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Thread: % Helium in stages to make them float

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    % Helium in stages to make them float

    In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is.

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    Re: % Helium in stages to make them float

    Quote Originally Posted by gallathan  View Original Post
    In the interest of streamlining, avoiding bad trim / tanks stirring silt, I'm interested in rules of thumb for how much Helium is needed in a stage to make it float. Here in the UK, seems an ALI80 / ali tanks need about 30 to 35% Helium to make them float, and at the weekend my buddy had a steel 232 bar 12ltr that had a floating tail with 60% helium in it. It was noticable too that with 10 bar less (i.e. 200 -> 190) bar, the tail cam up a lot. So wondering what the %He vs reducing pressure in the tank trade off is.


    Mt steel 10s float arse up with 250 bar 18/45in. My ali 80 sinks like a stone with 235bar 50% in.

    ATB

    Mark

    Fresh water its better in the sea.




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    Re: % Helium in stages to make them float

    for simple computation count 1,3 gramme for 1liter of air or of o2 ( 1,3kg for one cunic meter ) and zero for helium ( yes I know it isnt true ).

    For no computation at all and admitting that hélium count for nothing in the weight you deflate progressively in water your tank filled with air and note the pressure remaining in the tank when the buoyancy seems correct so what is NOT in the tank is the place for hélium.


    cheers

    Marc

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    Re: % Helium in stages to make them float

    I made up a buoyancy calculator for myself a while ago, I'm not a chemist or engineer so feel free to point out the errors :D

    Cheers,

    Stuart
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    Re: % Helium in stages to make them float

    Hi
    My two cents,
    This weekend i've been diving a wreek in -50 mtrs. Two stages:
    Ali80 Tx 17/40 200 bar FLOATS
    7Litrs Aluminium Tx 45/25 170 bar SUNKS
    And we found a tank that we lost two years ago. I took it with me to bring it to the anchor line to bring it up with the bouy. It was a 18 steel full of air. It was like a ton on my side.
    Hope that this will help you.
    Best
    Mikel

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    Re: % Helium in stages to make them float

    Have you been diving Helium in your fish pond AGAIN?

    Quote Originally Posted by Mark Chase  View Original Post

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    Re: % Helium in stages to make them float

    Quote Originally Posted by Ben Field  View Original Post
    Have you been diving Helium in your fish pond AGAIN?

    I had to get the bloody hours up some how M8 and Layborns £5.00 to get in ;)

    ATB

    Mark Chase

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