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Thread: He Grades for Rebreathers

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    New Member jqn will become famous soon enough jqn will become famous soon enough jqn will become famous soon enough jqn's Avatar
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    He Grades for Rebreathers

    I have read a number of posts where the poster suggests that the grade of He should be more pure with rebreathers than with OC. I am not sure I follow this and would like others views as to why this would be true.

    If I use 18/45 OC trimix and welding grade He, then with each breath I am getting 45% He at ambient pressure. To the extent there are impurities, they go along for the pressurized ride.

    On CCR if I have 45% He in the loop and it is the same grade, then I am breathing in the same impurities at the same ambient pressure. The only difference is, I don't expel them into the water. Does something happen when it recycles that affects them?

    Also, it seems that when I ascend and increase my FO2 to keep my PO2 constant, then I am reducing the exposure. So it seems to me, that if I'm okay with the risks associated with welding grade, or any other grade for that matter, on OC, I should be okay with it on CCR.

    Jerry

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    Quote Originally Posted by jqn
    On CCR if I have 45% He in the loop and it is the same grade, then I am breathing in the same impurities at the same ambient pressure.
    What are the impurities?

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    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    They use Helium for welding???????

    ATB

    Mark Chase

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    New Member jqn will become famous soon enough jqn will become famous soon enough jqn will become famous soon enough jqn's Avatar
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    What are the impurities?


    all of the differences between UHP and Welding grade.

    I am really trying to figure out if there is a reason to change my He grade with a rebreather. It seems there are some who think that the fact that it is delivered through a rebreather makes a difference and I would like to understand why.

    Jerry

  5. #5
    Sebastian Chander Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg's Avatar
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    HE Grades

    For What purpose is Helioum used in Welding, given that it's inert?

    Seb

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    Dude Andy M has a spectacular aura about Andy M has a spectacular aura about Andy M has a spectacular aura about Andy M has a spectacular aura about Andy M has a spectacular aura about Andy M's Avatar
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    Quote Originally Posted by Pelagian
    For What purpose is Helioum used in Welding, given that it's inert?
    Its used in Laser welding and high speed welding, because the helium suppresses the plasma plume coming off the hot spot very well. Helium-argon mixtures are more common.

    An inert gas is exactly what you want for welding anyway! We put inert gas into the weld area, called a shielding gas to keep away the nasty gas that will mess up the weld, such as oxygen. Welding grade He may well have some argon in it? BOC datasheets would clarify what the impurities are.

    Andy

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    Sebastian Chander Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg is a jewel in the rough Deep Smeg's Avatar
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    Thanks Andy that makes sense, Just couldn't see the use as something for burning, but shielding makes sense.

    Can you tell I know nothing about welding?

    Cheers

    Seb

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    RBW Member aquaxel is on a distinguished road aquaxel is on a distinguished road aquaxel's Avatar
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    helium

    some days i ago i posted a question regarding helium purities

    http://www.rebreatherworld.com/t1266-.html

    with tables showing the different impurities and grades.

    the yet unanswered question was which helium purity to use - either 99.999 or the 99.997 (us navy) / latter being more cheap than the high purity 99.999. considering that a tank of 50 liters/200bar costs here (cyprus) more than 500us$.

    in this and my post the question remains which helium purity to choose, which one is safe and why is the us navy using helium grade 99.997 instead of 99.999?

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    New Member jqn will become famous soon enough jqn will become famous soon enough jqn will become famous soon enough jqn's Avatar
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    aquaxel is asking the same basic question. I should have said industrial grade rather than welding grade. I buy my He from a welding supply. But the question of 4 9's vs 5 9's is the relevant question. Any reason not to use 4 9's if it is okay for open circuit?


    Jerry

  10. #10
    not RBW staff. EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT has a reputation beyond repute EBT's Avatar
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    I suspect you won't get any solid endorsement because we live in a litigious society. Personally, I'd be quite happy diving 4 9's, but Im evidently barking mad and shouldnt be trusted. Wibble.

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