Capacity Question from the UK

[gabriel]

Please can someone help me out with American cylinder sizes? In Europe we use cylinder volume (capacity) as a measure of cylinder size, commonly 12 or 15 ltr. This is the actual volume of the cylinder in metric measure.

So, what does 80 cu ft mean? Obviously this isn't actual volume, so what does the number actually mean? How is it worked out?

Any guidance on how American cylinder nomenclature relates to European cylinder volume gratefully received - is your 80 cu ft the same as my 12 ltr!?

I only ask this because I was recently diving in St Lucia (great diving!) and would like to work out my air consumption. I can only do this by knowing how much air the cylinder holds!

Many thanks.

 

[Web Monkey]

US Cylinders are rated in Cubic Feet of Air at 1 ATM, assuming the tank is filled to it's rated pressure, and is at room temperature. If you put a big plastic bag over the valve of an 80 Cu Ft tank, and opened it, when air stopped blowing, the bag would contain 80 Cu Ft (minus the internal volume of the tank).

Just for a rough estimate of size, 19 or 30 Cu Ft is usually used as a pony bottle, 40 is sometimes used for deco, 80 is the normal size found on boats. Steel 95's and larger are popular with people who own their own tanks.

Terry

Please can someone help me out with American cylinder sizes? In Europe we use cylinder volume (capacity) as a measure of cylinder size, commonly 12 or 15 ltr. This is the actual volume of the cylinder in metric measure.

So, what does 80 cu ft mean? Obviously this isn't actual volume, so what does the number actually mean? How is it worked out?

Any guidance on how American cylinder nomenclature relates to European cylinder volume gratefully received - is your 80 cu ft the same as my 12 ltr!?

I only ask this because I was recently diving in St Lucia (great diving!) and would like to work out my air consumption. I can only do this by knowing how much air the cylinder holds!

Many thanks.

 

[speedhound]

Hello Gabriel,
The 80cu ft refers to the approximate volume of air the tank holds - actually 77.4 cu feet. I have a link to the Luxfer tank website that has more details. The 80cuft would be the S080. I think the "80" has a water volume of 11.1l so would be smaller than a 12.

http://www.luxfercylinders.com/products/scuba/specifications/us_metric.shtml

Dive safe and have fun!

 

[Leadking]

U.S. tanks are in approx cubic feet when filled to rated pressure.

here is some additional help;
1728 cubic inches per CF / 61 cubic inches per liter

 

[roakey]

On your side of the pond, to determine how much gas your cylinder can hold, you multiply the water capacity by BAR (approximately). On this side of the pond we do that math upfront and that's the number we deal with; the *compressed* volume of gas.

Roak

 

[ericrd]

as someone said, 80cf refers to the gas contained in the cylinder at the working pressure, once brought to a pressure of 1bar.

1cf = 28.31685 liters

so 80cf=2265 liters, at 200 bars usually in europe, you'd have the same capacity with a tank of 11.325 liters filled at 200bars.

tanks are usually filled at 3000psi, given that 14.7psi=1bar, this is approx 204 bars, so you can estimate that the 80cf would also be equivalent to an 11.10l tank filled at 204 bars/3000 psi.

now that I've typed that, I realized I never accurately measured how much my AL80 did contain - next time i'll service them, I'll fill them with water, for curiosity. Hope it is around these figures...


eric