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rare gas usage
Tom,
> You said you go through a liter of gas in about 2 months or so with what you
>consider a medium amount of pumping throughput. I find that I use 1 flask in
>almost a year with what I consider a fair amount of pumping ( mostly neon
>repairs ). Are you sure there isn't a leak in the high pressure side? We
>only open the tank valve to pressurize the copper line to the fill valve and
>then shut it. That way if there is a leak or a mistake we will only lose that
>small quantity.
>
Um, are we talking one-liter GLASS flasks here? Or metal bottle
gas-transfer, with higher quantity?
My statistic for one liter of gas meant one liter at atmospheric pressure,
ie; the standard lead-glass bottle from a neon supplier. I'm rather sure
there's no leaks involved, as they start at atmospheric but are soon under
relative vacuum, and a leak would be atmosphere coming IN, not rare gas out,
and show up as contamination in the gas discharge color.
When I worked full-time cranking out glass in a two-person neon department
we used about 1 glass flask of each neon and argon per month, doing nothing
but bending and pumping all day, 40-60 hours per week.
I've now got 25-liter gas tanks (which started at 330psi) but these I expect
to last, oh, 10 years minimum at current rates of consumption. And with
these, same as yours, I crack the main tank valve to fill the intermediate
chamber, then shut it, doling out what I need with a seperate needle valve.
One other consideration for gas consumption is the volume of the manifold --
at 25 mm bore I'm using a fair amount of gas just to fill the manifold,
every time I fill a tube -- however I consider it a pretty nominal expense
compared to other things around the shop...
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> I usually have to give it a
>few shots of natural gas once the tube is up to temp and do a quick >bomb
on it t temp and the stains go bye bye.
So, you start with plain old air in the tube, then what -- when hot, vacuum
that out and backfill with nat. gas? To what pressure? What kind of
milliamps on the bombarder? Are the stains coming out in one bombarding
cycle then?
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> Plus you can't leak check them ( with a spark coil )
Actually, this was the main reason I bought a pirani gauge in the first
place -- to be able to troubleshoot for leaks. It first tells me if there's
a problem (long before I'd notice it in a tube, and long before pulling a
contaminated tube off the manifold!) and then if need be I can pull apart my
manifold section-by-section and isolate the problem.
The guage is handy too relative to the thread the other day on preheating
tubes -- When that occasional tube comes along that seems to bomb normal but
has a microscopic leak, it'll tell you about it right after that first
cycle, before you've done the final bombardment and cherried the 'trodes..
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I like the pyrex O-rings stopcocks too. I have two of the European type
(made by Eurovac in Holland, sold in U.S. by Eurocom) and I use one for a
glass Helium flask, one for my blowhose air-inlet. (At $110 each for
stainless it'll be awhile before I upgrade!) I've got 'em connected to the
metal system with Cajon-type slide-in O-ring connectors. They just kind of
go and go and go and the only time they ever fail (twice, I think) is when
some foreign material gets sucked in -- most recently a poor ant, going
after the goods left on the mouthpiece and musta been in the wrong place at
the wrong time when I let air into the manifold, then getting trapped right
where the stopcock O-ring sits. Moral of the story: don't eat candy before
bombarding (your hands might be clean, but...)
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> I went to school at The New York State College of Ceramics at Alfred
When were you there? I have a friend on Oahu, Kirk Tunningle, who came out
of there oh, 10-12 ? years ago. Good program from what I hear. Is Fred
Tschida still teaching there?
-- Ted Pirsig