***Ball Mill Explosion!***

[LambentPyro]

Bob, if I'm not mistaken, Steve Young adds Arsenic into his media too, can that make a difference?

[Bobosan]

Bob, if I'm not mistaken, Steve Young adds Arsenic into his media too, can that make a difference?

Maybe bump the hardness up, arsenic shows 3.5 on the scale. I'm not a metallurgist so have no idea if alloying lead+tin+antimony and arsenic drives the hardness beyond 3.5 on the Moh's scale. Below is a link and excerpt from a boollit casting website.

 

http://www.lasc.us/CastBulletAlloy.htm

 

Arsenic (As) Melting point, 1,503^o F. Arsenic is a catalyst to heat treating Pb/Sb alloys and only a trace is required (¼ to ½ of 1%), adding more than this will do nothing to further harden the alloy. Arsenic in itself does little to harden the alloy; its value is as a catalyst in heat treating (or quenching from the mould) lead/antimony alloys. Arsenic is of coarse very toxic but at the percentage in and temperature of bullet alloys the risk is nearly non-existent. However, the bullet caster should never attempt to alloy elemental arsenic into his alloy (if he could even get it). ^[9]At the temperatures required arsenic sublimes, that is, it transforms directly from the solid to a gaseous state, emitting highly toxic smoke. Leave this to the experts. In addition to arsenic subliming other forms of extremely toxic gases, such arsine are formed and this should be left to the professionals. Wheel weights, chilled shot and magnum shot are excellent sources of arsenical alloys for the bullet caster to enrich his alloy for quenching or heat treating. ^[10]Arsenic in combination with antimony, improves the strength. In the as cast condition arsenic raises the hardness about 1 or 2 BHN. Arsenic’s true value is in heat treating lead/antimony alloys. With a trace of arsenic a much higher BHN can be achieved while using a much smaller percentage of very brittle antimony.

 

edit - a not so good Moh's to Brinell conversion chart - http://www.cidraprecisionservices.com/mohs-conversion.html

Edited July 18, 2014 by Bobosan

[Bobosan]

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?

 

Brass and brass alloyed tools used to be the norm for use around combustible/explosive environments. Don't know if this is the case nowadays.

 

See post #90 above.

 

From a recent post by Lloyd Sponenburgh on Fireworking;

 

Or the glass itself emitting heat. It's not very elastic.

In credit to your experiments, black powder is not very impact sensitive.

For what it's worth, I just tried your experiment with a 1.5oz modeler's plain steel ball pein hammer.

I tried it "steel on steel". Nothing. It didn't even disturb the pile of powder, except to make a hole in it the size of the tip of the hammer.

Then I tried it on polished granite. I did not get an explosion, but I got a TINY puff of smoke and the distinct sulfurous odor of combustion. But no visible flash, no catching of the other powder -- although it did "clear a space" around the impact point about 1" in diameter.

LLoyd

[dagabu]

Maybe bump the hardness up, arsenic shows 3.5 on the scale. I'm not a metallurgist so have no idea if alloying lead+tin+antimony and arsenic drives the hardness beyond 3.5 on the Moh's scale. Below is a link and excerpt from a boollit casting website.

 

http://www.lasc.us/CastBulletAlloy.htm

 

Arsenic (As) Melting point, 1,503^o F. Arsenic is a catalyst to heat treating Pb/Sb alloys and only a trace is required (¼ to ½ of 1%), adding more than this will do nothing to further harden the alloy. Arsenic in itself does little to harden the alloy; its value is as a catalyst in heat treating (or quenching from the mould) lead/antimony alloys. Arsenic is of coarse very toxic but at the percentage in and temperature of bullet alloys the risk is nearly non-existent. However, the bullet caster should never attempt to alloy elemental arsenic into his alloy (if he could even get it). ^[9]At the temperatures required arsenic sublimes, that is, it transforms directly from the solid to a gaseous state, emitting highly toxic smoke. Leave this to the experts. In addition to arsenic subliming other forms of extremely toxic gases, such arsine are formed and this should be left to the professionals. Wheel weights, chilled shot and magnum shot are excellent sources of arsenical alloys for the bullet caster to enrich his alloy for quenching or heat treating. ^[10]Arsenic in combination with antimony, improves the strength. In the as cast condition arsenic raises the hardness about 1 or 2 BHN. Arsenic’s true value is in heat treating lead/antimony alloys. With a trace of arsenic a much higher BHN can be achieved while using a much smaller percentage of very brittle antimony.

 

Wheel weights contain about 1% Arsenic, there is also a small amount of Antimony (unknown) that make the lead cast from them ideal to quench harden. I was able to shoot gas checked .223 lead cast bullets at 2000fps.

[MrB]

There should be "real" scientific data on drop, or hammer-tests with BP. Not that i know how to find em, or where to look, but...

B!

[Mumbles]

Mohs isn't a very good scale for measuring metals, especially lead. The pdf Bobosan linked to lists lead at a mohs rating 1.5. For all intents and purposes, any alloying or hardening won't really change that value since Mohs isn't at all linear.

 

Here's a nice table of various lead alloys and their Brinnell hardness. I've seen Steve state that his hardened media is over 30 BHN. Even at 40 BHN, it is still two orders of magnitude softer than glass which is around 1500. Brass is somewhere between 120-200 BHN.

 

http://pnjresources.com/Hardness%20of%20Lead%20Alloys.htm

[Bobosan]

Mohs isn't a very good scale for measuring metals, especially lead. The pdf Bobosan linked to lists lead at a mohs rating 1.5. For all intents and purposes, any alloying or hardening won't really change that value since Mohs isn't at all linear.

 

Here's a nice table of various lead alloys and their Brinnell hardness. I've seen Steve state that his hardened media is over 30 BHN. Even at 40 BHN, it is still two orders of magnitude softer than glass which is around 1500. Brass is somewhere between 120-200 BHN.

 

http://pnjresources.com/Hardness%20of%20Lead%20Alloys.htm

 

Thanks Mumbles. A similar chart is on the arsenic linked page.

 

"Even at 40 BHN, it is still two orders of magnitude softer than glass which is around 1500."

 

That's the key point and why lead is the recommended media.

[MrB]

All this talk about hardness, and nobody has pointed at the pink elephant in the room. Ceramic media. I believe it's harder then glass?

B!

[oldspark]

All this talk about hardness, and nobody has pointed at the pink elephant in the room. Ceramic media. I believe it's harder then glass?

B!

Might not come into play if you are not shaking the jar.

[MrB]

I would hope not, thats just bad practice anyway. But it still makes you wonder. Could the pink elephant be an issue?

 

After all, ceramics are considered a "safe" media, just as safe as lead. But at this point it isn't really the media sparking or not thats the issue, it's media, on media contact, when shaking it.

B!

[gun410]

that is so horrible that gave me second thoughts about using one

[dagabu]

There are risks indeed!

 

IMG_1103.jpgIMG_8058.jpgIMG_5889.jpgIMG_5876.jpg

[oldspark]

Being aware of the risks is the key to avoiding these types of accidents, BB would have more then likely been fine if he followed safety rules we should all adhere to.

I'm almost 63 and have done my fair share of stupid things in my life but have been lucky for the most part.

[LambentPyro]

Just to publicize it since this is a trending topic on all forum websites and is being viewed quite often. How about an experienced member (esp. Dag, BB, and Mumbles who have went through the unfortunate tradegies and are very experienced) post a new separate thread topic on all of the vital PPE that one should wear while emptying a ball mill specifically. I think it would help many beginners and intermediates including myself. I would like to have a bit of confidence in my protection next time I empty a mill, especially considering I have a larger jar than the HF one and it's PVC.

 

I know Mike (MWJ here on APC) wears his full firefighting gear when he empties his mill, but I don't have $3,000 to spend and unfortunate enough I am not a fireman.

 

It seems that BP is the current culprit for Pyro Manufacturing (probably E-Match as the cause of accidents for display setups/transportation). It's great and all that we have loud and clear precautions for sensitive mixtures like Flash and Chlorate/Sulfur, but I think we should advocate very clearly the precautions for something simply that building fireworks can't be without, Black Powder.

Edited July 19, 2014 by LambentPyro

[Towskister]

How about an experienced member (esp. Dag, BB, and Mumbles who have went through the unfortunate tradegies and are very experienced) post a new separate thread topic on all of the vital PPE that one should wear while emptying a ball mill specifically. I think it would help many beginners and intermediates including myself. I would like to have a bit of confidence in my protection next time I empty a mill, especially considering I have a larger jar than the HF one and it's PVC.

 

Agreed, I have been looking for suggested protection and only recently found some good info on Dags page (sorry to hear about your misfortune, and am glad you are here to advocate PPE, Hang in there.)

[oldspark]

Well you could start by listing what YOU wear

Mine

FR rated pants and long sleeve shirt

Good pair of gloves

Respirator

Face shield

[oldspark]

Plus I recommend buy Lloyd's book as it covers ball milling safely.

http://www.amazon.com/Milling-Theory-Practice-Amateur-Pyrotechnician/dp/B00229ZI7W

[dagabu]

I'll wrap my recommendation in one sentence. Whatever you will consistently wear is what you should get.

[hindsight]

I'll wrap my recommendation in one sentence. Whatever you will consistently wear is what you should get.

Agreed. And what you should wear, you should get accustomed to wearing.

[carbonhalo]

I too wish BB a speedy recovery.

Thanks for this post. It has been an eyeopener. I am currently using glass marbles for milling charcoal, a practise I may discontinue in the offchance the charcoal jar somehow ends up with some BP in it. I had not considered the possibility of friction in screw threads, and will adopt a rubber cap/band on the BP jar as soon as possible. I will also invest in a face shield as opposed to just the glasses I currently use.

[Arthur]

Somebody please do the cost breakdown of a full set of PPE vs a month in a US hospital with consequent loss of income during during a home recovery time. I suspect there is a difference!!!!

 

Remember that with the www the knowledge of home pyro spreads to all, but being safe has only occurred to very few.

 

I managed to buy a pair of nomex jeans and a nomex shirt for a small fortune (£150 (USD 200ish)) but that much money wouldn't pay for the ambulance to the hospital, so they were a good investment. Full face and hands still to come in nomex but heavy leather suits so far

[Sparx88]

With all the dangerous things we have to go through to support our hobby, I'm surprised this doesn't happen more than it does. We just don't hear about them all. I don't want anyone to think that 2 down in 14 months is'nt that bad. If that was all there was, world wide, it would be a miracle. Let's not forget all the accidents that happen that stay on the down low because let's face it...the embarrassment, keeps most of them quiet. It's a scarey thing, you can't control it when it happens and we damn sure can't stop it but we can be as safe as we can and hope for the best. And with all the information we have at our fingertips, it should be a no brainer for anyone attempting to get into this to seek safety first. But don't let all that safety knowledge fool any of us, it don't matter who you are or what you know, or what you can do , this stuff has no consience or preference on who it will hurt or kill. Not like that's any big news for some I'm sure but for those who take this lightly please pay attention to the safety advice so we all can legaly enjoy this hobby to our graves.

 

Sorry that happened to you BB. Nerve damage is nothing light weight, just get well soon ok.

[BurritoBandito]

Thank you Sparks88. Aurthor, trust me, it is VERY expensive. The medical bills are outlandish, and even though I am collecting short term disability I have lost a substantial amount of my income (~40%). The whole experience has cost me an arm and a leg... and a pinky. PPE may not be cheap, but it is worth every penny.

[hindsight]

And if pain and suffering costs anything near what U.S. courts reportedly award for it, one could buy a 100,000 sets of PPE before you reached that cost. But, seriousy, the cost of the anguish is unmeasurable, so is the cost of PPE too high? What is your vision worth, and how much would a blind person give to have it back?
Recently I realized the old military aviator gloves are not only very dexterous, but have a Nomex backing with leather palms. Looking online for Soviet-era (or U.S.) military surplus they are less than 30USD.
In addition I continue to wear the full face respirator that has a polycarbonate face shield, ear plugs (muffs if firing), and cotton clothing.
I will admit, the heat of wearing long-sleeve thick cotton clothing in addition to the above is not feasible for an old man when the thermometer climbs, between the distraction/fatigue of the heat and sweat in the eyes as risk factors. So forearms may be sacrified to the gods of pyrotechnica should anything happen during the time of year when ESD is the least, except when behind a blast shield. The risk is reduced a bit by using smaller quantities , the least possible energetic compounds and following what the experienced individuals here advise.
Again, the safest thing is to find another hobby. Wish everone here well with that.

[oldspark]

"Again, the safest thing is to find another hobby. Wish everone here well with that."

I think about that a lot especially as I age, don't heal like I use too and not wanting to spend retirement crippled.