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Short Air Fills

Discussion in 'General Scuba Equipment Discussions' started by bug catcher, Jun 26, 2012.

  1. mala

    mala DIR Practitioner

    # of Dives:
    Location: old hampshire
    597
    198
    43
    the op asked how to do the calculation above water.

    for recreational diving i guess it doesnt matter much.

    if you were sharing air with your buddy and had a bit of deco it would be handy to do the maths rather than end up on the surface heading for the chamber.

    do the maths and save yourself the stress of hoping you have enough air.


    i'm not having a dig just airing a few thoughts.
     
    Last edited: Jun 26, 2012
  2. bug catcher

    bug catcher Solo Diver

    # of Dives: 200 - 499
    Location: Wisconsin
    46
    10
    0
    Thanks everybody! I got the calculations in my log book so I don't forget!
     
  3. Hatul

    Hatul Solo Diver

    # of Dives: 500 - 999
    Location: Tustin, California, United States
    4,196
    634
    113
    Yeah, but here in the US we all breathe in cu ft, not liters. The commies breathe in liters.
     
    supergaijin and Culcuhain like this.
  4. eelnoraa

    eelnoraa DIR Practitioner

    # of Dives: 100 - 199
    Location: San Francisco Bay Area
    3,920
    901
    113
    In one of my class, we are taught to remember "tank factor" for the tanks we commonly use. Tank factor is defined as cf of air per 100psi.

    Here is a few tanks that I commonly encouter, so I remember these

    AL80: 2.5 ( ~=77cf/3000 * 100)
    HP100/LP80: 3.0 (~=100/3442*100 or 80/2640*100) You get the idea
    LP85: 3.2
    LP95/HP120: 3.5

    Then it become easy to estimate how much gas is available by a quick glance at the spg.
     
    Hatul likes this.
  5. cascas

    cascas Instructor, Scuba

    # of Dives: 1,000 - 2,499
    Location: Netherlands
    251
    67
    28
    Glad I do metric... Much easier...

    Verstuurd van mijn HTC Desire HD A9191 met Tapatalk
     
  6. dfx

    dfx Regular of the Pub

    # of Dives: 200 - 499
    Location: Binbrook, ON
    1,834
    647
    113
    Not really. There's always three values involved: internal tank volume, max pressure, and amount of air. The only difference is that with metric, they usually tell you the first two and you have to calculate the third, while with imperial units, they tell you the last two and you have to calculate the first. I don't see how either way is inherently easier or harder. The only advantage metric has is that atmospheric pressure is an easy "1.0" number instead of an awkward "14.7".

    Sent from my stationary Linux PC using Firefox.
     
  7. cascas

    cascas Instructor, Scuba

    # of Dives: 1,000 - 2,499
    Location: Netherlands
    251
    67
    28
    that is more than enough... ;-)
    Sent from my stationary Linux PC using Firefox.[/QUOTE]



    Verstuurd van mijn HTC Desire HD A9191 met Tapatalk
     
  8. rhwestfall

    rhwestfall Woof! ScubaBoard Sponsor

    # of Dives: 200 - 499
    Location: "La Grande Ile"
    15,927
    18,562
    113
    [h=2]Okay, since the "hijack" happened - I use this: MARTEK NASDS SCUBA TIME CALCULATOR. A wonderful device from the 1970's that I happen to have. Wish they were still made.....[/h]
     
  9. Paladin

    Paladin Solo Diver

    # of Dives: 500 - 999
    Location: West Virginia
    2,338
    508
    113
    An AL80 does not contain 80 cubic feet of air. It holds 77 cubic feet.
     
    rhwestfall likes this.
  10. Peter_C

    Peter_C Solo Diver

    # of Dives: I just don't log dives
    Location: Santa Rosa, CA
    5,889
    741
    113
    At 3,117 psi it does contain 80cf! Although I am not for overfilling aluminum tanks.

    On the other hand my HP130's...well lets just say fortunately my regs are rated for 4,200 psi, but I never go that high.
     

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