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OPERATION
The 8072 is designed to sample process air at a pressure between -1 psig and +7psig.
This range of air pressure is typical of that found in a plastics drying system. If you are
sampling compressed air, consult factory for other model options. The plastic tubing
supplied with this monitor can withstand temperatures up to 275ºF. Higher temperature
air can be cooled to a safe level by sampling through a short length of copper tubing.
Older models with built-in copper cooling coils are supplied with clear PVC tubing.
This tubing should be limited to 180ºF.
NOTE: For best sensor life and response time, avoid sampling ambient air of high
humidity. Leave unit off when not monitoring a dryer or hopper.
Some units have a brass selector valve on the side panel. This valve should remain
closed during any operation to prevent ambient air from leaking into the sensor manifold.
The 8072 is packaged for convenient spot checking of dryers or hopper systems, but it
can be used continuously to monitor process conditions, with the beeper indicating
excessive moisture.
Dryer Output Sampling
The performance of a dryer can be evaluated by measuring the dew point of its output
air.
1.
Connect the 8072 sample tubing to a point in the drier’s output. Make sure not to
exceed the supplied tubing temperature rating.
2.
Turn on the 8072 and allow the reading to stabilize. It can take 10 minutes or
more for the unit to stabilize when first used. You can silence the beeper with the
switch on the side of the panel.
A constant high reading on the 8072 may indicate a malfunctioning dryer or one that is
overloaded by damp material in the hopper.
Hopper Output Sampling
Dryness of material in a hopper can be checked by measuring the dew point of air exiting
the hopper. When a hopper is initially loaded with material, high dew points at the
hopper air return are normal while moisture is removed. It can take significant time to
dry material in some systems.
1.
Connect the 8072 sample tubing to a point in the hopper’s air output. Make sure
not to exceed the supplied tubing temperature rating.
2.
Turn on the 8072 and allow the reading to stabilize. Plastics processing can
proceed when the dew point reading is low enough for your material.
