How to calculate SAC rate?

[teknitroxdiver]

I seem to have forgotten how to calculate my SAC rate. How is it done?

thanks

 

[Quarrior]

Try this website.

http://home.flash.net/~table/gasses/sac.htm

I seem to have forgotten how to calculate my SAC rate. How is it done?

thanks

 

[teknitroxdiver]

Thanks!

 

[headhunter]

You may want to figure out your SAC in Cu.Ft/min. I believe that this is the number that most of the people refer to on the board.

Using a "cubic foot" rate is useful if you have to use different sized tanks.

Here's a link to calculating your SCR (Surface Consumption Rate) which is the number that most people refer to as your SAC (Surface Air Consumption) rate:

http://www.scubadiving.com/training...d/calculating_scr_(surface_consumption_rate)/

Hope this helps.

Christian

 

[Kriterian]

The first one looks slightly similar to the one from SSI, the second one just went over my head, hehe.

Here is the SSI formula:

(PSI used / bottom time) 33*
---------------------------
(Max depth + 33*)

The 33* is for salt water. Replace them both with 34 for fresh water.

An example) I dove to 60 feet in fresh water for 40 minutes and used 2500 PSI.

(2500 / 40) = 62.5
62.5 x 34 = 2125
2125 / (60+34=94) = 22.6

So my SAC rate is 23 (rounded up) PSI/minute

 

[rab]

The 33* is for salt water. Replace them both with 34 for fresh water.

Your computer doesn't know fresh v. salt and is very likely calibrated for salt water. In any case, it's the pressure that matters so you can always use 33ft or 10m for the conversion to surface pressure.

-Rob

 

[HammerNoMore]

Your computer doesn't know fresh v. salt and is very likely calibrated for salt water. In any case, it's the pressure that matters so you can always use 33ft or 10m for the conversion to surface pressure.

-Rob

If I dive at altitude, my computer assumes it's fresh water.

James

 

[JimC]

depthToOneATM is typicaly 33ft.

DAC psi/min = (psiIn psi - psiOut psi) / runTime min
SAC psi/min = DAC psi/min / ((averageDepth ft / depthToOneATM ft) + 1)
RMV cf/min = SAC psi/min * ratedTankVolumn cf / ratedTankWorkingPsi psi

 

[eponym]

I seem to have forgotten how to calculate my SAC rate. How is it done?

You might find it helpful, when using the equations, to remember the principles behind the numbers.

surface air consumption measures

air consumed per minute at one atmosphere absolute*​

so, to figure your scr:

1. calculate air consumed (psi or volume)

2. divide by time

3. divide by atmospheres absolute​

that's all!

* remember that atmospheres absolute includes surface atmosphere, so for example at 66 fsw you have three atmospheres absolute.

Breathe easy,
Bryan

 

[roakey]

Here's a long discussion on how to calculate it: http://www.scubaboard.com/t3390-.html

Roak