***Ball Mill Explosion!***

[BurritoBandito]

Seymour, thank you, but please take no pity for me. I am man enough to accept responsibility for my own actions, and happy enough to have came out in as good of shape as I did. Dag absolutely deserves a pat on the back. He gave me some exceptional advice AND initiated this thread for me. Seeing his strength through everything he has suffered (way more than what I experienced) has been inspiring. Thank you Dag.

[DontTreadOnMe76]

I am sorry to hear about your explosion, but happy to know that you are okay. I am curious how this occurred though, can you walk us through the things you did leading up to the bang? Was your jar closed? Also, what do you personally think caused the ignition, static, friction or impact?

[MrB]

I am sorry to hear about your explosion, but happy to know that you are okay. I am curious how this occurred though, can you walk us through the things you did leading up to the bang? Was your jar closed? Also, what do you personally think caused the ignition, static, friction or impact?

I'm pretty sure that info is around in this thread somewhere,hold on...

 

BB was using glass marbles as his grinding media and a Harbor Freight rock tumbler rubber jar with the aluminum cap. When the jar became caked, he shook the jar to dislodge the caked BP and the jar exploded in his hands. I am sure there are other injuries and I am sure he is still very much in shock but he wanted me to share this with all of you as soon as i was able to implore you all to NEVER use glass marbles for media, to never shake or hit your jars and to always wear your PPE!

 

BB was just in a t-shirt and pants, no gloves, face mask, etc. He feels that the outcome of his hand may have been very different if he had worn the gloves.

 

First post. Pretty much covers it.

B!

[alpinecb]

First, I'd like to say "Godspeed BB" in your recovery. Do any of you guys see a problem with using a combination of some lead and some brass 1" cast ball media in a 8" sch 80 pvc mill jar? Also, one end of my jar is a threaded pvc cleanout. Now I worry about friction in the threads on opening it. BP always gets in the threads while milling my 1 kilo batches.

 

Charles

[MrB]

I wouldn't mix media, mostly since i have a feeling different hardness will cause excessive wear. Don't really see any problem with it from a safety point of view.

 

BP in threads... Thats something else.It's not going to be a problem a few thousand times. The last time of those, it's a PVC pipebomb. You cant replace the treaded bits with a reduction, and a rubber / plastic cap? I'm thinking like this:

 

http://www.skylighter.com/images/newsletter/91/skylighters-gallon-ball-mill.jpg

Image stolen from skylighter.

 

Yes... I have no shame. Skylighter is a good source of basic information.

B!

[alpinecb]

Thanks! I think I will figure out a way to get rid of those threads. I don't really want to empty the jar at this point, but will wearing full PPE (personal protection equipment). I already have my 1" lead and 1" brass media, so will continue to use it unless someone thinks otherwise.

 

Charles

[dagabu]

Unloading the ball mill has its hazards for sure! No need to add to the hazards by having threads. Just use a cap and band to cut down the friction.

[DavidF]

Burrito Bandito, I am sorry to hear of your accident- but happy that you fared better than some others have. I am also grateful that you have shared some details through Dagabu here and on Fireworking.com. We were having a pretty lively discussion about it, but folks seem to be separating into different 'knowledge' camps and conversation has stalled.

 

I think you have a lot more you could tell us. If I may be so bold as to ask a few more questions, maybe we could get folks back to discussing the dangers of ball-milling in a productive way again. I don't ask questions to defend a theory. I ask them to try to understand this accident better- for myself and others.

 

If you could tell us more things like if the mill was still running when you shook the jar, that would be great. What do you (or Dagabu) mean by shaking? Myself, I'd be inclined to bap the thing on the table if it was a big clump (if it wasn't BP). Is there any possibility that any powder could have leaked from the jar while it was being shaken, or even before that? Did you open it before the accident and SEE the clumping, or did you just feel/hear that the marbles weren't moving? Were they the normal size marbles or the large ones? I could go on and on but I hope you can see that more detail could be extremely helpful, and could help discourage excessive conjecture.

 

I would hate to see valuable discussion cease due to lack of information and possibly a ruffled feather or two. Would you please go that one step further and give us a bit more? In your words? Thank you for sharing thus far.

 

Dave F.

[BurritoBandito]

DavidF,

 

1) Yes the mill was running, but the jar was not on it (it was in my hands).

2) There were around 50 normal sized marbles. Not the shooters, just the little ones.

3) I doubt if powder leaked out of the jar, but I dont believe that was the issue. I was outdoors with no ignition source anywhere near my working area, except possibly the motor to my mill, which was 4 or 5 feet away and no large flame was observed.

4) I had opened the mill and tested a small amount of the BP. I was not satisfied, so decided to return it to the mill. As usual, I gave the jar a moderate shake to help decake the powder.

5) When I say shake, I mean it quite literally. I held it in my hands and gave it a few good shakes before it exploded.

 

If you have any more questions feel free to ask. That's what this thread is for.

[DavidF]

Thank you very much Burrito Bandito. It's nice to have as many pieces of the puzzle as possible to help rule things out and to be more confident in what we 'think' happened. I wish you well in your recovery.

Dave F.

[Bobosan]

DavidF,

 

1) Yes the mill was running, but the jar was not on it (it was in my hands).

2) There were around 50 normal sized marbles. Not the shooters, just the little ones.

3) I doubt if powder leaked out of the jar, but I dont believe that was the issue. I was outdoors with no ignition source anywhere near my working area, except possibly the motor to my mill, which was 4 or 5 feet away and no large flame was observed.

4) I had opened the mill and tested a small amount of the BP. I was not satisfied, so decided to return it to the mill. As usual, I gave the jar a moderate shake to help decake the powder.

5) When I say shake, I mean it quite literally. I held it in my hands and gave it a few good shakes before it exploded.

 

If you have any more questions feel free to ask. That's what this thread is for.

 

BB,

 

Number 4 raised a couple of questions and thoughts.

 

When you say tested, do you mean a burn test?

"I was not satisfied so decided to return it to the mill". - Had you previously emptied the entire jar thinking it was completed? When you said "return it to the mill", do you mean the jar to the mill or just the small quantity removed from jar for testing? Was the jar covered during your testing?

 

I'm thinking somewhere during that testing phase where you removed some amount of BP for testing, something may have been unknowingly introduced to the jar.

[Fireproofpyrotech]

Glad to hear you're recovering, and will keep you and your family in prayer.

[DavidF]

I also wonder how many grams of BP in the batch? How many hours milling? How many times marbles did not cause a problem? Not to defend marbles, just curious. Was an ammonia smell noticed? I have smelled it when milling just KNO3 in those rubber jars, way back. It is so rare that somebody can give an eye witness account, BB. Sorry to seem ghoulish with all the questions. The longer something like this is talked about the more potential benefit, I figure. Thanks for the candor.

[BurritoBandito]

1) Yes it was a burn test.

2) No I did not empty the jar.

3) I mean the whole batch.

4) Yes the lid was on the jar.

5) The batch was around 200 grams.

6) 8 hours?

7) Lots of times. More than I could count.

8) No ammonia smell was present.

 

FWIW, I don't think anything was introduced into the jar. The lid was only off long enough for me to scoop a small amount out for the burn test. I can not say for a fact, but I really doubt it.

[Bobosan]

1) Yes it was a burn test.

2) No I did not empty the jar.

3) I mean the whole batch.

4) Yes the lid was on the jar.

5) The batch was around 200 grams.

6) 8 hours?

7) Lots of times. More than I could count.

8) No ammonia smell was present.

 

FWIW, I don't think anything was introduced into the jar. The lid was only off long enough for me to scoop a small amount out for the burn test. I can not say for a fact, but I really doubt it.

 

Ok, will discount thinking something was introduced during testing. Couple more ??'s

 

Mill jar unusually warm after 8 hour mill run?

Source vendor of components? ie. C-S-KN03?

 

The last question asked because I have found foreign material in store bought lump hardwood charcoal.

 

Thanks BB.

[oldspark]

This has been discussed to death on fireworking with Lloyd doing a ton of math and the smart money is on the impact with the jar being shaken, the force on the small area of the marble can be considerable.

[Bobosan]

This has been discussed to death on fireworking with Lloyd doing a ton of math and the smart money is on the impact with the jar being shaken, the force on the small area of the marble can be considerable.

 

Yep, it has but not everyone on APC is a member of Fireworking and I haven't seen these questions being asked over there. If we can eliminate all possible problem areas, that leaves the impact theory that much more valid.

[BurritoBandito]

I am not a member of fireworking, and would like to know more about what is being discussed. If anyone cares to share the info posted there I'd appreciate it. Thanks.

 

1) No, the mill didn't seem abnormally hot.

2) The KNO3 was "Hi Yeild Stump Remover". Charcoal was cooked by myself using the TLUD method, and was crused with a 2x4 in a 5 gallon bucket, then screened through a window screen. The sulfur was "Flowers of Sulfur".

Edited July 16, 2014 by BurritoBandito

[Bobosan]

I am not a member of fireworking, and would like to know more about what is being discussed. If anyone cares to share the info posted there I'd appreciate it. Thanks.

 

1) No, the mill didn't seem abnormally hot.

2) The KNO3 was "Hi Yeild Stump Remover". Charcoal was cooked by myself using the TLUD method, and was crused with a 2x4 in a 5 gallon bucket, then screened through a window screen. The sulfur was "Flowers of Sulfur".

 

To quickly summarize the discussion on Fireworking, Dagabu initially posted the identical post at top of this thread. There are now 179 posts on the Fireworking thread. From the initial post, discussion led to two possible cause scenarios, one being static and the other impact. Lloyd has discounted the static theory by using basic charge flow properties and put forth the impact theory based on math calculations that indicate the impact of the glass marbles against each other created a large enough force to cause ignition.

 

Just curious, do you run a magnet through your charcoal after crushing?

 

I have found pieces of metal in my own cooked charcoal as well as store bought hardwood charcoals. Trees have a habit of absorbing wire as they grow along a fence line. Have even found a lead slug in one batch of Paulownia, no jacket just the lead.

Edited July 16, 2014 by Bobosan

[oldspark]

BB, due to the nature of the accident I assume I can give you any info you want but Bobosan gave a good overview of what the thread on fireworking covered. I thought maybe someone had given you an update via a PM or email.

A lot of math went into what Lloyd came up with.

Sorry for you not getting the nitty gritty on the details from fireworking.

Let me know what exactly you want for info and I will see if I can help.

[BurritoBandito]

Bobosan, no, I did not run a magnet over the coal prior to milling. Wouldn't have been a bad idea though. Thanks for the info about fireworking. OldSpark, that's what I get for not paying for a membership . I was just curious about the theories floating around.

[DavidF]

The problem with the discussion of Fireworking is that the entire thread was based only on the extremely basic information contained in the first post by Dagabu. Many folks were comfortable coming to conclusions without seeking any additional information. That's why I took a hop skip and a jump over here to ask some questions myself. If anybody feels that it is not important to have all the information, it is likely they have already come to a conclusion and don't want any new information to mess with that. But if we are in an earnest quest for the truth we should consider all the facts.

Again I thank Burrito Bandito for his candor, and Dagabu for initiating discussion. I'd sure like to see BB's additional details added to the thread on Fireworking.com and would be willing to add them myself if nobody else wants to do it. But I would like to know that it is OK first.

 

The thing that stands out in my mind about the discussion over there is that Lloyd, the guy that wrote the ball-milling book, made factual points backed up by science, and some folks found that exasperating. The folks that believe static was the cause were not individually or collectively able to make a case that refuted anything Lloyd said. And they found that frustrating. So everybody took their toys and went home. That's my personal impression only.

 

My personal interest in the whole thing is that I recently switched to using the Rebel 17 rubber-lined jars for milling 1 kilo batches with lead and brass. I have been lulled into a warm fuzzy safe feeling due to the quietness and the insulating qualities of rubber. I say this in a simple way because I am no scientist. If there was a risk of static inside the jar causing an ignition inside the jar, I would want to know about it. I'd also want to know why mills aren't blowing up left and right, if such a thing could happen. Nobody has detailed factually how that could happen in this scenario. A chart from science class was posted a few times, but I didn't see the relevance to this situation. Again, maybe I'm too simple to understand it. Or maybe the case wasn't made. I used ceramic in PVC without incident for a few years, but one day when I washed the media I saw craters in the surface of my media and never used it for BP again.

 

Dave F.

[BurritoBandito]

DavidF,

 

You're very welcome. I'm happy to offer whatever limited insight that I can, and I don't mind the details being shared anywhere. I don't believe it was static as the jar was closed tightly and rubber is a terrific insulator. There was no way for a ground to be established to accommodate ESD. I will not deny entertaining the thought at first (while medicated in my defense lol), but in retrospect, I do not see it as possible.

[Bobosan]

I also use the Thumblers barrels which are equivalent to the Rebel 17 so also interested in all data points of this accident. I lean towards the impact theory but won't ignore any information that may be pertinent. Just some of these basic questions that DavidF and myself have asked, have not been addressed on Fireworking.

[BurritoBandito]

Anyone from fireworking is free to drop by here. I'll answer any questions I can, and throw out a few assumptions of my own. If people are content assuming they know what happened that is their own per prerogative. I'd like to assess all possible scenarios personally. None of us know for sure, but right now I'd wager impact was the culprit.