US Diver Tank ID Help

[Waterskier1]

Freckles of rust could just be scattered flash rust or it could be a bit thicker and covering scattered pits.

You will probably either have to or will want to have them tumbled. Either before or after the hydro test. Before if it is anything more than flash rust as it has to pass a visual inspection as part of the requalification (hydro) process, but tumbling after will remove any flash rust that may develop during the hydro test.

I'm not familiar with which comes first, the hydro or the visual. I thought hydro, then visual. I have read about flash rust, and sometimes tumbling is required after hydro to remove it, and assumed that decision was made during the visual inspection. In any case, I'd like a warm fuzzy that the tank will pass visual before I pay for a hydro, I think.

An LP 85 would have a 2400 psi service pressure rather than 2250 psi. One thing to be aware of is that the steel 72 holds 71.2 cu ft at 2475 psi (2250 psi plus 10%) and holds about 65 cu ft at 2250 psi.

Thanks. I didn't know that the LP-72's had a " + " [plus] rating. Does this mean I'll need a REE number to have it Plus rated this time? I thought it was approx 72 cu ft at rated 2250 psi, since I've never heard of anyone getting a plus rating. So much to learn about these.

 

[Scared Silly]

Unless the hydro shop has it or is willing to do the calc, you will need the REE. Not sure anyone has found the docs from Norris for the REE. Several of us have them for PST.

As for which comes first. Often the visual is done first as it is easier than the hydro. If it passes off for requal. If that passes I do another visual to make sure it got dried properly and there is not too much flash rust.

For $15 I would not worry one way or the other as you can get some of money out of them as scrap.

 

[DA Aquamaster]

It's a chicken or the egg thing. Both a hydro and VIP are required as part of the requalification process. It makes no sense to do the hydro portion on a tank that will not pass the visual portion, so it tends to get done first. But thye hydro test involves water and the tank must be thoroughly dried, so as a practical matter you do at least a cursory visual inspection to ensure it is indeed dry and not excessively flash rusted once the tank is dried.

In the real world, I do a VIP before the hydro test and if needed tumble it prior to sending it to a test facility to ensure it will pass the VIP portion. Once it gets back, if there is flash rust, I will do a quick tumble to remove any flash rust before I O2 clean it.

But then again I used to work for a hydro test facility and have VIP and O2 tech certs as well as my own tumbler and inspection tools, so it puts me a bit on the anal end of the spectrum in terms of normal diver tank maintainence.

 

[idive2]

Were the 1/2 NPT threads found more on the earlier tanks than the
later tanks or were they found on any of these tanks throughout
the years ? If these were -1 to +1 empty that would put them at
about 4 to 6 pounds negative full depending on the 2250 or 2475 fill ?

 

[captain]

The 3/4" O ring tanks came out around 1960, most prior to that were 1/2" taper pipe thread.
There is less than a pound difference between 2250 and 2475.
2475 psi= 5.75 pounds
2250 psi= 5.28
.47 difference
500 psi= 1.15 pounds
If you end the dive at 500psi then the swing weight is between 4.6 and 4.13 depending on the start pressure.

Since all 3AA 72's are built to the same spec. the REE for any manufacture's tank should be the same but you may not get the hydro facility to go along with that.

 

[idive2]

Captain, thanks for the extra info on these tanks. You are right about the
weight difference between 65cf of air and 72cf of air being only about .5 pounds.
My range of 4 to 6 pounds negative when full was based more on the
-1 to +1 buoyancy when empty (I estimated the weight of the air at 5 lbs).
Anyway, lots of good info on these tanks and if I could find a couple of these
in very good shape I might end up with doubles sooner rather than later !