cylinder safety notice

[santy2506]

Here's a list of the cylinders made with 6351 T6 aluminium.

List of Scuba Tanks Made From 6351-T6 Alloy

This alloy has a problem with sustained load cracking, and may fail explosively. Any cylinder made before 1990 is suspect, and many dive shops will not service or fill any aluminium cylinder made before then.

Here's the homepage. (some photos can be gory if you follow the links)

The Latest Victim of 6351-T6 Scuba Tanks

 

[LeadTurn_SD]

Ummm, no.

Not "any" aluminum cylinder made before 1990 is suspect, and 6351-T6 alloy is not necessarily "bad". Shops that refuse to fill "any" cylinder manufactured prior to 1990 are employing a Draconian measure based on ignorance, non-rational fear, greed, or all the above.

First, please take the time to carefully read the actual DOT statement regarding these tanks, which is more current (and more authoritative) than the article linked above.

http://www.gpo.gov/fdsys/pkg/FR-2006-08-29/pdf/E6-14255.pdf

To summarize, there have been incidents of these tanks rupturing during filling (but nobody seems to worry about steel tanks, which have more reported ruptures).

The story on these ruptures is not cut and dry. There is some evidence that the tanks that ruptured at least in some cases had been overfilled in the past, and some had apparently been used in Florida cave country, where routine significant overfilling of LP Steel tanks is common; but significant overfilling of Aluminum tanks is not ok under any circumstances.

Neck cracking in some cases was also thought to be caused by over-torqueing the tank valve after VIP by a ham-fisted shop employee, causing cracks in the threads.

The final word from the DOT is that these tanks are fine to continue using, but they need to pass hydro and visual eddy testing. The visual inspection cannot be hap-hazard as may be the case with some shops.

Yes, I have a VERY old (1978) Aqualung Al80, yes it is the "bad" alloy, and yes I will happily continue to dive it for just as long as it passes inspection.... and my dive shop owner is also an "old timer", and has no issues with the "bad" alloy as long as they pass his inspection and hydro.

This article by PSI in 2011 is also worth a quick read:

http://www.psicylinders.com/inspectors/library/18-a-short-review-of-6351-alloy-aluminum-cylinders


Having said all that, there are shops who will not fill these tanks, even if they pass hydro and visual eddy testing. I agree that is their right, but have a suspicion that in some cases they want to sell you a new tank.

Best wishes.

 

[Glenn08]

I have 1974 vintage twin 50's. I was fortunate to find a shop that was informed, rather than alarmist. They passed hydro and inspection, and I am still using them. And it bears repeating that the failed tanks were suspected to have been repeatedly over-filled. Makes me wonder if the shop that refuses to fill them are guilty of hot-fills and over-fills ?

 

[chrpai]

If the second latest victim was from 12 years ago... what does that tell you?

Oh but if we could just save one life.... sorry, that argument falls flat on me.

 

[herr2720]

I usually take my tanks with me when I car travel, and as long as they have current testing I've never had a shop question my tanks or refuse to fill them. The only difference I've seen is requiring a Viz Plus for the 6351 T6 Aluminum and only a Viz for the 6031.
I have several Catalinas from the mid 80s and those are 6031, the one thing I have noticed with them vs my newer Catalinas is the neck is thicker but they have the same buoyancy properties as the older ones unlike my Luxfer tanks.
I know that Steel is a whole different beast and my oldest tank is a 1970 LP Steel which is always filled no questions asked. I also work in healthcare and found E Cylinders of oxygen with original hydro dates in the 50s.
As long as they pass hydro I have no concerns with my tanks, but I am curious as to the percentage of tanks that fail hydro due to age rather than improper use/care.

 

[LeadTurn_SD]

..... As long as they pass hydro I have no concerns with my tanks, but I am curious as to the percentage of tanks that fail hydro due to age rather than improper use/care.

Agreed. I'm also curious about the longevity of tanks.... I still have the original steel 72' I bought right after I was certified in 1976.

My understanding is that our tanks will outlive most of us, and our grandkids could still be using them years from now.....

Thousands of fill cycles are generally considered to be the norm before they fail hydro, but a small percentage do fail hydro at a relatively "young" age.

Not sure if that is due to abuse of some kind, or just an imperfect (flawed) tank?

Best wishes.

 

[akdeepdiver]

I run a hydroshop on Oahu. The percentage of tanks that fail each year is usually less than 1% and the majority of those are because of the owners fault (overfilling, corrosion, etc). I also own and will dive my aluminum tanks made out of 6351-T6 Aluminum alloy. As long as the tank passes hydro/Eddy Current/and visual inspections, it is good to use. I have tested tanks that are over 80 years old for industrial purposes and they passed fine. Anyone who is curious about the actual hydro process should get ahold of me and I can walk a person though what is involved.

I do want to thank the OP for helping to spread the 6351 misinformation panic.
Myles

 

[bletso]

I also run a commercial hydro business. Our policy is that we will hydro a SCUBA cylinder made of 6351. We will not however even hydro a medical or other 6351 cylinder. The rational is that the SCUBA cyls are visually looked at once a year and a crack developing will be found before it is a problem. (Our local LDS's do proper and diligent visuals). Medicals however are looked at only at hydro, (once every 5 years). Our experience is that they have cracked in that period. Luxfer and the DOT think once every five years is sufficient, but we have found cracks will propagate faster from no-see-ums to very prominent in just a couple of years. Be safe not sorry. Our facility stamp will not be affixed and the cyl is returned untested to the owner. They are free to send them to another facility. We still find a couple a month with cracks in the shoulder and threads. We test upwards to 2000 cylinders a month.

Dale
www.engineeredinspection.com

 

[toddthecat]

Any cylinder made before 1990 is suspect, and many dive shops will not service or fill any aluminium cylinder made before then.

Another individual with whom a scare tactic was successful. LeadTurn provided you with some good links. I'd suggest using them.

 

[keller34]

I have 2 that are from that era and just got them hydroed and vis this month. Never had an issue and the shop will fill them no problem. I asked them what they thought about it and they said that it was just a scare tactic used by some shops to sell more tanks and because they didn't know any better.

But wait, your house and car were built before this year! They are very dangerous and could kill you...Sign them over to me and I will dispose of them for you at no charge!

Plus just to show you how great of a guy I am I will help you buy another one.