, 100°F ambient air and PDP of -
10
0°F) is
taken through a small orifice in the outlet APV valve (V2) and used to regenerate the desiccant bed
in vessel 2 (T2) until
time
has been reached. The screen also shows the
(optional) dew point when
applicable. The timer on this step counts to 90 seconds (1.5-minutes).
There is a warning sign that will flash in the upper right hand portion of the
screen for any alarm. There is also a red LED alarm light that will flash on the PLC display for any
alarm. The user must scroll to the alarm screen to view the alarms (press the left arrow once from
the main screen to view the alarm screen).
Step 3: Vessel 2 Repressurizing
Vessel 2 (T2) purge exhaust pilot solenoid valve will de-energize
causing vessel 2 (T2) purge exhaust valve (V4) to close, this
allows vessel 2 (T2) to repressurize to line pressure, since air
continues flowing though the small orifice in the outlet APV
valve (V2) pressurizing vessel 2 (T2).
Step 4: Extended Drying Vessel 1
A few seconds before the end of repressurization the
A
LDP
-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.
The extended drying cycle timer will count to
30 minutes
unless the
outlet dew point
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,
outlet dew point
sensor value (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. This step will also be skipped if the dew point option is not installed.
28
Aircel Programmable Controller
Aircel
C
DP-Series Models 70 - 500
