PDA

View Full Version : sawdust explosion



Jared Larrow
12-11-2008, 9:47 AM
I'm not backing the validity of this video, but it makes me think I should clean out my sawdust bin more often... :rolleyes:

http://www.funnyhub.com/videos/pages/cool-sawdust-explosion.html

I also hope these guys don't live in my neighborhood...

Greg Cole
12-11-2008, 10:08 AM
Kinda cool, neat to see the fire run up the dust cloud.
BTW, I grew up in Essex Jct and lived in the Burlington area for 25 years!

Greg

Myk Rian
12-11-2008, 10:26 AM
Mythbusters did a segment on that. They produced some awesome fire.

Prashun Patel
12-11-2008, 10:54 AM
This is pretty scary stuff..

Jason Beam
12-11-2008, 11:58 AM
Everyone understands this isn't a risk in a workshop, right?

Unless you have an air hose under a drum of sawdust that is set off just before a flare is ignited, I guess. :rolleyes:

JohnT Fitzgerald
12-11-2008, 12:07 PM
Unless you have an air hose under a drum of sawdust that is set off just before a flare is ignited, I guess.


Darn, there goes my idea for a supplemental heating system for my shop... :)

Cliff Rohrabacher
12-11-2008, 2:55 PM
Where I live that would be construed as a weapon probably a flame thrower. The state police would arrest him and he would definitely go to prison.

On the up side it makes cool smoke rings.

Andrew Derhammer
12-11-2008, 4:18 PM
Very real hazard if there's too much dust in a room. There's an msds for sawdust.

Karl Brogger
12-11-2008, 4:28 PM
Where I live that would be construed as a weapon probably a flame thrower. The state police would arrest him and he would definitely go to prison.

Remind me not to move to where ever it is you live;)

Pretty cool video.

Tom Veatch
12-11-2008, 5:45 PM
Very real hazard if there's too much dust in a room. There's an msds for sawdust.

Yes, but it's a respiratory hazard, not a workshop explosion hazard.

Notice the density of the dust cloud at the time of ignition. The physics of flame propagation is such that in order to support a flame front (i.e., explosion) the dust cloud density has to be so high that visibility in the cloud is something on the order of a meter.

Note that I'm not claiming that dust explosions do not happen. They do. It's just that no one would let that much airborne dust collect in a work environment before doing something about it. Unless you have a mighty small shop, if you can see the far wall through the cloud, a dust explosion is the least of your worries.

Jason Beam
12-11-2008, 6:20 PM
I'm waiting for that one fluke ... that one comedy of errors ... that one chance occurance to come along ...

Man kicks on the completely-full plastic-bagged dust collector.

Dog leaps in fear, knocking over the broom that was leaning against the wall.

Broom falls onto a chisel handle just barely protruding over the edge of a benchtop.

Chisel flies over to the dust collector, ripping a gash in the plastic bag.

The gaping wound in the DC bag allows an insane amount of sawdust to instantly be released into the air just as the chisel bounces off the concrete wall behind the DC causing a spark that ignites the swirling cloud of dust into a massive explosion.

Seconds pass and then two hairless bodies emerge from the dust/smoke cloud. Man curses dog. Dog curses man. :P

Larry Edgerton
12-20-2008, 12:15 PM
Yes, but it's a respiratory hazard, not a workshop explosion hazard.

Notice the density of the dust cloud at the time of ignition. The physics of flame propagation is such that in order to support a flame front (i.e., explosion) the dust cloud density has to be so high that visibility in the cloud is something on the order of a meter.

Note that I'm not claiming that dust explosions do not happen. They do. It's just that no one would let that much airborne dust collect in a work environment before doing something about it. Unless you have a mighty small shop, if you can see the far wall through the cloud, a dust explosion is the least of your worries.

You are wrong.

There was an article in Woodshop News a few years ago that was very informative on the causes of buildings exploding. It does happen, and people die from it, and more often than people think. I may still have it in my library at the shop, I'll see if I can find it.

As far as your point that you never have a cloud thick enough, it is never the first explosion that blows the building down. A small explosion upsets settled dust and that blows, which upsets more settled dust and that blows, until the walls blow out. It is usually not the initial explosion that kills. All of this happens so fast that until experiments were done everyone thought it was just one explosion. Now we know different.

I now go through my shop every year cleaning the exposed trusses and purlins, and have come up with an ambient air purifier that runs continually when the lights are on to reduce the chance of an explosion. None of the shops that exploded in the article had huge dust clouds, in fact some exploded when they were closed.

To discount the possibility out of hand is doing a disservice to the woodworking community, and could be dangerous.

Jeffrey Makiel
12-20-2008, 3:51 PM
You are wrong.

To discount the possibility out of hand is doing a disservice to the woodworking community, and could be dangerous.

I believe Tom was referring to the purpose of a material safety data sheet (MSDS).

A home shop environment which is a much different situation than a commercial facility handling huge quantities of material. The main hazards that I've seen documented for a home shop are combustion from something causing a fire in a dust bag or dust bin (not exploding), and folks having asthma attacks or other repertory irritation from airborne dust.

However, I have never seen any real documented incidents, or even casual postings on any woodworking forums, of any sudden dust explosions in a home shop. Please feel free to share any relevant home shop incidents you are aware of…it would be very interesting to say the least.

-Jeff :)

Mike Henderson
12-20-2008, 4:10 PM
This isn't sawdust, but grain elevators used to blow up from dust explosions on a regular basis. I don't know if they still do, or if better dust control is now available.

Used to live near one long ago.

Mike

M Toupin
12-20-2008, 4:51 PM
It does happen, and people die from it, and more often than people think.

I've never seen a documented incident in which a hobby or small shop has exploded from a DUST explosion. If you have a documented case, please post it as I, and I'm sure a lot of others, would be very interested in it.

Mike

Tom Veatch
12-20-2008, 5:58 PM
This isn't sawdust, but grain elevators used to blow up from dust explosions on a regular basis. I don't know if they still do, or if better dust control is now available.

Used to live near one long ago.

Mike

There have been others since then, but the last one I know of was the DeBruce explosion June 8, 1998. I live about 5 miles from the elevator, was home when it blew, and the whole house shook. The overpressure as the blast wave passed my house was very, very noticable.

Of 27 people at the elevator:

5 dead at the scene
2 fatal injuries
10 non-fatal injuries
10 uninjured

http://www.osha.gov/as/opa/foia/hot_6.html
http://labs.lib.ksu.edu/dlib/grainElevator/Thumbnails/Wichita%201986%20a/index.shtml

Kyle Kraft
12-21-2008, 7:23 AM
I have a brother in law who is...how should I say this...frugal? "Fred" bought a pellet stove last winter and has been experimenting with different combustible solids mixed in with the wood pellets. Field corn, the unpopped kernels from the bag of microwave popcorn, etc. He noticed that the current batch of wood pellets had a significant quantity of fines in the bottom of the bags. Not wanting to waste a few BTU's he scooped the fines up with a garden trowel and dumped them into the fire pot of the pellet stove. He was in an adjacent room when he heard a loud "pop" sound. He rushed to the room to find the cat all puffed up and the lid of the pellet hopper blown open.

Dust explosions are not just for grain elevators. With the right particle size and ignition sources, they are a real possibility.

Larry Edgerton
12-23-2008, 12:14 PM
Here is an article on an explosion in Oregon that illustrates my point about how the air does not have to be a cloud for an explosion to happen, an explosion creates its own cloud as it progresses.

http://www.ohsu.edu/croet/face/reports/2003-21-1.pdf

Before you out of hand discount this explosion because it is a wood flour factory, consider that the dust that you creat with a RAS is the same thing, and can collect in your shop in places that do not normally get cleaned. The article points out it was NOT the first explosion that did the damage and killed this man, but at least the third. This is how buildings are blown up, not by a cloud that people are working in.

I have seen discussion of different heating solutions used in some of the shops here and many are open flame gas furnaces that are known to backfire when dirty, especially wall furnaces that do not have a filter system at all. One backfire could cause the chain to start. There are many situations that can start the progression, as illustrated by the article, and something as simple as dust in a fusebox. How many of you here have explosion proof wiring, I don't, I can't afford it.

My point is not that we are all going to blow up, but that it is a threat that is serious and at least life changing, and all we have to do to avoid it is admit the possibility and take precautions. Something as simple as cleaning nooks and crannys that would otherwise not get cleaned can make your workplace safer, and more pleasant to work in.

I have a friend that was severely burned in a flash fire, out in an instant, but his life was forever changed. His was off gassing of adhesives, but the superheated air in a wood explosion would do the same. I can think of nothing more terrifying that what my friend went and is still going through. I have raced all my life, have broken 62 bones, so I am not a chicken, but I would rather die than be burned badly and live.

I myself have had a very close call. I build, or did until this depression,:( fairly large houses, and I usually set up a full shop on site. At one house where we had a dust collector running one of the workers dropped a lighter when he was cleaning up the shop area, and sucked it into the DC. It blew. It was outside with the hose run through a hole in the wall, and was positioned outside a garage door. When it blew it caved in the metal insulated garage door, and the guys working on the third floor ceiling, 47 feet above the drive that the DC sat on said the fireball flashed past the windows. If that had been inside I hate to think of the consequences. No one was hurt, but if the temp had been high enough to work outside.....

The point made about never hearing of a home shop exploding is irrelivant, it is not the size of the box but the conditions. The size of the box only dictates the size of the explosion, not if it can happen. Further many people on this forum do have commercial enterprises, and most of the small ones I have visited in my area are nowhere as clean as mine, and sometimes I feel mine is too dusty. Larger concerns tend to be cleaner, but probably more because of the OSHA inspector than concern for employee health.

There used to be 4 shops on my street, now there are two. Both were destroyed by fire, but one blew the walls out. Both were careless in their cleanliness. Both burned at night so no one was hurt but when examining the aftermath, it will make you be more cautious, or at least it did me.

Just give it consideration is all I am saying.....