tank selection...al verses st. hp or lp. help!

[Mario S Caner]

Rick,
I can live with that, either way it's not a matter of how many pieces, but how little they're going to be huh! Kinda like that last B.S. shot in Jaws huh! LOL!

Mario

 

[Iguana Don]

Rick, this is the answer that rainreg gave me to the same question:
Hello don,
in answer to your question, there are several reasons to support hp over lp, the main one is; if you have two cylinders that are 80 cuft, and one is 3000 psi and the other is 2000 psi or less the total amount of gas in the hp cylinder is more than the lp. There are formulas in the U.S. Navy Diving Manual that can show you the exact difference in total usable gas per cylinder. But there is one advantage of lp cylinders over hp and that is in reference to high %'s of oxygen. When you have hp o2 there are great safety margins with lp tanks than with hp tanks, o2 is an extremely flammable gas and if the right conditions are present the hp gas cylinders have a higher tendency to accident or incident than with lp cylinders. I hope this answers your question if you need further clarification feel free to reply.

rainreg

Still haven't found the formula, but am still looking.

Don

 

[herman]

Here is a link to almost anything spec wise that you would want to know about scuba tanks, size, weight , pressure, bouyancy and the like http://www.diverlink.com/gear/tanks.htm It takes a bit to load, there are 16 pages of info.

 

[Rick Murchison]

Don,
There must be some misconception of the CF size rating of tanks here.. 80CF is 80CF is 80CF. Whether stored in a 2000 psi or 3000 psi or 4000 psi vessel is irrelevant. The interior volume of the three containers would be .6 CF, .4 CF and .3 CF respectively, making the usable gas from each 79.4CF, 79.6CF and 79.7CF respectively if they were each filled to 80 CF in the first place. And while a difference of .3CF *is* indeed "measurable," it is not significant. Certainly not significant enough to make it "the main reason" to support HP over LP.
Perhaps your friend is talking about the useable gas when the Scuba Nazis demand a 500psi reserve... in that case, your "useable" gas in the three tanks above becomes 60CF, 66.7CF, and 70CF respectively, and that is indeed significant... and explaining to those who demand 500psi remain regardless of tank type that the 2000 psi 80 has twice the gas (20CF)as the 4000 psi 80 (10CF) at 500 psi is probably a waste of time.
Then again, maybe he's referring the fact that the standard AL 80 holds 77.4 CF at 3000 while a HP 80 holds 80 at its rated pressure.
Rick

 

[Iguana Don]

Rick,
I understand all the numbers.
Perhaps rainreg (the moderator of this forum) can answer your question better. I just relayed the information he gave me when I asked the same question, HP vs LP tanks.

Rainreg, you out there?

Don

 

[mattiedread]

How many psi/ATM?

 

[Kevin]

Mario
I agree with you, that although the percentage of faulty cylinders is very small it is not worth taking the risk of using a cylinder without the test. As for your figure of 700 dollars, there is a great difference between that and the £10,000 which I was quoted by a local dive shop who has the equipment. His aguement was that because they cannot charge much for the test to be carried out it will take them a long time to recoup their cost of the machine and therefore not many shops will buy one. Since my last post another local shop has now said that it will not fill any aluminium cylinders which leads me back to the original point that for whatever reason it is becoming more and more difficult to get aluminium cylinders filled in my locl area.

 

[Mario S Caner]

Check out this link, if your dive shop doesn't use VIS plus, they should contact the right people and make sure they do. We are in the 21st century you know...

http://www.evcom.net/~n4mwd/vplus.htm

Mario

 

[Kevin]

Thanks for the link. There is some interesting stuff in there. It all seems to relate to 6351 aluminium, does that mean that there are other grades of aluminium tank which are safer ?
Do you know where I can find out about other grades as the only number which I can find on my cylinder is 1669. Is this a grade number ?