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Thread: Gas analysis for 94% O2?

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    RBW Member moose_grunt is an unknown quantity at this point moose_grunt's Avatar
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    Gas analysis for 94% O2?

    So, I just moved to Saipan a couple of months ago,and thought long and hard about bringing my CCR with me. No diving happens here outside of tourist single 80 dives. I ended up bringing it with me anyways, and last week got set up with the only gas supplier on the island for oxygen.

    "Pure oxygen--same stuff we sell to the hospital." Bought two bottles at a premium, got them filled, and came home happy thinking that I might actually get to use my CCR in this diving paradise. Until I filled and analyzed my tanks. 94%. I called the company and told them it only analyzed to 94%. Their response? "Of course, that's all we have." I asked what the other 6% was. "We don't mix it with anything. It's pure oxygen." The manager's response was the same. I asked for a gas analysis, but they said they don't do that.

    So. How do I figure out what the balance is? Its not CO, and not O2, and those are the only analyzers I have. I called 2 of the 3 labs on island to ask if they could do gas analysis; I might as well have called and asked McDonalds.

    I'm guessing its argon. I live on a tiny island in the middle of the Pacific. I bet they get their gas from a slightly larger island that has a plant with an oxygen concentrator. That would account for both the general o2 percentage, and the cluelessness of everyone at the supplier.

    Any way to test for this?

    I did a sofa test with it, then did two very cautious dives, and didn't have any problems, but I'd sure like to know what else is in there before I spend any more money on getting set up over here (booster, better whips, etc)

    Jim
    Last edited by moose_grunt; 18th July 2016 at 10:08.

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    RBW Member P-A is an unknown quantity at this point P-A's Avatar
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    Re: Gas analysis for 94% O2?

    It probably Nitrogen. It's not uncommon to have lesser levels of O2 on remote locations due to inadequate O2 generator systems. I have dived with as low as 80% on some destinations.

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    RBW Member broncobowsher is on a distinguished road broncobowsher is on a distinguished road broncobowsher's Avatar
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    Re: Gas analysis for 94% O2?

    Might have to ship a sample off to a real lab.
    Based off the percentage I'm going to guess that the Oxygen concentrator is just stripping the Nitrogen and leaving the Argon with the Oxygen. But that is only a guess.

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    RBW Member Snusmumrik will become famous soon enough Snusmumrik will become famous soon enough Snusmumrik will become famous soon enough Snusmumrik's Avatar
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    Re: Gas analysis for 94% O2?

    AFAIK typical oxygen concentrators provide mix containing ~95% of O2 and ~5% of Argon.
    This was due to O2/Ar rate in air is 0,209 to 0,934. So, if you boost up O2 percentage
    by removing nitrogen, Argon percentage is also boosted.
    Argon is, IMHO, bad companion to CCR grade O2 due to it is 3 times more
    narcotic than Nitrogen.
    Last edited by Snusmumrik; 18th July 2016 at 21:26.

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    RBW Member moose_grunt is an unknown quantity at this point moose_grunt's Avatar
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    Re: Gas analysis for 94% O2?

    I'm also guessing that it's an oxygen concentrator, which is what leads me to guess argon.

    About shipping off to a lab--anyone got a lab they use that won't break the bank?

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    RBW Member nadwidny has a spectacular aura about nadwidny has a spectacular aura about nadwidny has a spectacular aura about nadwidny has a spectacular aura about nadwidny has a spectacular aura about nadwidny has a spectacular aura about nadwidny's Avatar
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    Re: Gas analysis for 94% O2?

    Quote Originally Posted by moose_grunt  View Original Post
    I'm also guessing that it's an oxygen concentrator, which is what leads me to guess argon.

    About shipping off to a lab--anyone got a lab they use that won't break the bank?
    I work at a lab and we do analysis on samples from O2 concentrators once in a while from the few medical facilities that get their O2 this way instead of from supplied O2.
    When we do the analysis we don't check for inerts as that is not part of the standard, just O2 percentage and methane, etc.

    I'll look at the specs tomorrow when I'm back in the lab and see if I can find anything relevant to your question. You may want to check with a concentrator manufacturer and see what they say about the whole process. It's quite possible that the 5% is nitrogen as I don't think those units are 100% efficient at stripping off the nitrogen.

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    RBW Member moose_grunt is an unknown quantity at this point moose_grunt's Avatar
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    Re: Gas analysis for 94% O2?

    Thanks all. I guess this has done a pretty good job at pointing out that I don't really understand how oxygen is made, much less how it's made here. I always thought that oxygen concentrators (like the small medical units) remove the nitrogen but also concentrate the argon, which could result in the 6% being argon. It seems like the alternative possibility is that PSA generation (I thought this was the same as a concentrator, though?), done cheaply, could result in incomplete nitrogen removal, thus making my 6% nitrogen.

    I'm still curious if there's a way to test for either of these. AFAIK, the trimix analyzers out there calculate nitrogen by math, not by actual analysis. The Google tells me that argon detection is not really a thing, except for welders, and they mostly just test for low O2 anyways.

    In the end, if it's nitrogen, I'm not worried. Even if it's argon, the main concern seems to be the narcotic effect (as opposed to seizure/unconsciousness/spontaneous human combustion/alien invasion).

    I'd still love to hear if anyone has got any other theories or suggestions. Lab recommendations, that do mail-order, would be awesome as well.

    Jim

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    RBW Member Chris_H is an unknown quantity at this point Chris_H's Avatar
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    Re: Gas analysis for 94% O2?

    I don't believe there is enough Argon in the atmosphere to leave the argon as the 5% impurity. If I recall correctly Argon makes up about 0.9% atmospheric air. I'd guess nitrogen is the primary impurity. I work in a gas lab as well, but we have the luxury of getting oxygen from an air separation plant, so it is typically around 99.7 or 99.8%. It is a long shot, but you could see if you can find the manufacturer of the Oxygen Concentrator the supplier is using and contact the manufacturer to find out the potential impurities? Argon can be detected easily on a GC (Gas Chromatograph), unless you are using it as the carrier gas.
    Before I began working in the lab, I used a Lawrence Factor lab to analyze a sample from my compressor. http://www.lawrence-factor.com/sec_analysis.html
    They had a lower pressure vessel to capture the sample in. They may offer oxygen testing too.
    On a side note, I analyzed my new T of diluent on the GC today. It was overkill, but it is a nice option to have.
    Last edited by Chris_H; 20th July 2016 at 00:42.

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    RBW Member moose_grunt is an unknown quantity at this point moose_grunt's Avatar
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    Re: Gas analysis for 94% O2?

    Quote Originally Posted by Chris_H  View Original Post
    I don't believe there is enough Argon in the atmosphere to leave the argon as the 5% impurity. If I recall correctly Argon makes up about 0.9% atmospheric air. I'd guess nitrogen is the primary impurity.
    My understanding, based on 5 minutes on Wikipedia (i.e. very likely incorrect), was that concentrators (and possibly generators?) stripped ONLY nitrogen from air, leaving both oxygen and argon. A proportional increase of ~4.5x of both could result in o2 in the mid 90s, and argon in the 4-5 ish range. But then again, I might be completely missing the way it works. I'm hoping someone in the know will chime in.

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    RBW Member ECho is an unknown quantity at this point ECho's Avatar
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    Re: Gas analysis for 94% O2?

    Quote Originally Posted by moose_grunt  View Original Post
    My understanding, based on 5 minutes on Wikipedia (i.e. very likely incorrect), was that concentrators (and possibly generators?) stripped ONLY nitrogen from air, leaving both oxygen and argon. A proportional increase of ~4.5x of both could result in o2 in the mid 90s, and argon in the 4-5 ish range. But then again, I might be completely missing the way it works. I'm hoping someone in the know will chime in.
    Your math looks correct to me... If "standard dry air" is 78.08% N2, 20.95% O2, 0.93% Ar and 0.04% CO2 and other trace gases (http://scifun.chem.wisc.edu/chemweek/pdf/airgas.pdf), then stripping all of the N2 would result in a blend of 95.57% O2, 4.24% Ar and 0.19% CO2 and other trace gases...

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