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Re: Tesla Coil Firehazards (Exploding paint cans) (fwd) (fwd) (reverse) (fwd)
---------- Forwarded message ----------
Date: Sat, 11 Aug 2007 15:43:58 EDT
From: Davetracer@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: Tesla Coil Firehazards (Exploding paint cans) (fwd) (fwd)
(reverse) (fwd)
Dear Peter,
Nathan has gone ahead and replied to Scott Hanson's questions about
power level, strikes, and so forth. You'll find the answers to your technical
questions there.
Peter, you are technically correct that the inside of a paint can may be
a good Faraday cage. I do wonder about the seam running vertically; I don't
think it's built for its electrical characteristics, though. It's built to
hold high internal pressure. Perhaps someone on the list knows if it is crimped
tightly, glued, or what. (You know, this is interesting; I just picked up a
Pepsi can, and I can't feel a seam. Does anyone know? )
However, I don't think Nathan is saying that the sparks reached down
into the can via the can's "push-to-spray" button.
Nathan writes that streamers appeared to punch a hole in the seam of the
can. My guess would be the can either went rocketing around, venting from
that hole, with the venting on fire, which must have been ... quite
interesting, or the can ripped and vented all at once, and if there were streamers to
ignite the mist, wow, that must have been ... even more interesting. I note
that Fuel-Air Explosives yield more bang than C-4 pound for pound, so...
... I bet Nathan has a fire extinguisher.
There's a lesson here: If you're running anything more than a very small
Tesla Coil, get a fire extinguisher!
(And if you have one: How old is it?)
My guess as to why it happened more than once is that a lot of us run
Tesla Coils in our garages, basements, or whatever ... particularly those of us
who are married, and have such experiments banished roughly to the same
place as the dog, the kitty litter, and the bug spray.
Peter, the people on this mailing list have put up with me, and other
relative beginners, with patience that is wondrous. Right now they're helping a
guy that isn't getting the length of spark that he should. I've seen the
same questions come up, over and over, and they get answered, for the love of
doing it and passing on the knowledge. There's a (relatively) new and
incredibly interesting thing happening, the digitally driven Tesla Coil. There are
electrical engineers here who just blow me into the weeds. But, when I've asked
questions, I've gotten replies, and some of them are just so beautifully
clear it's incredible. I understand many things far better for being on this list.
Go easy on the accusations, okay? The list tends to be self-correcting.
This is a hobby, not a trial.
-- thanks,
Dave
---------- Forwarded message ----------
Date: Sat, 11 Aug 2007 09:32:22 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Tesla Coil Firehazards (Exploding paint cans)
I'll call your bluff on this one and say that you made this one up.
You say you have encountered explosions with paint "most often".
Two reasons I find it hard to believe you.
A can is almost a full Faraday cage and it is hard to imagine how a strike
could give a spark inside a can. The contents are probably not flammable
themselves (hydrocarbon propellant and paint) until mixed with air.
Striking the outside of a can results in very little heat transfer. Try
heating a full coke can and you will be very disappointed.
So as you started this, please give details of :
1 Exactly how many explosions you have had?
2 What were your TC details including power?
3 Was it just streamers that ignited the cans as you say, not direct sparks?
4 Did the cans have caps on them?
5 Why didn't you stop having the TC strike the cans after the first flash
fire?
6 If no-one on this list can reproduce your findings and we believe that
you have lied, what should the group response be?
Peter
http://tesladownunder.com
> ---------- Forwarded message ----------
> Date: Fri, 10 Aug 2007 10:15:58 -0700
> From: Nathan Stokely <50kva.54uf.750a@xxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Tesla Coil Firehazards (fwd)
>
> Paper and wood are the least of your worries. Any flammable/explosive
> vapours such as petrol or methane can ignite very easily from the
> streamers.
> Also, strikes to aerosol containers (such as bug spray, spray paint, or
> anything else you have where you operate your coil) can cause the
> hydrocarbon fuel in the aerosol to rapidly expand bursting the can and
> causing a flash fire. I have encountered this with spray paint the most
> often. The can will explode and then the paint (which burns hot) flies
> everywhere and can catch your garage on fire. Always stay away from
> aerosols
> and fuels while operating a coil.
-------------------------------------------
MORE RECENTLY,
> ---------- Forwarded message ----------
> Date: Fri, 10 Aug 2007 17:30:27 -0700
> From: huil888 <huil888@xxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Tesla Coil Firehazards (fwd)
>
> Nathan -
>
> You wrote about the danger of aerosol containers "bursting" due to strikes
> from Tesla coil streamers. Further, you noted that you have encountered
> this
> "most often" with spray maint, implying that you have experienced burst
> containers multiple times.
>
> Can you provide more details on your experiences?
>
> 1. What was the input power level of the coil, in VA?
> 2. What was the streamer length that contacted the cans?
> 3. Where on the can did the streamer make contact (and I assume melt a
> hole
> through the steel shell)?
> 4. Were the cans sitting on a grounded metal shelf, wooden shelf, cement
> floor, etc.
> 5. How many times have you personally witnessed bursting/flaming cans?
>
> If pressurized spray pain cans can indeed explode when contacted by Tesla
> coil streamers, then all coilers who run their coils in their garages or
> workshops should be made aware of this danger.
>
> Regards,
> Scott Hanson
>
-----------------------------------------------------
---------- Forwarded message ----------
Date: Sat, 11 Aug 2007 08:58:42 -0700
From: Nathan Stokely <50kva.54uf.750a@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Tesla Coil Firehazards (fwd)
The input power level of my coil was 125VA.
The streamer length was approximately 26 inches.
The streamer made contact on the seam of the can where the aluminum is
connect when it is rolled into a can. The strike appeared to break the weld
which holds the can together.
I used to always keep my spray paint on the concrete floor. Now I keep it in
a wood cabinet.
I have witnessed this twice in my garage, but I have a friend who has had
this happen more often.
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