I think I have been "had" just a bit

[rstofer]

The service life of an AL tank is approximately 40 years unless condemned for several issue one of which is SLC that lot's of folks fail to look for when VIP'ing the bottles so as opposed to trusting the last monkey to VIP it they used their monkey to VIP it.

Although 40 years seems like a long time, I don't know where the 'number' comes from. Luxfer rates their tanks for 100,000 cycles and cycles is what exercises the metal.

One hundred thousand cycles at 4 per week, 52 weeks per year is about 480 years.

Even if the tank were filled twice a DAY, 365 days per year the life expectancy would be about 136 years.

I have never seen SLC discussed in the context of 6061 tanks anywhere except on SB.

Luxfer: Sustained-load Cracking FAQ

Note the ultimate sentence on that page (emphasis added):

Only Luxfer’s proprietary 6061 aluminum alloy—which is not susceptible to sustained-load cracking—was used for Luxfer Australia cylinders.

Richard

 

[syntaxerrorsix]

Although 40 years seems like a long time, I don't know where the 'number' comes from. Luxfer rates their tanks for 100,000 cycles and cycles is what exercises the metal.

It's in the CFR. I can't quote it because I don't have a copy sitting in front of me.

One hundred thousand cycles at 4 per week, 52 weeks per year is about 480 years.

Even if the tank were filled twice a DAY, 365 days per year the life expectancy would be about 136 years.

I have never seen SLC discussed in the context of 6061 tanks anywhere except on SB.

Luxfer: Sustained-load Cracking FAQ

Note the ultimate sentence on that page (emphasis added):



Richard

This is true, there are no examples of 6061 alloys exhibiting SLC.

 

[mathauck0814]

You weren't "had". You just got what you paid for.

I tend to think of aluminum tanks as disposables anyway. As many have noted in this thread, buy steel and you'll never have to deal with this problem (and you'll get the added benefits of the superior tanks as well).

 

[Captain Larry]

I am assuming if they wanted to do there own visual eddy test on it, it would take some time, and if so how long, because I dropped the tank off at 1, and it was ready by 5, I am not sure if that is enough time to run a VE test on it.

It takes just a few minutes to do a Eddy Current test provided the shop has a certified eddy current tester available. The inspector threads a probe into your cleaned neck threads and then slowly unscrews the probe.
We eddy test every tank that comes in for VIP. The VIP+3 system (which we use) actually provides us with the opportunity to print out the results which will show each thread in a different color. If cracks are present it will show the depth, and angle of the crack as well as its location on the thread and whether or not it crosses additional threads.
We save each inspection result for future reference. We also provide a color printout to our customer.
We always back up the eddy current test with a visual inspection using a magnifying inspection scope.
We provide each customer with a color copy of the test results and we save a copy on our computer for future reference or for liability issues. We also back up all eddy current tests with visual inspections using a magnified scope. After seeing the results of the eddy current tester I would never trust my tanks to a shop that uses only a dental mirror and light to inspect tank threads.

 

[rstofer]

It's in the CFR. I can't quote it because I don't have a copy sitting in front of me.

I would be interested if you could find it. AFAIK the service life of a 3AL cylinder is not restricted so long as it continues to pass periodic testing. Various composite and aircraft tanks do have restricted life.

Here is a "Fact vs Fiction" list of tank issues:

Facts & Fictions

Search for "15 years" to get to the appropriate fiction.

I'll grant that this page doesn't carry the weight of 49 CFR 173 but I just can't find a service life restriction in that document by searching for 3AL. Sure, I can find it for 3HT tanks and I can probably find it for other composite tanks but that isn't the issue at hand.

At the moment, all I can document is the 100,000 cycles specification from Luxfer.

Richard

 

[LIVES4SHARKS]

I just finished the PSI course and if you have questions about your tanks, I would contact Mark Gresham at PSI for more information psi@psicylinders.com. PSI is not recommending the 6351 tanks be scrapped, but they should have current VIS/HYDRO/EDDY testing done by qualified professionals. The 6351 tanks had a much greater incidence of neck cracks due to sustained load cracking caused by the alloy used and the amount of lead in the material used during that time period. The fill operator is the one most at risk from the tanks since these issues with rupture do happen at the fill stations. It is still up to each shop to fill or not fill. It does sound like the 2nd shop was not up to par if they did a VIS/EDDY and did not put their sticker on the tank. They are the last to inspect it so they are the last to take responsibility for the inspection.

A short Review of 6351 Alloy Alu

Carolyn:shark2:

 

[syntaxerrorsix]

I would be interested if you could find it. AFAIK the service life of a 3AL cylinder is not restricted so long as it continues to pass periodic testing. Various composite and aircraft tanks do have restricted life.

Here is a "Fact vs Fiction" list of tank issues:

Facts & Fictions

Search for "15 years" to get to the appropriate fiction.

I'll grant that this page doesn't carry the weight of 49 CFR 173 but I just can't find a service life restriction in that document by searching for 3AL. Sure, I can find it for 3HT tanks and I can probably find it for other composite tanks but that isn't the issue at hand.

At the moment, all I can document is the 100,000 cycles specification from Luxfer.

Richard

I'll do my best to research that further. As Luxfer started pumping out AL tanks in the '70s and Catalina in the 80's we haven't even run across any of that age yet. It may be a side note on life expectancy or may have been a hazmat containing aluminum bottle or some other such restriction. As stated the only 15 year life expectancy that is certain are the SCBA's and paintball bottles which stands at 15 years currently. Not much to contest there as it's labeled as such. I'll take a look when I get back from PR on Friday.

 

[rstofer]

I'll do my best to research that further. As Luxfer started pumping out AL tanks in the '70s and Catalina in the 80's we haven't even run across any of that age yet. It may be a side note on life expectancy or may have been a hazmat containing aluminum bottle or some other such restriction. As stated the only 15 year life expectancy that is certain are the SCBA's and paintball bottles which stands at 15 years currently. Not much to contest there as it's labeled as such. I'll take a look when I get back from PR on Friday.

Yes, I don't recall the details but there are some restrictions for hazmat use where, in this case, compressed gas is not being considered hazardous for purposes of determining service life for scuba use.

As you say, we're not going to run into the 40 year thing right away. It's just that some shops aren't always fully aware of the 'real' requirements. Kind of like that '15 year' thing. It pays to keep them honest.

Actually, around here things go exactly as they should. My old Al 80 is known to be 6061, it keeps passing hydro and it keeps getting O2 cleaned and filled. No problems whatsoever.

But if I missed something in the PSI VIP course, I want to get up to date.

Enjoy your trip!

Richard

 

[DaleC]

We can only assume. The OP didn't offer the manufacturer.

No we cannot assume. That is exactly the problem being discussed. "Some" tanks of a certain alloy have "some" risk That a fill operator may or may not choose to address (fair enough). Instead of thinking however, many shops (like you) just assume and discard "all" older tanks. That is what assuming gets you. Until the OP tells us which alloy it is we don't know. Someone in a technical business should approach things in an intelligent sort of way. But... you have a bone and you love to chew it so any opportunity... real or imagined, will do I guess. Continue on with your 6351 rant..

What technical business do you suppose he's going to drum up with his penitent for vintage gear?

Who? What? Did you post into the wrong thread here?

 

[syntaxerrorsix]

No we cannot assume. That is exactly the problem being discussed. "Some" tanks of a certain alloy have "some" risk That a fill operator may or may not choose to address (fair enough). Instead of thinking however, many shops (like you) just assume and discard "all" older tanks. That is what assuming gets you. Until the OP tells us which alloy it is we don't know. Someone in a technical business should approach things in an intelligent sort of way. But... you have a bone and you love to chew it so any opportunity... real or imagined, will do I guess. Continue on with your 6351 rant..




Who? What? Did you post into the wrong thread here?

Aren't you clever. The OP's tank was made in '84 Catalina did not produce AL80's until '86 and Luxfer and Walter Kiddie used the 6351 alloy in the US from 1972 through mid-1988.

Got a calculator handy or can you do the math?