Posted by tleemay on November 13, 2000 at 18:40:34:
In Reply to: Re: DIR question (long) posted by Gerry on November 13, 2000 at 17:48:34:
Gerry,
On you tank specs for the difference empty between
an alum 80 and an empty steel 72;
Using a Luxfer AL 80 - actually a 78.2 (service
pressure of 3k psi), the tank weight swings from
-3.6 when full to +2.3 when empty per their specs.
The used gas accounts for about 5.9 of the
difference.
Using a current ScubaPro steel 72 - actually a 71.4
(service pressure 3k psi), the tank weight swings
from -11.3 full to -5.9 when empty per Faber's
specs, the manufacturer of the ScubaPro branded
tanks. The used gas accounts for about 5.4 pounds,
obviously less than the higher capacity Luxfer
tank.
I don't have the specs for the really old narrow
neck steel 72 tanks, but I suspect they are close
even they only held 2250 psi.
Regardless of the actual characteristic of the
tanks when empty (- or +), there is much more
than a "...tiny, couple of pounds" at play here.
The real differential between the two is closer
to 8.2 accoring to the manufacturers specs.