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350-2100 cfm Dryers Chapter 6: Maintenance 38 of 58
9. Remove the restriction from the filter element and re-install the clean filter. The alarm light should
remain off.
6-6 Dewpoint Control System Service
The Dewpoint Shift feature on dryer models 350 through 2100 depends on the proper operation of the
dewpoint sensor and its control board. The dewpoint sensor is in the process airstream and is therefore
susceptible to contamination.
Dewpoint sensor life is dependent on:
• Air temperature and flow passing over the sensor.
• The amount of fines [dust] in the process air.
• The amount of plasticizer vapor in the process air.
The dryer operator should monitor the initial dewpoint sensor readings and establish a periodic
replacement schedule as needed.
Note: Note: Do not attempt to check the continuity or resistance of a dewpoint sensor. The
sensor will be destroyed.
If you suspect that the dewpoint readings on the dewpoint meter are incorrect, a dewpoint simulation
calibrator is available from the manufacturer [part number A0549143]. This device simulates various
dewpoint outputs. It can confirm proper operation of the dewpoint sensor and dewpoint system control
board.
To check the dewpoint sensor and dewpoint control board:
1. Remove the sensor cable from the sensor hex nut adapter.
2. Connect the cable to the plug on the rear of the simulator.
3. Turn the rotary knob on the simulator to each position and note the readings on the dewpoint meter
on the dryer's control panel. The readings should correspond within a degree or two across the
entire range.
4. If the readings agree, the control board is OK. Dewpoint sensor replacement is recommended. If the
readings do not agree, replace the control board and run the test again to rule out the possibility of a
bad sensor.
Do not attempt to make any adjustments to the components on the dewpoint control board.
5. When testing is finished, re-connect the control cable to the sensor adapter.
6-7 Symptoms of Worn Out Desiccant
The moisture adsorption capacity of the desiccant used in ACS dryers degrades after an indefinite
period of time. Useful life depends on variables such as material moisture content, plasticizer vapors in
the return air and number of regeneration cycles.
Your dryer may need new desiccant if it exhibits any of the following symptoms:
• The plastic material is not being dried sufficiently (high scrap/reject rate).
• The air temperature at the top of the regenerating desiccant bed rapidly climbs to 350°F or more
shortly after the start of regeneration, even though a saturated bed has just started heating.
• The process air dewpoint, measured with a portable dewpoint monitor, is higher than -10°F
throughout the process drying cycle.
• Smoke or dust is being blown out of the process air outlet.