New guy bought a used AL tank: A story

[300bar]

Uh, thanks, I think???



PROBE=LONG NEEDLES IN YOUR BRAIN,DON"T THANK ME YET.WAIT FOR THE PROBING

I have learned that getting the science down FIRST is the best way to approach any new discipline.

That's very true and therefore I thank you for the links,they might come in handy when we go to AL tanks over here
But for now it's very interesting stuff to read

 

[Stu S.]

Hey, Pete. Do you know the percentage of the 6351 cylinders fail VIP or eddy? There is an inspector (and dive shop owner) in our area that told me he fails most of them. And, he only fills ones with his VIP stickers.

Saying that he is my main source of air and nitrox, I ended up sending my oldie out of state, rather than possibly scrap it due to a false failure.

What do you know? Thanks / Stu

 

[tnrussell50]

Dang, you guys have been busy with the posts!

Just updating, I got that sucker filled at Crazy Scuba..... then the ambulance came and... nah, jes kiddin , worked good, no sweat. Thanks for the great info guys.

 

[DA Aquamaster]

Hey, Pete. Do you know the percentage of the 6351 cylinders fail VIP or eddy? There is an inspector (and dive shop owner) in our area that told me he fails most of them. And, he only fills ones with his VIP stickers.

Saying that he is my main source of air and nitrox, I ended up sending my oldie out of state, rather than possibly scrap it due to a false failure.

What do you know? Thanks / Stu

The shop I used to be asociated with had a hydro test facility onsite and out of probably a hundred or more 6351 tanks inspected per month found 2 or 3 per year that had cracks. So I would estimate based on that experience that the failure rate is still well below the 1 percent range even on tanks over 20 years old.

The type of tank made a difference though. SCBA tank were more commonly found with cracks, with the thought being that they were more likely to be slam filled. Medical O2 and CO2 tanks were less likely to be cracked, but they operate at lower pressures. The incidence of cracks would still be well below 1% though.

The crack versus fold issue really is an issue here as well since folds are fine (and normal), cracks are not, but an improperly trained inspector could fail a tank due to a fold.

 

[evensplit]

...The crack versus fold issue really is an issue here as well since folds are fine (and normal), cracks are not, but an improperly trained inspector could fail a tank due to a fold.

According to Luxfer's SCUBA cylinder inspection guide:

"CONDEMN all cylinders with one or more folds in the interior crown area
deeper than 0.060 inches (1.53 mm). Contact Luxfer with this information
and findings."

 

[oxyhacker]

Luxfer puts the number of 6351 tanks failing for SLC at 1.25%, so add all the other reasons a tank might fail, and you still are only at 5%, if even that.

However, if an inspector has a first generation eddy current tester and has never learned to properly use it, and doesn't know the difference between valleys, folds, tool marks and cracks, then the sky's the limit.

Some shops have a zero tolerance policy towards 6351 tanks, and will fail them for minor problems they'd probably let go on other tanks. This will run up the failure rate a bit. However, if a shop is failing "most" of the 6351 tanks they see (or most of the steel 72s, or a lot of the HP steels) then there is something seriously flawed with how they are doing their inspections.

Hey, Pete. Do you know the percentage of the 6351 cylinders fail VIP or eddy? There is an inspector (and dive shop owner) in our area that told me he fails most of them.

 

[rjack321]

According to Luxfer's SCUBA cylinder inspection guide:

"CONDEMN all cylinders with one or more folds in the interior crown area
deeper than 0.060 inches (1.53 mm). Contact Luxfer with this information
and findings."

Folds cannot grow or change. And ones this big are serious manufacturing defects that should never have been delivered to customers. I have seen some folds in AL80s and PST steels, but never even close to these kinds of sizes.