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STT40 / STT70
Troubleshooting 9-2
Problem Possible cause Corrective action
Process heaters are faulty.
Check for open heaters. Replace
if required.
Solid-state temperature
controller faulty.
Replace.
Loss or reduction of process air
temperature.
Process temperature was
adjusted in error by plant
personnel.
Make sure that plant personnel
are aware of the proper
temperature set point. Post an
appropriate sign next to the
controller.
Process heaters are faulty. Replace.
Desiccant beds are
contaminated.
Replace desiccant.
Material being dried differs
from material specified at the
time of purchase.
Drying systems are designed for
the material which was
originally specified. Different
materials may need a longer
residence time or a different
drying temperature.
Break in flex hose to/from
drying hopper.
Inspect for air leaks; replace as
needed.
Airflow valve sticking or failing
to shift.
Check for proper operation of
valve actuators. Repair or
replace if necessary.
Remove blower side plate,
clean baffles, replace.
Loss or reduction in drying
capacity.
Blower fins filled with dust or
contaminants.
Replace filter elements.
Insufficient power to PLC
(Power LED is off).
Check power supply and power
wiring to PLC.
PLC Regeneration Bed LED
indicators both off.
Faulty PLC (PLC Power light is
on, Run light is off, and/or Error
light is on).
Replace PLC.
Regenerating bed cooldown. None.
Blower Input indicator is off.
Verify that blower contactor is
on. Check input wiring to PLC.
Process air in high-temperature
condition.
None.
Insufficient power to PLC
(Power light is off).
Check power supply and power
wiring to PLC.
PLC Regeneration Heater
Left/Right output indicators both
off.
Faulty PLC (PLC Power light is
on, Run light is off, and/or Error
light is on).
Replace PLC.