"Invisible Electrostatic Wall"
jeeze Reddit it's after twelve PST, don't you have to get up early
tomorrow? [Hafa adai other
SESSION 7: SPECIAL SESSION, 17th Annual EOS/ESD Symposium
THURSDAY, SEPTEMBER 14, 1995, 8:00 am
SESSION 7: SPECIAL SESSION: ELECTROSTATIC CONSIDERATIONS IN INDUSTRY
MODERATOR: D. Swenson, 3M
7.7 CASE STUDY - LARGE PLASTIC WEB ELECTROSTATIC PROBLEMS,
David Swenson of 3M Corporation describes an anomaly where workers
encountered a strange "invisible wall" in the area under a
sheet of electrically charged polypropelene film in a factory. This
"invisible wall" was strong enough to prevent humans from passing through.
A person near this "wall" was unable to turn, and so had to walk
backwards to retreat from it.
This occurred in late summer in South Carolina, August 1980, in extremely
humidity. Polypropelene (PP) film on 50K ft. rolls 20ft wide was being
slit and transferred to multiple smaller spools. The film was taken off
the main roll at high speed, flowed upwards 20ft to overhead rollers,
passed horizontally 20ft and then downwards to the slitting device, where
it was spooled onto shorter rolls. The whole operation formed a cubical
shaped tent, with two walls and a ceiling approximately 20ft square. The
spools ran at 1000ft/min, or about 10MPH. The PP film had been
manufactured with dissimilar surface structure on opposing faces. Contact
electrification can occur even in similar materials if the surface
textures or micro-structures are significantly different. The generation
of a large imbalance of electrical surface-charge during unspooling was
therefore not unexpected, and is a common problem in this industry.
"Static cling" in the megavolt range!
On entering the factory floor and far from the equipment, Mr. Swenson's
200KV/ft handheld electrometer was found to slam to full scale. When he
attempted to walk through the corridor formed by the moving film, he was
stopped about half way through by an "invisible wall." He could lean all
his weight forward but was unable to pass. He observed a fly get pulled
into the charged, moving plastic, and speculates that the e-fields might
have been strong enough to suck in birds!
The production manager did not believe Mr. Swenson's report of the strange phenomena. When they both returned to the factory floor, they found that the "wall" was no longer there. But the production workers had noticed the effect as occurring early in the morning when humidity was lower, so they agreed to try again another day. The second attempt was successful, and early in the morning the field underneath the "tent" was strong enough to raise even the short, curly hair of the production manager. The "invisible wall" effect had returned. He commented that he "didn't know whether to fix it or sell tickets."
Reference: Article about the "Wall" in ESD Journal (IT'S BACK! 8/2000)
From: Beaty, William J
Also: I wonder if the (I assume) huge quantity of air ions had anything to
do with your weird phenomenon. Maybe the "wall" effect involves a plug of
ionized air which is held in place by the opposite charge on the film. If
so, your repulsion phenomenon would not occur if the "tent" of film was
replaced with highly charged metal plates, since the source of
oppositely-polarized electric wind would then be missing. I'm still
convinced that the charged film should produce an attractive force upon a
human body. Repulsion requires that the human be charged with the same
polarity as the PP film, yet induction should produce an *opposite* body
charge, so attraction is expected. But if a plug of oppositely-charged
air was strongly attracted into the "tent" of PP film, it might produce a
significant pressure-gradient in the surrounding air. A fraction of a PSI
per foot would be more than enough to prevent someone from walking
forward. If this is the origin of the effect, then the repulsion forces
you experienced involved air pressure rather than electrostatic
This might be an entirely new way to accomplish levitation. Attract
a whirling blob of ionized air to an oppositely-charged plate, then use
the resulting pressure gradient to lift and manipulate uncharged objects.
Sort of like a fluidized bed, but using charged air instead of sand.
Why doesn't the population of opposite ions "plate" itself onto the
plastic surface? Maybe it tries to do so, but the air within the moving
tent is swirling like a horizontal tornado, so the charged air cannot
simply move straight to the plastic film. If true, then the phenomena
would not appear if motionless charged air and oppositely charged plastic
were present. The tent shape and the motion of the plastic would also be
required. Incredible coincidence that all the required components could
ever come together in one place! (if this is indeed how it works!)
Speculative, untried experiments: MOVED TO http://amasci.com/freenrg/iontest.html