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Old 27 April 2011, 07:25   #11
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IMO, this is not going to achieve your aims and you should stick with the fungicidal additive.

The Oxygen Factor - most plastics are O2 permeable, so the filling gas is irrelevant.

The Nitrogen Factor - with air being already 79% Nitrogen, will removing O2, a gas of not wildly dissimilar mass, really make a measurable difference to your tubes? I suspect not.
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Old 27 April 2011, 07:32   #12
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This is what I calculate....

Pressure of a fixed volume of 1) Nitrogen and 2) air starting from 10 degC 0.1 barg heated in 10C steps to 50C

T P(N2) P(Air) Diff
10 0.10000 0.10000 0.000%
20 0.13980 0.13910 0.503%
30 0.17930 0.17860 0.392%
40 0.21870 0.21800 0.321%
50 0.25820 0.25740 0.311%

Nitrogen pressure rise approx 0.5% higher.

Peng-Robinson equation of state.

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Old 27 April 2011, 07:47   #13
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Originally Posted by willk View Post
IMO, this is not going to achieve your aims and you should stick with the fungicidal additive.

The Oxygen Factor - most plastics are O2 permeable, so the filling gas is irrelevant.

The Nitrogen Factor - with air being already 79% Nitrogen, will removing O2, a gas of not wildly dissimilar mass, really make a measurable difference to your tubes? I suspect not.
But is it not the "dryness" which matters? Nitrogen just being a 'relatively' easy way to get a dry gas rather than trying to dry compressed air.
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Old 27 April 2011, 08:25   #14
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But is it not the "dryness" which matters? Nitrogen just being a 'relatively' easy way to get a dry gas rather than trying to dry compressed air.
Sorry, I forgot to say, SCUBA grade air is very dry. This happens during the compression process, the water being vented from the compressor. They might well be "making" their own nitrogen on site, so I'd expect similar levels of moisture there too.
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Old 27 April 2011, 18:01   #15
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A lung full of N2 wouldn't kill you, at worst you'd feel a tad faint.
A lung full of pure 100% N2 will kill you.
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Old 27 April 2011, 18:21   #16
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A lung full of pure 100% N2 will kill you.
A single lung full? Being shut in an atmosphere of pure n2 yes, but one lung full no.
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Old 27 April 2011, 18:30   #17
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A single lung full? Being shut in an atmosphere of pure n2 yes, but one lung full no.
As a rule you take one lung full and fall unconscious, your then in that N2 enriched atmosphere and can't think, nah I don't like this so I'm off, result is you are dead.
Why do you think you don't stick your head in nitrogen purged vessels and use a gas monitor instead?
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Old 27 April 2011, 18:52   #18
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As a rule you take one lung full and fall unconscious, your then in that N2 enriched atmosphere and can't think, nah I don't like this so I'm off, result is you are dead.
Why do you think you don't stick your head in nitrogen purged vessels and use a gas monitor instead?
Can't argue against that in a pure nitrogen atmosphere,but to kill someone from venting a tube they'd have to be inhaling directly from the valve while it was venting.
They'd have to do it several times too,which would be pretty difficult and unbelieveably stupid.
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Old 28 April 2011, 02:51   #19
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For Cookee,

http://www.kwajaleinscubaclub.com/
http://www.smdc.army.mil/rts.html
http://www.googleearthcoolplaces.com...rshall_islands

We do have a tank of Helium next to the tank of Nitrogen - we save it for parties.

Looks like a fantastic place - I take you are US military then? I'm guessing that there isn't much to do around there except scuba and fish - although I am assuming both are pretty much as good as it gets anywhere?
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When a boat looks that good who needs tubes!!!
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Old 28 April 2011, 03:30   #20
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Chewy,

You really need more than one lung full to fall unconscious. With one proper deep lung full you might start to feel a bit dodgy/weak - and probably pull away from the valve but not so bad you'd actually hit the deck. In terms of asphyxiation risk its no different from Helium which people inhale for fun to make them sound squeaky. I have actually seen someone pass out by breathing in Helium, direct from a valve (not on a tube!) but it took quite a lot of effort, and as soon as he hit the deck he was recovering (because the valve pulled out his mouth). There appeared to be no lasting effects although he was a bit thick to start with!

On an open boat, with tubes full of N2 you'd have to try really hard to pass out - and someone else would almost certainly have to force the valve into your mouth to actually suffocate you.

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Can't argue against that in a pure nitrogen atmosphere,but to kill someone from venting a tube they'd have to be inhaling directly from the valve while it was venting.
They'd have to do it several times too,which would be pretty difficult and unbelieveably stupid.
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