Re: Digest Number 221

Commercial practice is to do just that...install optical flame detectors in
the ducts leading
to the dust collector, be it a cyclone or fabric filter. If a spark is
detected, the systems
automatically close a damper (quickly) to isolate the dust collector or
inert with Halon or whatever to prevent an explosion. At least the
commercial ops that have had a "big one". Definitely gets your attention.
Any time you have a combustible dust, be it wood, powdered sugar, oats, or
whatever suspended in air it can light up real easily and if confined when
burning, it goes boom. A pile of sawdust will most likely just smolder and
possibly start a slow burn, but if left unattended that could get pretty
exciting too. An attached vacuum system would certainly be able to fan the
flames if it sucked in a hot spark or ember. I don't think it would ever be
all that advisable to let shop machinery run attended, too many unexpected
things can happen. And darn few of those are desirable.

Steve Gunsel

At 11:48 AM 10/21/99 +0100, you wrote:

>From: Andrew Werby <drewid@...>
>
>
>Message: 2
> Date: Wed, 20 Oct 1999 15:18:14 EDT
> From: PTENGIN@...
>Subject: Re: Re: What do we want?
>
>In a message dated 10/19/1999 9:09:11 PM Hawaiian Standard Time,
>clintbach@... writes:
>
><< I once had a unique problem with a
> recycled piece of plywood I was engraving a sign on. I noticed the
> cutter was sparking. This is the only time I actually caught the work
> piece on fire while machining it! In retrospect if I had been using the
> vacuum system this could have been way too exciting! A fire in the
> vacuum system could be devastating. >>
>
>Hello all,
> My day job machine did catch fire once. When you plunge cut materials, you
>often get a small disk of same on the end of the bit. If this doesn't fly
>off, it gets dragged around in the cut. The friction ignited the particle
>board top. This Thermwood machine draws vacuum right through the particle
>board. (It's 40 Hp vacumm pump!!) The fire spread fast. Lucky someone was
>watching. We usually run lightly tended. You must put a fire extinguisher
>close by....
>Peter
>
>[Yow- "Thermwood" is a good name for it! Recently, I was trying to cut
>some wood with a 4-flute cutter, and I guess it didn't get the material out
>of the way fast enough- I noticed some charring on the surface. This could
>easily have started a fire, with all the sawdust that piled up in the cut.
>(Switching to a 2-flute cutter solved the problem.) If these machines are
>running unattended, this could be a significant hazard. Perhaps we should
>give some thought to an automatic fire detection and extinguishment system
>to go along with our automated cutting equipment. Would a smoke detector
>work to trigger the thing, or would it be fooled by a haze of sawdust? Any
>other ideas?]
>
>Andrew Werby
>
>Andrew Werby - United Artworks
>Sculpture, Jewelry, and Other Art Stuff
>http://unitedartworks.com
>
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