Author Topic: Aluminium Dust  (Read 3758 times)

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Offline Bizzybee14

  • Posts: 2
Aluminium Dust
« on: October 15, 2014, 11:12 AM »
Hi,  we have a CT48 and want to use it on fine finishing aluminium components. We have the ATEX rated version so should be ok from the explosion protection angle but understand there is a potential fire risk if someone sands ferrous metals like bracketry etc. Does anyone have any experience of this? Should we use dedicated filters?  Or just keep a fire extinguisher handy?

Offline fdengel

  • Posts: 854
Re: Aluminium Dust
« Reply #1 on: October 15, 2014, 12:41 PM »
I believe you might need a spark trap - these are sold as optional accessories for the CT vacs (and they are not cheap) - but as I have no actual experience with this it would be good if someone else could verify that.

Offline Alex

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Re: Aluminium Dust
« Reply #2 on: October 15, 2014, 01:43 PM »
There is no fire risk when you sand metal. There is a fire risk when you grind or saw it. 

Festool does make the spark trap 484733 fdengel mentions, but it is very expensive, and according to the description only suited for situations with occasional sparks. If you're worried about sparks occuring, you can always install one. 

But you really don't have to worry about sparks when you sand metal, the sanding action is very slow and gentle compared to sawing or grinding. You will not be able to overheat the metal to a dangerous temperature.

Not sure what you mean with "dedicated filters", but the filters in the CT48 have no influence on sparks in the CT. The sparks travel through the hose to the bag/tub and potentially ignite material there. The filters won't be able to stop that if it happens.

And about a fire extinguisher, aren't they mandatory anyway in a professional workplace? You should always have one within reach.

Offline Bizzybee14

  • Posts: 2
Re: Aluminium Dust
« Reply #3 on: October 16, 2014, 04:22 AM »
Thanks for the responses.  We don't think sparks are the problem. We've been told there is a fire risk if really small aluminium dust particles come into contact with metal oxides as you would get from fine grinding or sanding steel which then rusts. Its apparently the 'thermite' process , a reaction which generates a lot of heat.  I can't believe it's a big risk but thought it worth asking if anyone else had come across it.

Offline jaguar36

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Re: Aluminium Dust
« Reply #4 on: October 16, 2014, 07:53 AM »
Thermite is a mixture of a metal powder and a metal oxide, of which aluminum and iron oxide dust is the most common and  is what you would have after switching from sanding between aluminum and steel.  The reaction is very exothermic, releasing huge amounts of heat, but is not explosive.  Since it has its own oxygen source in the iron oxide, its very difficult to put a thermite fire out.  In industry it is frequently used for things like welding railroad rails together or underwater welding.  So if it were to light it would be very very bad, however its pretty unlikely that would happen.  First you need to have the right ratio of aluminum to iron oxide, and second the thermite needs to get very hot before it begins to react, hotter even than a red hot spark would be.  If you compare this with sawdust, which is much easier to light on fire, its not very dangerous.

That being said, I'd probably use a different, or at least switch bags when switching between aluminum and iron.

Offline Alex

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Re: Aluminium Dust
« Reply #5 on: October 16, 2014, 08:19 AM »
Allright, thermite. Wouldn't have thought about that when you mention a fire hazzard, and certainly wouldn't have deducted that from your description either.

Thermite is hard enough to create and make it do what you want if you actually try, let alone by coincidence. Not something that happens a lot to the common craftsman. I suspect the chance of a thermite reaction is extremely small. Like lightning strike or lottery jackpot small.

     

Offline fdengel

  • Posts: 854
Re: Aluminium Dust
« Reply #6 on: October 16, 2014, 11:35 AM »
Thermite is hard enough to create and make it do what you want if you actually try, let alone by coincidence. Not something that happens a lot to the common craftsman. I suspect the chance of a thermite reaction is extremely small. Like lightning strike or lottery jackpot small.

I know someone who was struck by lightning twice.  And people do win the lottery now and then, or so I've heard...

Offline Alex

  • Posts: 7791
Re: Aluminium Dust
« Reply #7 on: October 16, 2014, 11:58 AM »
I know someone who was struck by lightning twice.  And people do win the lottery now and then, or so I've heard...

Yep, I've heard so too.

Offline gkaiseril

  • Posts: 329
Re: Aluminium Dust
« Reply #8 on: October 16, 2014, 05:30 PM »
Thermite used to be used to weld rails to together for street cars. One buts the rails together and dams some thermite around the joint and then lights the mixture and when it is done the rails are welded.
George Kaiser

TS 55 REQ, RO 90, RO 150, CT 26, PSB 420, MFT/3