lamont
Contributor
pwl:even the whole concept of "tank size by air capacity" is bizarre
quick, what is physically bigger: a 2640 psi 104 cu ft tank or 3500 psi 119 cu ft tank?
IIRC, its fairly easy in metric. you've got SAC rates in L/m, tank size in L (water volume), pressure in bars.
so total gas capacity = tank size * fill pressure
SAC rate * ata = L/m consumption rate at depth
SAC rate * ata * secs = L consumed at depth
L consumed at depth / tank size = pressure in ata for rock bottom
EXAMPLE:
so, i think 50 L / min is a reasonable elevated 2-person SAC rate (?). Doing rock bottom for a 7 minute ascent from 4 ata (30m) with 'average' depth of 2.5 ata on a 10L tank:
50 L / min * 2.5 ata * 7 secs = 875 L
875 L / 10L = 87 bar
where you guys really, really, really suck is that 87 bar works for all 10L tanks no matter what the fill pressure is. this value works for all 15L tanks:
875 L / 15L = 58 bar