Exhaust valves and/or exhaust mufflers may have to be cleaned due to dusting in shipping and start-
up.
A desiccant dryer should never be suddenly pressurized or depressurized. This will cause fluidizing and
dusting of the desiccant bed.
After start-up, some dusting may occur. This will diminish with time. Some dusting may occur with
normal operation. The Exhaust Mufflers should be cleaned regularly and an Afterfilter should be used.
Flow direction is Upflow Drying - Downflow Purge. Switching Failure Alarm is optional and the dryer
must be operating over 70 PSI for proper function of the alarm. Dryer valving is “fail-safe” on power
loss. This means the inlet valves open and exhaust valves close, allowing system to remain
pressurized and air to flow through both towers, and down stream.
The standard AIRTEK dryer has been designed for drying service to 150 PSIG.
A repressurization valve is standard on TW- 75 and up. The dryer must repressurize before
switching.
Variable Cycle Control
The AIRTEK heatless dryer is equipped with Variable Cycle Control. This control allows for easy
adjustment to meet varying plant loading. By using this control, the dryer can
be set to one of four standard fixed time cycles, a) standard 100% load (10 minute), b) 75% load (15
minute), c) 50% load (20 minute), d) short cycle -80°F dew point (2-1/2 minute). Complete cycle times
are given below.
Cycle Times (time in minutes: seconds)
PER TOWER TIME
CYCLE
TOTAL
TIME
DRYING REGEN. REPRESS.
100% Load 10:00 5:00 4:15 0:45
75% Load 15:00 7:30 4:15 3:15
50% Load 20:00 10:00 4:15 5:45
Short (-80) 5:00 2:00 2:00 0:30
The 75% and 50% settings adjust the dryer cycle for inlet conditions where the moisture load is less
than 75% or 50% of design. The short cycle will provide a -40°F to - 80°F dew point when operating at
or below design conditions. Always set the purge as if you had a full inlet flow when using these 3
cycles. The cycles automatically compensate for the light loading; there is no need to turn the purge
down. The dryer must be operated in the standard 10 minute 100% load cycle when equipped with a
Pro Purge.
Section 7 Shutdown Procedures
Isolation
1. Allow dryer to reach repressurization step and fully repressurize
2. While fully repressurized, remove power from the dryer by turning off disconnect.
3. Open bypass pipe.
4. Close outlet isolation valve.
5. Close inlet isolation valve.
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