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What is your average Air Consumption?

Discussion in 'Basic Scuba Discussions' started by Diver0001, Sep 21, 2003.

Choose range for avg air consumption

Poll closed Oct 5, 2003.
  1. 6-10 lpm (0.2-0.35 cf/min)

    7 vote(s)
    8.4%
  2. >10-12 lpm (0.36 - 0.42 cf/m)

    11 vote(s)
    13.3%
  3. >12-14 lpm (0.43 - 0.49 cf/m)

    15 vote(s)
    18.1%
  4. >14-16 lpm (0.50 - 0.57 cf/m)

    22 vote(s)
    26.5%
  5. >16-18 lpm (0.58 - 0.64 cf/m)

    11 vote(s)
    13.3%
  6. >18-20 lpm (0.65 - 0.71 cf/m)

    10 vote(s)
    12.0%
  7. > 20lpm (0.72 or higher)

    7 vote(s)
    8.4%
  1. divemed06

    divemed06 Barracuda

    336
    1
    18
    0.85....:wacko: ....let us never speak of it again!:rolleyes:
     
  2. DeepScuba

    DeepScuba Manta Ray

    724
    1
    0
    Divemed06:

    The most honest guy around!

    I applaud you sir, and don't think for a second you're as bad as everyone else makes you look,...... you're NOT.

    I here LOTS of tank PSI readings after a dive (sometimes we do that) and the difference from the worst to the best isn't enough to bring a SAC rate from 0.90 to 0.30

    I know guys who pad the numbers to make themselves look better.

    I on the other hand, when working out Gas requirements, for just about any dive that requires that amount of time, regularly use 0.90 PLUS my reserve.

    It would suck to run short on account of ego.

    Anyone who thinks "work" brings a rate up to 0.90 has never "worked" at all under water. I have seen up to 6 over short hauls, and yes THAT'S working!
     
  3. freedive

    freedive Barracuda

    200
    0
    16
    OK call de dense but I'm still not following some of the examples :( I'm using Al80 with air (21%). Filled to 3000 PSI returning with 500 PSI and with a bottom time of 60 min at 25 feet.
    In laymans terms what would be my SAC?

    Thanks
     
  4. Atticus

    Atticus Instructor, Scuba

    # of Dives: 500 - 999
    Location: Lake Tahoe
    609
    2
    18
    I'll probably get this wrong since everyone's watching :)

    2500 PSI consumed from an 80cf tank = 67 cf consumed
    67 cf / 60 minutes = 1.117 cfm
    25' / 33' per atm = 0.76 atm + 1 surface = 1.76 ata
    1.117 cfm / 1.76 ata = 0.63 SAC
     
  5. James connell

    James connell Barracuda

    204
    1
    0
    about 2/3s of what i'm carrying
     
  6. Diver0001

    Diver0001 Blue Whale

    # of Dives: None - Not Certified
    Location: Somewhere
    19,144
    5,885
    113
    I'll walk you through it..... you know that 33ft is 2 ata.

    that makes 25 ft 1.75 ata (roughly).

    That means at 25 ft you'll go through your air 75% faster than on the surface.

    SAC is the *surface* air consumption. But you need to first work out how much air you used at 25 ft.

    In your case you are using an AL80, which actually contains 76cf of air when it's full if I'm not mistaken.

    according to your pressure you used 2500 psi or 83% of your air during the dive.

    That means that you used 83% of 76cf or about 63cf of air in the 60 min you said it took for the dive.

    So per min at 25 ft you're using 63/60 (that's 63cf / 60 min) of air

    That's 1.05 cf per min

    Now you just need to adjust to bring it to the surface. We already established that we're at 1.75 ata so to bring it to the surface you go 1cf/1.75ata. That's about 0.57cf per min SAC.

    Follow that?

    In some circles people also make the distinction between measuring sac in a volume of air and pressure per min and they give them different names. Measurnig volume of air makes more sense to me because it doesn't depend on how big your tank is.

    R..
     
  7. divemed06

    divemed06 Barracuda

    336
    1
    18
    Pit-a-full!!! I sometimes last 40 minutes at 25 feet with an Al100:wacko: Next time I go in to fill my tanks, I think I'll just tell my LDS not to fill my tanks and ask him if I can instead take the fill cylinders....2 or 3 of those bad boys straped to my back should be good enough to keep up with my buddies..hehehe :D Maybe I can get me one of these and put a reg on it.....

    http://www.salvagesale.com/offer_docs/5720010703360950.jpg
     
  8. freedive

    freedive Barracuda

    200
    0
    16
    Man you guys are great :bounce: Thanks for the info and complete explanation, it certainly made it much easier to understand.
     
  9. Butch103

    Butch103 Instructor, Scuba

    # of Dives:
    Location: Southeast Ontario (Marmora)
    1,470
    1
    38
    ... on the dive and what I am doing. I have had SAC rates as low as .33 and as high as 1.07.


    If I am just diving with buddy usually the SAC is around .42, if I am with the students ( I am working on my DM) I am around .55.

    The higher SAC rates are from when I started diving and also when I am doing some "heavy" labour under water......
     
  10. Diver0001

    Diver0001 Blue Whale

    # of Dives: None - Not Certified
    Location: Somewhere
    19,144
    5,885
    113
    LOL. Imagine a twin-set made from these :)

    There's something new on the market here now (and I'm drooling). It's twin 7 litre (50cf) tanks at a working pressure of 300 bar (about 4350 psi). That's 4200 litres of air (almost 150cf) in a tidy little package.....

    I'm thinking christmas present :) LOL

    R..
     

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