Why are AL80 tanks often refered to as 12L tanks (rather than 10L?)

[afieldofblue]

Hello all,

I work in Asia, and we mostly use AL80 tanks, along with "15L" aluminium tanks.

We have a lot of European customers, and the AL80 tanks are refered to as 12L tanks.

I've been trying to get my head around this 80 cubic feet conversion, and read up on the following threads:

Untangling cubic feet, litres, PSI, bar for scuba tanks and RMV / SAC calculations

Cuft to liter conversion

I do understand that liters refer to liquid internal volume of a cylinder whereas
U.S. measurements refer to the total CF of gas at a maximum rated pressure, but
also found the following OMS conversion chart for steel tanks listing:

Air capacity (cuft) - Liquid capacity (L)
130cuft - 17L
100cuft - 13L
80cuft - 10L
65cuft - 8L
45cuft - 7L

and US manufacturer websites listing the following conversions:

steel 66/72 cuft = 10 L
steel 98 cuft = 15 L

A little confusing, but seems to point to AL80 = 10L rather than 12L.

If this is correct, I'm trying to understand why the AL80 tanks are not simply metrified to 10L (or 11L?) and refered to as 12L tanks.

Is calling AL80 tanks 12L just a habit to align them on common European steel tank sizes?

Thanks a bunch!
b

 

[Storker]

seems to point to AL80 = 10L rather than 12L.

I've always reckoned Al80s to be 11L 207 bar. Wikipedia seems to agree pretty well (it says 10.94L 210 bar, but 3000 psi is closer to 207 than 210 bar): Diving cylinder - Wikipedia

 

[Centrals]

11L.

 

[afieldofblue]

I've always reckoned Al80s to be 11L 207 bar. Wikipedia seems to agree somewhat (it says 10.94L 210 bar): Diving cylinder - Wikipedia

Yes that's also what I have found - not sure where this floating measurement oscillating between 10L (manufacturers listing ) 11L (calculations) and 12L (usage) comes from.

But I'd like to be 100% sure if I start telling people that the tanks we have, AL80, are 10L or 11L tanks rather than "12L" tanks.

 

[afieldofblue]

In Philippines it is always refer as 11L.

Interesting - I've mostly heard 12L in Thailand and Indonesia, which never felt quite right, but not being the most mathemathical person around I just let it fly

I'll also check what our "15L" aluminium tanks are really tomorrow - guessing they're AL100, which would mean...? 13L? argh!

 

[Centrals]

Remove the valve, weight the empty tank, fill it with fresh water and weight again.
1L of fresh water = 1kg

 

[afieldofblue]

Remove the valve, weight the empty tank, fill it with fresh water and weight again.
1L of fresh water = 1kg

I'm sure someone's (manufacturers?) has done this already since AL80's have been around...

11.1L, right?

So does everyone here agree AL80 are 11L (11.1L) tanks rather than 12L
and also that AL100 are really 13L (13.2L) rather than 15L?
Or am I missing something?

And are the common (at least in my neck of the woods) 12/15L references used to align them with standard European steel tanks capacities?

 

[Centrals]

I'm sure someone's (manufacturers?) has done this already since AL80's have been around...

Calculating SCUBA Cylinder Capacity | Dive Gear Express®

 

[afieldofblue]

Calculating SCUBA Cylinder Capacity | Dive Gear Express®

Interesting, this gives a metric measurements but 678 in3 water volume for the AL80 - ie 11.1104L according to my cubic inch to liter calculator.

So everyone agree that AL80s are undeniably 11L tanks and that calling them 12L is a mistake?

 

[RainPilot]

And are the common (at least in my neck of the woods) 12/15L references used to align them with standard European steel tanks capacities?

A metric, steel 10L tank will have 2320 L of gas at rated pressure (232 BAR)
An imperial, 11L AL80 will have 2277 L at rated pressure (207 BAR)

In terms of gas carried, an AL80 is therefore equivalent to a 10L steel, I believe that is where the verbal shortcut has come up. The tank is in fact 11L but breathes like a 10L steel.