How old is too old

[hermosadive]

What do you do with old tanks that they won't refill anymore, besides hang my hat on it?

If it's an old Luxfer, made with 6351 alloy, they use to have a trade in program to take the tanks out of circulations.

 

[down4fun]

If it's an old Luxfer, made with 6351 alloy, they use to have a trade in program to take the tanks out of circulations.

How can I tell? What would it say?

 

[Leadking]

How can I tell? What would it say?

any Luxfer cylinder dated before May 88 is assumed to be 6351 alloy

Please see http://www.psicylinders.com/library/6351_review.htm for full story.

 

[DA Aquamaster]

Yea, filling the Pre 88 Luxfer Aluminum tanks is a trickey question. Not many do it in Dallas anymore either. I got talking to a friend of mine that owns a shop here in town, and he is a trainer for PSI... And he quoted me a statistic that he throws out in his classes.... There have only been 7 tanks from that vintage that have blown up... and there were millions of them made. Intersting stat... but then I asked, of those Millions made, how many are still being used? I'd bet that millions of them have long since been thrown away, or are in a basement somewhere and haven't been filled in 20 years. And the other way to look at it, is there are about 2000 dive shops and fill stations in the US. 7 tanks blew up, which means for any shop filling them, there is about a 1 in 300 chance you won't have a dive shop after you fill a tank.

Just a different way to look at the stats. A lot of risk to make 3 bucks...

Gosh larry, you are normally one of voices of reason on the board and this post is a little out of character.

Of the 7 million tanks produced, I would bet that mearly all are still in service and that most still see at least several cycles per year as most are in fact medical O2 tanks rather than scuba tanks. (If all 7 million were scuba tanks every diver in the US would have several sitting in the closet.)

Our shop hydros several thousand tanks per month, so the sample size is fairly large. In our shop it is very rare for a 6351 T-6 tank (medical O2 or otherwise) to fail a hydro. In most cases a 6351 tank is failed after the hydro when a neck crack is found during the VIP portion of the hydro test. It's important to note that even with a visible crack most 6351's will survive a hydro to 5/3rds the service pressure and it is also important to note that it takes an average of 6 years for detectable crack to progress to the point of failure. With an inspection mandated at least every 18 months, this is a 400% safety margin.

Given that the stress of hydro testing a tank to 5/3rds pressure is much greater than filling a tank to it's service pressure and that far fewer than 1 in 300 6351 T-6 alloy tanks fail a hydro test or are found to have a neck crack, the assertion that the odds of one exploding in the dive shop are approximately 1 in 300 is totally without merit.

The odds of a properly tested, inspected and maintained 6351 tank exploding is essentially zero given that there have been no explosions of 6351 T-6 alloy tanks attributable to a sustained load cracking since the implementation of the current inspection standards.

I suspect shops that are refusing to fill them are either ignorant of the facts or are more concerned with selling new tanks to owners of 6351 T-6 alloy tanks.

That said, if someone still has a 6351 T-6 scuba tank in current hydro and VIP and is worried about it, PM me to arrange shipping, I'll be glad to take it off their hands.

 

[Leadking]

PSI, who everyone seems to agree is an expert in inspecting cylinders for safety, has a web page (http://www.psicylinders.com/library/6351_review.htm)about 6351 cylinders. I suggest everyone read it before commenting further. As a distributor of steel and aluminum cylinders I am extremely concerned about safety. It boggles my mind when someone ruthlessly condemns 6351 alloy with one breath and then suggests we can fill certain 2400-psi cylinders safely to 4000 psi in another.
Just because you are getting away with it, does not mean it is safe! All cylinders are capable of failure and 6351 cylinders, while in the current limelight, have an impressive safety record.

 

[Frank Kohler]

i also got tanks that were that old and out of hydro and everything i had them checked out and they were just fine.