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Semi OT - A Cool Demonstration; Why Magnesium Fires are so Dangerous

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  • Semi OT - A Cool Demonstration; Why Magnesium Fires are so Dangerous

    Some time ago, there was a post on here about a machine shop accident that could have been disastrous but was turned around by a quick thinking employee. There was a lathe that had been turning magnesium with a chip tray full of turnings. Something went amiss and the magnesium turnings caught fire. Luckily, they were able to grab up the lathe with a forklift and carry it outside on a gravel pad and let it burn out with no damage to the shop. The lathe was not so fortunate...

    As most of us know, you cannot use water to extinguish or cool a magnesium fire because of it will actually disassociate the water as it burns, producing hydrogen gas - which is also flammable! What may be less well known is that it burns in both nitrogen and carbon dioxide atmospheres so CO2 extinguishers have no effect. The only practical way to fight a magnesium fire is to bury it in dry sand or let it run its course.

    Here's a cool video I stumbled across of burning magnesium shavings in a block of dry ice. The result of the flames through the ice is pretty cool.

    http://www.youtube.com/watch?v=_xCbal2YyaE

  • #2
    Magnesium fires can be extinguished in two ways other than those you have mentioned. There is an extinguishing agent, Met-L-X, a powder that will extinguish magnesium fires. Another method uses water under about 100 PSI from a straight stream nozzle to accomplish several things. Initially it accelerates the burning causing the magnesium to form a molten puddle, second it cools the exposures and lastly it blows the molten/burning magnesium away from the remaining solid not yet involved magnesium basically removing the heat from the fuel and ultimately extinguishing the fire. As this takes place there is quite a fireworks display and it can be an exciting experience for new firefighters the first time they attempt it.
    I have used this method many times on vehicles to extinguish magnesium fires in the various components of newer cars.

    Comment


    • #3
      Originally posted by firbikrhd1 View Post
      Magnesium fires can be extinguished in two ways other than those you have mentioned. There is an extinguishing agent, Met-L-X, a powder that will extinguish magnesium fires. Another method uses water under about 100 PSI from a straight stream nozzle to accomplish several things. Initially it accelerates the burning causing the magnesium to form a molten puddle, second it cools the exposures and lastly it blows the molten/burning magnesium away from the remaining solid not yet involved magnesium basically removing the heat from the fuel and ultimately extinguishing the fire. As this takes place there is quite a fireworks display and it can be an exciting experience for new firefighters the first time they attempt it.
      I have used this method many times on vehicles to extinguish magnesium fires in the various components of newer cars.

      I had heard of Met-L-X but didn't consider it practical for shop use because of the cost. The water technique on the other hand ... WOW! I bet that would be cool to watch. Thanks for sharing your professional knowledge. My hat goes off to the firefighters out there. I've had the pleasure of working with several as a pyrotechnician and I'm grateful for all you do!

      Comment


      • #4
        Originally posted by firbikrhd1 View Post
        Magnesium fires can be extinguished in two ways other than those you have mentioned. There is an extinguishing agent, Met-L-X, a powder that will extinguish magnesium fires. Another method uses water under about 100 PSI from a straight stream nozzle to accomplish several things. Initially it accelerates the burning causing the magnesium to form a molten puddle, second it cools the exposures and lastly it blows the molten/burning magnesium away from the remaining solid not yet involved magnesium basically removing the heat from the fuel and ultimately extinguishing the fire. As this takes place there is quite a fireworks display and it can be an exciting experience for new firefighters the first time they attempt it.
        I have used this method many times on vehicles to extinguish magnesium fires in the various components of newer cars.
        Glad to hear new products and techniques have been developed for class D fires. When I went to the Navy's firefighting schools (1 a year for 4 years) we were taught to never use water but isolate them and let it burn out, like what the people did with the lathe. I used this when some students accidentally added magnesium to a crucible when we were casting aluminum. It kinda gets your heart started when you look over and a large "Roman candle" is going off in your hot metals lab.

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        • #5
          I used to burn mag two different ways - one was to fill a beer can full of it and light it at the opening - let it spread internally and then toss it in our creek out back, spectacular for sure,,,


          the other was to fill a coffee can full - light the top, let it get up a good head of depth on it, about 1/4 or 1/3 ,then stand back as far as you can with a garden hose and use your thumb to create a nozzle, get it dialed to where you have a good stream going with perfect distance and all's you got's to do is move over 5 feet sideways to make your connection, it's unreal, it's spectacular even in broad daylight... at night it's Mag-nificent... but you might want to wear sunglasses, so hot you will end up with about half the steel coffee can you started with...

          To tell you the truth I think if I had some kinda mag fire in a shop like FS stated id have to look at the situation,,, Actually - besides the intense heat Mag fires are pretty docile - till you add water that is, depending on the situation and the lathe design and such I could see putting on some welding leathers and helmet and just going in with a rake and slowly pulling the majority of it out of the chip pan and onto the cement floor,

          if you can achieve this your pretty much home free,,, then either let it burn out there or drag the majority of that outside,,,

          just like any solid form fuel the more you separate it the more it loses the ability to transfer and keep burning - small mag particles sometimes won't even survive on their own and will burn out before they consume all their usable potential,
          You will however pay an initial price when stirring it up as you expose hot spots and add oxygen, hence the protective measures (esp. as it's dropping to the floor)...

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          • #6
            In high school we used burn it on purpose everytime we had a sub & when my kids were scouts we'd bring VW cases to the campouts & show the kids metal burning.
            Last edited by flylo; 05-21-2013, 10:52 AM.

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            • #7
              yes that's where I got mine - VW and Porsche engine cases,

              the beer can method I mentioned was cool cuz it would sink 5 ft down and put on one hell of a show as it continues to burn under water, its so hot it sets up a steam vapor barrier around it...

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              • #8
                Originally posted by A.K. Boomer View Post
                just going in with a rake and slowly pulling the majority of it out of the chip pan and onto the cement floor,

                if you can achieve this your pretty much home free,,, .
                Boomer,

                Don't ever burn magnesium on a cement floor either. When I was an apprentice many years ago I had some magnesium to machine. One of the journeymen told me that it would burn. Of course, I had to bring some home and try burning it. I put a little pile of it on the concrete out front of my shop and lit it. After about a minute or so, there was an explosion about like a centerfire handgun. The magnesium was gone and there was/is a crater in the concrete where it exploded. Probably thermal expansion or something like that. That was the last time I burnt magnesium.

                Brian
                OPEN EYES, OPEN EARS, OPEN MIND

                THINK HARDER

                BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

                MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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                • #9
                  Good point - just like you don't want to use river rocks for campfires or they could take someones head off - cement is very porous but mag is so hot and it happens so quick the steam does not have time to escape,

                  you can drop it one the floor and then just drag it outside in the dirt - Or - You could drop it on the floor and "git" - if it means saving your lathe I would rather fill in a pock mark in the cement and patch a hole in the ceiling

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                  • #10
                    Originally posted by bborr01 View Post
                    Boomer,

                    Don't ever burn magnesium on a cement floor either. When I was an apprentice many years ago I had some magnesium to machine. One of the journeymen told me that it would burn. Of course, I had to bring some home and try burning it. I put a little pile of it on the concrete out front of my shop and lit it. After about a minute or so, there was an explosion about like a centerfire handgun. The magnesium was gone and there was/is a crater in the concrete where it exploded. Probably thermal expansion or something like that. That was the last time I burnt magnesium.

                    Brian

                    That is also why they tell you not to torch near concrete. There is some amount of moisture trapped in the concrete and when you heat it, it turns to steam. Just welding or torching close to a concrete floor can cause this on a smaller scale. Small chips will pop off the surface where ever molten metal hits it. Apart from tearing up the floor, it also has the potential to splatter you with molten metal! I will admit to being a victim on more than one occasion

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                    • #11
                      I think the key to working with the stuff is simple, frequent cleanings, as in never letting any substantial amount build up in the first place...

                      Comment


                      • #12
                        Originally posted by A.K. Boomer View Post
                        To tell you the truth I think if I had some kinda mag fire in a shop like FS stated id have to look at the situation,,,
                        Remember to use a blue filter to protect your eyes...

                        George

                        Comment


                        • #13
                          A forgotten hazard is a linisher.

                          Nice pile of rusted steel dust + Aluminium dust + spark = flash burns.
                          Paul Compton
                          www.morini-mania.co.uk
                          http://www.youtube.com/user/EVguru

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                          • #14
                            for sure that's one of the reasons I said to grab a welding helmet - that and because it gives your face protection, an auto-darkening welding helmet would allow you to see but as the chips fell to the floor it would go off into darkening mode,,,

                            if you keep things clean this situation should never occur in the first place, but if you don't and it does it just depends on a bunch of other things,

                            Im not saying people should resort to this every time, Im just saying for me and what I know about the stuff it could very well be an option VS letting my machine and house burn down...

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                            • #15
                              My Mag experiences, besides burning the mag strips in chem class.

                              All fires on purpose. Back in the day had to machine these stupid mag castings, going at it kind of wussy mostly with HSS, tiny chips and fines, that stuff,
                              in a piece of paper would spark up like nothing.

                              Had the same job come back around recently... several times, and since I'm older and wiser, better tools, bigger chips. Couldn't get this crap to light
                              for anything... Hmmm lets wash the coolant residue off and let it dry out real good. Hey it lights.... sort of... even with a torch, hit it with water...
                              pretty spectacular.

                              So the size of the chips seem to matter, surface area to volume I'd guess.

                              We have a 2" bar of magnesium that came from some job a while ago. Our exterminator asked if he could have a little slice... He takes a couple of
                              little shavings off with his pocket knife to get his camp fires going fast.

                              Titanium.... 2.5" x 3.5" plate/bar, sawing at a 45 degree angle on the little 7x12. The little saw lives outside because it doesn't rain here, so its on
                              an extension cord, which was apparently damaged. And Ti on a little saw makes nice fluffy birds nests of chips. Like steel wool but lighter and fluffier.
                              So I'm doing my thing in the shop, the saw is doing its thing outside one of the rollup doors and I BOOM, and a big giant puff of smoke. Go out and there
                              are little piles of Ti swarf burning all over the place on the ground and one big pile, and a big black hole in the extension cord.

                              Take that lesson for what its worth. Don't leave the extension cord under the saw.

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