[Jewelry making - Article 00458] - Re: [Orchid] Dust and static electricity explosions

[David Phelps]

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    When I was in High School, my Physical Science teacher did a
    demonstration with a metal paint can into which he put a candle next
    to a little coffee stirring spoon attached to a rubber hose with a
    squeeze bulb. The tube was aimed so as to puff powder from the spoon
    into the area above the flame when the bulb was squeezed. He filled
    the spoon with about one gram of powder of any number of different
    materials, iron filings, wheat germ, flour, very fine sand, etc, and
    then put the cover on the can, tapping it with a mallet to make it
    really tight. We students tried burning the materials before the
    experiment to determine their reactive qualities and then made
    predictions about which powders would react, and which ones wouldn't.
    With every single type of material, when he squeezed the bulb, the
    powder exploded with enough force to blow the top of the can up to
    the ceiling. Even talcum powder and concrete dust. Made a believer
    out of me. 

    Many a grain silo in the farm belt of the US has exploded due to
    dust, as have many different kinds of factories. The type of dust or
    powder is almost completely unimportant, only that it is fine enough,
    suspended within a closed area in the right ratio of particles to
    air, and there is an ignition source. 

    I worry about this enough to make it absolute non-negotiable policy
    in my shop, that no one grind on steel or any material that causes
    sparks at the polisher. One spark down the dust collector not only
    can cause a fire, but also could cause an explosion of awesome,
    potentially deadly force. Although this is not a likely scenario and
    one I've never heard of actually happening, it is definitely a real
    possibility with very serious consequences. After my experience in
    Freshman Physical Science class, I take the possibility of an
    explosion in a dust collector (or any other dusty environment) very
    seriously. 

    I'm glad your daughter wasn't hurt and my thoughts and prayers go
    out to those who were not so fortunate. 

Dave
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