Tank measures - Imperial vs Metric

[Tigerman]

Ok, when it comes to tanks, and how you guys describe them, thats when I get sorta lost. I know the most common tank size appears to be the trusty old aluminium 80cf, which says me just about nothing, except its made of aluminium and it holds 80 cubic feet of air when its filled..
In Norway we measure tanks in volume in liters when empty and the pressure it can be filled to, in BAR, for example 15l 200 BAR.
You also use HP and LP prefixes when talking about tanks, which I assume would be high pressure and low pressure tanks. LP thereby I would assume to be 200 BAR (2900 PSI) and HP 300 BAR (4350 PSI).

Using the above assumptions, and the fact that 10, 12 and 15 liter tanks are quite common here, would the following be correct? (assuming the tank combinations is obtainable)
10liter 200 bar = 2000 liters/70CF -> LP70?
10liter 300 bar = 3000 liters/105CF -> HP105?
12liter 200 bar = 2400 liters/85CF -> LP85? (is this the AL80?)
12 liter 300 bar = 3600 liters/127CF -> HP127?
15 liter 200 bar = 3000 liters/105CF -> LP105?
15 liter 300 bar = 4500 liters/159CF -> HP159? (That sounds awful)

Then we also have the 230 bar tanks in there, like my 15l 232 bar bottle..
Id love to get this thing straightened out, its been bugging me a fair bit ever since I came around here that I cant really get my mind wrapped around those tank descriptions

 

[H2Andy]

that looks about right, but the common imperial tanks are 72, 80, 95, 100, 104, 108, 120 and 130 ... in various LP and HP models

BUT

keep in mind that sometimes the ACTUAL capacity of a tank is LESS than the stated capacity ... for example, an 80 cf tank really holds about 77 cf

 

[Tigerman]

that looks about right, but the common imperial tanks are 72, 80, 95, 100, 104, 108, 120 and 130 ... in various LP and HP models

BUT

keep in mind that sometimes the ACTUAL capacity of a tank is LESS than the stated capacity ... for example, an 80 cf tank really holds about 77 cf

Now that is why Im wondering you see. Cause the tanks themselves I doubt very much are that different. I have a hard time imagining faber making a tank very different for the US market vs. the Norwegian market and the numbers dont match up that exact either, but that could of course be a matter of bar vs atm again just to make it all a bit more messy..
And would a 15 liter 230 bar bottle, which ideally hold 120 cf be a hp or a lp?

 

[H2Andy]

i am aware of 119 HP and 120 HP tanks, as well as 120 and 121 LP tanks

(but i am by no means an expert on this stuff... there are likely others)

 

[jefffalcone]

The 15L 230 bar sounds like a HP120 to me. In the US, tanks are generally not filled beyond about 3500 psi or 230 bar, so we don't have 300 bar tanks. I suspect we have the same tanks, but the working capacity is lower here. For instance, a 12L 300 bar tank, is probably sold in the US as a HP100 which has a working capacity of 3500psi or 230 bar.

Your conversions seem acurate to me. The reason the numbers seem funny is that we use different pressures. HP refers to anything over 3000 psi (usually 3500 or 3442). LP is anything under 3000 psi (I think the common ones are about 2450 and 2650), and if the tank is not designated as HP or LP it means it's capacity is 3000 psi. I'm pretty sure that you're right that the 12L 200 bar is the AL80.

 

[Charlie99]

The common AL80 is the S080 in the Luxfer line. It is listed by the manfufacturer as a 11.1 liter, 207 bar cylinder with free gas capacity of 2192 liters. Ref: http://www.luxfercylinders.com/products/scuba/specifications/us_metric.shtml

In imperial measurements it is 77.4cu ft of free gas when filled with air to 3000psi.

In practice, since air deviates a few percent from ideal gas laws, and 207 bar is only 204.3atm, multiplying 11.1x207 doesn't come up with 2192.

 

[Tigerman]

if the 12L 200 bar bottle is the AL80, which according to H2Andy holds 77 CF, using the same math as in the OP, it would have a working pressure of 180 BAR or 2610 PSI, which would actually make sense since the pressure of the gas drops a bit after the tank being filled. Think the 12L tanks we used for the OW class generally had a nice 180 BAR in them after being filled to 200..
Now that would bring me a fair bit closer to understanding a couple of things with your imperial measures of tanks

Edit: Or not quite after reading the post above this one..
11,1*207 is 2297.7 btw

 

[The Mushroom King]

I'm in the same boat as Tigerman. Here is all metric and the most common sizes are:
10L 200 bar
12L 200 bar

which would then be (roughly) equal to 70 and AL80 respectively. Is that right?

 

[Jimmer]

if the 12L 200 bar bottle is the AL80, which according to H2Andy holds 77 CF, using the same math as in the OP, it would have a working pressure of 180 BAR or 2610 PSI, which would actually make sense since the pressure of the gas drops a bit after the tank being filled.

An AL80 has 77 cubic feet at 3000 not at 2610.

 

[Luis H]

Now that is why Im wondering you see. Cause the tanks themselves I doubt very much are that different. I have a hard time imagining faber making a tank very different for the US market vs. the Norwegian market and the numbers dont match up that exact either, but that could of course be a matter of bar vs atm again just to make it all a bit more messy..
And would a 15 liter 230 bar bottle, which ideally hold 120 cf be a hp or a lp?

Not all European cylinders are available in the US and perhaps the reverse may be also true. I own several European cylinders that have never being commercially available in the US. They are not DOT (Department of Transportation) stamped.

Different countries have there own specifications for pressure vessels. Even if the requirements are equivalent, qualifying a cylinder to other countries specifications can be at times more trouble than it is worth.

For example, I have heard of Scuba cylinders in Australia that I don’t believe are available anywhere else. I can only assume that the manufacturer is not going to bother to have them qualified for the US or European standards, since they would probably not be competitive with the cost of shipping.

Even cylinders that may look the same and have the same basic dimensions could easily be made out of different alloys. This is one of several reasons why some tanks that look alike are rated for different pressures.

Faber makes cylinders for the US and they are probably very similar or even the same cylinder that they sell in Europe, but even a small variation in material properties would make it a different cylinder.