Is my U.S. Diver’s Cylinder still OK to use?

[WI Scuba Dave]

Sorry in advance if this has been answered over and over, I’ve looked through a number of old threads and I’m not sure what to think. I just had the cylinder hydro’d and visually inspected and it passed at one shop. But another shop refused to fill it.

it’s marked DOT-E6498-3000

I have attached a photo as well.

Thanks in advance!
Dave

 

[Zef]

Aluminum cylinders made from 1972 to 1988 from 6351 alloy can suffer from what is known as sustained load cracking (SLC) which can cause the cylinder to catastrophically fail, particularly while being filled.

For the US, the following markings are indications that the cylinder was made from 6351 alloy:
DOT SP6498
DOT E6498
DOT E7042
DOT E8107
DOT E8364
DOT E8422

There are few shops that are willing to risk filling 6351 alloy cylinders and some shops are applying a blanket "will not fill" policy to any aluminum alloy cylinder that is 20 years old or older.

Unfortunately, since your tank bears the mark "DOT E6498" and it was made circa 1978, yours is among the affected.

My recommendation is to drill the neck and turn it into garden art or sell it for scrap. Then put the cash towards a new cylinder.

Good luck.

-Z

 

[WI Scuba Dave]

Damn. That’s disappointing. But thanks!! It’s good to know.
I’ve had that cylinder since I was certified at 16. It was brand new then.

 

[broncobowsher]

Since it was just hydro and VIPed, I would go ahead and use it for now. You know the shop that will fill it. And one that won't. So long as you keep using the shop that will fill it you do shill have a usable tank. But you will have the reality that the number of places that will fill it is limited and probably shrinking. At this point I wouldn't bother with the next hydro. Time to retire it. But you have time to shop for a new tank. Above is the list to avoid.

 

[WI Scuba Dave]

Since it was just hydro and VIPed, I would go ahead and use it for now. You know the shop that will fill it. And one that won't. So long as you keep using the shop that will fill it you do shill have a usable tank. But you will have the reality that the number of places that will fill it is limited and probably shrinking. At this point I wouldn't bother with the next hydro. Time to retire it. But you have time to shop for a new tank. Above is the list to avoid.

Great suggestion. Thanks!

 

[bletso]

I really am conflicted on this subject. If a cylinder is properly visualed every year it should be OK. I regularly hydro 6351 material scuba cyls for the local dive shop. We do find cracked necks fairly regularly. I will not hydro medical or scba's of the same vintage as they can go 5 years before a look. I never believed Luxfer and their pronouncements of crack progression/time. The DOT allowing a two thread crack is bull in my opinion. (Once started they can progress quickly.) Oh, and the cracks generally start below the threads and move up. Eddy current doesn't look there. The best tool I have found is the Optical plus. I would also never use a 6351 material for O2 service.

 

[Zef]

I really am conflicted on this subject. If a cylinder is properly visualed every year it should be OK.

That is all well and good, the bottom line is whether any particular dive shop will fill the OP's cylinder or not. If there is a shop comfortable enough with the level of risk to fill his cylinder then great for the OP, and anyone else in a similar situation.

The ultimate question the OP needs to ask themself is whether they want to deal with the hassle of this tank...in the US a visual inspection is required by the SCUBA industry every year, additionally a 6351 alloy cylinder needs an eddy current test along with that visual inspection. Lets say the tank was hydrostatically tested, VIPed and eddy current tested and passed today....the OP could show up at a the same shop tomorrow and they can decide they will not fill the cylinder due to their perception of risk, the OP would have few if any choices of other places to go to get the cylinder filled. Lets take the same test scenario but fast forward to the following year....each year is a gamble whether or not the cylinder will pass the eddy current test...many find it money better spent with more piece of mind and less hassle to ditch the cylinder and invest in a non 6351 alloy cylinder.

The fact the cylinder was first stamped in 1978 means it is 42 years old...that is a long time for a cylinder made from an alloy subject to both sustain load cracking and work hardening. I am surprised the OP found a shop willing to service the cylinder at all, and even more surprised there is even a shop willing to fill it...I am also surprised that the OP did not mention anything in their post about eddy current testing which makes me wonder if the shop that did the visual inspection overlooked the type of material the cylinder is made from.

-Z

 

[lexvil]

I use my old tank all the time, for setting up gear.

Several years ago my only bad alloy tank passed all the tests but as I researched things the thought of that bomb sitting on my back just wasn’t a go anymore, I do need to drill a hole in it.

A new al 80 isn’t all that high, certainly not worth the risk.

 

[broncobowsher]

The long term plan is going to have to be a new tank. With the current limitations of where and who will fill it and it is only going to get worse. The short term solution is to use the one shop that will fill it. That will get through until a good deal on a good tank will be found. Might find a good deal this afternoon, maybe an end of the year sale. It is not urgent to get a new tank right away, but you know that what you have has limitations and that will be a problem in the future.