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Weight of air?

Discussion in 'Tanks, Valves and Bands' started by Divin'Hoosier, Oct 27, 2006.

  1. Divin'Hoosier

    Divin'Hoosier PADI Pro

    # of Dives: 200 - 499
    Location: Southwest Florida
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    All of the tank specs tell you how much a tank weighs when empty. After looking around, I haven't been able to find the formula to use to approximate how much a full tank weights. How much does compressed air weigh? Is there a common value per cf of compressed air? Does it differ by max pressure (2640 v. 3000 v. 3442)?
     
  2. victor

    victor Solo Diver

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    1 cubic foot of air weighs 0.0807 lbs at standard preasure and temperature
    there is approx 80 cubic feet of air in a normal rental tank at 2400 psi
    so the air in the tank weighs approximatly 6.4 lbs
    If you enter at 2400 and exit at 500 then you will be about 5.1 lbs lighter than when you went in.
     
  3. SparticleBrane

    SparticleBrane DIR Practitioner

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    ^ Most rental tanks here in the US are Al80s, thus they have 77.4cf at 3,000psi, not 2400. ;)
     
  4. victor

    victor Solo Diver

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    Sorry more used to BAR
    Weight of air 77.4 cubic feet = 6.25 lbs
    Swing between 3000 psa and 500 psi = 5.2 lbs
     
  5. xiSkiGuy

    xiSkiGuy Manta Ray

    # of Dives: 200 - 499
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    You can roughly say that every 13cf of air weighs one pound. So a E8-130 has 10lbs of air in it when full.
     
  6. donacheson

    donacheson Solo Diver

    # of Dives:
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    Each 13 cubic feet of air (at 1 atmosphere and normal temperature) weighs about 1 pound. Hence, an aluminum 80 holds about 80/13 = 6 pounds of air. For the metric folks, an 11 liter tank filled to 200 bar holds about 2200 liters of air (at 1 atmosphere and normal temperature), which weighs about 2.6 kilograms, or roughly 1.2 kilogram per 1000 liters.
     
  7. padiscubapro

    padiscubapro Cave Instructor

    # of Dives: I'm a Fish!
    Location: New York
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    also remember a tank filled with nitrox or trimix will have a different weight than air.. Nitrox is not significantly different but a high He mix will be considerably lighter..

    see this thread at rbworld
    http://www.rebreatherworld.com/decompression-gas-choices/813-how-much-does-gas-weigh.html?highlight=weight+GAS#post7356
     
  8. jeckyll

    jeckyll Solo Diver

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    http://www.techdivinglimited.com/pub/tanks.html

    That should give you a fair bit of data :)
     
  9. donacheson

    donacheson Solo Diver

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    Location: Maryland
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    True, but probably well beyond the scope of the info Divin' Hoosier needs. <G>
     
  10. Divin'Hoosier

    Divin'Hoosier PADI Pro

    # of Dives: 200 - 499
    Location: Southwest Florida
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    Great info. Thanks. Everyone has provided me the info that I need, and then some. Thanks again.
     

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