6-22 l Trou ble sh oo ti ng
Poor Material Drying
Troubleshooting
Occasionally, processing problems that are suspected of being caused by poor dry-
ing are eventually determined to be the result of other issues in the process setup.
The information can assist you in determining if your drying system is performing
properly. However, the only way to know definitely if your material is properly
dried is to perform moisture analysis of small samples as it leaves the bottom of
the hopper or just as it enters the process. Conair does not sell moisture-analyzing
equipment, but there are many brands of this equipment available on the market.
You should also be aware that some processing problems may actually be the
result of over drying material. Most materials will degrade to some extent if they
are exposed to their specified drying temperature for a time significantly longer
than the residence time specified by the supplier. If you want to maintain its dry-
ness, it is recommended that you reduce the process air temperature. If your Conair
dryer is equipped with the Setback feature, you should familiarize yourself with it,
and make use of it. If not, you may want to contact Conair to determine if it can be
added to your dryer.
A majority of customer questions to Conair are related to dewpoint. It is important
to realize that dewpoint is one of four requirements that need to be satisfied.
There are four requirements, listed in order of importance, necessary to
properly dry hygroscopic plastic resins:
1 Drying temperature of the air entering the hopper must be at the proper
drying temperature for your material, as specified by your material supplier.
2 Residence time is the time, determined by your material supplier, that the
material in use must be heated to achieve proper drying temperature.
3 Airflow during the process drying circuit must be adequate to carry and
distribute the heat throughout the entire bed of material inside the hopper.
4 Dewpoint of the process air must be low so it can efficiently collect the
moisture as it is released from the heated material and carry it to the dryer to
be removed in the desiccant.
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