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Calculating refills from a higher pressure tank

Discussion in 'Basic Scuba Discussions' started by WetSEAL, Nov 17, 2020.

  1. Brett Hatch

    Brett Hatch ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: Monterey, CA
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    Holy cow, no wonder there is confusion -- that website is a godawful nightmare :eek:
     
  2. WetSEAL

    WetSEAL Nassau Grouper

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    Not sure what the standard way to describe this is, but seems to me that if the volume is 550 cubic inches or 0.31 cubic feet, then by definition it always holds 0.31 cubic feet of compressed air (though that's not very meaningful because pressure is not specifiied), but more specifically it can hold up to 97 cubic feet of air that is at atmospheric pressure. ie, it can hold up to 97 cubic feet of uncompressed air
     
  3. Storker

    Storker ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
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    Use the tanks' water volume. The pressures will equalize, and then all you have to do is to multiply water volume with pressure.

    This is one of the many reasons I love our (metric) way of expressing tank capacities. Water volume times pressure is surface volume.
     
    Southside and DivingColeridge like this.
  4. Aviyes

    Aviyes Barracuda

    # of Dives: 100 - 199
    Location: Colorado
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  5. ATJ

    ATJ Barracuda

    # of Dives: 1,000 - 2,499
    Location: Sydney, NSW, Australia
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    Use metric! Far far easier!
     
  6. ATJ

    ATJ Barracuda

    # of Dives: 1,000 - 2,499
    Location: Sydney, NSW, Australia
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    Approximately... air doesn't compress linearly but is close enough up to 200 bar for most uses. Between 200 and 300 bar it is quite a lot off.

    But yes, metric is so much easier.
     
  7. lermontov

    lermontov Manta Ray

    # of Dives: 500 - 999
    Location: christchurch
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    Attached Files:

    Brett Hatch likes this.
  8. Storker

    Storker ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
    16,495
    12,988
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    I know. And if "quite a lot" means "up to about 10%", I agree.

    I use these fudge factors:
    200 bar: pretty accurate
    232 bar: close enough for government work
    300 bar: subtract 10%
     
    DivingColeridge likes this.

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