Thoreson-McCosh Inc
EDITION 05/07/10
20
IB201001.doc
SECTION 9 PRELIMINARY TD DRYER CHECKS
SECTION 9.1 VISUALLY CHECK DRYING SYSTEM
Check dryer hoses and hopper. Be sure that delivery and return hoses are in good
condition routed with a minimum of length and sharp bends. Hopper lid should be in place
and well sealed. If a hopper loader is used, it should be mounted so that drying air leakage
is minimized.
SECTION 9.2 CHECK DRYING HOPPER INLET TEMPERATURE
At the hopper air inlet, the drying temperature should match the recommended temperature
specified by the material supplier. In general, as hot as possible without allowing thermal
degradation or discoloration of the material being processed If the hopper inlet temperature
is lower than the dryer discharge, the dryer temperature setpoint should be increased to
compensate for the temperature drop in the process air flow hose.
SECTION 9.3 CHECK THE HOPPER TEMPERATURE DISTRIBUTION
Let dryer run for 3 - 4 hours. Air/material temperature in the hopper should be uniform
around the hopper at any level, and hot (within 15°F/ 9°C of inlet temperature) up to 80% of
the full hopper height when material is being added at the designed drying rate. Under
static drying conditions (no new material added to hopper) the discharge temperature
should approach inlet temperature after approximately 4-5 hours of operation. Should
these checks show that the heat is not progressing upward through the hopper, the dryer
should be checked for low airflow.
SECTION 9.4 CHECK DRYER RETURN AIR TEMPERATURE
After 4 hours of residence time, check the return air temperature. If the return air
temperature exc
eeds 165°F / 74°C, than your unit should be equipped with some kind of
After-Cooler. This will protect the process blower and allow the desiccant to work at
optimum efficiency.
SECTION 9.5 CHECK DISCHARGE DEW POINT OF DRYER
For standard dryers, it should be approximately -
40°F/
-
40°C or lower. Should the dew
point run higher than specified, check dryer.
