In the course of moving cut or chopped scrap trim through
ducting using vacuum forced air, the scrap (or recycled) trim can pick up
static electric charges. This is more common with light films (cast,
blown, etc.) than with heavy paper, laminates or non-wovens.
Scrap moves through ducting at speeds that exceed 5000
ft/min (slightly less than 60 miles/hr). Even in areas of the world where
humidity is high, air inside the ducting (and any trim that is conveyed
with the air) will dry through long duct runs to an air separator then a
compactor, baler or recycling unit.
The friction created by the combined movement of air and
trim in ducting generates electrostatic charges that are picked up by the
trim. Voltages can be as high as 20 kV.
Duct clogging caused by electrostatically charged trim
may occur if the trim is not conveyed with adequate air volume (thus
velocity). These highly charged particles exhibit a tendency to cling and
attach to other highly charged scrap pieces and to the walls/elbows of the
ducting. These highly charged scrap pieces will continue to collect and
build up until they clog ducting or "bridge" openings, such as a cyclone
exit. At that point, the suction provided by the material handling fan is
negated. Or, if the air separator is bridged, a back-pressure formed from
pushing air and trim against a rigid clog will cause the system to stop
delivering scrap material.
The in-line Static Eliminator produces an alternating
series of positive and negative ions through electrodes mounted in brushes
mounted inside a polyvinyl chloride (pvc) tube. As the ions come in
contact with the charged scrap material, the scrap is neutralized. This
eases the flow of material to its end destination. The Static Eliminator
should be placed in ducting prior to entry to an air separator or prior to
entry to a fan.
CTM Systems, Inc. has designed, built and tested (at several "beta" sites) its in-line Static Eliminator to handle these static problems. The
test results have been excellent. The Static Eliminator is offered in 4,
5, 6, 8, 10 and 12-inch diameter tubes. Contact CTM Systems when static
problems arise. We have the best possible solution to your static
problems.
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