Causes of ball mill accidents?

[Arthur]

Some TENS leads are pure carbon fibre, lots of conductors in ionisers etc are also carbon fibre, both are usually insulated. It's essential to use a crimp ring or sleeve because the fibre does not solder.

[Guest]

I guess the point I'm trying to get to is where there isn't any static buildup at all. Like, if there is no separation of electrons, there's no problem to dissipate in the first place, right?

 

We're trying to equalize a potential that is created from the non-conductive rollers' action against the jar, correct? Like in the Van de Graaff generator example, would an electrically conductive path, created through conductive rollers to a metal axle, through metal bearings (or other means.), then through the frame effectively 'short out' the charge separation between frame and jar?

 

okay, okay...getting lost down the rabbit hole here. Jeez, this entire site could be renamed "The Rabbit Hole". I hardly ever get the answers I came looking for, but get way more answers to questions I didn't even know I had yet. It's amazing. Anyway, I looked up this Van de Graaff scheme to refine my understanding, and learned words like triboelectric and coronal discharge (btw, I already knew that one as St. Elmo's Fire. Not to be confused with St. Anthony's Fire...)

 

1.) Would the Van de Graaff generator work if the rollers themselves, the bearings, shafts, and support tube were all electrically conductive (eg.- metal, conductive rubber), providing a conductive path from one roller to the other? I don't think any charge separation would be able to occur. Or rather, if it did, it would be shorted immediately.

 

2.) Seems like letting the charges build then trying to dissipate through some sort of em radiator, is like trying to lock the barn door after the horse has run off. When the problem could be solved simply by using conductive materials to prevent the buildup in the first place.

[Bourbon]

https://stopstatic.com/shop/

 

Why not use what paper, plastic and other mills use. Course, reinventing the wheel is fun and challenging...

Edited August 24, 2021 by Bourbon

[Guest]

Okay, Bourbon! Great stuff!

 

The website shows the string being draped across the rolls, and the string goes to ground. I assume earth ground, ultimately. That was what I was thinking about with the tens esd brush idea, having the fibers actually brush against the jar.

 

The jar is grounded to the frame by the brush, and the frame is grounded to earth through household wiring.

 

If/when I build my own mill (which will probably have a wood frame...at least the first iteration, anyway...), I can use the jar brush technique, just connect the brush to the ground wire in the power cord, right?

 

 

Still, it seems simpler to use conductive rubber rollers and ground them instead, since they rarely get removed. I don't know if that will work, though.

 

 

Shouldn't this be a standard safety modification that all newbs should know? I was shocked by what I was seeing!

Edited August 25, 2021 by Guest

[Bourbon]

I like the idea of conductive rubber rollers, along with all the bells and whistles.

 

As a 20 year Small I/C Engine & Equipment Tech, I'm also a fan of as many ground straps as possible. As you know, (amazing how many don't) having a third prong on a cord doesn't exactly mean it is grounded. For a few dollars, I recommend everyone buy a good plug tester for a positive ground presence (as odd as that sounds.) Check that the motor is "actually" grounded via wiring. For insurance, remove all paint from mating surfaces between motor and case if that be the setup. Remove paint anywhere ground straps are placed. Add as many ground straps as you might need (cheap and easy). Daisy chaining is fine, but I prefer a grounding bar. Break out the fluke and do some ohms testing. Finnish off with the brushes, or the static string mentioned above.

 

Once you pick up that jar... You're on to a whole new grounding issue. All that crap above, was just for your mill... It really never ends. Play your cards the best you can.

 

Edit in: As a side note. Not all house wiring and earth grounds are the same. HF Radio Operators deal with this all the time. They have some good detail in a few youtube vids about this "earth grounding."

Edited August 25, 2021 by Bourbon

[Guest]

I was taking apart some fiberglass tent poles to make paper tube rolling mandrels, and rammers for small rockets and saw that the "shock cord" that holds the sections together looked a lot like that ESD elastic cord. I thought 'Shock Cord?!' and wondered if that stuff was conductive. I don't think so. But while searching for information about it, I came across this stuff. Think it will work for our application? https://www.wellscroft.com/electric-bungee-rope

[Bourbon]

I didn't even know it existed till you just showed me.. I have no idea. Might be worth looking into.

[Guest]

I tested the tent pole bungee with an ohmmeter, and it is no more conductive than air.

[Guest]

EDIT: I was re-reading my post above and realized I wasn't making BP, I was milling charcoal! I always do that outside because of the dust, and just mis-remembered. I'm almost as burnt out as my retort cans lol, sorry.

 

Anyway, I just tried the ESD brush thing with the TENS pad electrode.

Results: Successful!

 

MadMat, you're a frigging genius! The brushes don't have to touch the jars at all to dissipate the static! I scraped the paint off the frame/chassis to get a good ground, stuck the electrode on, (with the insulation removed from the conductors, so they were like really long, thin paintbrush bristles) and instantly the arcing was gone. I could peel the pad back off the bare spot, and the arcing would immediately start again. Pad on metal...arcing gone. Did it about 2 dozen times just to be sure I wasn't imagining it. I will make a video sometime to show how it works, but it does work. I feel a lot safer now, and suggest that this be some sort of standard thing for everyone.

 

Word of caution- It's anecdotal evidence for sure. I don't know how effective it will remain in different environments, or in different weather conditions. More research is needed. (as always...)

[Guest]

Quick update:

 

After a season change and over 120 hours of milling, I still haven't seen the static spark again. The brush is still on, doing it's job.

I don't know what happened to the video, I will make another and repost when things slow down.

Thanks for all the great information, and stay safe everyone!

[Guest]

As promised, here's the video again. Youtube takes a lot of the quality out, sorry about that and the shaky video. I'm not the best videographer...

 

https://youtu.be/rfGMRw7IJEo

 

Please let me know if there are any problems viewing the video. This is the first video I've ever uploaded to Youtube, so it's all a learning experience for me

[Arthur]

If you want conductive rubber then you have to add "acetylene black" during the compounding, it can't be added later.

If you want conductive fronds then look for simple carbon fibre tow probably available from places that do carbon fibre panels for cars (etc) or their wholesalers, take an inch of carbon fibre tow (lots of strands!) thread it into a cable ferrule with a suitable piece of wire and crimp it

[Guest]

https://www.osha.gov/laws-regs/standardinterpretations/1987-07-18

[GoldenStars]

Hi all,

I'm digging up this old topic. I will give a quick sketch of my safety concern and what I want to do.

 

I have have recently bought 25kg potassium nitrate "for gardening purposes ofcourse", i'm not new into the scene and did pyro when I was young kid for approximate 4 years in total duration. Because I don't like to create large batches of compositions I decided not to build my own ballmill but just buy a mini rock tumbler. I think I had milled a few batches with the mill and then because circumstances I had to move from a "house" with woods in the backyard to an appartment. I did mill outside of course, and in a spot where explosion "would not be a problem". I had a long extension cord to pull before approaching the mill. I used ceramic ball media and had not problem at all. But time has passed and didn't do pyro for 10 years or so "I came across some potassium nitrate".

 

I didn't kept the ballmill and equipment and sold it (and all other stuff). So i'm thinking to buy again just the simple rock tumbler, and put it on my different appartments balcony. The balcony has sadly a lot of glass so when things go awry I will have cheese holes in my windows. I was indeed thinking as people suggested in this topic to create a explosion barrier just in case.

About the static discharging issue, my home has only electrical earth at a few places. So conducting an eventual charge to earth can be a problem. And also i'm not sure anymore if the rock tumbler is double insulated, but I think there must be an earth connection because of the metal parts it can have. I'm pretty sure the vessel is of rubber which has non-conducting electrical properties, which can be the problem part.

So what do you think, should I "risk" the pyrotechnic benefit, or "blow up my house" :-)?

The good news is that I'm only planning blackpower and blackpowder-like compositions, which are low risk.

Have a good day all.

Edited September 4, 2022 by GoldenStars

[mabuse00]

 

or "blow up my house" :-)

Is even your house...?

 

Considering the circumstances you describe, I would assume there are other tenants in this house beside you?

Then it's a little against common sense to pursue pyro at all...

 

In terms of ball milling safety, my solution is double & double component milling:

https://pyrodata.com/PyroGuide/index.php%5Etitle=Black_Powder_Manufacture.htm

 

You still have to sieve the parts together but if you do that outside in humid climate I'd say the risk is acceptable - very low.

Some years ago I compared the burn rates of the standard and the double & double processes - I found no difference (any different opinions/experiences here?)

 

 

PS:

 

imho the smaller tumblers all suck... If the setup runs well you get some 120-140g/3h. Refilling the jar every few hours makes a huge mess, every time...

Personally I like nozzleless rockets, and with these you use up a days production in no time...

I bigger mill would be much more efficient and reduces the workload significantly.

[stivec]

Hi! Im new to this and are currently in the stage of doing reaserch. I have read that using sublimated sulfur can be dangerous when ball milling, is that true? Dont want to take any risks with this.

Edited November 1, 2023 by stivec

[Arthur]

Really old sources of sulphur had minor traces of acid included, modern supplies of sulphur have come from the production of low sulphur road fuel and offer little hazard.

 

HOWEVER this is pyro, things we make can burn! SO mitigate the risks that you can and mitigate the harm that could happen when an accident does happen.

[cmjlab]

Usually you don't ball mill completed pyro comps except B.P., and for those old timers and more experienced, a couple exceptions of partial comps milled together. I am curious where you red about ballmilling sublimated sulfur? I wouldn't think that would have much effect on KN03, and charcoal.

[cmjlab]

I probably wouldn't ball mill it with any other oxidizer / fuel combo, just in case. The ones that come to mind as most non-compatibpebare Perchlorates and Chlorates. I wouldn't use that sulfur with those two at all, let alone in a ball mill.

[stivec]

I know i have read it on a couple of places but have no idea how good the sources are. Here is one:

https://www.jamesyawn.net/bp/index.html

 

It says: ""Flowers of sulfur" as found in the pharmacy, is also known as "sublimed sulfur." It is a crystalline form made by heating sulfur, and condensing the vapor thus generated. It is rumored to cause spontaneous ignition, thus should not be used in making black powder. Flour sulfur is much cheaper anyway"

[cmjlab]

I see - most modern sulfur is made / acquired as a biproduct of industrial processing of crude oil, and is not as much of a concern for the spontaneous combustion concern from sublimated sulfur, or naturally collected elemental sulfur from around volcanic activity.

 

So unless you acquired something labelled as "sublimated sulfur" (probably in old packaging, or as "flowers of sulfur" (NOT ""sulfur "flour"), I wouldn't be overly concerned of that risk.

 

Either way, ballmilling of b.p. should be undertaken as if it WILL explode and cause death/injury/damage. Meaning done remotely, and in an area with enough stand-off or sufficient barrier to mitigate that risk.

Edited November 2, 2023 by cmjlab

[Arthur]

BP needs to be milled together to get proper function, therefore you make choices that suit the slight risk of explosion, distance is your friend here.

 

Every other mixture that I've ever heard of needs to be mixed from pre-milled ingredients, some may explode if milling the mix is attempted.

 

Try to buy ingredients from known pyro suppliers, that way you get stuff selected for this use.

[stivec]

This is the one easily available around here:

https://dovital.nl/en/product/backs-sulfur-flower-600g/

 

I will stick to milling the ingredients separately. Safety is no 1 for me. Thanks for the replies.