well this bites...

[pescador775]

Thanks for mentioning "cycling". It gives me a chance to vent :^) I bought a US Divers aluminum tank in 1972. After one year of diving with it, I decided to set it aside as an air bottle for operating pneumatic tools, etc. This tank was stored fully charged (and occasionally refilled) over 34 years before I disposed of it last month. During that time, it was hydroed once (five years ago) and visualed a number of times. The tank passed the hydro and numerous visuals (with no cracks or other problems). I decided to dump it based on age and, or course, the barrage of stories. I still maintain that the so called "sustained" or static problem is a misnomer. Bauer Kompressoren specifies the life of their aluminum filter canisters in number of cycles, and not "years", sustained load, or anything else. Notably, two or three of these canisters have exploded while in use aboard Australian head boats. It seems, incredibly, that these canisters had exceeded the design life of 50,000 cycles having been in constant use for over 30 years. I believe the aluminum tanks made of 6351 alloy develop cracks in response to normal cycling, corrosion, and hydrostatic tests, not a static condition. Having said that, I mention a single case, also in Australia, in which a Luxfer tank stored in a shed exploded without warning. By law, the Aussies require YEARLY hydro testing which is nuts, IMO. Draw your own conclusions.

 

[rjk75]

I'd read some of those links. I cannot deny the fact that this is an old tank and it's made out of a "bad" batch of aluminum. However, as long as it passes hydro and passes well, then it should be safe to fill it. For hydrostatic testing, they overfil the tank (I believe to 5k psi for a 3k tank), which would be more than enough to burst it, if it were going to burst at 3k, it will burst at 5k. Secondly, they measure how much it expands. If it were going to expand much at 3k, it will expand all the more at 5k. Then they measure howmuch it shrinks when pressure is removed. If it passes a test at 5k, then I have no problem trusting it at 3k.

Not to be a kiljoy JahJah but those tanks that burst in the URLs I listed were all hydro-tested successfully. From what I gather (annecdotally) they burst during air fills soon after a hydro test. Even it passes everything, doesn't mean a shop has to fill it.

Be car

 

[DennisW]

There has never been a 6351 alloy tank that has failed after a proper hydro and properly performed eddy current test.

 

[BHB ScubaTroll]

I'd read some of those links. I cannot deny the fact that this is an old tank and it's made out of a "bad" batch of aluminum. However, as long as it passes hydro and passes well, then it should be safe to fill it. For hydrostatic testing, they overfil the tank (I believe to 5k psi for a 3k tank), which would be more than enough to burst it, if it were going to burst at 3k, it will burst at 5k. Secondly, they measure how much it expands. If it were going to expand much at 3k, it will expand all the more at 5k. Then they measure howmuch it shrinks when pressure is removed. If it passes a test at 5k, then I have no problem trusting it at 3k.

If I get it back and they tell me that it passed butjust barely (there are ranges for passage of the shrinking/expanding test) then I won't use it. I'll ask them if they can overstamp the numbers on it, condemning it, but not drill through it. My dad might use it as a 150 psi storage tank or something. If he doesn't want to use it, then I'll dril a hole in it.

How many people will you kill when your time bomb goes off? Hopefully, only the fool who chooses to wear the time bomb.

Unfortunately, the fool is usually the only one who comes away without a scratch.
===

Many of the tanks that burst were under current hydro and visual... Take the stupid thing out back and use it for target practice.
===

In this town you can get a AL80 brand new for $119.00 - The life you save may be someone elses.

 

[JahJahwarrior]

Look, could you all please cite specific incidences and statistics? I'm sick of hearing this "most tanks.." "some tanks..." "I heard once about..." If you are going to try to make the point that tanks go bad after a certain number of years, can you please be competent in this area of study? Please tell me exactly how many tanks have exploded in America since say the 70's. Then tell me of those tanks, which were made of which alloy, which years were the tanks hydroed, visual tested? How many cycles? When did they explode? how much damage was caused? Were there other factors that influenced the explosion?

So far, all that has been tossed around is hearsay and some shoddy statistics. On person did give links to many URLs, he's done the best job so far of showing credibility for his points. DennisW has also done a decent job: he made a strong point, that no tank of this particular alloy has failed soon after a proper hydro test and proper eddy current test. If you can prove him wrong, then please do so. If you can't, would you please stop posting here complaining that I'm going to kill people? I appreciate your concern, but I do not feel that many of you have made valid points with any credibility. If I'm wrong, then repost your post and tell me why it's so credible.

 

[TheRedHead]

I have to agree with CoolTech because the amount of money between a new tank and an old clunker is miniscule.

 

[letterboy]

Does this make me evil???

 

[MikeFerrara]

Look, could you all please cite specific incidences and statistics? I'm sick of hearing this "most tanks.." "some tanks..." "I heard once about..." If you are going to try to make the point that tanks go bad after a certain number of years, can you please be competent in this area of study? Please tell me exactly how many tanks have exploded in America since say the 70's. Then tell me of those tanks, which were made of which alloy, which years were the tanks hydroed, visual tested? How many cycles? When did they explode? how much damage was caused? Were there other factors that influenced the explosion?

So far, all that has been tossed around is hearsay and some shoddy statistics. On person did give links to many URLs, he's done the best job so far of showing credibility for his points. DennisW has also done a decent job: he made a strong point, that no tank of this particular alloy has failed soon after a proper hydro test and proper eddy current test. If you can prove him wrong, then please do so. If you can't, would you please stop posting here complaining that I'm going to kill people? I appreciate your concern, but I do not feel that many of you have made valid points with any credibility. If I'm wrong, then repost your post and tell me why it's so credible.

Several tanks of this alloy have exploded. People have been hurt or killed and property destroyed. Those investigating the causes of the explosions have identified and named the failure mode and linked it to a specific alloy. For a time at least one of the manufactureres even offered a rebate on the tanks.

I have never seen any cycle test data. Maybe some life test data on a reasonable number of samples might convince me of something. As far as I know, that has never been done or at least not published. Beyond that, I perosnally just don't know and when it comes to things getting pumped up with compressed gas to 3000 psi ...when in doubt, don't do it. It's just not worth it for what you make on an air fill or for that matter what a new tank costs.

You're the guy who wants someone to stand next to it and fill it. Why don't you come up with some data? Prove to the owner of the fill station that it's worth it for him to stand there and fill it. It would seem that in this case that if you want the thing filled the burden of proof is on you. You want somebody to dive you statistics...ok then...lots of shops don't want to fill them and if you really want to own one, you are going to have to put up with that. Maybe I'll do a phone survey to gather numbers so I can calculate the probability of you getting a fill at a randomly selected fill station.

The funny thing is that in the amount of time you've spent posting about this tank of yours, you could have mowed a couple of lawns and had enough money to buy a brand new shinny tank that everybody would be willing to fill.

 

[Bob3]

Just for folks pulling up this thread during a search, here is a list of authorized hydro retesters from the DOT: http://hazmat.dot.gov/sp_app/approvals/hydro/hydro_retesters.htm
Luxfer says they design their dive bottles for [at least] 10,000 fill cycles. It's fun to calculate the supposed number of years an aluminum tank will last based on number of dives per day, week, whatever.
I saw one lad make a post about his tank being empty between dives; this happened over 3 consecutive weekends.
After lots of helpful folks suggesting things like o-rings, bad valve seat, etc., someone guessed the actual culprit; a neck crack.
I'll stop rambling now.

 

[BHB ScubaTroll]

blah blah and more blah!

For me...

You have just crossed from "hard-to-inform" into "TROLL". If the entire world told you no, you would proceed to argue with them about it.

I'm done... If you should happen to find a way to arm this bomb and go diving with it, please let everyone you dive with know about it before you dive with them... especially any dive charter boats you board. They may want to take extra cautions to ensure the safety of their customers.