Average Gas Consumption

[Thombalabomba]

So stupid question maybe,
My shearwater apps tells me i average about 1.3 bar/min SAC. I dove 10 times in the last week in bonaire all with a 12L tank, which i guess is actually 12.2 and 100 cf?

Would this sac rate put me at .50-.59, or is my math off?

 

[inquis]

Would this sac rate put me at .50-.59, or is my math off?

I would guess that you used an AL100 in Bonaire (rated capacity of 101.2 cuft at 3300 psi), which works out to 12.6 liters water volume. A SAC of 1.3 bar/min in that tank is an RMV of 16.4 liters/min or 0.58 cuft/min.

 

[Dan]

The cold SAC is lower because it's in doubles. RMV works out to 0.6 cuft/min cold+doubles, 0.5 cuft/min warm+single.

True, but based on a full pressure of 205 bar and @Dan's penchant for travel, I'm assuming a single AL80.

Correct!

 

[MT_Shadow]

You don't need AI to know your RMV. All you need is the gas used, time, and average depth. Gas used is easily found from starting & ending pressures and tank size. I'm sure the math is described up-thread, but many dive logging programs do all the math for you if you give it the start/end tank pressures. AI is a nicety, as it can give you an RMV during subsections of the dive.

Oh interesting. yeah i could get an idea from my notes in my log i guess. I do log my entering and exiting PSI, bottom time and depth.

 

[Mike1967]

Yes as soon as I posted that I noticed the "doubles" part and edited my post, you two were very quick to jump lol

 

[inquis]

@Mike1967 Ha! It was either elaborate or clean the leaves out of the gutter... and it was 22°F outside.

 

[Dan]

Oh interesting. yeah i could get an idea from my notes in my log i guess. I do log my entering and exiting PSI, bottom time and depth.

Average depth, not bottom depth.

 

[scubadada]

Average depth, not bottom depth.

and dive time, not bottom time

 

[Thombalabomba]

I've been scratchen mu head a bit.... does an AL80 refer to the amount of surface pressure air it can hold at max pressure, as opposed to the size of the actual tank? I'm used to referring to tanks as size in liters, then just multiply by the pressure which is not always consistent on holiday destinations.

Some seem to say the al80 equals a 12L and others say it's the 10L. If i convert 12L to cubic feet i get to roughly 0.425?

 

[BoltSnap]

an AL80 refer to the amount of surface pressure air it can hold at max pressure, as opposed to the size of the actual tank?

How much air volume it can hold at working pressure. It is actually not 80cuft, it is 77.4cuft. AL80 is 11L<AL80 <12L