michael lowe wrote:
>
> Randall,
> I don't think it was Rex this happened to. But, did you know about the
> possibility of creating a thermite fire from hot iron chips hitting a mix of
> aluminum and iron powder? Some things are obvious to the all knowing, but,
> some of us may have forgotten the obvious. This sort of thing might rate a
> mention. Or, would you rather all be exposed to a Darwinian moment each time
> we start to use a tool?
Thermite is actually roughly equal proportions of iron powder and
aluminum powder, densely packed. And, yes, it produces a _really hot_
fire. Thermite was perhaps the earliest welding process for large
diameter pipe before the advent of arc welding.
What the fellow in the message probably encountered was an aluminum
fire. As Randall has explained, enough aluminum dust in one place will
produce a helluva pop, with a lot of heat generated in a flash, and
steel grinding produces a lot of sparks to get that aluminum ignited.
As for safety concerns, the first and obvious means of avoiding this
situation is to keep the workplace clean (that includes doing
woodworking well away from areas where metal grinding is going on), and
if that's not immediately possible, putting a water mist down in the
work area, which both traps the dust and reduces its chances of
igniting.
Once ignition begins, the convective currents raise a lot of the dust
into the air, exposing more surface area of the aluminum and encouraging
further burning.
It's quite amazing the number of dusts which are dramatically
combustible.
Most people, for example, think of sugar as just the granulated stuff
that comes in the package, and how could that cause an explosion? It
does, with extraordinary consequences. Sugar granules, rubbing against
each other, produce a very fine dust which, in the right concentration,
can explode with a force which is hard to imagine. I lived near a sugar
processing plant in eastern Washington. In 1964, that plant had an
explosion in one of its storage bins which leveled the plant, and broke
windows in buildings seven miles away. Pure carbohydrate (high fuel
value), lots of surface area and the right conditions to ignite it....
Metals can behave the same way, if reactive enough. Potassium, sodium,
magnesium, aluminum. Highly reactive given the right conditions. Some
things really like oxygen. (!)
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
`70 GT6+ (being refurbished, slowly)
`72 GT6 Mk. III (organ donor)
`72 GT6 Mk. III (daily driver)
`64 TR4 (awaiting intensive care)
`80 TR7 (3.8 liter Buick-powered)
`86 Nissan 300ZX (the minimal-maintenance road car)
`68 VW Type II Camper (Lancia twin-cam powered, but feeling its age....)
Remember: Math and alcohol do not mix... do not drink and derive.
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