Ball Mill Explosion!

[dagabu]

We speak of accidents and try not to point fingers, we look at all the probabilities and go from there.

 

There were several factors that could have contributed to the explosion but the point is to learn from our mistakes and change.

 

Over on PF, the consensus so far (by the really smart ones) is that an impact explosion took place so use small jars for small batches and big jars for big batches.

 

Don't worry, I will share what comes up next, Mumbles and Swede are keeping tabs too, they will correct me if I am telling lies

[Swede]

I've often wondered about the so-called ceramic media "sparking" which is supposed to create flashes of light in a darkened room. To test, I loaded a crystal-clear plastic container with a handful of my ceramic media, went into a closet, let my eyes adjust, and started shaking the jar.

 

Nothing. I shook harder, harder, pretty soon I was WAILING away as hard as I could with this thing 6 inched from my eyes, and I never saw a thing. A wintergreen life saver makes more sparks in your mouth. If you've never tried it, Google it, it's cool.

 

Anyhoo, at least with my media, VIOLENT agitation did not produce anything remotely resembling a light flash, let alone an ignition effect. I don't know what sort of ceramic media he was using, or if it was contaminated, but the stuff I have does not spark, and this test eased my fears a bit. I believe what I have is "burundum grinding media" from Cole Palmer and similar. It can also be found on eBay.

[Mindphreak]

Has anyone had an issue with coinage (nickles) for ball milling? I've never heard of an explosion off of them, but they are a pretty uncommon media. Ive never had an issue, but I sure dont want one.

 

And swede Ill keep it in mind to never use lifesavers for ball mill media

[dagabu]

Has anyone had an issue with coinage (nickles) for ball milling? I've never heard of an explosion off of them, but they are a pretty uncommon media. Ive never had an issue, but I sure dont want one.

 

And swede Ill keep it in mind to never use lifesavers for ball mill media

 

There are a few that use coins to mill but I found it to be a complete waste of time and only slightly better then phenolic balls.

[Swede]

Yeah, Wintergreen life savers would not be an ideal media!

 

The ceramic stuff the guy was using is being referred to as "Mentos" shaped media on Passfire. I am not familiar with what they are referring to. It sounds like one of those normal Passfire giant group-buy discoveries, where one fellow finds a particularly good deal, then posts it, and everyone jumps on board. If anyone is familiar with the media source used in this case, then it'd be helpful to know the EXACT source.

 

My ceramic media came from an eBay guy, and is shaped like little barrels with heavily rounded ends. The sizes vary.

 

The thing with ceramic media is that there are probably dozens of formulations. The better ones are dense, with zirconia being the best, but very expensive. Since the formulations vary wildly, unless one knows exactly what's in the media, it isn't appropriate to say "Ceramic media is dangerous" because that encompasses such a large group of materials. It is like saying "salt is dangerous." WHICH salt? There are millions.

 

There is a notion that ceramic media is fragile and will chip. We mentally picture porcelain which is entirely different from alumina. When I had those dozen alumina media in that liter plastic jar and was flailing it as hard as I could looking for sparks, I expected a chip or two, but there was NO chipping or damage at all.

 

Conclusion: I think that if the "ceramic" media is engineered to grind in a ball mill, it will perform well and do so without danger. If the media is NOT specifically engineered to do this, or if it is an unknown material, maybe it'd be best to stay away from it. The good news is that alumina-based milling/grinding media is not expensive, and is dense enough to do a good job, if one wanted to switch from Pb.

Edited January 18, 2010 by Swede

[dagabu]

My ceramic media came from an eBay guy, and is shaped like little barrels with heavily rounded ends. The sizes vary.

 

I have the same media, It came in different sizes, works great and cleans up well.

[Ventsi]

I agree with Swede, contamination, a week or two ago I was emptying out my jar of freshly milled BP when I found something that should NOT have been there.

http://i102.photobucket.com/albums/m100/asota_2006/P1080757.jpg

 

YES! That is a nail, a galvanized steel one, which was like;y straight before it went into my mill. Now I have NO idea how this SOB made it in there or the small pebbles behind it but it was definitely not from the BP part, perhaps it just slipped into my open jar of media, I don't know.

[NightHawkInLight]

Wow. That's...something. You had better start storing your barrels in a better environment it seems

[pyrogeorge]

Amazing

 

i can't believe it..

[Mumbles]

When I worked at the pyro factory they screened all of their compositions before ball milling. They said it was to keep out nails, staples, and rocks. I though that was a bunch of BS until now.

[swervedriver]

I recently found a small piece of scrap steel in a bag of commercial hardwood lump charcoal. Not surprising really, it looked like a bent and twisted piece of strap of some kind.

[dagabu]

Yup, every bag of cowboy lump charcoal seems to have some junk in it too. I screen everything before I mill it, dont know why, just do.

 

D

[scarbelly]

Wow that's really sketchy... Is there a chance that the little pebbles are charcoal? If I start out with large charcoal chunks, there's almost always little bits like that. I can't say the same for the nail...

[swervedriver]

yeah this piece of metal was about an inch long and covered with charcoal dust, it looked like a small gnarly piece of charcoal.

[xetap]

The last 'garbage' I found was after milling charcoal- not BP- and it looked to be #8 bird shot in size, but had been through the charring process. Maybe that steel shot that's used? I didn't put a magnet to it. Edited February 11, 2010 by xetap

[NightHawkInLight]

The last 'garbage' I found was after milling charcoal- not BP- and it looked to be #8 bird shot in size, but had been through the charring process. Maybe that steel shot that's used? I didn't put a magnet to it.

Sure look like a few rocks to me. If a nail got in it's not a leap to think some pebbles got brushed off the shelf into the barrel too. Otherwise, a lot of times the bark of trees will have pebbles contained in it that got grown over. That's one good reason to debark all your charcoal wood. For that matter, if you make your charcoal out of large pieces of wood a nail could have been in the tree. That could go unnoticed if you just brake the charcoal into manageable pieces and let the mill do the grinding like I do.

[longwaytofall]

Are you using commercial charcoal? The mesquite charcoal you can buy around here does sometimes have contaminants in it. You have to imagine, they are taking whole trees and grinding them up for the charcoal vessel, so little pebbles embedded in the roots and whatever else goes along with it. They also do not remove the bark, which does effect the characteristics of the charcoal. (I smoke allot of hookah, you can call me a mesquite charcoal expert haha) It probably makes lousy BP anyways, so who knows.

[xetap]

Sure look like a few rocks to me.

I agree- the reference to birdshot was from a batch I had milled.