[BProckets] Ceramic Milling Media Explosion: A Clarification?

[Dave Stoddard]

There are plenty of reports of mill explosions using lead,
lead/antimony, brass, 316 stainless, and other media.  As I
mentioned in a previous post, contamination in the contents
of the jar is the likely culprit.  Using lead media or brass
does not eliminate the potential for a mill explosion.  Also
note that milling metal powders can result in a pyrophoric
reaction with oxygen in the air when the jar is opened.  There
are plenty of opportunities to be injured using a ball mill,
whether you use ceramic media or not.

The advantage with ceramic over lead is that is takes less
time to complete the milling process, and it leaves less
impurities in the resulting comp.  When I had a ball mill,
I used ceramic media without any problems.  Stay Green,

Dave S

On 24 Sep 2004 at 16:40, Doug wrote:
> Here is a cut and paste from the PML archives describing one of the the incidents and the media type used. In my opinion, it is better to mill chems individually if using this type media, and then combine ingredients by other means, or with a brass or lead media, or by other means.  You can search the PML archives for "ceramic" for more information.  Using this media is just to risky in an already risky process in my opinion.
> DougK
> 
> At 06:29 PM 5/1/2002 -0500, Ken D wrote:
> >Does anyone have any definitive evidence that the ceramic media has known properties that would make it hazardous to use? I have heard stories from people that say the ceramic media can spark. While I cannot invalidate personal testimonies I have found no one who can back up the claim that ceramic media was the actual culprit in any accident or ball mill blowing up.
> 
> OK. I can't PROVE that the ceramic media was the culprit when my ball mill blew up. But I don't have any other strong suspects. And I will never use ceramic media for BP again....
> 
> I have high alumina media purchased from CoorTek and I have tried rubbing, grinding and smacking this stuff together in a very dark room, ( sounds kind of kinky doesn't it? ) without ever creating a spark. I have even scrapped the stuff across cement and failed to produce any sparking.
> 
> My mill was a fairly aggressive mill - "lift and drop", rather than cascade - and my personal theory is that it was the hardness of the media, rather than sparking which caused the explosion. Spherical media hitting each other cause a point impact with the possibility of significant heat generation. The harder the media, the more concentrated the energy, and the more heat.
> 
> I know people have been using this type of media to mill black powder and have never reported any problems. But I would like to know if anyone has any real evidence that this media is unsafe to use. I can't think of anything else, so I assume that the ceramic media was the culprit.
> 
> >Like any safety minded pyro hobbyist if this media truly is proven to be unsafe to use than I will stop using it. I was told at the time I purchased mine that the high alumina content media would definitely NOT spark.
> 
> No proof, but the mill did blow up. As I said, I think very hard media could cause an explosion (and may have in my case) without sparking. 
> 
> > 
> > From: "David Sleeter" <d.sleeter at adelphia.net>
> > Date: 2004/09/24 Fri PM 04:11:14 EDT
> > To: <bprockets at amateurrocketry.com>
> > Subject: [BProckets] Ceramic Milling Media Explosion: A Clarification?
> > 
> > Doug said:
> > 
> > "There is at least one documented incident where ceramic media was used in a
> > ball mill (milling BP), that ball mill exploded.  It has been reported on
> > both the PML and the r-BP lists."
> > 
> > Dave Sleeter asks:
> > 
> > When Doug says that "ceramic media" caused an explosion in a BP mill, what
> > was this ceramic media made of? "Ceramic" is a generic term, and there are
> > MANY kinds of ceramic. For example, if the media that caused the explosion
> > was made of regular porcelain, that would be dangerous. But the media that I
> > get from Coors is NOT porcelain, and I'm not even sure it would qualify as a
> > true "ceramic". It is 90% aluminum oxide, which has vastly different
> > properties. As a matter of fact, it's VERY HEAVY, a fact which you notice
> > the moment you pick up a handful. Did the PML and r-BP posts about this
> > explosion clarify what the media was made of? If not, someone should try to
> > find out, because that information would be important and valuable.
> > 
> > Dave Sleeter
> > 
> > 
> > 
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