Retiring Tanks based on age alone

[MrNrge]

I am the tank house manager for the Kwajalein Scuba Club and have been so for about a year. As part of my duties I get the tanks hydroed and inspected. I just had a member that came back from the DEMA conference in Florida and he told me that many of the state side shops (in FL specifically) will no longer refill tanks greater than 20 years old regardless of them passing all the inspection requirements. Is there any documented reason for this? If there is could you please send the link or reference?

Thanks in advance
MrNrge

 

[tomfcrist]

Pure ignorance is the reason for this . They are worried about sustained load cracking, which isn't an issue in the majority of those old tanks . Do an eddy inspection annually if they are your tanks, quarterly if you are renting them out or using them daily. Problem solved.

 

[herman]

And there never was an issue with steel tanks...then there is profit to be made selling new tanks to those who would otherwise not need tanks.

 

[Rich Keller]

If they pass all the tests there is no reason to take them out of service. This is being done by people who either do not know what they are doing or just want to sell new tanks. In either case they give the sport a bad name and may someday cause there to be government of the sport.

 

[Superlyte27]

We won't fill bad alloy tanks. Everything else is fair game. No reason to refuse a tank simply on age. We've got steel tanks in our rental that are 40 years old and still pass hydro.

 

[Rich Keller]

I would even disagree with not filling bad alloy tanks if they pass all the tests but at least there is some science behind making that choice. As for the rest of the tanks there is no good reason not to fill them due to age. If some shop owner tells me he will not fill a tank due to age I would want to see the age of his rental tanks.

 

[Superlyte27]

I would even disagree with not filling bad alloy tanks if they pass all the tests but at least there is some science behind making that choice. As for the rest of the tanks there is no good reason no to fill them due to age.

I have a friend whose shop and shop employee got blown to pieces filling a bad alloy tank. You can have a visual eddy done two weeks ago and develop a crack next month. But that's a thread that's been beaten to death. Not filling these tanks is a choice I've been quite comfortable with for some time now. I don't lose any sleep at all over it.

 

[Scared Silly]

The 20 year limit is based loosely on the AL6351 cylinders:

Is my cylinder made from the "bad" alloy aka AL6351?

Many shops used it as rule to weed out Al6351 cylinders. Unfortunately, it has morphed into an all in compassing rule including not only AL6061 cylinder but also steel cylinders.

As for the Al6351 cylinders, the cracks are slow growing, if properly inspected they can be detected and removed from service before they are problematic. The issue is the properly inspected. While there are many in the scuba industry who can competently do such inspections they are far too may who can not.

 

[Glenn08]

The aluminum cylinders that failed were suspected of having been repeatedly hot filled and over filled. I have 1974 vintage aluminum tanks that passed testing - done by an 'informed' shop that didn't just want to sell me new tanks. The "+" rating for 10% overfill was for steel tanks only.

 

[scwdive]

The decision to not fill a tank by a business owner is definitely a personal decision. And I respect that right. Several shops across the US have made that decision.

Here are some links about the tanks in question made from the 6351-T6 alloy

http://www.sozogaku.com/fkd/en/hfen/HB1011002.pdf

http://www.hawaii.edu/ehso/diving/Cracking and Ruptures of SCBA and SCUBA Aluminum Cylinders.pdf

http://www.ctcseminars.com/files/te...fety Advisory_ High Pressure Aluminum~950.htm

Hope this helps.

Best