Dust collector explosion in Montreal

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http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1111715156535_18/?hub Κnada and http://cnews.canoe.ca/CNEWS/Canada/2005/03/24/971474-cp.html
No mention of the cause of the DC fire. Betcha it wasn't a static spark. Luigi Replace "nonet" with "yukonomics" for real email address www.yukonomics.ca/wooddorking/humour.html www.yukonomics.ca/wooddorking/antifaq.html
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http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1111715156535_18/?hub Κnada
This is an interesting comment: "A student who didn't give his name said he and a teacher smelled smoke before the explosion."
Evidently is was already burning. I wonder what actually exploded? Gas leak? Chemicals? Seems to have been quite a bit of damage from just dust even in a good sized commercial DC. There was not even any mention that the DC was running at the time. I hope you see the follow-up of the investigation so we can see what did really happen.
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I've seen stuff in well-supervised classes that still make me really nervous.
The fellow sharpening chisels in the disk sander (connected to the DC) comes immediately to mind.
There will be a very complete after-incident investigation. The chances of the details of the report making the news are pretty small.
Every fire department leader I've ever met, or seen on the news, impressed me as a pretty serious, caring person. I'm _very glad_ they are around.
Patriarch
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I've seen 'em too. In my previous life as a h.s. science teacher I was often called on to "sit in on Mr. Blurfles class" during my 'conference' period. I can remember, on one occasion, I spotted Mr. Blurfle outside in the alley behind his wood shop pouring water into the large metal plenum of his dust collector. He told me he had to put out fires every once in a while because some student would drop his lit cigarette butt into the intake of the dc.
Larry
--
Columbia, MO
www.llhote.com
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Thank You, Thank You, Thank You!! <BG>
Max D. (retired Deputy Chief)
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On Sat, 26 Mar 2005 12:14:28 -0600, Patriarch

Really ? I'd expect it to be the perfect excuse to STOP THESE DANGEROUS WORKSHOPS IN OUR SCHOOLS (Think of The _Children_)
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I live near Boulder - the place where they pulled all the motors from the woodworking equipment.
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Acetone.
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wrote:

And things had just settled down a bit, troublemaker.
;-)
Patriarch
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scribbled:

This is weird. According to "Le Soleil de Montreal":
"Un representant du Service des incendies de la CUM a declare que la cause de l'explosion dans l'atelier d'ebenisterie a l'ecole Cavelier-de-Lasalle est une etincelle generee par l'electricite statique dans la tuyauterie en plastique de polychlorure de vinyle. Le service des incendies procedera a des inspections dans toutes les ecoles de la region pour s'assurer que ces dispositifs soient bien mis a terre, ce qui permettra d'eviter d'eventuelles deflagration. De sa part, la CSST reccommande aux entreprises d'ouvrage de bois de verifier que leur depoussiereurs soient pourvus de dispositifs de mise a terre pour eviter les deflagrations du meme genre."
Rough translation:
A representative of the Montreal Urban Community fire department declared that the cause of the explosion in the furniture-making shop at the Cavelier-de-Lasalle school is a spark generated by static electricity in the PVC plastic piping. The fire department will proceed to inspect all schools in the region to ensure that these systems are well grounded, which will allow avoiding eventual deflagrations. On its part the CSST [the Quebec equivalent to OSHA] recommends to all woodworking enterprises to verify that their dust collector systems be provided with grounding systems to avoid deflagrations of the same kind.
It seems that we have the first documented case of static sparks causing an explosion in dust collection systems.
Luigi Replace "nonet" with "yukonomics" for real email address www.yukonomics.ca/wooddorking/humour.html www.yukonomics.ca/wooddorking/antifaq.html
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On Fri, 01 Apr 2005 12:05:18 -0800, Luigi Zanasi wrote:

... snip ...

I wonder what evidence points to such a thing, sufficient to distinguish it from a burning cigarette butt having been sucked into the system, for example.
--
Art Greenberg
artg AT eclipse DOT net
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Art Greenberg wrote:

Well, they may have looked for a cigarette and not found one, though I'd not be inclined to draw too certain a conclusion from that.
OTOH I used to work with some prototype pneumatic conveyors. We used PVC pipe and got some HUGE sparks off of ungrounded systems. That translates to high voltage (several hundred thousand volts) NOT high current. I think the ignition source for rare but spectactular grain elevator explosions is also typically attributed to a static spark.
--

FF


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On 1 Apr 2005 12:40:35 -0800, snipped-for-privacy@spamcop.net wrote:

Most of those of which I've read have been due to electrical shorts -- most often sparks from one of the grain-moving motors. Much more current and energy in those sparks than in a static spark.
+--------------------------------------------------------------------------------+ The absence of accidents does not mean the presence of safety Army General Richard Cody +--------------------------------------------------------------------------------+
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On Tue, 05 Apr 2005 20:40:42 -0400, "J. Clarke"

It is. But the mechanism by which they start, and the paths between "energy stored on a surface" and "discharge in the gap" vary.
If the discharge takes place between insulators, then it's of the non-spark type. In these cases we understand some physical limitations to its maximum energy and can make engineering decisions based on this. Energy in a non-spark discharge is limited.
If it's a conductor, then _because_ it's a conductor the charge can flow around it and thus charge from a very large area can be delivered to one small point. Energy in a spark-type discharge is not limited by the materials of the duct (until you know the capacity of the conductor). These can be _much_ bigger discharges than the brush discharges.
For woodworking dust collectors, we know the energy needed to ignite the mixture and we can show that this is always more than is available from a propagating brush discharge.
For the case of an insulating duct with a metal pipe-joiner flange, then there have been industrial accidents where flammable vapour explosions were caused by spark-type discharges from this flange acting as a capacitor. These were in systems designed to be safe for non-spark discharges - the ignition energy was above that of a brush discharge, below that for possible sparks. This is the case were earthing is useful; it's necessary, and it's effective.
--
Smert' spamionam

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Shall we discuss _lightning_? An air-to-air discharge is, by definition, 'between insulators'. Thus it is a 'non-spark discharge', by your terms.
The energy in the discharge may be 'limited', but the value is *way* up there. Various kinds of indirect measurements put the figure well into the multiple- megawatt range.
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Robert Bonomi wrote:

I think the "insulators" under discussion are somewhat limited in size relative to those involved in meterological events...
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On Wed, 06 Apr 2005 18:11:22 -0000, snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote:

No, because I'm talking about real-world engineering in dust collectors. If we want to troll, then do it on your own time.

Clouds are conductors - their charge carriers are mobile. Some of their behaviour differs from a classical insulator precisely because of this.
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Think of it as if it were a "discussion" on r.c.w, where some make more light than heat, and others the reverse.
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And any other day of the year, I MIGHT believe you.
Patriarch
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On Fri, 01 Apr 2005 14:36:04 -0600, Patriarch

;-)
Ah well, I only caught two "poissons d'avril", "April fish" as they are called in French. Eisan is still the king.
For the record, there is no such newspaper as the "Soleil de Montreal", and no news yet as to the cause of the explosion. My bet goes for a Player's or Export "A" rather than a duMaurier.
Luigi Replace "nonet" with "yukonomics" for real email address www.yukonomics.ca/wooddorking/humour.html www.yukonomics.ca/wooddorking/antifaq.html
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