Scuba Tank Sizes

[Papa Bear]

First I know it is Cubic just like BTW and other abbreviations I use for the qft. Just shorter and easier. Next the "old 72's" were rated at 2250 not 2150! Next I dive with 105s and 120s that ARE 2400psi! So I not sure where you info comes from and I don't care weather it is right or wrong, but don't correct me about tanks, I use quite a number of them in a lot of different circumstances. If you want to state you opinion then fine! But don't speak for me please or change what I said in anyway. I live and dive in the real world all over it and see a lot of combos and know that some places in the world you are lucky to get 2800psi! And some of those places are right here in the states! I have been on many dive boats in California that advertise 3500psi fills. What they don't tell you is you will be waiting a long time for hot fill. My 2400psi 120 is filled to 2800 with ease and that my friend equals almost 20% over and then I have over 140 CUBIC Feet of air. So my point was not to be too technical, but to suggest the differences in tanks and amount of air each will hold. Some people think that a smaller 119 HP 3500psi tank is going to hold as much as my 120 LP 2400psi steel and my point is now way no how! Not in the real world all theory aside! So please don't quote me in the future when opinions are being given! C U later!

[rubber chicken]

Several things need clarification here....<snip>

7. Volume of gas in a cylinder is noted as cu. ft. and is the quantity of gas that the cylinder is capable of handling. All other nations rate this in "BAR"s (derived from the Greek "baros", which is a weight measurement)

8. P.S.I. (pounds per square inch) is the "power", or better yet, the number of gas molecules that are crammed into a specific space. So the rush of gas that escapes the valve as it is turned on can be a good indicator of the psi. in a cylinder. .....<snip>

Just a small correction on these points.

Most of the rest of the world measure cylinder volume in LITRES, 3, 5.7, 7, 10.5, 12, 15, 18, 20.... whatever.
"BAR" is the SI unit of measurement for pressure, being slightly less than 1 atmosphere. 1 bar = 14.5 psi,
Hence a 12L steel cylinder at 232bar contains 2784 litres of gas, a 10.5L cylinder at 300bar contains 3150 litres etc etc.

HTH.



PS: Come on America, get with the program, Join the Metric system!

[Like2dive]

I'm not an expert on this. My wife & I just switched over to Steel Tanks 2 months ago. I wish I had switched sooner. We had alum 80's. Actual capacity on an alum 80 is 77 CUft. On our steel 80's it is 80 CUft.Pressure rating for our Alum 80 was 3000 psi on our steel 80 it is 3550 psi. So I am carrying 20% more air in a much smaller tank. The steel tank is 9 inches shorter than the equiv. Alum tank. I was able to shed 8 pounds of lead from my belt, I now dive with only 4 lbs instead of 12 lbs and I do not go buoyant and the end of my dive. Pamela has shed all her weights. Lets see... mmmm... lighter smaller package that carries 20% more air and lets me shed up to 10 lbs weight. Since you have to wear a tank anyway - It's a no brainer Steel ROCKS!! We do a lot of deep wreck diving, I find myself surfacing with 1500 - 1600 psi after a deep wreck dive, the extra air increases my safety margin, and the higher capacity in the smaller package has made our diving experience much more satisfying.

[hbh2oguard]

Lotte as long as you learned and everything is clarified, the post was well worth it!

[acelockco]

I'm not an expert on this. My wife & I just switched over to Steel Tanks 2 months ago. I wish I had switched sooner. ......... I now dive with only 4 lbs instead of 12 lbs and I do not go buoyant and the end of my dive. Pamela has shed all her weights. .................
and the higher capacity in the smaller package has made our diving experience much more satisfying.

Steel cylinders are great, but aluminum do have their place as well. After using some steel cylinders on vacation, I have to agree with you 100% on how much of a difference they actually do make. The additional air you get really increases your margin of safety as well, giving you enough air to get to your no-deco limit with a nice amount to spare.

The one thing I would warn is about your wife loosing all of her weight. Remember you should have enough ditchable weight that in an emergency situation she could drop it if necessary.

The only reason I still dive aluminum cylinders is because I own 9 of them right now and don't really want/have to spend the money it would take to replace them all.

[BamaCaveDiver]

I'm not an expert on this. My wife & I just switched over to Steel Tanks 2 months ago. I wish I had switched sooner. We had alum 80's. Actual capacity on an alum 80 is 77 CUft. On our steel 80's it is 80 CUft.Pressure rating for our Alum 80 was 3000 psi on our steel 80 it is 3550 psi. So I am carrying 20% more air in a much smaller tank. The steel tank is 9 inches shorter than the equiv. Alum tank. I was able to shed 8 pounds of lead from my belt, I now dive with only 4 lbs instead of 12 lbs and I do not go buoyant and the end of my dive. Pamela has shed all her weights. Lets see... mmmm... lighter smaller package that carries 20% more air and lets me shed up to 10 lbs weight. Since you have to wear a tank anyway - It's a no brainer Steel ROCKS!! We do a lot of deep wreck diving, I find myself surfacing with 1500 - 1600 psi after a deep wreck dive, the extra air increases my safety margin, and the higher capacity in the smaller package has made our diving experience much more satisfying.

Not quite...you are only carrying slightly less than an additional 4cuft (3.89610 cuft) in the steel 80 versus the AL 80. The fill pressure is just shy of 20% difference; 3550psi is about 18.333% greater than 3000psi. The higher fill rating on the steel cylinder is what allows you to carry an equal amount of gas in a smaller container.