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Richard Hayward wrote:
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Building a mixing panel for nitrox and trimix use, just wondering if =
Teflon is ok to use on the oxygen line, or is some other tape =
recommended for the plumbing, is Teflon oxygen compatible, I have the =
Oxygen Hackers guide, using it for reference but it does not mention the =
tape.
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I don't mean to insult you, but if the Oxygen Hacker's Guide and this list are
your only references for what to do regarding oxygen service components in a
mixing system, you have a long difficult journey ahead of you.
To answer your question, some teflon tape is OK for use in oxygen service and
some is not. You need to check with the distributor and find out whether they
recommend it for use with oxygen. Alternatives to tape ("dope", lock-tite,
etc)don't work nearly as well, and those that are for oxygen are hard to find
and expensive.
In addition to the teflon tape, you have issues with seals and seats used on
the valves, materials used for interconnect components (tubing, hose,
fittings), flow rate (in particular pressure rise rates) within valves,
fittings, etc. and on and on. Are you going to use non-return (aka check)
valves on the o2/he/ar gas lines, or just hope that there is never an operator
error that results in the gas tanks being contaminated with gas from scuba
tanks or other tanks? If you will use check valves, where will you find ones
that are suitable for oxygen service (does a poppet style check valve that
"flutters" at low flow sound like a good idea in an oxygen line)? How will you
control the flow? Will the operator need to develop a "feel" for how fast to
flow the gas?
Buy the book, Mixed Gas Diving, by Gilliam and Mount. I wrote a chapter in
about Oxygen cleaning and handling that addresses all sorts of materials
issues. Much of the information is out of date (my references were from the
1980s), but it will give you a good idea of how to proceed. Alternatively, you
can buy a premade panel from many suppliers (including me -- although UAC is
closing, I still have parts to build a lot of stuff). When comparing apples to
apples, it is rare that you can build it yourself for less than what it would
cost you to buy it from me. If you don't believe me, get quotes on the
following:
1. about 6 feet of stainless tubing from a local supplier
2. 1-2 stainless steel manifold blocks with 5 ports (1.5" dia by 6" long).
3. 2-4 stainless steel check valves for o2
4. 2-4 flow restrictors for o2
5. a painted aluminum panel blank with stainless steel threaded inserts for
attaching components (sheet metal shop).
Most likely, these 5 items will come from different suppliers. Add 'em up, then
contact me for a quote on the same parts. If you don't think you need any of
these sort of parts for your system, then you can probably do it for much less
than I or any other manufacturer would charge. But, then again, you wouldn't be
getting the same product (apples and oranges).
Good Luck,
C. Randy Bohrer, President
Underwater Applications Corp
www.geocities.com/~uwapplications
email: underwaterapplications@cs*.co*
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