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Exploding Sawdust

Started by etat, January 19, 2004, 09:09:24 PM

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L. Wakefield

   Bleach and brake fluid!!?? Who knew? Now I gotta finger that one out.. lw
L. Wakefield, owner and operator of the beastly truck Heretik, that refuses to stay between the lines when parking

PatrickG

 :) Bleach and brake fluid... There are lots of "home" chemicals that are generally safe to use but can be dangerous when mixed.  Bleach can give off chlorine gas when mixed with the wrong stuff.  I choose to not elaborate here but trust me there are lots of wrong combinations.

See also: "Anarchist's Cookbook"

Now then back to the topic... dust explosions.  A Jr. Highschool science demonstration to illustrate the danger of dust goes like this...

Required materials:

1. A closed container, don't use a compression lid (paint can style) as it will explode too violently. A large metal can with friction fit lid like you see for potato chips and such is good.
1.1  OK you can use a 5 gal can with a compression lid but for goodness sakes do it outside away from windows and anytihing that a flying lid might damage.  After you understand the process, ask yourself how you will safely get the large compression lid on the can withought risk.  Some folks have hust layed a piece of plywood over the can.  Beware exploding seams!

2. a few feet (3-10) of flexible tubing (plastic, rubber, I don't recommend garden hose or large diameter tubing if you detonate by blowing by mouth)
2.1  You can use a shop air hose instead of blowing by mouth.

3. a candle

4. A few teaspoons of plain white wheat flour or extremely fine sanding dust.

Assembly directions:  Punch a hole in the bottom of the can near one side not near the center (About half the diameter of the large end of the funel from the sidewall.) It should be a snug fit to the tubing. Insert the tubing through the hole and insert the small end of the funnel into the tubing.  You want a tight fit between funnel and tube. With a little fussing you can make the tube fit tightly to the hole in the can and to the funnel.

Place a couple teaspoons of regular flour (not Bisquick or other baking mix but plain white flour OR alternatively sanding dust from sanding wood) into the funnel.

Place the can on a table or workbench or better yet on a chair located outside.  

A. Put on your hearing protection

(The rest of these instructions are to be performed in rapid succession.)

B. Place a lighted candle inside the can on the side opposite the funnel.

C. Place the lid securely on the can without bumping the can much or allowing your head to be over the top of the can.

D. Hunker down with your head under the chair (or whatever is supporting the can)

E. Blow sharply into the tube.

Expected results:  Relatively violent explosion that may rupture the side seam of the metal can and will likely shoot the lid to quite a height.

This used to be a relatively common demonstration of a dust explosion.  Of course, coal dust, fine sawdust, or whatever burnable substance can be substituted.  The finer the fuel dust the more violent the explosion. Finer fuel gives more surface area in contact with atmospheric oxygen and a faster burn rate per unit weight of fuel.

When I was in the USAF a Senior Master Sgt special ordered "Electrical Safety Shoes" for everyone in the Training Devices Section" flight simulators and such.  We worked around dangerous voltages.  Everyone was trying on their new safety shoes but I read the labels and instructions in the shoe box first.  There were instructions on how to measure the conductivity of the shoes to ensure they were operable.  Another sticker went on say how they met bureau of mines specification such and such.  Well my little light came on to a dim glow as I realized that THESE ELECTRICAL SAFETY SHOES were built for the purpose of grounding the wearer to prevent the build up of static charges that could set off an explosion in a mine, grain elevator, spray booth, flour mill, gun powder or explosives plant or wherever explosive or highly combustable products were handled.  

Unfortunately we needed shoes to insulate us from ground not directly connect us to it.  These shoes could have got one of us killed.  I did a slightly unprofessional thing like shouting. "Sgt. Mc Bride, you idiot, you're going to get us killed" as I threw the shoes about 50 ft in his direction.  To save face at base supply he refused to return the shoes.  He told veryone to take them home and wear them to work on their cars or something where the steel toes would make you safe.

 8) 8)   Pat    8) 8)

Buzz-sawyer

LW
You remind me of me.....with all the curiosity and experimentation.....have you studied wood gasification...that will run your car!!!! people were doin it 60 years ago .....
    HEAR THAT BLADE SING!

L. Wakefield

   no, I haven't seen that- I've seen propane cars. Is it like that- gasify, collect in a tank etc- or do ya load a few chunksa wood inta the hopper and drive off?  lw
L. Wakefield, owner and operator of the beastly truck Heretik, that refuses to stay between the lines when parking

L. Wakefield

Quotesnip

2. a few feet (3-10) of flexible tubing (plastic, rubber, I don't recommend garden hose or large diameter tubing if you detonate by blowing by mouth)
2.1  You can use a shop air hose instead of blowing by mouth.

snip

 

   I'm a mite skeered of that one- whatever you do, don't inhale!   :D :D :D
L. Wakefield, owner and operator of the beastly truck Heretik, that refuses to stay between the lines when parking

Hunter

One of my good friends works at a mill in Maine.
He is in the bagger house, bagging the shavings.
They have to be super catuios about the dust. all of there wood is dried and they get all the by products in there room. they have massive air movers and absolutly no open flames.
 One guy did try to light a cigerette and the forman punched him in the mouth and asked him if he was wanting to kill them.
Needless to say, they have very strict rules and they dont take it lightly.
Hunter
Jmccomas@insight.rr.com
614-554-2169
Dolmar / Efco / Redmax / Silvey Grinders Sales



james

its also refered to as a fuel-air explosive used by the military and for demolition :o

sawguy21

Just about any fine dust suspended in the air is a recipe for a ka-boom. A co-worker was using corn starch in a media blasting cabinet. I heard a loud WHOOOMP and ran over to see him standing there, his gloved hands inside the cabinet and his eyes and mouth the size of hubcaps. He had bumped the light in the cabinet
Reminds me of Halloween when us kids bought calcium carbide at the local machine shop until they figgered out what we were doing with it but that's another story.
old age and treachery will always overcome youth and enthusiasm

ksu_chainsaw

Thats the reason that grain elevators explode too.  When I was woking on them to repair them, we couldnt use a torch on the larger elevators because of the exlposion risk, and we had to wet down everything around the area we were working.  Seveal years ago, an elevator in the Witchita area exploded from a buildup of too much grain dust.

Charles

Ianab

Not that I've been experimenting or anything...
but a cupfull of that really fine sawdust from the belt sander dust bag should only be thrown on the rubbish fire from a safe distance upwind... :D

Disclaimer... If You or any of your dumb buddys try this and loose your eyebrows... dont blame us

Another version is Milk Powder.. Dairy factory up north of here lost part of it's roof after a flash fire in stray powder.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

sawguy21

Careful of them Darwin Awards. Don't want one.
old age and treachery will always overcome youth and enthusiasm

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