A SAC question

[dfx]

the op is from montreal.

is that near canada?

size of tank has no effect on sac rate.

Seriously?

12L tank with 200 bar = 2400 liters of air. Using 24 lt/min, you'll have air for 100 minutes, making your consumption rate 2.0 bar/min, or 29 psi/min.
10L tank with 300 bar = 3000 liters or air. Using 24 lt/min, you'll have air for 125 minutes, making your consumption rate 2.4 bar/min, or 35 psi/min.

Get it now?

 

[mala]

Seriously?

12L tank with 200 bar = 2400 liters of air. Using 24 lt/min, you'll have air for 100 minutes, making your consumption rate 2.0 bar/min.
10L tank with 300 bar = 3000 liters or air. Using 24 lt/min, you'll have air for 125 minutes, making your consumption rate 2.4 bar/min.

Get it now?

yes thanks-
the sac rate is the same no matter what tank is used.

things will get a bit more complicated underwater when you start to look at water pressure.

and even more complicated when you use square feet,inches and pounds.

 

[dfx]

yes thanks-
the sac rate is the same no matter what tank is used.

... unless you understand SAC rate as tank pressure per minute, as per the post I linked to above...

I'll stop now, have fun.

 

[mala]

... unless you understand SAC rate as tank pressure per minute, as per the post I linked to above...

I'll stop now, have fun.

ok its been fun,

just do me a favour and dont try to dive a 12ltr with 200 bar at a sac of 24lts/ min underwater for 100 mins.

 

[dfx]

ok its been fun,

just do me a favour and dont try to dive a 12ltr with 200 bar at a sac of 24lts/ min underwater for 100 mins.

Why would I do that?

 

[t4e]

ok its been fun,

just do me a favour and dont try to dive a 12ltr with 200 bar at a sac of 24lts/ min underwater for 100 mins.

please explain this then

The Surface Air Consumption Rate (SAC Rate)

• A surface air consumption rate, or SAC Rate, is a measurement of the amount of air a diver uses in one minute on the surface. SAC Rates are given in units of pressure; either in psi (imperial, pounds per a square inch) or bar (metric).

• Because SAC Rates are given in terms of tank pressure, and not in terms of volume of air, SAC Rates are tank specific:

• 500 psi air in a standard 80 cubic foot tank corresponds to 13 cubic feet of air whereas . . .

• 500 psi of air in a low pressure 130 cubic foot tank corresponds to 27 cubic feet of air.

And so . . .​

• A diver who breathes 8 cubic feet of air/minute will have a SAC Rate of 300 psi/minute when diving with a standard aluminum 80 cubic foot tank but a SAC Rate of 147 psi/minute when diving with a low pressure 130 cubic foot tank.
​

 

[mala]

please explain this then

the definition of sac rate is correct.

the second part is quite misleading .

sac rate is sac rate.-you cant change the definition just because of cylinder size.

the pressure gauge may fall slower with a bigger tank but this isnt because your sac rate has changed -its because you have more air.

 

[dfx]

the definition of sac rate is correct.

the second part is quite misleading .

sac rate is sac rate.-you cant change the definition just because of cylinder size.

the pressure gauge may fall slower with a bigger tank but this isnt because your sac rate has changed -its because you have more air.

You're confusing your definition of SAC with the definition of SAC. I fully agree that it makes a whole lot more sense to measure SAC in terms of volume per minute consumed, but that doesn't change the fact that some people understand SAC as pressure change per minute. You can ignore that all you want, it doesn't change reality.

 

[rongoodman]

SAC and RMV are often used interchangeably but as I've seen it explained before, SAC has units of pressure and RMVs are given as volumes, which are tank independent and strike me as more useful.

 

[Blackwood]

There's no good or bad, there's what you breathe (i.e. need).

I need less gas than some of my friends, but put me in the water with someone like Ligersandtions and I'll probably go through 30% more gas than she does. That's not bad, that's just the way it is.

The closest you'll come to good or bad is right or wrong. Knowing what you need and equipping accordingly is right.