***Ball Mill Explosion!***

[mkn]

Hi All,

 

BB- prayers are with you for a speedy recovery!

 

Thank you all for discussing and exploring this issue, as a newbie, BB and Dagabu 's incident's have me concerned, and rethinking my steps. It is good to read and think about the various possibilities for an issue.

 

I started to think about the actual components being milled

 

This weekend I was crushing charcoal, making BP , and started to think of the potential areas for contamination, sand or foreign matter on the 4 x4 rammer, in the bucket, maybe on the wood that was coaled, tree bark is well known to have debris contamination, we're not supposed to have much bark in our coal, but a little can happen. If your in a dusty area with wind, air born debris. Sand can have materials that are magnetically attracted, metals, irons and such. Run a magnet thru sand sometime, lots of stuff sticks to it.

 

Contamination of KNO3 is also an issue, I have found various small unknown particles left after screening coffee milled , and ball milled KNO3, this KNO3 was supposed to 99+% pure and probably is because only a few small particles are found, but what are they? could be a problem making BP.

 

Sulfur, I don't know, have not screened much of it by it's self.

 

Static does concern me, I though about making one of the PVC mill containers, but the static properties of PVC is keeping me from doing that, I guess I'll stay with my small rubber container , but that does have a hard plastic lid......

 

 

 

I recently questioned my hand ramming of FeTi and Ti in my rocket delay comps. Seems there is potential there for impact/ spark/ friction related accidents. Relating that to ball milling, impact sure seems possible with an dusty airborne BP comp floating around in the mill container if hard mill material is used. (Similar to any grain or wood sawdust environment, in a plié they extinguish matches or ignition sources. But get them floating in air and extremely explosive situation is created.

 

 

Anyway, I am probably restating information, but thought I would point out the potential contamination areas in the components themselves, as they are always present and changing in each new lot, or batch of component.

 

Matt

[pyroman2498]

I wish you a speedy recovery BB, you said that you used the flower grade sulfur stuff , I heard it's acidic and was wondering if that would increase the sensitivity of the BP , that's just theory and has no proof to back it up.

[BurritoBandito]

Pyroman2498, thank you. I suppose that is plausible, but have no data to confirm or deny it. Someone like Mumbles would know much more than I would about H2SO4 sensitizing BP. I don't think it's regarded as an issue for BP though. Anyone have any feedback here?

[MrB]

With the amount of charcoal in our PB, i don't really think H2SO4 is a problem. es it's an acid, but it gets absorbed in to such a large volume that it shouldn't really do any harm here. But thats just "my logic" wenting, got nothing to found it on.

B!

[Mumbles]

Acid shouldn't really do much to BP. In any case, even the best charcoals have 5-6% ash in them, which is basic and would neutralize the acid right away.

[oldspark]

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.

Well I will go back to fireworking and look but I don't remember any questions not being addressed, I know there were a few posts were some people had missed the information in the thread. What basic questions are you referring to?

[Bobosan]

Can you point out which post had the type and supplier of the BP components? We're just trying to eliminate or prove possible reasons for BB's accident and I guess I missed the post about component sources.

 

If you haven't experienced it yet, making your own charcoal has it's own set of precautions.

[oldspark]

Not sure how that could have been answered over on fireworking with out BB being a member.

I thought you were talking about questions that were able to be answered in the scope of the thread.

[LambentPyro]

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".

This raised a question or two in my head BB.

 

I find a couple things with the charcoal materials to be questionable. I've noticed that 2x4's and other stud lumber have staples on the ends of the pieces of wood and sometimes are dug in a small length inside. I always cut 5" of wood off the ends with a table saw to eliminate any metal possibilities.

 

I use Home Depot's whitewood 2x3's (not 2x4's) for my MCRH and it produces extremely hot powder when the charcoal is fully cooked. So that's why I am asking if maybe a staple from the 2x4 could've fallen into your charcoal or if there are any metal bits that could've came off because of the rough ends of the wood that can possibly trap the metal particles as it's being transported and moved around.

 

I know it may seem insignificant to some, but this is the question that can be slipping through our minds because it seems so unlikely, but we have to put ourselves into a Forensic aspect. They look at every single piece of physical evidence that's present, and that's essentially what we are trying to do, investigate.

 

Now, another question, you used a 5 gallon bucket, is it possible that the steel could've chipped off the bucket or somehow contaminated your charcoal? I know that my retort always gets very ashy from the resin that they coated it with when I cook my charcoal. Even after I burned all of it off and have used the retort over 20 times. There is always this pink or some oddly colored resin on the steel or ash building up on the inside of the lid or even on the outside of the retort. Maybe the slightest bit of metal could've came off. Even if it's galvanized, because I think some Zinc can fall into the charcoal as well. Maybe not to others, but to me it's worth to keep in mind.

 

I try to be aware of all the possibilities of something going wrong, just keeps my defense up. Kind of like defensive driving, pretend like someone is always trying to hit you.

 

Dylan

Edited July 16, 2014 by LambentPyro

[oldspark]

^{So some of you are not buying the impact being the cause, having metal in your charcoal would be all bad but I personally am not going to make charcoal out of crappy wood that is going to have any metal in it, not sure what BB made his out of but I like to give him some credit.}

^{Having foreign materials in your chems. is a whole other can of worms.}

[Bobosan]

^{So some of you are not buying the impact being the cause, having metal in your charcoal would be all bad but I personally am not going to make charcoal out of crappy wood that is going to have any metal in it, not sure what BB made his out of but I like to give him some credit.}

^{Having foreign materials in your chems. is a whole other can of worms.}

 

We're still gathering info, oldspark but yes, impact looks to be the most likely culprit here. No one deliberately uses crappy wood either but small metal particles can slip by an initial screening process. "What if" a small granule of metal was caught between those banging glass marbles? Many people use larger chunks of charcoal in their mill and that can hide a variety of things. I found a small piece of fence wire in one of the lumps of Cowboy brand hardwood charcoal while milling it down.

 

No one is discrediting BB and he readily admits to errors that are known to him. For those who cook and mill their own charcoal, it is a simple task to pass a magnet through the screened or airfloat charcoal.

[LambentPyro]

I'm not saying that impact wasn't the cause, but again, look at all possible causes and then take an approach to form your opinion on the culprit.

 

Maybe someone could explain it to me, but if impact is the cause, how come we don't lose our limbs when we ram BP rocket motors? I would think that more impact is generated by that than shaking a mill around.

[DavidF]

I can't help but wonder about the significance of the jar having been opened and re-closed moments before the ignition. It would be great to just blame the marbles and be done with it. But what about pyrophoricity? Burrito Bandito got away with this lots of times, which is not to say it was a good idea. But it seems like a big coincidence that moments after it was opened, it ignited. I'm not ignoring the shaking. Just adding another factor for consideration.

 

And with this new information, maybe static could be a factor. I'm not saying it is. But the (closed) environment was changed moments before the accident. This new information needs careful consideration too IMHO.

 

Also, BB said the powder was caked. It didn't sound to me like he meant clumped into a solid mass. So the marbles DID bang together, is that right BB?

[nater]

Lambent, read Lloyd's posts on Fireworking. The surface area of impact is much, much smaller when 2 spheres collide. Glass is hard and does not deform like lead does on a molecular level. This could create enough pressure on a tiny ammount of BP to ignite it. His theory is the velocity of the cascading marbles is not sufficent to cause ignition, but shaking them could have.

[Bobosan]

I'm not saying that impact wasn't the cause, but again, look at all possible causes and then take an approach to form your opinion on the culprit.

 

Maybe someone could explain it to me, but if impact is the cause, how come we don't lose our limbs when we ram BP rocket motors? I would think that more impact is generated by that than shaking a mill around.

 

Lambent,

 

There's a reason to make sure we have BP well are over the top of the spindle before using that flat rammer. You pinch the BP between a rammer and small spindle top and it could be the same result as two marbles hitting each other with BP caught between. Normally, the force or pressure on the rammer is spread over a much greater area than the two point of a spindle top and rammer face.

Edited July 16, 2014 by Bobosan

[BurritoBandito]

Okay. So the 2x4 was a piece that was left as scrap after I built my chicken coop. It had been cut on both sides, so I doubt there was a staple or anything like that, but it's plausible.

 

The five gallon bucket is just what I broke the charcoal up in, and was made from plastic.

 

The "retort" was just an empty paint style can.

 

When I say caked, I mean lots of powder was stuck to the walls of the jar.

[Shadowcat1969]

BB, there is some debate over at Fireworking over: "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."

 

Does this mean you removed some powder, tested it, then returned left over powder to the jar? Or (my read) you tested a portion of the powder, and when it was unsatisfactory you returned the JAR to the mill, without placing anything new in the jar?

[Maserface]

If anything would sensitize it, I would bet on foreign ferrous oxides, but impact still seems the cause, as it was being shaken when it went up

[Paravani]

If anything would sensitize it, I would bet on foreign ferrous oxides, but impact still seems the cause, as it was being shaken when it went up

 

Yes, MF, I agree. I've been reading all of the posts on this thread and others, and Burrito has been extremely generous with information about the accident. Like everyone else here, I'm very happy that he lived to tell about it.

 

The glass marbles do seem to be the culprit, as BP is known to explode on impact (why it is used in bullets) and to become more sensitive the longer it is milled, and glass doesn't "give" the way that lead does.

 

(For that same reason, I would hesitate to use even brass as milling media. Myself, I'm staying with lead, only lead.)

 

While a spark due to steel inside the jar is possible, it seems unlikely, considering how much Burrito had already handled and inspected the powder before the accident. And since the jar was closed, no outside source of electricity could have affected its contents (basic physics -- charge stays on outside).

 

I think the general consensus wrt this accident is, "Always handle your BP gently; always mill it with lead, only lead; and always, always, ALWAYS wear your PPE!"

 

-- Paravani

Edited July 17, 2014 by Paravani

[Peret]

I don't believe static can be ruled out. I just posted on Fireworking.com that "flowers of sulfur" is a different allotrope from "roll sulfur", which is milled from a cast pig. According to one authority (Wardell, available in the files section here), flowers of sulfur is electro-positive and regular sulfur is electro-negative, and that's a key observation. Given the date of the article, before electrochemistry was properly understood, it can only mean that flowers of sulfur generates a positive electrostatic charge when rubbed and regular sulfur a negative charge. Glass, on the other hand, always generates a negative charge.

 

Bear in mind also that all electrostatic generators are "closed systems", including a van de Graaff generator, a Wimshurst machine, or you rubbing a glass rod with a piece of fur. A closed system is only proof against electrostatic from outside, not what it generates itself. All that's necessary is some friction to separate positive and negative charges, some surfaces for them to collect on, and some form of insulation to keep them apart. Since the powder was packed into lumps I can envision a situation where the sulfur particles picked up a positive charge and were packed into the lumps against the rubber wall of the barrel, making it in effect one plate of a charged capacitor, the other being the interior of the mill, everything there having a negative charge with respect to the sulfur. Note that a capacitor doesn't need metal plates - the charge is stored in the insulating dielectric. When the barrel was tapped the lumps broke away from the rubber wall, allowing the static to discharge possibly with a spark.

 

So the problem may have been the different electrostatic properties of the glass balls and the type of sulfur used. It's just a hypothesis, but I wouldn't rule it out. Incidentally, Wardell says flowers of sulfur makes poor gunpowder.

[BurritoBandito]

BB, there is some debate over at Fireworking over: "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."

 

Does this mean you removed some powder, tested it, then returned left over powder to the jar? Or (my read) you tested a portion of the powder, and when it was unsatisfactory you returned the JAR to the mill, without placing anything new in the jar?

Yes, you are correct, I meant the jar. I mistyped when I wrote mill.

[LambentPyro]

Lambent, read Lloyd's posts on Fireworking. The surface area of impact is much, much smaller when 2 spheres collide. Glass is hard and does not deform like lead does on a molecular level. This could create enough pressure on a tiny ammount of BP to ignite it. His theory is the velocity of the cascading marbles is not sufficent to cause ignition, but shaking them could have.

I had been reading them, but I got lost. I understand things visually better than just words. Diagrams and visual aids are the most helpful. But since you dumb'd it down right here, makes it easier to understand.

 

So, can hardened Lead do the same thing as glass did? I'm using a PVC jar made by Hobfir.

 

Lambent,

 

There's a reason to make sure we have BP well are over the top of the spindle before using that flat rammer. You pinch the BP between a rammer and small spindle top and it could be the same result as two marbles hitting each other with BP caught between. Normally, the force or pressure on the rammer is spread over a much greater area than the two point of a spindle top and rammer face.

Ahh okay, that's what making the switch rammer marks does for safety. I've heard that before, it pinching the BP, never understood what that meant though.

[Bobosan]

So, can hardened Lead do the same thing as glass did? I'm using a PVC jar made by Hobfir.

 

Nater mentioned that lead is much softer than glass and will "give" when hitting another lead ball. Take a look at page two of the link below and you can see the differences between the lead and glass hardness. At most, the lead would only reach a 3.0 on the Moh's scale if alloyed with tin and antimony.

 

http://www.sedonagemandmineral.org/resources/Updated_Mohs_Scale.pdf

[oldspark]

"It was not the flowers of sulfur that I think is important, but I'll admit that it caught my eye on first reading. I cannot be certain that the product he had was pure, but it probably was.

Modern flowers of sulfur are made from approximately the same quality of sulfur as the "sulfur flour" we use in pyro.

It is not the highly acid stuff of past years, where it was collected from sublimation and condensation apparatus (lately), and originally from fumaroles and other volcanic features, in its native, high-acid state.

It's not the stump-remover, either."

 

From Lloyd on Fireworking.

[taiwanluthiers]

It begs the question, are brass media safe enough? It's pretty hard, certainly harder than even hard lead but is it possible for brass to spark hitting each other?

 

I never expected bp to go off from impact, I mean people ram them all the time without any ill effects.

 

Has anyone done sensitivity tests with bp to determine what amount of impact will cause it to go off?