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AIRTEK 4087 WALDEN AVENUE, LANCASTER, NY 14086 Tel: (716) 685-4040 Fax: (716) 685-1010
Models TW10 & 15 are provided with a needle valve for
purge adjustment. A purge indicator for this low a flow is
not practical. The purge flow should be set to feel. As a
minimum it must be set high enough so that the dryer
achieves full repressurization prior to switching. If perfor-
mance is unacceptable, increase purge flow. Purge flow
can be determined if there is a system flow meter in place,
via addition or subtraction from the flow meter.
Models TW25, 40 & 55 are provided with a needle valve for
adjustment and an orifice and pressure gauge for metering
and indication. Adjust the needle valve so that the purge
(center) pressure gauge reads the correct purge pressure as
determined above. The setting may vary slightly with line
pressure.
Some special models are equipped with flow meters that
read purge directly in SCFM. Adjust the needle valve so
that the flow meter reads the correct purge flow..
8. C. DRYER OUTLET FLOW:
Dryer outlet flow is equal to the dryer inlet flow minus the
purge flow.
9. A. DRYERS EQUIPPED WITH POWERLOC:
The PowerLoc is a Digital Dewpoint Monitor and Demand
Cycle Controller. The sensor is a thin film gold aluminum
oxide design. The PowerLoc monitors the outlet pressure
dewpoint of the dryer and digitally displays it.
The Demand Cycle Control feature tailors the dryer cycle to
actual loading conditions, maximizing energy usage.
Without the PowerLoc the cycle is fixed and “worst case”
design conditions are assumed.
The Demand Cycle is accomplished by providing a discrete
dry contact closure across the CycleLoc terminals on the
Sequence Annunciator. The Variable Cycle Switch must be
set to the 100% load setting and JP1 must be removed for
the PowerLoc to work!
If the dryer is maintaining a good dewpoint AFTER the first
five minutes of drying, the PowerLoc will override the fixed
cycle and keep the current tower on-line until it is saturated
to design loading (switchpoint valve), usually –40º. If this
occurs the offline bed, which has just finished being
regenerated, will repressurize and be ready to go on-line.
The CycleLoc light on the Sequence Annunciator and the
PowerLoc Mode light on the PowerLoc will be on at this
time. Once the dewpoint degrades to the switchpoint valve,
the freshly regenerated bed will go on-line, and the satu-
rated bed will depressurize and begin regeneration.
Note that the PowerLoc cannot shorten the cycle. The
drying tower will always be on-line a minimum of five
minutes and the regenerating tower will always undergo a
design regeneration cycle of 4 minutes and 15 seconds.
Thus the PowerLoc can only compensate for “under”
loading, not overloading conditions.
If there is any error with the PowerLoc, the dryer will default
to the fixed time cycle. There is also a PowerLoc On/Off
switch located in the control enclosure. If this switch is
turned off the dryer will operate in the fixed time cycle. The
PowerLoc will continue to display dewpoint.
The PowerLoc is fully programmed and wired at the
factory if ordered with the dryer. All that is normally
required is sensor installation. The sensor should be
installed (without cable attached) only after the dryer has
cycled 3 or more times and the sample line has been “blown
out”. Do not allow the probe to bottom out in the sample
line. Do not tighten ferrule on sensing tip. Hand-tighten
nut, wrench tighten 1-1/2 turns. Open the probe isolation
valve slowly to full open position. This allows operation at
full line pressure for correct reading of pressure dewpoint. A
coil of capillary tubing is provided to allow a small sample
flow over the sensor and prevent ambient moisture from
infiltrating the system. Check the bleed periodically to
ensure it is not clogged.
Following sensor installation allow the sensor to stabilize at
line pressure for four hours prior to attaching the sensor
cable.
Failure to follow the above precautions may result in sensor
failure not covered by warranty.
Upon installation the sensor may be saturated. Even if the
dryer is producing a good dewpoint, it will not be indicated
immediately as it will take a period of time for the sensor to
dry out and come to equilibrium with the system. The
sensor will also become saturated if the air system is shut
down and allowed to depressurize. Upon restart of the
system, the dewpoint may appear to be poor, even though
the dryer may be producing clean, dry, air.
Although the probe can be exposed to occasional, brief
periods of liquid saturation, it can not be exposed to
continuous wet conditions. If your dryer is overloaded and
saturated, or if it will be shut down for an extended period of
time; remove or isolate the probe until the problem is
resolved.
Refer to the separate PowerLoc Manual for additional
information.
10. A. MAINTENANCE PROGRAM:
DAILY:
1. Check dewpoint or humidity level, if instrumentation is
available. Any difficulty with the dryer will result in poor
dewpoint performance.
2. Check for correct purge setting and air flow from purge
exhaust.
3. Check gauge readings & sequence of operation
through complete cycle.
4. Check auto drain operation on Prefilter, Separator &
Receiver. A manual drain valve installed (in addition to
the automatic drain at these points will ease checking
of the automatic drains.
5. Ensure there is no backpressure in the regenerating
tower (Pressure = 0 PSIG).
