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Dust Collectors - Safety Warning

Discussion in 'Grinders' started by BigUglyMan, May 7, 2018.

  1. BigUglyMan

    BigUglyMan Active Member

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    I'm not sure if this is the right place to post this but I wanted to get it out there right away. Mythtaken can move it if there's a better spot.

    Yesterday I spent the afternoon grinding a set of steak knives. Because I was working with such thin material (.072") I decided to do my grinding post-HT. As I was grinding the third of six knives something caught my eye at my dust collector. I am running a 2HP Pro-Point (Princess Auto but essentially the same as the Craftex from Busy Bee) with a top and bottom fabric bag. When I looked closer I realized that the damned bag was on fire at several points! I put the fire out and investigated a little but could find no cause for the bottom bag to have caught fire. I patched the holes and kept on grinding...still had three blades to go. In short order I had more fire, mostly around the top of the bag where it clamps onto the metal centre portion. The fire was quite hot, hotter than the burning bag should have been on it's own. It would appear that metal dust had collected and the sparks from the steel I was grinding had ignited the dust which burned quite hot. This is frightening because a person could have a fire smouldering in the bottom of the collector and not realize it until they shut down the machines and leave the shop. In my case with a detached shop I would have had no idea something was amiss until the shop was fully engulfed! And for you guys with a shop in the basement the prospect is even worse! I ended up dumping a bunch of water from my cooling bucket into the duct under my grinder and letting the fan suck the water in and atomize it. That appears to have done the trick with no more fire or hot spots. I went back out an hour later and took the bag off and there were no issues.

    Now, I'm not sure why this came to pass. I wonder if it's because I was grinding hardened steel and, perhaps, the sparks were hotter? I was mostly grinding with an 80 grit Klingspor belt and, because the material was thin and already hardened I wasn't working it particularly hard, yet here we are...a dust collector bag that looks like swiss cheese.

    So what's the go forward? I think it would be wise to switch up the bottom bag to a metal drum of some sort...just have to take some measurements and hopefully find some suitable fire-resistant material to form a collar between the drum and the structure of the collector. But that doesn't preclude hot sparks from igniting wood dust in the bottom of the bin (or, even scarier, aluminum dust). Maybe this is a problem more associated with grinding hardened steel, which I don't do very often, but I think some method of fogging the inlet occasionally with water would prevent the chance of fire, though it might make for what the Old Man would have called "a hellacious mess".

    So, thoughts? let's talk about how we can prevent burning our shops to the ground!
     
  2. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Glad you spotted it, Big! That could have been very bad indeed.

    I'm guessing it was because of grinding post HT. What was coming off was much lighter than normal grindings, so more easily carried into the filter, where it found lots of dusty fuel and airflow to ignite it.

    Going forward, I've read about adding a series of baffles or screens in the intake of the dust collector. Apparently any hot stuff will cool quickly as it bounces off those before it reaches the filter. The only other suggestion I have is to use the dust collector when working handle material and a mask when grinding metal.
     
  3. ToddR

    ToddR Putterer, Tinkerer, Waster of Time Staff Member

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    I dont know much about dust collectors as I've never used one. I use shop vacs mostly and am now going to be checking those too. (I had one used for cleaning out fireplaces too). I did learn about why not to wear artificial fabrics in the shop though. I once set my jacket on fire from grinder sparks. I was reccomended to switch to natural fabrics. Much less flammable. Great info to know guys.
     
  4. BigUglyMan

    BigUglyMan Active Member

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    I burned through a set of cotton pants while cutting with a zip-cut. It's a good reminder that were playing, literally, with fire.

    Hadn't thought that the sparks were, in fact, lighter grinding post HT. I wonder if it might be wise to increase the length of my intake duct. A long series of spirals, perhaps. I already use ear pro, a respirator and safety glasses when grinding. Can't be too safe.
     
  5. John Noon

    John Noon Well-Known Member

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    I use a bucket of water to catch sparks and if that ignites I am off to the coffee shop
     
  6. dancom

    dancom Dust Maker Best Shop Tool

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    I find that grinding hardened steel makes like this glomy, fluffy steel wool kind of stuff that sparks and catches fire really well. I have never noticed this with annealed steel. Be careful.
     

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