A spreadsheet comparing gas capacity and buoyancy of various tanks

[altaskier]

I decided to upgrade from Aluminum 80s, and made myself a spreadsheet to look at the characteristics of various tanks: http://bit.ly/15qdGuq. I decided to buy a HP steel 120.

 

[dfx]

Wouldn't it make more sense to calculate the values for "reserve" not in terms of pressure (500 psi), but rather in terms of amount of available gas?

 

[Rich Keller]

This would be another way to go. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

 

[Dsix36]

or here:

Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400.URL

 

[TSandM]

Thank you for figuring out the volume in liters! I am always confused when people from the sensible rest of the world write about buying a set of twin 12s -- what the heck are those?

 

[tracydr]

When are we going to metric? I keep waiting.
I prefer to think in metric, but its always hard,when we are used to having tanks marked a certain way in the US. Good job for figuring out the metric volumes. I like that! Great spreadsheet, although my Worthington HP 80s aren't on it.
I do hate the fact that our Scuba system is both US/metric. It's very confusing, especially tank capacity. Liters are so much easier to work with! When studying for my DMC, I did all of the problems in metric. The PADI workbook drove me crazy, the way it had both metric/US mixed together everywhere and seemed to randomly convert from one to the other.

 

[Scared Silly]

Probably want to account for the plus rating and the fact that many cylinders are rounded numbers i.e. a AL80 actually holds 77.4 cuft. (or something like that).

 

[dfx]

I do hate the fact that our Scuba system is both US/metric. It's very confusing, especially tank capacity. Liters are so much easier to work with!

I kinda like the fact that the imperial convention is to specify tank capacity not in terms of internal volume, but rather in terms of how much air it can hold. I don't really care much about the volume of a tank, I want to know how much air I can get out of it. I know it's a simple calculation, but it's nicer if I don't have to do it in my head.

 

[xdjio]

I really prefer litres. This way I can see my full pressure and know how much gas I actually have. A 16l tank at 200 bar has less gas than the same tank at 230 bar.

I guess it helps that everyone I dive with also dives metric though

 

[altaskier]

This would be another way to go. Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

I've heard of some people not able to get HP tanks filled to 3440 PSI, so that's why I included those same tanks filled to 3000 PSI. This is not included in that chart.

---------- Post added September 1st, 2013 at 11:22 AM ----------

or here:
Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400.URL

Again, it doesn't show what you get from a lower pressure fill. I also prefer to know how to do the calculation, which is contained in the spreadsheet once you know the liquid volume in liters. The tables don't tell you how to arrive at the numbers; they just give the answer.

---------- Post added September 1st, 2013 at 11:25 AM ----------

Probably want to account for the plus rating and the fact that many cylinders are rounded numbers i.e. a AL80 actually holds 77.4 cuft. (or something like that).

You are right that an AL80 only holds about 77 cubic feet of gas equivalent; the liquid volume equivalent of the tank used in the spreadsheet is correct for AL80s, though.

Speaking of a volume at pressure (i.e., a 120 cubic foot tank) is really a mixed unit. It should not be a volume but a volume-pressure product in cubic feet times atmospheres. The liquid volume in the metric system makes it all clear, as liquids are (to first order) incompressible.