Odd tank ID

[DaleC]

Here's a bit of a mystery I'm hoping someone can solve.
An Al tank (two actually) that is the same size as a ST72 with the following markings:

On neck: HO AL 4 CP 3000 PSI TP 5180 PSI 7/73 SER NO 130A 6984 (four arrows, two on top of two) and a hydro stamp of 8/76

On bottom: 1885 AE99/987

Tank

What appears to be a 3/4" thread butterfly valve

Base

Rubber boot that says "Nemrod by Seamless" with an archer.

 

[tregrrr]

cant help in ID, but I do seem to recall that there are no currently exempted or allowed Al tanks with non flat bottom... there was some military ones If I recall correctly, but they are no longer legal for hydro so far as I remember without digging up inspection guidelines.....

 

[Luis H]

That is an aluminum tank made by Luxfer in England. That one was made in 7/73.

They are about 65 cu ft at 3000 psi (that is the working pressure). And the test pressure is also stamped as 5180 psi.

They originally all came in a baby blue color. That may have been repainted.

They came out before about 1971 when the only aluminum tank in the US was the 2475psi US Divers 72 cu ft tank.

I believe that they are made out of al 6351 (I am fairly sure).

I have one that has been re-painted black and was built in 1972. I have recently retired it since I don’t want to deal with the old aluminum, but in reality when you look at the neck design it looks like it can handle a lot more load than any other tank.

That is not a DOT tank and even do we used to import them, they were never actually approved for use in the US.

The neck is a standard 3/4" NPS straight pipe thread.

I always thought that was an interesting bottom for a tank.

 

[WD8CDH]

cant help in ID, but I do seem to recall that there are no currently exempted or allowed Al tanks with non flat bottom........

Actually, DOT 3AL allows for non-flat bottoms on aluminum tanks, including the same contour as steel SCUBA tanks. I have 3 rounded bottom DOT aluminum SCUBA tanks and rounded bottom aluminum paintball tanks are quite common.

 

[oxyhacker]

I don't think the DOT cares whether an aluminum tanks is flat bottomed or not, it's just there have been so few of them that the odds are very high that if one finds one it will not be a DOT-legal tank.

I would love to know more about your round bottom DOT tanks - markings and size and manufacturer if known.

Actually, DOT 3AL allows for non-flat bottoms on aluminum tanks, including the same contour as steel SCUBA tanks. I have 3 rounded bottom DOT aluminum SCUBA tanks and rounded bottom aluminum paintball tanks are quite common.

 

[DaleC]

Thanks once again Luis!
Indeed they have been painted, two or three times it seems. I will check to see if baby blue is under there somewhere. I was given them from my air supplier (who got them from a client) who didn't feel comfortable filling them anymore. I don't know what I will do with them yet.
I had thought of banding them together with a simple military harness and writing something on them in cyrillic. With the butterfly valves I figured that would get a few stares in the parking lot

 

[akdeepdiver]

Dale,
If your going to discard them, let me know. Ill buy them off you if the price is right so I can use them as training examples for classes.
Myles