Would previous overfilling have damaged an Aluminium tank that passes tests?

[whaylonsmithers]

I recently looked at buying a second hand LP Aluminium tank. Service pressure is 2015psi. As this is very low it occurred to me the previous owner/s may have been filling it to 3000/3500psi through error, especially if it went onto a fill station with HP tanks.

If if passes hydro, visual and eddy testing how bad would that be? Its a post-2000 Luxfer so I'd assume its not made of AL6351.

I recognise the soundest advise is probably to not buy it but am interested in some knowledgeable opinion.

Regards and thanks,

Michael.

 

[chrpai]

I'd first want to understand what tank you have. Is it meant for diving? I did some googling and found some luxfers that are meant for medical oxygen:

http://www.luxfercylinders.com/prod...l-medical-cylinders?format=pdf&tmpl=component

Assuming this tank is otherwise a good choice for diving, I'd think that a hydro would be enough to forgive any past transgressions assuming there were some. I doubt there were any though.. we don't generally go around overfilling AL tanks by 50%.

 

[whaylonsmithers]

Thanks for the link Chrpai. I'm confident that it is a diving cylinder. I'm not confident it hasn't been filled to 3500psi due to possible imperial/metric confusion that I noticed when the service pressure was orginally quoted to me.

Before anyone lets fly about overfilling, that is not what I want to do with my tanks. I am concerned that it might have been accidentally greatly overfilled on a regular basis and am interested to know if normal testing is suffiencient to identify problems this would cause on a non-6531 alluminum.

 

[chrpai]

What are the tank markings? I'd love to know the actual specs of this tank and what kind of valve it has on it.

That should be a 6061 tank not needing eddy current testing. Back in my day you couldn't convince an LDS of that.. I don't know if that has changed. Hydro and vis the tank and you should know. Problem is if it's bad you probably already paid for the tank and the tests. Right?

 

[wedivebc]

What size is it? I have seen the 14cuft (same physical size as a 3000psi 19cuft) used for travelling rebreather tanks.
I would hydro and vis it and paint 2015psi in big letters on the side so shop monkeys don't overfill it.

 

[PfcAJ]

If it passes everything it's probably fine. Id dive it.

 

[whaylonsmithers]

Webdivebc - its a 14' LP that broadly looks like a 20' HP from the outside. It seems an odd tank amongst similar sized HP Luxfer/Catalinas but does have the redeeming features of being a lb lighter and a bit cheaper. I've read elsewhere that people use them for argon and nitrox deco but that's not my sort of diving.

PfcAJ - Knowing me I'd definitely dive it but that doesn't mean I'm doing the right thing! I'm thinking best not to buy it in the first place because I'll always be wondering about metal fatigue and that distracts from the fun. For $50/$100 more I can get one new, same dimensions, more gas and rated to the same pressure as my single tank. But I can be such a tight wad sometimes.

What got me thinking about massive overfilling was the seller quoted figures in bar and then later corrected himself in PSI, but to a much lower pressure(conversion accounted for). I wondered if at some point in this tank's life 2015psi was mentally rounded off to 2000. If you deal in bar you might think 2015psi~2000psi=200bar and be massively overfilling it (200bar=2901psi according to google). Unlikely but possible and it got me wondering if such a tank that passes hydro has still been damaged.

I'll ask the guy outright and probably find there's an easy explanation. He was certainly honest enough to correct his mistake. I'm still curious about the question because it must happen a bit. Shouldn't, but all it takes is one person to put it on a bank with some HP tanks, open the valve and go get a coffee or deal with some paperwork while they all fill up. Let alone anyone who might see a 14'LP as a cheap way to make 20'HP.

 

[chrpai]

So I take it you just want to use it for a pony. If it passes hydro, it's fine.

 

[PfcAJ]

So if you decide not to buy it, forward the contact info to me because I want to buy it.

 

[Doc Harry]

The whole purpose of hydro is to detect whether or not the cylinder is still within its elastic limits.

If it passes hydro then obviously it has not been functionally damaged by overfilling.