Untangling cubic feet, litres, PSI, bar for scuba tanks and RMV / SAC calculations

[ScubaFeenD]

Since I was never taught any of this in my more mainstream courses, I would vote for moving it to the advanced forum. However, the math and info are quite basic, so a vote for moving it to the basic forum as well. Either way thanks for the post. Nice to see someone put the time and effort in to inform others.

 

[fire_diver]

Since I was never taught any of this in my more mainstream courses, I would vote for moving it to the advanced forum. However, the math and info are quite basic, so a vote for moving it to the basic forum as well. Either way thanks for the post. Nice to see someone put the time and effort in to inform others.

You know, all this has been posted over and over and over again if anyone did a search for it.

 

[Kern]

In Oz the faber equivalent of a US HP steel 100cft doesn't have a WC of 12lt, it's 12.2lt. With a working pressure of 232 bar it holds 2830.4lts. There are 28.32lt to a cft so 2830.4/28.32 = 99.95cft.

 

[sschlesi]

Nice job, I only have one issue

please note these calculations are using Australian conversions where 1 ata = 1 bar = 14.5 psi and 1 cu ft = 1 Litre

That's taking rounding off for convenience a little too far.

 

[Kern]

OK, I'm feeling really pedantic today, so I'm going to suggest that when diving, the convention in Oz, is 1 bar = 1 ATA & that 1ATA = 14.7 psi.

 

[Lemmeron]

Nice job, I only have one issue



That's taking rounding off for convenience a little too far.

Oops, thanks for that - it was a typo, I used 1 cu ft = 28.32 Litres - fixed it in main text.

 

[Lemmeron]

OK, I'm feeling really pedantic today, so I'm going to suggest that when diving, the convention in Oz, is 1 bar = 1 ATA & that 1ATA = 14.7 psi.

Kern, when talking about tank sizes and pressure ect in Oz, we use the standard 1 ata = 1 bar, thus = 14.5 psi, which is used in calculations involving Litres and pressure in bar

When using it in US formulas 1 ata = 14.7 as you have written, but this is when you are talking cu ft, cu inches and psi

It is silly that there are 2 different conventions, but i guess that is why the world still uses metric and imperial /shrug they like it complex

 

[chokdeekap]

all i need to know is i use my 12 lt on my deep dive and 10 lt on my 2nd dive 236 bar in each tank .
interesting post though

 

[elan]

I have looked around the forums, done a number of searches, and also looked at various wikis ect to find an easy way to switch between the US standard of cubit feet and PSI and Australian Litres and Bar.

Just a dumb question - are Australian Littles and Bars are different from the litre and bar used all over the globe ?

 

[nealdc]

Dear Lemmeron,

Very fine posting and thanks for it. I posted a follow up question on the "advanced" thread, but I wondered if I should also post it here. It is really simple, so here goes:

Australia Tanks vs US
I am going to Australia to dive the GBR. I have read a very excellent analysis of comparing the sizes and amounts of air posted by Lemmeron on the "basic" version of this site, and saw that others wanted this subject to be referred to the "Advanced" page. In any event, what I want is a simple thing: if I get a tank in Australia, then how much air will I get in comparison to a tank in the US. For example, if I get a 12 litre tank with 200 BAR, will I have more or less air than I get with an 80 cu/ft tank filled to 3000 psi? Can I expect more or less air "time" based on a comparison of the tank types? Thanks in advance for your interest and this is a great site.
nealdc
rescue diver [PADI]