Round Bottom Aluminum Tanks

[WD8CDH]

Hi,

Does anybody know of information or history of round bottom aluminum tanks? I was given one with standard 3/4" NPS SCUBA threads. It is about the size of an 80 but with a compleatly round bottom. It's heavily painted so I haven't been able to read any of the stampings.

Thanks,
Ron

 

[captain]

All the round bottom aluminum tanks I have seen are U S Navy tanks. They were made by rolling closed the ends of a length of aluminum tube. There is a plug in the center of the bottom because it could not be rolled completely closed. Somtimes the plug would start leaking. They are 90 cubic feet at 3000 psi. They have no DOT markings, only the service pressure, 3000 psi and the test pressure, 5000 psi. They were made for millitary use only at a time before aluminum tanks were available to the general public. The Navy needed non-magnetic tanks for EOD to use when dis-arming magnetically detonated mines. Unless you own a compressor or are really tight with a shop I dought you will be able to get it filled. They were used as double 90's

 

[WD8CDH]

Thanks captain,

I don't ever plan to dive with it. It's in pretty bad shape but the guy who gave it to me used it within the last year or two. I will look closer for the plug. I looked in the past and couldn't find one. My plans are to use it on my shop compressor at under 200 psi unless it is "collectable".

What years were they used? Were there any other sizes with round bottoms? Any idea what alloy they were made from?

Thanks,

Ron

 

[Jimmer]

My plans are to use it on my shop compressor at under 200 psi unless it is "collectable".

You mean like an air pig? That would be one very heavy and rather low volume air pig!

 

[bajashack]

Even with a 200 psi presure I think you are either brave or foolish. IF you don't see the plug on the outside look inside the tank for the plug. Just hope that the plug is not rusted.

 

[Luis H]

The tanks that Captain is referring to were made out of 6061-T6.

I have only seen pictures of them, but my understanding is that the plug is not visible from the outside, only from the inside. The plug will not rust since it is also aluminum and it was all pressed together to formed the bottom.

I have also heard that by now in many cases the plugs may be leaking. If the plug is not leaking and they haven’t being exposed to fire, intense heat, or other mechanical or corrosive damage, the tanks should be structurally sound.

You could have it hydro tested, but the hydro station would only stamp a date, not his code since they are not DOT tanks. Unless they are badly damaged, the 200 psi would not even face them.

I am not sure how much one tank would be as a collectible. If you had the pair, they could be assemble with a US Divers valve/ manifold and reproduction bands and harness in close to their original configuration.

 

[WD8CDH]

From an engineering standpoint it would be safer than any shop air tank out there at 200 psi........and it won't rust.