4. ALARM LED AND RELAY OUTPUTS: These will
only be reset by pushing the button.
CAUTION
This unit may be damaged by electrostatic
discharge. Follow procedures for static sensitive
parts when handling, shipping or installing this unit.
OPTIONAL CONTROLS AND ALARMS
1. DEWPOINT DEMAND SEQUENCE CONTROL:
The dewpoint demand mode function will be
operational if there are 12 seconds before the end of
the drying cycle, and the dewpoint is below the
preset level. When in the dewpoint demand mode,
all of the timing functions stop. The yellow LED on
the timer will light up. When the dewpoint reaches
the preset dewpoint level, the towers will switch and
the normal mode cycle will commence. The
dewpoint demand mode function will be disabled if
the dewpoint is above the preset level or normal
cycle is selected.
2. HIGH HUMIDITY: The high humidity alarm function
is indicated by a red LED on the timer. The high
humidity relay will energize for remote annunciation.
All the normal functions will be maintained.
3. FAIL TO SHIFT: The fail to shift inhibit will be
energized if the inhibit switch remains closed for 5
seconds beyond the normal cycle. Fail to shift will be
indicated by the red LED on the timer and the fail to
shift relay will be energized for remote annunciation.
The fail to shift inhibit is an indication of a
malfunction of the tower switching valves or purge
exhaust valves.
Sequence of Operation
The sequence of operation of the Heatless Regenerative
Dryer can be readily followed by referring to the following
flow schematic on Page 12. The operation is fully
automatic, controlled by a DMP, pneumatic timer or PLC
controller.
During initial start-up, before ON button is pushed and
the towers pressurized with air, both inlet valves stay in
the OPEN position and the purge valves stay in the
CLOSED position. This type of fail safe valve operation
allows the air to dry through both the towers, without any
purge in the event of loss of power to dryer. This will give
you extended drying time until desiccant chambers are
saturated.
The desiccant is designed to handle air saturated with
water vapor only. Any liquids or slugs of water tend to
decrease the efficiency of the desiccant and retard the
regeneration process to provide the designed dewpoint.
At time equal to 0.0 minutes, the right tower air inlet
valve is open to allow the air to pass through the right
tower. The left tower inlet valve is closed. The saturated
compressed air/gas passes through the desiccant in the
right tower, where the desiccant adsorbs the moisture.
The dry air, at a pressure dewpoint of -40°F/C or less,
exits through the right outlet check valve and goes out
into the plant air system through the afterfilter.
At time equal to 0.1 minutes, the left tower purge valve
opens to fully depressurize the desiccant bed, and
commence the regeneration cycle.
NOTE: As soon as the purge valve has opened, adjust
the purge adjustment valve to the recommended purge
control setting. This adjustment should only be required
once, and then the locking mechanism should be locked
in place.
A portion of dry outlet air is diverted and passed through
a series of regulating and flow control valves to meter
the measured quantity of air for regeneration. The
pressure of this purge air is regulated by the purge
adjustment valve at the specified purge pressure on the
meter gauge. This dry purge air at low pressure passes
through the right purge check valve and is introduced
into the right tower. The purge air picks up the moisture
from the desiccant and exhausts into the atmosphere
through the purge valve and purge muffler
CAUTION
Frost or ice development on the regenerating tower
is a sign of low inlet air temperatures. Due to the
expansion of the purge air, cooling may develop
icing in the desiccant. Temperature of the purge air
is determined by the temperature of the air during
the drying cycle and should be greater than +70°F (>
+70°F). Adsorption of moisture by the desiccant
results in the release of heat of adsorption, which is
retained in the bed to assist in desiccant
regeneration.
NOTE: During the regeneration air flow through the
desiccant bed, the tower pressure gauge should read 0
PSIG. Any higher pressure is an indication of a plugged
muffler, which will retard the regeneration of desiccant.
10
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