Unusual Tank....Stumped on size

[Scared Silly]

Sounds like a 55 yr old door stop... Want to see a tank explode?

I am going to add my "Thbbbt" to this response. If you are not able to reply in a manner that provides factual information please keep your replies to yourself. Especially given that you are instructor - please set an example. There is enough hysteria in the dive industry over cylinders.

Now as others have said get it requaled and if it passes go use it.

 

[porbeagle]

Thanks to all for their posts, I have been diving with old steel 72s since 1959,(still have my late Dads first tank and reg.). This 2015 is in great shape and would make
a sweet set of doubles if I could ever find a mate.Not likely. For those who are distainful of old 72s and the like, you might find reading "scuba Knowtes" by pete
(SPECTRUM) (The evil Al 80 ) interesting. They trim out beautifully,allow you to take weight off your belt, are safer in cold water if you're wearing 5 or 7 mil. wet-
suit because of their bouyancy characteristics. and as long as folks don't realize
their worth, I'll keep buying them for $20. I don't have as many as I'd like, or as many as the CAPTAIN ( yeah, I read your posts),but I'm working on it.
Thanks LUIS for your knowledge,insight,and activity on the board.
and last but not least,thanks to MSELENAOUS for the formula for volume of a
cylinder. PORBEAGLE

 

[halocline]

I'm just starting to get some LP72s. Honestly I don't know why they're not made anymore. I guess the closest thing would be the Faber LP85. It's an inch taller, 0.1" larger in diameter, and a little higher pressure. I'd be interested in the structural difference (i.e alloy and wall thickness) between these two tanks.

 

[Jim Lapenta]

I have a pair of 72's dated 53 & 55 and still use them as singles. They have the old pipe thread necks.

 

[Luis H]

This is a great link, but be aware that the steel cylinders volume equation has a mistake.
Cylinder Volume

The equation should read as follows:

Vol = 0.000153 (dia-0.37)^2 * ((Length * Pi)-10.42) * (1+(0.068 * Working Pressure)

The last number in this equation has a typing error:

The value of 0.068 is just the inverse of 14.7, which is the number of psi per atmospheres. The equation has 0.68 which is just a typing error.

I will call PSI/PCI later and talk to Mark (PSI manager) and will point out the mistake so they can correct it.

The aluminum cylinder equation has it correctly.

I don't know about the accuracy of the rest of the coefficients (constants) in the equation. The form of the equations is correct, but the constants seem to include some fudge factor to take into account the shape of the ends of the pressure vessel. I ran a few numbers and the results are not too far off as compared to published data, but I was hoping they would be closer.

Be aware that this equation is intended for a conventional Scuba steel cylinder with convex bottom end. When used with the cylinder you have, the results will have somewhat larger error. It is still an approximation.

Again, the best way to get an accurate volume is to actually measure the water capacity, by either water volume or the weight of the water that the cylinder will hold. This is very easily done during hydro.

 

[porbeagle]

Thank you luis,
You're always right there.
I'll have my answer when I hydro.
PORBEAGLE

 

[Luis H]

I don't know how far you are from Portland, but Maine Divers Scuba Center has their own in house hydro station and they are capable of "+" stamping a steel 72 (the "+" stamp doesn't seem to apply to that unusual tank). I help them with the calculation for an REE number for a steel 72 (basically it is a conservative estimate of the REE number since I only have values for minimal wall thickness).

Maine Divers Scuba Center



Make sure that whoever does the hydro, follows the pre-hydro round out procedure required by PST (it doesn’t matter if they are PST tanks or not). Not following the required pre-test procedure substantially increases the chances of incorrect hydro test tank failures.

Here is a copy:
http://www.vintagedoublehose.com/downloads/PST-D-100.pdf

 

[DoubleHoseDiver]

I just put together a set of steel 72's. One is from 1973 and the other is like 1963, I think. I also have a set of steel 38's that was put back into service. Last hydro was 8/1959 and they were built in 1943! Steel tanks rule! I need to add to my collection also. Tim

 

[CamG]

Thanks porbeagle you made my night!
I just ran out to the garage and as fate would have it found two older tanks used for co2. One of them is very close to the same size you described. How awesome is that!
It never ceases how parts of a mans past come back to visit him in the present!
Long story, short version...a friend gave me the tank when I had my Keg-a-rater!
This was pre-diving and my wife made me sell the Keg-a-rater but I kept the tank.
Now I am forced to ponder a conversion for the fun of it! Why not?
I own 72's also and they are great tanks! I enjoy the size and love the buoyancy characteristics of steel! A man can never have enough tanks until it's VIP and Hydro time!
It is refreshing as well as interesting to study the history behind vintage / older gear!
Imagine where some of the 72's have been? Now that is cool to me!
Have a great night and safe diving!
CamG Keep diving....keep training....keep learning!