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On Fri, 14 Apr 1995 08:40:14 +1000 (EST) Jason Rogers wrote:
> Why don't you just use pure oxygen for deco rather than high ntx.
> The research seems to indicate that it is safer, and it gets
> you out of the water in about the same time. It is also *way*
> cheaper.
>
Hi Jason,
Thanks for responding. I haven't fully thought this out yet. We are
not using nitrox for dives or deco yet...but 6 of us are on a 'advanced nitrox'
IANTD course next w/e, so maybe we will have a clearer picture then.
I can't comment on the commercial cost in England of 100% O2 yet, but we
did think about it. One of the advantages of using deco on (say) 50% nitrox is
that in a real emergency you might just be able to shoot to the deco stop from
depth using it as a bailout...so long as you were quick enough on the initial
ascent that O2 toxity didn't have time to set in.
I'm not sure if this is a real advantage though. We are all diving on
redundant twin 10 litre (85 cu.ft. ?) cylinders, either independently valved or
manifolded with an isolation valve. With this setup there should never be a
real need to bailout on the deco cylinder.
Another thought is how to get high pressure O2 into the deco cylinder
efficiently & without a booster pump (expensive !). Our standard 'J' storage
cylinders in England I think come 'full' with 150 bar of O2. I'm not sure how
large they are, but they stand about 6 foot tall & are probably 50 litres or so
(sorry about the mixed units..). Even with a 'full' O2 J cylinder you are
going to get less than 150 bar on the 1st decant into a 4 litre deco cylinder.
The 2nd decant gives even less..& the 3rd & so on. Even if we get a stack of 3
O2 storage cylinders & decant in sequence from low to high pressure, at best we
are going to get significantly less than 150 bar of 100% O2.
Using (say) 50% nitrox, we can decant to 'a bit less' than 115 bar (to
allow for the 21% O2 in air...I can work it out) and then pump up to a full 230
bar using a compressor.
Are you using 100% O2 for deco ?
If so, how do you get a full cylinder ??
Any other comments ??
Regards, Steve M.
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