Conversion Table

[Aquamore]

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

 

[MNScuba]

Not sure if this will help, but:

http://www.caribbean-yachting.com/converter.html

OR

http://www.iol.ie/~discover/measure.htm

 

[Aquamore]

Thanks Murdock

The most useful line was

"litres/(ers) = Cubic feet x 28.32"

so therefore using a little mathematics:

cubic feet = litres multiply by 0.0353 (approx)

This would mean:

an International cylinder size of 10 litres is about 280 Cubic feet

and International cylinder size of 12 litres is about 340 Cubic feet

and International cylinder size of 15 litres is about 420 Cubic feet

and International cylinder size of 18 litres is about 510 Cubic feet

Does this sound correct or am I way off target here?

Aquamore

 

[MNScuba]

Unless I smoked something and can't remember doing it, I think the most common US size is 80 cubic feet... So a tank that is 280 cubic feet would be huge!

Am I wrong?

 

[Stone]

I don't know if this will help, but here's a link to Tank Specs that gives Metric and English units for actual makes of tanks.

 

[Rick Murchison]

OK gang, here we go again...
The European measurement is of absolute interior volume - that is, how much water you can put in the tank.
In America, we size tanks by how much gas they'll hold at their rated pressure.
So - a 13L tank that's a LP tank and is full at 2250 psi is a 70 CF tank; a 13L tank that's full at 3000 psi is an 95 CF tank, and a 13 L tank that's full at 3500 psi is a 108 CF tank.
Rick

 

[Stone]

The charts on the link I provided in my previous post differentiate between "Capacity" and "Internal Volume". It does not say "capacity at service pressure" but I'd guess that's what is listed.

 

[The Chairman]

First off, the methods used to measure imperial and metric tanks are W-A-Y different, and I'm not just talking units Chester. Imperial tank volumes are given in the volume of the gas contained in the cylinder at it's working pressures IF the gas was allowed to expand to be at only 1 atmosphere of pressure (Boyles' Law). Metric volumes are given at only one atmosphere... they are the actual factual volume of the tank. SO...if

1 cf = 28.32 liter THEN

a 10 Liter tank would hold only 0.353 cf of air at 1 atm (14.9 psi) ( 10 l / 28.32 l/cf= 0.353cf). SO if you were going to pressurize that tank to 3000 psi than the ATM would be 3000psi/14.9 psi/atm= 201.34atm (or Bar, if you prefer) AND
201.34 atm x 0.353 cf/atm = 71.1 cf @ 3000 psi Now THAT sounds reasonable... lets work it backwards...

80 cf @ 3000 psi... 80 cf/ 201.34 atm= 0.397 cf (or cf/atm)
0.397cf x 28.32 l/cf= 11.25 liters.

That sounds reasonable too... things to note... I did not compensate for Absolute pressure (a tank with 3000 psi is really holding 3014.9 psi (don't forget the ambient atmosphere)) Also, tank manufacturers like to round things... and they don't always follow convention.

Did I lose anyone beside myself???

 

[MNScuba]

I'm lost... but it looks good!

 

[The Chairman]

3514.9 psi (absolute) /14.9 psi/atm= 236 atm (absolute)

120cf/236atm= 0.508cf/atm or 0.508cf actual volume.

0.508cf x 28.32 l/cf = 14.4 liters

I know that they would round this, but up or down, I am not sure. I don't think that they follow normal convention, but rather one that favors them commercially. It's probably considered a 14 l tank.

BTW, if they calculated "compressed liters" of air my tank would hold...

14.4 l/Bar x 236 Bar = 3400 liters