http://www.ctv.ca/servlet/ArticleNew...18/?hub=Canada
and
http://cnews.canoe.ca/CNEWS/Canada/2...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

"Luigi Zanasi" wrote in message
...
http://www.ctv.ca/servlet/ArticleNew...18/?hub=Canada
and
http://cnews.canoe.ca/CNEWS/Canada/2...971474-cp.html

No mention of the cause of the DC fire. Betcha it wasn't a static
spark.

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.

I am almost certain the cause will be a carelessly-disposed-of
DuMaurier.

On 26 Mar 2005 09:25:07 -0800, wrote:

I am almost certain the cause will be a carelessly-disposed-of
DuMaurier.

Employing a shop teacher named Danvers was never going to end well.

Luigi Zanasi wrote:
No mention of the cause of the DC fire. Betcha it wasn't a static
spark.


The conspiracy theorist are already at work on this one
though. Someone said they say an elderly woman with a
G-suit dabbing her face with make up.

UA100, reporting many miles from the Sinai...

"Edwin Pawlowski" wrote in
m:


"Luigi Zanasi" wrote in message
...
http://www.ctv.ca/servlet/ArticleNew...1111715156535_
18/?
hub=Canada and
http://cnews.canoe.ca/CNEWS/Canada/2...971474-cp.html

No mention of the cause of the DC fire. Betcha it wasn't a static
spark.

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.


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

"Patriarch" wrote in message
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.

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

wrote in message
oups.com...
I am almost certain the cause will be a carelessly-disposed-of
DuMaurier.


Half a million years ago, when I was in high school wood shop, in the winter
time kids would hang out in a back corner of the shop smoking cigs near a
collector port. If the teacher was coming the cig got tossed into the port.
You may be right!
Greg

"Patriarch" wrote:


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

Thank You, Thank You, Thank You!! BG

Max D. (retired Deputy Chief)

On Sat, 26 Mar 2005 12:14:28 -0600, Patriarch
wrote:

There will be a very complete after-incident investigation.

Really ? I'd expect it to be the perfect excuse to STOP THESE
DANGEROUS WORKSHOPS IN OUR SCHOOLS
(Think of The _Children_)

In article ,
"Edwin Pawlowski" wrote:

Evidently is was already burning. I wonder what actually exploded? Gas
leak? Chemicals

Acetone.

Robatoy wrote in
:

In article ,
"Edwin Pawlowski" wrote:

Evidently is was already burning. I wonder what actually exploded?
Gas leak? Chemicals

Acetone.


And things had just settled down a bit, troublemaker.

;-)

Patriarch

On Sat, 26 Mar 2005 08:33:48 -0800, Luigi Zanasi
wrote:

http://www.ctv.ca/servlet/ArticleNew...18/?hub=Canada
and
http://cnews.canoe.ca/CNEWS/Canada/2...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

Someone huffing near an inlet!

"Andy Dingley" wrote in message
...

Really ? I'd expect it to be the perfect excuse to STOP THESE
DANGEROUS WORKSHOPS IN OUR SCHOOLS
(Think of The _Children_)

I live near Boulder - the place where they pulled all the motors from the
woodworking equipment.

On Sat, 26 Mar 2005 17:14:05 GMT, "Edwin Pawlowski"
scribbled:


"Luigi Zanasi" wrote in message
.. .
http://www.ctv.ca/servlet/ArticleNew...18/?hub=Canada
and
http://cnews.canoe.ca/CNEWS/Canada/2...971474-cp.html

No mention of the cause of the DC fire. Betcha it wasn't a static
spark.

I hope you see the follow-up of the
investigation so we can see what did really happen.

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

On Fri, 01 Apr 2005 12:05:18 -0800, Luigi Zanasi wrote:
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.

... snip ...

It seems that we have the first documented case of static sparks
causing an explosion in dust collection systems.

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

Luigi Zanasi wrote in
:

On Sat, 26 Mar 2005 17:14:05 GMT, "Edwin Pawlowski"
scribbled:


"Luigi Zanasi" wrote in message
. ..
http://www.ctv.ca/servlet/ArticleNew...1111715156535_
18/
?hub=Canada and
http://cnews.canoe.ca/CNEWS/Canada/2...971474-cp.html

No mention of the cause of the DC fire. Betcha it wasn't a static
spark.

I hope you see the follow-up of the
investigation so we can see what did really happen.

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


And any other day of the year, I MIGHT believe you.

Patriarch

Art Greenberg wrote:
On Fri, 01 Apr 2005 12:05:18 -0800, Luigi Zanasi wrote:
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.

... snip ...

It seems that we have the first documented case of static sparks
causing an explosion in dust collection systems.

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.

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

On Fri, 01 Apr 2005 14:36:04 -0600, Patriarch
scribbled:


And any other day of the year, I MIGHT believe you.

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

On 1 Apr 2005 12:40:35 -0800, wrote:


Art Greenberg wrote:
On Fri, 01 Apr 2005 12:05:18 -0800, Luigi Zanasi wrote:
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.

... snip ...

It seems that we have the first documented case of static sparks
causing an explosion in dust collection systems.

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.

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.

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
+--------------------------------------------------------------------------------+

On 1 Apr 2005 12:40:35 -0800, wrote:

OTOH I used to work with some prototype pneumatic conveyors. We used
PVC pipe and got some HUGE sparks off of ungrounded systems.

If you study electrostatics as a safety discipline, one of the
categorisations you learn pretty early on is that PVC and similar
insulator will generate various sorts of static discharge, but not
"sparks" - a distinct category of static discharge.

The discharges around insulators are relatively small and have maximum
energies that can be calculated. You know the behaviour of the bulk
material and you know how much of it there is in a particular volume.
Typical discharges are tiny energies, because there's simply little
energy available and stored in that are of insulator. The big
discharges in insulators are those like "brush discharges" (they leave
characteristic tree-like patterns behind) where a disharge can travel
over an insulated surface, effectively discharging the energy from a
large area in one go. These are still prety small though, which is
why we know there aren't dust collector explosions causing by static
ignition of wood dust.

A spark OTOH is a discharge from an isolated conductor. Because the
capacity of this can be huge, particularly the capacity that is
available to discharge rapidly through a tiny area (i.e. a big
conductor with a sharp edge), then the energy of these is almost
unlimited (for simple calculations of the local pipe). These are the
biggies, but they just can't happen unless there's a conductor
involved.

--
Smert' spamionam

Andy Dingley wrote:

On 1 Apr 2005 12:40:35 -0800, wrote:

OTOH I used to work with some prototype pneumatic conveyors. We used
PVC pipe and got some HUGE sparks off of ungrounded systems.

If you study electrostatics as a safety discipline, one of the
categorisations you learn pretty early on is that PVC and similar
insulator will generate various sorts of static discharge, but not
"sparks" - a distinct category of static discharge.

The discharges around insulators are relatively small and have maximum
energies that can be calculated. You know the behaviour of the bulk
material and you know how much of it there is in a particular volume.
Typical discharges are tiny energies, because there's simply little
energy available and stored in that are of insulator. The big
discharges in insulators are those like "brush discharges" (they leave
characteristic tree-like patterns behind) where a disharge can travel
over an insulated surface, effectively discharging the energy from a
large area in one go. These are still prety small though, which is
why we know there aren't dust collector explosions causing by static
ignition of wood dust.

A spark OTOH is a discharge from an isolated conductor. Because the
capacity of this can be huge, particularly the capacity that is
available to discharge rapidly through a tiny area (i.e. a big
conductor with a sharp edge), then the energy of these is almost
unlimited (for simple calculations of the local pipe). These are the
biggies, but they just can't happen unless there's a conductor
involved.

So let's see, on a cold dry day I shuffle across a nonconductive rug and
then touch a grounded piece of metal and a long white glowing something
moves between my finger and the metal. From your description I am forced
to conclude that that is not a "spark", so what is it? Or have I
overlooked an "isolated conductor" somewhere?


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

On Tue, 05 Apr 2005 17:08:28 -0400, "J. Clarke"
wrote:

So let's see, on a cold dry day I shuffle across a nonconductive rug and
then touch a grounded piece of metal and a long white glowing something
moves between my finger and the metal. From your description I am forced
to conclude that that is not a "spark", so what is it?

Yes. In everyday terms this is a "spark", in the vocabulary of
electrostatics the terms get more specialised and it isn't. If you
want a broad term, they're all "discharges".

Stroke a cat and you'll get "corona discharge", because the fur is
sharply pointed (this causes a locally high field gradient, the
condition for corona discharge). In general though, discharges with at
least one insulator will be a "brush discharge". These can be quite
large - enough to cause flammable vapour explosions - but they're
still not "sparks" as we're using the term here.

Another form is the "propagating brush discharge" and these can be
particularly powerful - but they need particular conditions to cause
them (puncturing an insulating film - Faraday could work out the
rest).


I don't make these words up, I'm just using the standard terminology
so I can read the big boy's books with the long words in. That's how I
know that dust collectors don't explode from static triggering a dust
explosion.

Here's a quickie,
http://www.ce-mag.com/archive/1999/novdec/mrstatic.html
or else Google, or read this (pricey but worth it)
http://www.amazon.com/exec/obidos/tg/detail/-/0750627824/codesmiths-20

Andy Dingley wrote:

On Tue, 05 Apr 2005 17:08:28 -0400, "J. Clarke"
wrote:

So let's see, on a cold dry day I shuffle across a nonconductive rug and
then touch a grounded piece of metal and a long white glowing something
moves between my finger and the metal. From your description I am forced
to conclude that that is not a "spark", so what is it?

Yes. In everyday terms this is a "spark", in the vocabulary of
electrostatics the terms get more specialised and it isn't. If you
want a broad term, they're all "discharges".

Stroke a cat and you'll get "corona discharge", because the fur is
sharply pointed (this causes a locally high field gradient, the
condition for corona discharge). In general though, discharges with at
least one insulator will be a "brush discharge". These can be quite
large - enough to cause flammable vapour explosions - but they're
still not "sparks" as we're using the term here.

Another form is the "propagating brush discharge" and these can be
particularly powerful - but they need particular conditions to cause
them (puncturing an insulating film - Faraday could work out the
rest).


I don't make these words up, I'm just using the standard terminology
so I can read the big boy's books with the long words in. That's how I
know that dust collectors don't explode from static triggering a dust
explosion.

Here's a quickie,
http://www.ce-mag.com/archive/1999/novdec/mrstatic.html
or else Google, or read this (pricey but worth it)
http://www.amazon.com/exec/obidos/tg/detail/-/0750627824/codesmiths-20

Sounds like the distinction between a "spark" and other types of "discharge"
is kind of like the distinction between "isocyanate" and "non-isocyanate
blocked isocyanate".

The spark I get out of the rug looks an awful lot like the one I get out of
a van de graff, where there is a charge stored in an isolated conductor.
And that spark looks the same if it's to my finger or a grounded metal
ball.

So is the distinction by properties of the actual discharge or is a
discharge in which the flow of charge carriers is identical different in
nomenclature depending on the surfaces?

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Andy Dingley wrote:
On Tue, 05 Apr 2005 17:08:28 -0400, "J. Clarke"
wrote:

So let's see, on a cold dry day I shuffle across a nonconductive rug
and
then touch a grounded piece of metal and a long white glowing
something
moves between my finger and the metal. From your description I am
forced
to conclude that that is not a "spark", so what is it?

Yes. In everyday terms this is a "spark", in the vocabulary of
electrostatics the terms get more specialised and it isn't. If you
want a broad term, they're all "discharges".

...
I don't make these words up, I'm just using the standard terminology
so I can read the big boy's books with the long words in. That's how
I
know that dust collectors don't explode from static triggering a dust
explosion.


In our case we were conveying sodium sulfate so there was no explosion
hazard. Probably there were ungounded conductors in the system, like
segments of metal pipe, thermocuple wells and so on.

Do you suppose home dust collection systems might have some components
like hose clamps or a nail used to pin two segments together?

Would that make a difference?

--


FF

On Tue, 05 Apr 2005 20:40:42 -0400, "J. Clarke"
wrote something
.......and in reply I say!:

John

I was going to step in here, but looks as if you are doing OK so
far....G

Sounds like the distinction between a "spark" and other types of "discharge"
is kind of like the distinction between "isocyanate" and "non-isocyanate
blocked isocyanate".

The spark I get out of the rug looks an awful lot like the one I get out of
a van de graff, where there is a charge stored in an isolated conductor.
And that spark looks the same if it's to my finger or a grounded metal
ball.

So is the distinction by properties of the actual discharge or is a
discharge in which the flow of charge carriers is identical different in
nomenclature depending on the surfaces?

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

************************************************** ****************************************
Whenever you have to prove to yourself that you are
not something, you probably are.

Nick White --- HEAD:Hertz Music

remove ns from my header address to reply via email

!!
")
_/ )
( )
_//- \__/

On Tue, 05 Apr 2005 20:40:42 -0400, "J. Clarke"
wrote:

The spark I get out of the rug looks an awful lot like the one I get out of
a van de graff,

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

"J. Clarke" wrote in message
...

So is the distinction by properties of the actual discharge or is a
discharge in which the flow of charge carriers is identical different in
nomenclature depending on the surfaces?


Think of it as if it were a "discussion" on r.c.w, where some make more
light than heat, and others the reverse.

In article ,
Andy Dingley wrote:
On Tue, 05 Apr 2005 20:40:42 -0400, "J. Clarke"
wrote:

The spark I get out of the rug looks an awful lot like the one I get out of
a van de graff,

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.

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.

Robert Bonomi wrote:

....
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.

I think the "insulators" under discussion are somewhat limited in size
relative to those involved in meterological events...

On Wed, 06 Apr 2005 18:11:22 -0000,
(Robert Bonomi) wrote:

Shall we discuss _lightning_?

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

An air-to-air discharge is, by definition,
'between insulators'.

Clouds are conductors - their charge carriers are mobile. Some of
their behaviour differs from a classical insulator precisely because
of this.