How old is "too" old for aluminum cylinders?

[landlockeddivingdoc]

So I was visiting an uncle I hadn't seen in a while, and he found out I was a diver, and wanted to "give me a tank that he doesn't have any need for," and he came back with this:

So, the story is, he's not a diver, but was friends with a public safety diver that died about a year ago. Said DPS diver had retired 20 years ago, and his son said he just "put everything in the basement." When he died, that son gave this tank to my uncle to "maybe use for charging an air rifle" (which my uncle never did.

I called the DPS diver's former employer, and they confirmed he worked there, and that back then their divers were volunteers; they got a stipend, but any equipment purchased was theirs. So after they gave me the green light I took the tank, which is an aluminum luxfer 80.

Aside from the interesting paint job that has an appointment with Zip Strip, it's in excellent condition--there was a valve cover in place, and the o-ring was still good enough to hook up a pressure gauge, which read just shy of 3000psi!

But, the last hydro was in 97, and the last VIP sticker is from 2002, consistent with the last reported use. The stamping at time of manufacturing shows 1992. This should mean I shouldn't have to worry about any 6351 issues, but... Is there anything else I should worry about with the age of the cylinder? I believe the reported provenance of being stored under pressure for 20 years, rather than subjected to an unknown number of pressure cycles, and assuming it passes a hydro and VIP (at which point I'd also have the valve replaced) I would be comfortable using it... Assuming there's not something I'm forgetting to be worried about.

Anyway, I don't want to pass up an extra tank that I can get back on track for $75 at the shop and some elbow grease on the stenciling, but don't want to be unsafe, either... Any help is appreciated.

 

[tursiops]

I see no issues. Clean, Hydro/VIP, fill, dive.

 

[USdiver1]

Have them Eddy current tested when doing the hydro, if 6351 alloy. I have several from 1978 that are still going strong.

 

[rhwestfall]

While that tank was not part of the "bad alloy", there are numerous shops I've come across over the years, and a number most recently, that refuse to fill a tank of that age, tested or not. It is stupid, but their rules as it is there compressor....

 

[OMyMyOHellYes]

There is no reason to have the tank Eddy Current testing. It is not 6351 if manufactured in 1992.

Have it hydro'ed. Call around to some local fire extinguisher shops to see if they do hydro testing. Here they do. Almost all the local scuba shops use one fire extinguisher shop to do most all of they hydro test done for local scuba shops. This one charges $24 to have the same tech do the same test that most shops are charging $65+. Have the valve rebuilt (or at least change the burst disk assembly and torque to spec) or better yet, buy a new convertible pro valve from the bargain basement at DGX to spin on Two new ones likely for less than what a shop would charge for one. Or even a rebuild for one. Get it VIPed and filled and dive it. If your shop is too stupid to think it is too old, go somewhere else. They don't deserve your business FOR ANYTHING. And you should run scared of their absolute ignorance.

We make fun of those "ex-perts" (which I take to mean what was once cool and pert is now just saggy and sad.)

Thermo Pro DIN/K 3000 Standalone Valves (Typical Side) - Pair

Value priced as a pair! This version of the the Thermo Standalone Valve has a 5000 psi burst disk suitable for use with cylinders up to 3000 psi service pressure.

www.divegearexpress.com

 

[Bowers]

I still dive ali tanks older than that. If it passes viz and hydro then it’s fine. I will say that i have found cracks in a few aluminum cylinders when vizing tanks from the early 90’s even though they weren’t the 6351, so age could still be a factor. But again if they pass viz and hydro i’d have zero concern.

 

[USdiver1]

My 1978 cylinders are indeed 6351 alloy, so Eddy current testing will show stress around the neck threads; Later 6061 alloy cylinders may give false positive results if Eddy current testing, indicating stress fractures where there are none.

I have had no problems getting 6351 tanks with Eddy current tests that pass hydro filled.

 

[Green Frog]

I just had a tank hydro’d last Spring. It was vintage 1992 and last hydro’d about the turn of the century, then left partially filled in my basement for over 20 years. It made it through hydro and after a valve rebuild, it was back in service for my January trip to Florida.

ETA I should have mentioned it was a good old aluminum Luxfer.

 

[boulderjohn]

A couple years ago I did a little research for a thread like this. I don't remember what got me started, but I found several very old articles from Undercurrent magazine that said aluminum tanks go bad after several years. The articles were several years apart, and they differed on how long you could use an aluminum tank before scrapping it. I am going from memory, but I believe the articles were giving totals like 15-20 years. I came to believe that those articles are the true source for the belief some shops have that you should not fill tanks more than 20 years old.

So what was the scientific source for the Undercurrent articles? Well, "scientific" was probably going too far. Both articles were quoting some guy filling the tanks at a Force E scuba shop in South Florida. If you check, you will find that Force E refusing to fill an older tank was the subject of a ScubaBoard thread. It turns out that they do not have any such policy of not filling 20-year-old aluminum tanks.

 

[tursiops]

Have them Eddy current tested when doing the hydro. I have several from 1978 that are still going strong.

Luxfer recommends doing Eddy Current tests ONLY on the 6351 alloy tanks, to avoid erroneous readings.