Australia Tanks vs US

[nealdc]

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]

 

[nielsent]

This is all just conversions, in north america, we talk about the amount of compressed gas in the tank, in other words an AL80 has 80 cubic feet of gas in it we can breathe when at 3000 psi. In Australia they talk about the absolute volume of the tank, which is the amount of water it will hold. so if you filled a 12 liter tank with water, it would hold (surprise surprise) 12 liters of water. As a result, there is 12 liters of air in that tank at 1 bar of pressure. Bar and psi are both measures of pressure and can be converted, 1 bar = 14.7psi. Cubic feet and liters are both measures of volume, and can be converted, 1 cubic foot = 28.34 liters.

So coming back to your original a 12 liter cylinder at 200 bar holds =

12 liters per 1 bar x 200 bar = 2400 liters of air

convert that to cubic feet

2400 liters / 28.34 liters per cubic foot = 84.69 cubic feet of air.

In comparison a standard catalina brand AL80 cylider in north america has a absolute volume of 10.3 liters

so if we filled the tank to 3000 psi, that is the same as saying we filled it to =

3000psi / 14.7psi per bar = 204.8 bar

10.3 liters per bar X 204.8 Bar = 2102 liters

2012 liters / 28.34 liters per cubic foot = 74.17 cubic feet.

This means that you do get more breathing air in a Austrailian 12 liter scuba tank at 200 bar than you get in a AL80 at 3000 psi.

 

[nealdc]

Wow. That is a significant difference of 10 cu ft of air, or more than 10% more breathable air. Thanks, and we can use that expectation when planning multi-level dives, and especially when planning when to head for a safety stop. Thanks!

 

[Sas]

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]

Do you know for sure what kind of tank you'll be getting on the GBR? Just curious. I know up north they usually have aluminium rental tanks but down south it is steel.

 

[bracko]

Wow. That is a significant difference of 10 cu ft of air, or more than 10% more breathable air. Thanks, and we can use that expectation when planning multi-level dives, and especially when planning when to head for a safety stop. Thanks!

he's comparing a 80 to a 100 cf essentually though... while 12L is the standard in Australia for hire, my assumption would be that 100's are the hire standard in America??

or perhaps we just breath more :s

 

[kaerius]

From a DM experience in thailand, with "thai 12L" tanks, which I think were actually 11.5L, I would, depending on depth, tell my fun divers to tell me when they hit 100-120 bar, and again at 70 bar when we're just going to be circling around near the buoy line. 100-120 bar would be time to turn around and head for the area near the buoy line, and 70 bar would be time to head for the safety stop, the idea being to be back at the boat with about 40-50 bar minimum.

Mind you the morning dives also had some time pressure, 45 minute dives(a little bit longer if you could manage to be first in), because the boat had to be back for afternoon customers. I often surfaced with 100 bar or more when I was leading, and on rare occasion, so did the customers(I particularly remember a japanese AOW couple who were about as air conservative as myself). Afternoon dives had laxer time limits, and lesser depths.

Personally I've been to 30m(90'), with gradual multi-level ascent, and had an hour long dive on those tanks, as well as dives for an hour and a half at 10m(30')(and surfaced with 70 bar...)

 

[FishDiver]

I did not read the entire thread on conversion and tank sizes. Every charter on the GBR will give you an aluminium 80 filled to 200 BAR (3000 PSI).

 

[cloudswinger]

he's comparing a 80 to a 100 cf essentually though... while 12L is the standard in Australia for hire, my assumption would be that 100's are the hire standard in America??

or perhaps we just breath more :s

al80s are the standard in America

 

[Doc Harry]

Yoke or DIN on GBR charters?

 

[Sas]

Yoke or DIN on GBR charters?

Mostly yoke. Check in advance if you need DIN, some operators don't have them and others only have a few.