explosive situation?

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Well this nonsense comes up two or three times a year so didn't even bother to read most. A research done 3 - 4 years ago found that according to Gov. specs. you would have to reduce something like a 6" x 6" x 1 ft. pc. of Oak to dust in one minute to get enough concentration of dust to support an explosion. Anyone got one of these machines in their shop? Anyone actually have FIRST HAND evidence of a home wood shop explosion?
Wheat dust, bean dust, corn dust in grain elevators, etc, is not wood dust in home workshop.
Walt Conner
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WConner wrote:

Why would that work with oak and not pine? Of course it would and this is my point: That is plainly not plainly not the ONLY way to get a wood dust explosion.
Suppose you sand away with your ROS or belt sander and collect a nice large volume of dust. Then when you are emptying your dust collector you drop it and the dust you created over the course of several hours all goes airborne at once.
Now, that could make a nice impressive fireball--but only if there is an ignition source like a pilot light or a spark from an electric motor. A static spark may not be enough, but static sparks are not the only ignition sources.
One should be careful not ot give an overly broad answer to a rather specific question.
--

FF


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Any documented cases of that happening?
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Edwin Pawlowski wrote:

Yes.
I've thrown hanfulls of sawdust into a fire.
That's pretty much the same thing as dumping a load of dust on the floor next to a gas water heater with a pilot light, right?
--

FF


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Did the room explode?
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Edwin Pawlowski wrote:
egarding dumping a dust colector:

And later wrote:

Yes. In fact I was killed.
Seriously, I did it outdoors.
--

FF


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Not to diminish any dangers or recommend against any safety practices, but it's often difficult to get a lit match to light a flammable liquid, let alone a handful of dust.
--

Larry Wasserman Baltimore, Maryland
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snipped-for-privacy@fellspt.charm.net wrote:

Dead wrong!
It is easy to light a _flammable_ liquid (e.g. gasoline) with a match, that follows from the formal definition of 'flammable'.
It is not easy to light a _combustible_ liquid (e.g. kerosine) with a match as you have to heat it to the flashpoint before it will ignite.
--
FF

"Flammable, nonflammable, inflammable--why are there three?"
-- George Carlin
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Which of course demonstrates that it's not the liquid, but the gas which ignites....
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George wrote:

Precisely.
The flashpoint for a liquid is approximately the temperature a which the partial pressure of the vapor over the liquid reaches the LEL.
In theory, I suppose they are exactly the same but in practice flashpoint is determined in a laboratory and there are at least two methods used that can give slightly different results--open cup and closed cup.
--

FF


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Once again, the big picture. If your ignition source is continuous, it will burn away the smaller amounts as they come within range, preventing an explosive situation. You've got a ways to go to figure out how to get a bolus of properly dispersed dust to duplicate that in a tube....
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George wrote:

What is to stop the flame front from progessing through the dust cloud after the edge of the cloud reaches the ignition source?
The answer is nothing.
So don't dump your dust collector out near a continuous ignition source. Seems straightforward enough for me.
But it is wrong to make an overbroad statement implying that you cannot light a cloud of sawdust on fire. I've done it.
--

FF


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Best person to ask is your local fire department. They might have some good stories to tell.
Fuel + Oxygen + Heat (spark) = Fire
I think a DC can catch fire, although I'm not sure how likely it is to happen.

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RE: Subject
What everybody is dancing around is "LEL" or "Lower Explosive Limit".
It is that point where the dust volume in the air WILL explode.
An entire industry exists to provide instrumentation to measure "LEL" for various products.
There are published tables of LEL values and are usually available from the instrumentation manufacturer.
Been there, done that, but that was a while ago.
Lew
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wrote:

No, not at all. Fill a reasonable router extractor hose with typical levels of fine larch dust, initiate it pyrotechnically and I have no doubt at all that you can have your very own wood dust explosion.
You'll not do it from static though. That's the demonstrable case where you can't initiate it.

No, far from it. It's the lower limit for where the mixture _can_ explode. Below this it's impossible to explode, at this limit it's barely possible. It isn't especially likely (depending on other conditions regarding ignition sources) and it certainly isn't any sort of spontaneous ignition as suggested by your emphatic "WILL explode" comment.
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I previously wrote:
>>It is that point where the dust volume in the air WILL explode.
As written, not true.
It should have read: It is that point where the dust volume in the air WILL explode IF an ignition source is provided.
Blame it on a lazy typist, ME.
Lew
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No disrepect intended, but I've read dozens if not hundreds of MSDS and had some training as well, and I have never seen a reference to LEL/UEL that was not for gas or vapor concentration in air. In fact, for dust any LEL would vary with the particle size.
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Larry Wasserman Baltimore, Maryland
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The RayV entity posted thusly:

<snippage>
Yes, I do believe in facts.
No idea of the concentrations or how hot a spark it would take to set it off.
I was, however, rudely awakened one Sunday morning in North Vancouver when a grain elevator about 5 miles from me was subject to a grain dust explosion. That was in the mid-70s or so, if you feel like looking it up.
I also participated in several experiments in which we ignited clouds of flour, cornstarch, and sawdust. No real explosion, because it was a small and unconfined cloud, but it was, nonetheless, spectacular.
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Oleg Lego wrote:

My mother couldn't explain the seemingly rapid disappearance of her cache of corn starch when I, unbeknownst to her, would sneak baggies of it down to the creek bed to huff it out my mouth at a candle held before my face--much to my inner pyromaniac's delight.
er
--
email not valid

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<...snipped...>

That must have been fun, but how many times were you successful igniting it with a static discharge?
--

Larry Wasserman Baltimore, Maryland
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