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Safety of Alumina milling media


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#1 CrossOut

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Posted 07 June 2016 - 09:51 AM

Ball mill is a must have. Look on Craig's list and eBay for rock tumblers. I got my large ball mill for so cheap it was a steal.. guy basically paid me to take it. For media also keep an eye on Craig's list and eBay. I got my alumina there for cheap. Lots of food companies will sell our give their used media away.

#2 lloyd

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Posted 07 June 2016 - 10:14 AM

If you intend to make black powder with your ball mill, I recommend against high-alumina media for a couple of reasons:

 

1) There's a nagging suspicion that it sparks -- this may be due to its EXTREME hardness, which causes impacts of very tiny area, and therefore of immense forces (per square area).  This might be what has ignited powder before with high-alumina ceramics, rather than actual 'sparking'.

 

2) Partly because of the tiny surface area of impacts mentioned above, and partly due to its low mass, alumina media is not very effective at milling black powder efficiently.  Lead is often the preferred media, although a lot of folks are now using 300-series stainless steel.

 

Get a 'real' ball mill.  Rock tumblers usually have to be re-engineered to operate efficiently as ball mills.

 

LLoyd


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#3 CrossOut

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Posted 07 June 2016 - 10:39 AM

Alumina also has microscopic pours which trap material very well... Though the amount is minimal, metals can get trapped in there and cause issues. I hadn't had issues withmy media but my drum isn't gigantic either. As long as your drum isn't too big the hardness won't be an issue.

Alumina media comes in several sizes. I use 1/2" rounded cubes. My mill actually reduces material with alumina faster than lead. + no less contamination and higher media durability. If you find the right source cheaper as well. I got mine 20# for 40$

My drum uses 18# and used the same media for 6 years now with little signs of wear.

Certain rock tumblers will more than suffice, the main modification needed would probably be the rolling speed. I have an 8" diameter drum rotating at about 60 rpm off a 1/3 house motor. Works like a dream. Those small mods may prove to be cheaper than buying an actual mill.

You can easily build your own, but a proper drum will probably be the most expensive part.

Edited by CrossOut, 07 June 2016 - 11:04 AM.


#4 Mumbles

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Posted 07 June 2016 - 12:54 PM

If you intend to make black powder with your ball mill, I recommend against high-alumina media for a couple of reasons:

 

1) There's a nagging suspicion that it sparks -- this may be due to its EXTREME hardness, which causes impacts of very tiny area, and therefore of immense forces (per square area).  This might be what has ignited powder before with high-alumina ceramics, rather than actual 'sparking'.

 

2) Partly because of the tiny surface area of impacts mentioned above, and partly due to its low mass, alumina media is not very effective at milling black powder efficiently.  Lead is often the preferred media, although a lot of folks are now using 300-series stainless steel.

 

Get a 'real' ball mill.  Rock tumblers usually have to be re-engineered to operate efficiently as ball mills.

 

LLoyd

 

 

I agree with you on lead being the first choice.  If one were to go with a ceramic material, do you have any other preferences or insight?  The reasoning behind high alumina ceramics I've always heard, including from another well known proximate pyrotechnic manufacturer, was that high alumina by definition is low silica.  Silica is a known piezoelectric material.  I am aware that piezoelectric sparks tend to be rather low temperature.  Then again there doesn't necessarily need to be a spark for ignition via impact.  


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

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#5 lloyd

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Posted 07 June 2016 - 01:21 PM

Hmmm... somehow my response to Crossout was lost!  I told him, "Sorry... Never mind.".

 

I'll strengthen it:  He doesn't know a thing about milling (except what he's "gotten away with"), and is going to hurt himself or someone else if he doesn't pay attention.

 

Ok -- Fully Vented now.  I feel so much better! (I wonder if he bought my book on ball milling?  Nahhh.... probably not! <G>)

 

I won't use anything but non-sparking metals on BP.  PERIOD.  I love alumina media for its longevity and cost, but I use it ONLY on single chemicals, or non-explosive mixtures.  I never mill BP with it, with glass, or with non-alumina (silica-based) ceramics (which are _essentially_ glass).

 

LLoyd


Edited by lloyd, 07 June 2016 - 01:23 PM.

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#6 Mumbles

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Posted 07 June 2016 - 02:12 PM

I deleted it.  Sorry, based on the contents I thought it was a post made in error not an actual response to CrossOut.  


Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

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#7 lloyd

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Posted 07 June 2016 - 02:23 PM

<G>  "Kinda Cryptic", no? <G>

 

Anyway... Ball milling should be safe (to people... safety to hardware is your choice).  If you MUST use media suspect of sparking or causing impact ignitions, then do so in a FULL BUNKER, designed to contain every scrap of what leaves when the jar finally explodes.

 

I wrote an AFN article about the explosion of a mill jar. (Done deliberately, CrossCut, in order to evaluate the dangers.)

 

Lloyd


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#8 WindowLicka

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Posted 07 June 2016 - 03:18 PM

<G>  "Kinda Cryptic", no? <G>
 
Anyway... Ball milling should be safe (to people... safety to hardware is your choice).  If you MUST use media suspect of sparking or causing impact ignitions, then do so in a FULL BUNKER, designed to contain every scrap of what leaves when the jar finally explodes.
 
I wrote an AFN article about the explosion of a mill jar. (Done deliberately, CrossCut, in order to evaluate the dangers.)
 
Lloyd


I read that article. The actual explosion picture was a tad bigger than I would have thought would happen. I haven't run my rock tumbler in the garage since.:) Strictly outback with lead sinker weights and 2 rubber HF cans keeps me safe.

#9 lloyd

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Posted 07 June 2016 - 03:31 PM

Good for you!  Never run a ball mill with an explosive mixture in it (regardless of media) in any structure you don't want damaged! <BSEG>

 

Lloyd


Edited by lloyd, 07 June 2016 - 03:32 PM.

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#10 CrossOut

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Posted 08 June 2016 - 12:21 AM

I never saw the post.. I guess you got away with murder... I've read your article and seen what I assume to be your video about the topic and intentionally blowing up a ball mill.... Ball mills can explode shocking!

Rest assure safety is always my top priority.

That said I have yet to hear of any explosion proven to be caused by alumina media. I've thrown my media against a multitude of surfaces hand have yet to witness any spark forming from the media. Yes impact injuries are a possibility buy there is no media exempt from this issue. Hence I said for my size mill this is not a concern.

The primary thing to consider is what you are milling. How sensitive is it? Can it react with existing materials? Can any accident occur with what you are doing? I'm willing to bet that the majority of mill accidents occur as a result of milling the wrong materials.

There is a reason everyone ball mills their. There is a reason the majority of amateur pyros use this method with great success and few accidents of any.

I believe it is important that the noobie understand the risks, dangers, and challenges.

I do not believe there is reason to sow fear in them because of some urban myths or unconfirmed observations. If our odds such a concern go test it. But don't go spreading the concern based only on opinion

I can guarantee that my media is safe for my mill and my applications. Of you wish to prove me wrong please do the experimentation your self and show me the data.
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#11 CrossOut

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Posted 08 June 2016 - 12:29 AM

As for the type of alumina media I can't guarantee a specific type. Especially if you are getting your media used. Few companies will divulge the composition of the media or even know when buying it used... That said do some testing! Go out in the dark and use a sling shot to impact it against different surfaces and the media its self. Look for a spark.

This simulates worst case sinerio and Confirmation is pretty obvious.

#12 lloyd

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Posted 08 June 2016 - 05:02 AM

This simulates worst case sinerio and Confirmation is pretty obvious.

----------------------------------------------------------------------------------------

 

Wow!  You didn't even READ my post, and now you tell others (potentially beginners) that it's unequivocally 'safe'?   You say anybody who claims otherwise is just "sowing fear"? 

 

It is NOT fear-mongering to let people know of any real or suspected reasons why a product might be unsafe in a particular application.  On the other hand, it is MALICIOUS to deliberately lie about those same potentials in order to trick people into using them in an unsafe manner.

 

You, sir, are welcome to blow yourself up, if you choose to do so.  I hope you do not.  But I will gladly testify in court to have you imprisoned if anyone else becomes injured by your advice!

 

Try that for a "sinerio".  I'm sure you'll argue that correct spelling is 'optional', and my insisting on proper spelling in a technical forum where exactitude is of first-order importance is just "criticism mongering".

 

Oh... that video probably wasn't mine; I've never made one.  Hmmm... I don't even remember ever hearing about one. 

 

Lloyd


Edited by lloyd, 08 June 2016 - 05:50 AM.

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#13 CrossOut

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Posted 08 June 2016 - 09:33 AM

Yes I actually have read your entire post. I'm still waiting on your data and results.. so far all I have heard is that you have a suspicion on the subject with no evidence to support your claim. Yet you choose to spread your suspicion without testing your self.

Your argument was: Alumina media can cause sparks. False alumina is a non sparking material. As I have said I have ran the tests and have concluded my results.

Your supporting statement was about impacts on a small area on hard surfaces..first this is not spark generation due to the media.
Second, No media is exempt from impact igntion. For the case of ball milling alumina media is no harder than stainless steel bearings. Forces created in The milling Action will be the same for all media regardless of mass (gravity). The other component will be mass which alumina has the lowest of the three. Therefore media of higher mass will present a higher risk of impact ignition. Lead will be an exception as it is a softer.

And yes it is fear mongering to present a concern without any evidence. In this case your claim is false. This is the same concept of those to believe vaccines cause autism. There's a sneaking suspicion but no evidence to support it.

As an example of my claim. glass is known to be a sparking material. Therefore it shouldn't be used. Lead, stainless steel bearings, and alumina are not sparking and may be used.

I do agree lead is probably the best option but can be much more expensive than alumina.


Tbh I'm not sure why you have so much hatred for alumina media.
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#14 PhoenixRising

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Posted 08 June 2016 - 10:23 AM

CrossOut, no says that you HAVE to listen to anyone on this forum.  We are simply trying our best to give advice and keep others safe.  If you feel you are safe then proceed at your own risk like anybody else.  

 

That being said, I would personally heed Lloyd's advice.  That's a personal opinion.     



#15 PhoenixRising

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Posted 08 June 2016 - 10:47 AM

Also, I was a bit curious about your testing methods, so I just had a couple of honest questions. 

 

When you refer to looking for sparks with your media during high-speed impacts, what was your method of capturing an image of the side which was making the impact?  Were you using a high-speed camera?  Any camera at all?  It would be impossible for you to see this with your own eyes as the back side of the media will obscure the line of site, making another view point a necessity.  

 

Also, when you reference using slingshot, did you record the amount of force with a pressure plate?  Did you record the force in Newtons or pounds?  Grams?  Just curious, as this kind of information would benefit a lot of people.  

Thank you, we appreciate the information.    



#16 lloyd

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Posted 08 June 2016 - 11:42 AM

CrossCut... apparently you did NOT read my post -- ever.  You may have 'skimmed' it for what you thought were arguments you could counter.

 

If you read my very FIRST point, it says that alumina is suspected of sparking,  then concludes that sparking may NOT actually be the cause of the accidents that have happened.  I'm going to repeat it here, and highlight salient parts so that you cannot continue to mis-report what I said:

 

"1) There's a nagging suspicion that it sparks -- this may be due to its EXTREME hardness, which causes impacts of very tiny area, and therefore of immense forces (per square area).  This might be what has ignited powder before with high-alumina ceramics, rather than actual 'sparking'."

 

How could you possibly turn that into a case of my arguing that "it sparks".  I NEVER said that -- and in fact, I stated explicitly that I suspect it does NOT.

 

All I said, and will continue to say is that, with that suspicion, one should avoid using it for milling explosive mixtures, in favor of media known not to spark.  Regardless of your disdain for its potential, there have been mill ignitions while using it.
 

 

I guess it's possible you don't know what "nagging suspicion" means.  Is THAT what caused you to think I expressly stated that it sparks?

 

You do whatever you please with your mill on your time.  I have no problems with that.  But don't deliberately misquote me and then claim I am wrong, and please don't teach beginners who might know less than you do about the subject.  (although I can't imagine how that could be the case).

 

LLoyd


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#17 MrB

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Posted 08 June 2016 - 12:15 PM

 

Your argument was: Alumina media can cause sparks. False alumina is a non sparking material. As I have said I have ran the tests and have concluded my results.
 

 

It's a simple fact, "Ceramic" alumina media has been in BP mill detonation, where as other, known not to spark, media hasn't. It's still generally considered a "safe enough" media, IF you can confirm that the manufacturer claims it's none-sparking. Which, point made here, not all media are. Second hand media? All bets are off. You have no idea what the specifications for the media was when it was brand new, and you have at best a vague idea what it's been used to mil since then.

 

 

 

Lead, stainless steel bearings, and alumina are not sparking and may be used.

 

 

In reality only the lead media in your list, is actually non-sparking. Stainless steel bearings are made from quite the range of stainless types, not all of which are even spark resistant, much less non-sparking.
 

More off, then on topic. lLoyd can come of as a bit of an arse every now and then (no joke) but he's generally willing to share what he can of what knowledge he has, and that is quite a bit. He can't share everything he knows, simply for business reasons, be it that he's under contract, or that he's simply making a living of specialty knowledge, and cant share those details, but the bottom line is, he simply doesn't have to make shit up and lie to you, to try and show of. What he say's is his genuine opinion. Take it at face value, and see it as advice. What ever you choose to do after receiving said advice reflects mostly on you. Everyone here suffers every time some pyro blows them self, anyone else, or property, to bits. Some of us suffer mentally, hating every accident that strikes a fellow pyro, but all of us feel the force from the authorities that try to make us stop doing pyro all together. So, trust me when saying this. Nobody here is trying to piss on you. Everyone shares whatever knowledge and information they have in an effort to make everyone as safe, and free to pursue our pyro interests as we please.

 

But then again, this is just me, and my opinion. You can take this at face value, and decide for your self what you want to do with it. Enjoy.

B!


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#18 lloyd

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Posted 08 June 2016 - 12:24 PM

"Loyd can come of as a bit of an arse every now and then (no joke)"

000

 

Oh!  Yeah... I'll agree with that.  <G>

But I don't lie to folks... there's nothing in it for me OR them!

 

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#19 CrossOut

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Posted 08 June 2016 - 12:27 PM

Ok I'll lay this out for you from a scientific standpoint.

You have a hypothesis which you have not tested. I have tested this and find your hypothesis to be false. Alumina is a known non sparking material... Literally only you are thinking otherwise. That said please provide evidence which suggests otherwise. If you wish to argue this topic do some research your self.

Now I'll address your later statement.. Sparking is not the same as impact ignition hazard. You seem to be confused there as you keep bringing it back up.

If you read my last post I've already acknowledged the understanding of impact ignition hazard. And have already concluded that all media poses this hazard. Not just alumina as you hold to claim.

Yes we all already agree don't use media that sparks.. I am telling you alumina is within that category. If you are not referring to the actual attribute of spark producing then stop using the term.

Nagging suspicion means there is insufficient evidence to support either side of the argument.. I am proposing there is enough evidence to show the truth... If you wish to argue otherwise please provide evidence our a source.

I would like to point out you quoted your self using "nagging suspicion" with The term sparking. I'm beginning to think you aren't quite sure of what you are saying.

I would like to advise you to do more research on the topic before telling people false information. There's nothing wrong for wanting to stress safety. But at this point you are giving incorrect information whether you are willing to admit it or not.....

Tip for future post...

Oh I was under the impression alumina media had a potential a sparking hazard. Thank you for correcting me on that.

Feel free to copy and paste that.

#20 PhoenixRising

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Posted 08 June 2016 - 12:33 PM

BTW, this is not directed towards this post, but in general:

I've seen from a few sources that some stainless steel is supposed to be non-sparking?  

 

I work with steel on a daily basis, and I never met a steel that wouldn't produce sparks.  Steel is essentially iron and carbon.  Stainless varieties simply contain at least 13% Chromium (as defined in the industry) which gives them their corrosion resistance.  It is true that in most cases I find that stainless does produce "less" sparks.  Some 'marine' grade stainless (300 series?) has much lower Carbon content meaning they will spark much less as well.  But IMO any steel containing Carbon will spark if impacted hard enough to make the Carbon disassociate from the Iron.  But I digress....  I simply don't feel comfortable using steel ever.  My Dad was a machinist his whole life as was his Dad and his Dad, my brother works in a steel mill and my other in a machine shop until he died.  I've seen a lot of steel in my life.  

 

Again, this is not directed at this post, just a general observation of something I've seen more than once.  Sorry if this is off topic.  


Edited by PhoenixRising, 08 June 2016 - 12:41 PM.





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