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Re: WARNING !! (HYDROGEN GAPS)




> Original Poster: "Paul Marshall" <klugmann-at-hotmail-dot-com> 
> 
> If anyone is using a DC current to power a coil beware. Direct current 
> can turn your gap into a plasma torch (No Oxygen required). Hydrogen is 
> normally diatomic and has a very small nuclear radius. When pure 
> hydrogen gas is passed through a DC arc (providing there is enough 
> power)it will become monotomic (VERY EXOTHERMIC). Gap temperatures could 
> reach 50000 C. Goodby gap, goodby floor and anything else that happens 
> to be close.
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Hydrogen is no different in a practical sense from air as far as plasma
torches go. The gap temperature doesn't get that high, just the plasma (of
course, the plasma radiates to the electrodes, etc.). In a plas cutter, the
working gas (air, hydrogen, what have you) is blown through an arc to
dissociate it and heat it. The extremely hot gas is then blown into the
workpiece where it melts it and blows the molten metal out of the way.
(Personally, I find the plasma cutter one of the "coolest power tools";
nothing like using electricity in a small hand held probe (with a big
transformer behind it) to cut through 1" stainless steel like it was
butter.) Typical plasma cutter open circuit voltage is about 200V, they use
a small resonant HF transformer circuit to stabilize the arc (a mini tesla
coil), and a small plas cutter draws about 5 kW.

The overheating problem you mention would be an issue if you ran a
continuous gap, whether in hydrogen or any other gas.  In TC use, though,
the gap is pulsed, with a very short duty cycle. And, in fact, the working
gas does completely ionize to a plasma (and a very hot one, to boot).

I might also point out that hydrogen filled gaps have been around for at
least 50 years in commercial service, so if they were to melt through the
floor, etc., someone might have noticed.