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12,240 Posts
Discussion Starter · #1 ·
Imported post

OK, let's see how many of ya can elucidate on this then?? Just blagged from D-net.

DaveW asks:

"Hi All,

Just a quick question (I hope) I see that the American cylinders seem to be sized differently from European cylinders (75.8,95.1,etc) So hope some one can enlighten me. What is the American equivalent for the following cylinders (at 230-300 bar):


10 litre
12 litre
15 litre
18 litre


10 litre
12 litre

Many thanks in appreciation
-Bye- "

Or is it indeed a valid question??? Let's be aving yer.

1,121 Posts
Imported post

There's no difference as to steel or ali as the tank volume (measured as water capacity in the UK) is the internal volume so a 12l ali holds the same as a 12l steel for the same pressure. Confusion often occurs as the US et al use 207bar alis.....

1 cu.ft. = 28.316846592 litres

Or there abouts. So for 232bar

10l cylinder = 10*232 = 2320l = 81.9cu.ft
12l clyinder = 12*232 = 2784l = 98.3cu.ft
15l cylinder = 15*232 = 3480l = 122.9cu.ft
18l cylinder = 18*232 = 4176l = 147.5cu.ft

300bar, the same cylinders are.....

10l cylinder = 10*232 = 3000l = 105.9cu.ft
12l clyinder = 12*232 = 3600l = 127.1cu.ft
15l cylinder = 15*232 = 4500l = 158.9cu.ft
18l cylinder = 18*232 = 5400l = 190.7cu.ft

and just for interest, at 207bar

10l cylinder = 10*207 = 2070l = 73.1cu.ft
12l clyinder = 12*207 = 2484l = 87.7cu.ft
15l cylinder = 15*207 = 3105l = 109.7cu.ft
18l cylinder = 18*207 = 3726l = 131.6cu.ft

Now you might get slightly different values as the conversion factor I've used are calculated for PSIG and delivered volume (Van der Waals). For example, a one litre cylinder at 0 psig (ambient sea level) has a delivered volume of 0 litres at 70F.

Okay? The actual valvues you will see on cylinders are slightly different as 232bar works out to about 3360psi and 3200 is normally used (I think) so hope this helps.

162 Posts
Imported post

Bren, it's confusing like #### here in the west. May be it's me?
? :banghead: I like the English or European way = actual volume of the container X pressure = contents.

Canada, US and some times Mexico (the NAFTA club) doesn’t have it that simple.

10L steel old (don't know the date) is pumped to 160 Bars and referred to 72 Cu ft [very wrong in my opinion]. :nonono:

Common pressures here are

160 bars
160 bars with a + (means extra 10% = total 180 bars)
200 bars - not that common on steel
232 bars – rare on both steel and ali
300 bars - very very rare

It seems that the 160 and 180 bar tanks have been unofficially labeled “”low pressure”” and any thing more is “”high pressure””. It is confusing to me because I know that 200 and 232 in Europe is a common like a cup of tea.

Common size reference for here (don't necessarily mean actual size) is -
20cf - pony
30cf – pony (like mine = 4L)
65 cf – good for stages – these are OMS actual size
72 cf – good for stages and shallow diving
80 cf  - great for twining
85 cf  - made by Faber for OMS
90 cf – good size tank
95cf – made by Faber for OMS
104 cf – can be too heavy
120 cf – too chunky for me

There might be more but these are common. To give you an e.g. I have a 104 cf by Hyzer that takes 160 bars with a plus. When I measured it I found that it was actually 15.9 some thing liters. Close enough to 16L for me

I got twin 80's by Faber that take 160 + 10%. When I measured them they came to 12L each.

What ticks me off is that the same model tank built for a European country will be pumped to 232. On top of that we have to have a burst disc.

Some more detail about the + sign; some of the Hyzers are stamped for the US d.o.t. and Canada TC. The dot shows 2400psi with a + which equates to 2600psi (MAX) or 180 bars. Then on the other side of the tank is our Transport Canada stamp in metric and states 180 bars without the +. I interpret that as always fill the tank up to 180 regardless of date. :0

Hope this gives you a good picture and will help you sort out through the confusion.

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