Conversion Table

[Aquamore]

So the next time one of my European Neighbors asks "What is the Cubic capacity of my cylinder?", I give the response

"AT WHAT PRESSURE?".

:upset: That will probably be as welcom as a F*rt in a spacesuit.

I'm going to try a different kind of diving!

 

[Rick Murchison]

never mind

 

[Aquamore]

I needed those condolences, I was feeling down as I have a conversion table (somewhere in my mountains of diving memorabilia), which is based on 200 Bar fills. What I wasn't aware of was the US system takes into consideration the maximum working pressure of the cylinder when calculating it's SIZE.

We simply work on the capacity of the cylinder if it was filled with water - a non compressible medium as it is a liquid (OK forget hydraulics for the moment)

Aquamore.

 

[The Chairman]

When it comes to having enough air under water, anal is "OK" by me...

 

[Aquamore]

my contents guage is only calibrated in Bars any way.

Stone? Does the 197.4 atm taste different to the Bar?

If the answer is yes then I think we are talking about a different kind of Bar?

Aquamore

 

[devjr]

Aquamore, the 11 liter aluminum and 12 liter steel are the most common tanks in America but are gradually losing ground. Examples include the 71.2cf steel tank, the 100cf steel HP tank, the 80cf aluminum, the 94.6cf steel, the 82cf steel LP, and some others. Lately, due to the increasing size of American adults, higher air consumption, and social trends among divers, the cylinder size has been creeping upward.

The liter capacities of cylinders manufactured in the US are rounded numbers for illustration purposes.

 

[Aquamore]

Thanks for your input regarding commonly used US cylinders, (Approx 11 and 12 litres).

When we were in Germany we taught hundreds of US Military personnel and their families how to dive under the BS-AC training schedules. They were all fully aware of the European metric SI units so I think when they returned to the USA cylinder sizes may have been a bit of a culture shock for them.

I only hope they got the hang of it quickly and fully converted over to US standards.

My personal thanks to everyone who contributed to this thread and I am sure I am not the only one who found this a valuable enlightenment!

Aquamore
PS Did I mention that I have now found my original conversion table?

 

[Fridaysniper]

Very useful thread, thanks!

Heading to Florida this week and was a bit concerned when I thought a Nitrox refill would cost me 11 cents per cubic foot for more than 1,000 cubic foot each day! Luckily I now realise that I am unlikely to use that much Nitrox on a daily basis

 

[Storker]

I thought a Nitrox refill would cost me 11 cents per cubic foot for more than 1,000 cubic foot each day!

So, you were originally planning on using about 13 Al80s per day? That'd be pretty impressive

 

[Kevrumbo]

I have recently relocated all my diving records and useful information and as usual I can't find anything when I need it.

Does anyone have a conversion table at hand for US/Imperial Cylinders (Tank)
:tanker: sizes to Metric Litres.

i.e what the standard size US cylinder capacities equate to in liters and the Metric size cylinders equate to in Cu. Feet

Thanks
Aquamore

Update and simplest explanation of this very old thread but common topic:

It's easier to fundamentally explain and conceptualize the rated volume and service pressure of a scuba cylinder based on the European/Asian surface atmosphere reference convention of 1 bar: The common Aluminium "AL80 tank" has a metric cylinder rating factor of 11 liters/bar, or in other words, at the surface of 1 bar, if you pour water into the cylinder, the measured volume it can contain is 11 liters. (It's easier to work with integer Metric Cylinder Ratings like 11L/bar, rather than a confusing and non-intuitive number value like 0.025 cf/psi at 14.7psi surface pressure US Imperial reference for the AL80 tank).

However when pressurized with breathing gas to any value up to its recommended Service Rating (207 bar for the 11L per bar Alu cylinder in this example ), a cylinder carries an equivalent volume of free gas much greater than its water capacity, because the gas is compressed to several hundred times the standard surface atmospheric pressure of 1 bar (as opposed to water which is incompressible). So if you have a gas pressure reading of 200 bar in your AL80 tank, you have a total available ideal free gas volume of 200 bar multiplied-by 11 liters/bar or 2200 liters.

Here's my representative, approximate & rough look-up table that I figured out with tanks used over the years (with some minor volume differences between today's high pressure Faber steel tanks and older PST steel cylinder ratings):

Cylinder Size | Service Pressure
11L/bar tank (AL80): 207 bar (3000 psi);
12L/bar tank (Steel HP100): 232 bar (3442 psi);
13L/bar tank (AL100): 228 bar (3300 psi);
15L/bar tank (Steel HP119): 232 bar (3442 psi);
16L/bar tank (Steel HP130): 232 bar (3442 psi).

Faber Steel Tanks:
Steel Cylinders