Results 1 to 6 of 6

Thread: Determine your SAC rates?

  1. #1
    SMN Publisher The Publisher's Avatar
    Country
    USA
    Join Date
    Apr 2007
    Posts
    2,231

    Default Determine your SAC rates?

    What are some of your favorite methods for determining your SAC rates?

  2. #2
    Registered Users Zero's Avatar
    City
    Sydney
    State
    NSW
    Country
    Australia
    Join Date
    Jan 2007
    Posts
    575

    Default

    Breathe off a tank at the surface and time it from one pressure to the next or time it over say 10 minutes and figure it out that way. Or buy an air integrated computer that just tells you as you go. Never use it for hard calculations on air as it fluctuates depending on what your doing and how much your working.

    Matt

  3. #3
    Master of Mask Mold seasnake's Avatar
    City
    Sydney
    State
    Nova Scotia
    Country
    Canada
    Join Date
    Jan 2007
    Posts
    651

    Default

    Lately I've been assuming an RMV of 1.0 just to be conservative.

  4. #4
    Cave Diver amtrosie's Avatar
    City
    formerly So. Florida and missing it!
    State
    Washinton
    Country
    USA
    Join Date
    Jan 2007
    Posts
    300

    Default

    To determine my SAC rate I first determine the Tank Factor (TF) of the cylinders I am using. Because I am diving doubles, I then multiply that by 2 (doubles....it works). I multiply the TF by the total gas pressure used, in the portion of the dive I am calculating, giving me the Gas Consumed (measured as: cu.ft.) Divide this by the dive time( in minutes), giving us a gas consumed per minute. Divide the Gas consumption by the depth of the dive in ATA's (atmospheres). All this equals SAC rate. Now for practical example:

    The word problem: A dive is undertaken to 115 feet (figure a square profile) for a time of 35 minutes. The "hearty diver" is diving with 2 aluminum eighties. and consumes a grand total of 1755 psi.


    The math: Aluminum 80's TF=.027 x 2 =.054

    .054 x 1755(psi. Gas consumed) = 94.77( cu.ft.)

    94.77 (cu.ft. gas used ) / 35 min. (dive time) = 2.7077.....(2.71 cu.ft. (gas used per min)


    2.71 (cu ft per/min) / 4.48 ATA = .6049 (.61) SAC rate


    Our diver is a figment....but he/she enjoyed the dive immensley!


    The math may be a bit intimidating, but it is fairly easily mastered with some practice.

    Note: some Tank Factors Al 80 =.027 Al 100 = .030 LP 95's = .036 LP 104's = .039

    I hope this will obscure the elementary with all this jiberish.

  5. #5
    Registered Users Finless's Avatar
    Join Date
    Feb 2007
    Posts
    103

    Default

    I have a whizzo spreadsheet I created to calculate a) actual SAC and b) a planner to confirm I have enough gas for a future dive.

    If anyone would like a copy then PM me your email.

    Unfortunately, I use ltrs/mtrs/bar, and I think most of you use cu ft/ft/psi?

    The spreadsheet was created for me and my diving so it is basically for square profile diving (wrecks) and up to 2 gas mixes. If only using one mix then leave mix two at zero and ..............

  6. #6
    Registered Users
    Join Date
    Jan 2011
    Posts
    3

    Default

    Each diver needs to know the speed at which his breathing gas consumed. This information is important to choose an appropriate point of view, as well as the size of cylinder diving with others, with different rates, and to be able to predict how much gas is needed to dive deep into the most famous of the period known time.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •