SAC Question

[Dnaber]

I know this has been discussed many, many times. But I'm having a small problem with the correct formula. My math says one thing, but my computer says another. I'm going to throw some numbers out and just see what you folks come up with for an answer. I'll respond later with the answers I get. Thanks

Tank size - 117cf
Starting Pressure = 3371psi
Ending Pressure = 1624psi
Avg. Depth = 53' (ata 2.63)
Time 32 min
FO2 32%

 

[saxman242]

Over what period of time?

 

[Dnaber]

I know this has been discussed many, many times. But I'm having a small problem with the correct formula. My math says one thing, but my computer says another. I'm going to throw some numbers out and just see what you folks come up with for an answer. I'll respond later with the answers I get. Thanks

Tank size - 117cf
Starting Pressure = 3371psi
Ending Pressure = 1624psi
Avg. Depth = 53' (ata 2.63)
Time 32 min
FO2 32%

Nevermind, I see the issue. The two answers I'm getting are one in PSI/min and the other is CF/min

.68CF/min
20.95 PSI/min

Sorry for the drill.

 

[scubadada]

Your RMV is 0.71 cu ft/min

3371-1624 psi/32 min/(53/33 +1) atm x 117 cu ft/3442 psi = 0.71 cu ft/min/atm

 

[BlueTrin]

Nevermind, I see the issue. The two answers I'm getting are one in PSI/min and the other is CF/min

.68CF/min
20.95 PSI/min

Sorry for the drill.

Many computers will display in pressure per minute because they’d need you to input the tank size to display in volume.

This is because the AI sensor is only measuring the pressure.

 

[dflaher]

Just curious, does FO2 matter in the calculation? I.e is SAC breathing gas- dependent?

 

[scubadada]

Just curious, does FO2 matter in the calculation? I.e is SAC breathing gas- dependent?

No