17 replies to this topic

[12345]

Hi, i know flash powder mixtures are sensitive to static electricity with some types more than others. My question is: if you have a firecracker from cardboard tube with sealed both ends, that contains a sensitive flash powder mixture to static, and you shake the firecracker, so you feel the powder moves inside the tube, can the friction of the powder and the walls of the tube generate static electricity inside the tube and ignite the flash powder? Are there any chances for this to happen? What if you have a plastic tube instead of cardboard? 

 

Please replay only if you are sure about the answer. Thanks.

[cooperman435]

It's very unlikkey that in the scenario you post that static electricity could be generated.

Cardboard is universally deemed as a non static material

[12345]

Even paper can hold some static

Read: http://mobile.na.sap...ty in Paper.pdf

 

What do you think about plastic??

[cooperman435]

Indeed it can yep. I'm only quoting the "recognised" stance that it poses a very low risk

Plastic would largely depend on type I suspect but personal opinion is it would be a vastly increased risk of static generation

However it's with noting for a static discharge you need somewhere for it to discharge from and to, inside a sealed unit this is again unlikely to occur.

[GMetcalf]

No one will be able to give you a certain answer but only a probability.

 

The chances of a tube containing Flash Powder detonating if you shake it are low, higher if the tube is a plastic such as PVC, but still low (although why Flash Powder is being encased in a plastic tube is beyond me...). However, as with all things in pyrotechnics, it's not a certainty that it won't. Basically don't go shaking the hell out of a salute, but if it gets shaken around a little in the back of your car on the way to a display site, it shouldn't be a problem.

[Arthur Brown]

I've seen flash salutes made professionally for sale to the SFX trade with up to 15g of fast flash, Some have card bodies and some have plastic. I'd class both housings as "commercially acceptably safe when handled professionally" BUT I'd NEVER say there was no possibility of accident. The smallest flash maroons are 0.15grams -often these are quite loud enough.

[12345]

No one will be able to give you a certain answer but only a probability.

 

The chances of a tube containing Flash Powder detonating if you shake it are low, higher if the tube is a plastic such as PVC, but still low (although why Flash Powder is being encased in a plastic tube is beyond me...). However, as with all things in pyrotechnics, it's not a certainty that it won't. Basically don't go shaking the hell out of a salute, but if it gets shaken around a little in the back of your car on the way to a display site, it shouldn't be a problem.

 

I don't like to play with probabilities. I want to do something only if i am 100% sure that it is safe. If you are ok with the conference that there is probability to lose your life i don't have problem with this. I thinking the same way you think before years when i had a terrible accident and i lost temporary part of my hearing. I thanks GOD today i am ok.

I don't looking for the perfect answer, i want an answer from someone who had some scientific knowledge. 

Edited by 12345, 05 May 2015 - 06:20 PM.

[Vic]

Life is full of risks, you have to accept that or you would not get out of bed in the morning.

There is no such thing as 100% safety, it's up to you how much risk you are prepared to take.

Edited by Vic, 05 May 2015 - 06:58 PM.

[cooperman435]

Agreed, if you want 100% safety then don't involve yourself with pyrotechnics at all. At 99% safe you have options lol

[digger]

OK. How I would tackle this problem is to look at the minimum ignition energy required to initiate the flash powder.

 

There have been plenty of military studies done on this.

 

The following link is to a military study that details this information. Page 275 has the minimum ignition energy for a relatively standard flash powder.

 

http://www.dtic.mil/...df&AD=ADA096248

 

The next stage is to calculate the maximum static charge that the container can generate/hold to see if you can give a positive 100% guarantee.

 

That leaves a little bit of homework for you to do. However 0.37J is a large charge, so I am guessing that it is not possible to generate a potential difference large enough to generate a spark of this energy. So let us know how you get on with the research.

Edited by digger, 05 May 2015 - 07:09 PM.

[digger]

Oh and by the way you would need a sink for any static to cause a spark inside the container.

Edited by digger, 05 May 2015 - 08:34 PM.

[12345]

Life is full of risks, you have to accept that or you would not get out of bed in the morning.

There is no such thing as 100% safety, it's up to you how much risk you are prepared to take.

 
I agree life is full of risks. I mean i like to do the best to avoid the risk. 

 

@digger Thanks for the pdf i saw that kclo4/al is the least sensitive as i expect. I will stay with this composition. I have not knowledge to calculate the static inside the container. But my opinion is like cooperman435 said even if there is static inside the tube you need a discharge inside to ignite the flash. So if you seal good the container it's impossible i think especially with kclo4/al. 

There are many big companies in Italy that makes very large firecrackers even 100gr fast flash inside cardboard. If you turn the firecracker upside down you can feel the powder move. The firecrackers have ce certification that means they have pass tests and are 100% safe if you follow the instructions, as they say. For years i haven't hear any accident with these firecrackers.

[digger]

In industry turbula mixers are used to mix large amounts of flash in remote buildings, without incident during the mixing operation as far as I am aware. So small tube mixing is about as safe as it gets.

[Arthur Brown]

Small tube salutes or maroons are as safe as you can get in pyro, BUT there is always a tiny risk of incident. Pyro is NOT inert so there is a risk, but it's small. BUT this incident is usually BAD and there is a lot of energy in flash.

[Crazy Cat]

I have not knowledge to calculate the static inside the container.

If you want to research static electricity charges on different materials, you'll need an Electrometer.

Electrometer. http://en.wikipedia....ki/Electrometer
Kolbe's Electrometer/Electroscope. http://www.orau.org/...pes/MaxKohl.htm

Electronic Electrometers

electrometer schematics. http://www.next.gr/c...ics-l35901.html
http://www.circuitla...schematics.html

Simple Electrometer. http://www.vk2zay.net/article/9

An Experimenter's Electrometer. http://amasci.com/el...p1.html#Electro

Or, you can purchase one. http://www.pasco.com...c-electrometer/

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