DOT Expiration date on early Tanks?

[JamesBon92007]

At my store, we do have a very nice eddy current tester. We simply choose to follow the guidance of the DOT in helping remove these cylinders from service.

I don't think I've heard about the DOT guidance thing yet. Could you please give me more details?

 

[Delta_P]

The information I read also said there was no recall on the cylinders and I also read about the $50 credit from Luxfer. I also read that Luxfer recommends a VIP every 2.5 years for their "questionable" tanks for normal use and more frequently for heavy use (rental tanks, perhaps). But every dive shop I've ever heard of insists on a VIP annually. This DOES seem like somewhat of a money grab to me but I'll wait to see what you dive shop owners have to say about that

Where are you reading this stuff? I assume you mean "hydro" and not "VIP".

http://www.luxfercylinders.com/downloads/docs/scubaguide.pdf

Minimum for a VIP (as per the manufacturer) is annually, more often under heavy use.

Also, I could only find one article concerning one incident where a 6351-T6 tank exploded and the report was rather confusing. They said the tank had not been filled yet and that the guy merely connected the fitting to the tank valve and possibly opened the tank valve when all hell broke loose. So, what I would like to know is did anyone ever determine WHY it exploded?

Keep looking using the term "Sustained Load Cracking". There have been at least a half a dozen cases worldwide. Metallurgists were able to determine the problem was too much lead in the alloy allowing cracks to develop in the neck over time.

Luxfer: Support

A very rare event so far, but when it happens it tends to kill and maim fill station operators, not divers. If I'm remembering the report correctly that I think you're referring to the tank was observed hissing slightly immediately before the explosion. Even an almost empty tank can still do a lot of damage in the wrong situation.

I'l be happy to remove my tanks from service if someone convinces me they are not safe. But so far, according to the information that I have found, the tanks should be fine as long as they pass the VIP and hydro etc. I read mention of other tanks that failed but couldn't find any details but it sounds like they were probably all problems with cracked necks or heat treated paint jobs or some other physical damage. I would think that a VIP should reveal a neck crack. As for the eddie current test, I've read a little about it but so far nobody has told me I needed one but it's still early.

I've noticed that paranoia about this depends on how close you were to an incident. Shops in B.C. and Florida seem to be quite sensitive about it, California not so much.

Anyone who tells you SLCs can be picked up reliably during a normal visual inspection has never seen the real thing. Some may be obvious but others are very difficult to see even when the eddy current test has told you where to look. If the threads aren't properly cleaned before inspection they're even harder to find.

Back in 1999 when an incident happened near us I had 20+ 6351 tanks in my inventory. One of the local shops bought an eddy current test machine and I took them all in for testing. They came back with an 80% failure rate. Luxfer indicated this was far too high and probably operator error so I sent four of them to another agency that had the machine but didn't have a vested interest in selling equipment. Of this batch two passed, one was suspect, and the fourth had multiple cracks forming in the neck .

Not a good feeling.

I took a cold chisel to all the tanks and took them to recycling. Was this a rational decision? Probably not. The risk is something happening to a particular tank is like 2 million to one, but in the end I decided I needed to be willing to sit on each cylinder while it was filling and I wasn't comfortable with that idea.

Rationally, if you know the history of the cylinder, have it hydro tested every 5 years and VIP'd by a well trained, knowledgeable inspector who uses an eddy current tester as part of his kit and takes the time to clean and inspect properly there should be minimal risk.

The fact that the shops in your area aren't insisting on eddy current tests for these particular cylinders makes me wonder how knowledgeable and up to date they're keeping their staff. But I guess the risk is minimal and there's a ready supply of 17 year olds if that one in a million does happen.

More homework:

Neck Cracks

 

[MattCrunk]

I believe the cylinder in question was an SP6498 cylinder. It had not been over-stamped with the 3AL stamp. Further, we have chosen not to fill 6351T6 cylinders. I think the instruction to Matt was that certain hydro facilities would possibly do the over-stamp at this late date and would hydro the cylinders. That said, local filling would not be possible at our store.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

Hey Phil,
You may have indeed advised me that certain hydro facilities might test and overstamp it. I'm sure your memory of the details is probably better than mine because you deal with this stuff every day. I don't. I probably figured at that point the tank just wasn't worth the trouble to pursue it further. All this talk of vintage equipment has just got me thinking about all the old stuff I've had over the years, most of which I wish I'd hung on to - as a wall hanger if nothing else. I bought an old steel tank the other day and wondered if I might have a similar problem with it.

 

[John C. Ratliff]

As I said earlier, I have a pair of twin 50s that are these kind of tanks. I used them today in three dives in the Clackamas River. Starting pressure was 2700 psig, ending is now about 350 psig. I like them as twins, as they sit on my back nicely, and allow me to place my double hose regulators low on my back. I have had these tanks since the 1980s, when I bought them from a recently widowed woman who's husband died tragically in a bridge accident (he was wearing fall protection, when part of the bridge he was working on gave way, along with his anchor). These tanks have been overstamped with the "AL" designation, visually inspected (and eddie tested) every year, and hydroed every five years. Their last hydro was late last year. So at this point, I'm rather reluctant to drill them and condemn them. But, I would do that if I felt that the shop's safety was on the line. I just thought of something too, SLC (sustained load cracking) probably would be difficult to occur if there were no sustained load. So, with my tanks at 350 psig, I think they will remain there until just before my next use of these tanks.

I have condemned one set of double tanks, which I got while in the US Air Force. They were from the same source as our pararescue jump tanks; piano-wrapped 40 cubic foot cylinders from 20-man life rifts (originally CO2 cylinders) with a pressure rating of 2100 psig. In the USAF, we unwrapped them, tapped the cylinder to 1/2" pipe thread (they had originally an outside neck thread) and set them up for twin doubles. I used these throughout my almost ten-year USAF career as a PJ. But in the early 1990s I heard that these cylinders were being condemned by the USAF, and pararescue had ceased to use them. I therefore had them drilled (cannot hold air with a hole in them), and sent out as scrap metal. Recently, a set of these tanks appeared on EBay, and I bid for them. I would not go over $233, as I knew there was a very high likelihood that they would not pass a hydro. I was outbid, and I think the went for a little over $200. These tanks, if they pass a good hydro, are comfortable and light. I was really reluctant to discard my set of them, but did so because the prospect of something happening to someone at the dive shop left me feeling it was worth it. Since I had the necks tapped, and there was an obvious broken thread, the decision was not hard even though they had passed several hydros. I've enclosed the EBay photo of this set of like tanks, along with some of my 1967 and 1969 photos of the tanks in use.

SeaRat

 

[JamesBon92007]

Where are you reading this stuff? I assume you mean "hydro" and not "VIP".

http://www.luxfercylinders.com/downloads/docs/scubaguide.pdf

Minimum for a VIP (as per the manufacturer) is annually, more often under heavy use.



Keep looking using the term "Sustained Load Cracking". There have been at least a half a dozen cases worldwide. Metallurgists were able to determine the problem was too much lead in the alloy allowing cracks to develop in the neck over time.

Luxfer: Support

]

According to the Luxfer VIP Guide you are right and I am wrong. I don't *think* what I read was hydro testing and not VIP but I can't find that info right now. Perhaps it was some outdated material and I didn't notice the date. If I find it I'll post it--I can't find where it says 2 1/2 years for hydro testing either.

It was easy to find info searching for "Sustained Load Cracking." Thank you. According to Luxfer only 11 scuba (reported) tanks have blown up. That seems like a very small number, unless you are the one filling the tank.

Luxfer says it takes 8-9 years for a crack to "grow." That *seems* like a long time and it *seems* like it should be safe to use the tanks but now I'm leaning toward getting some new tanks and wondering what the old ones might be good for.

Anyone have any specific info on Walter Kidde 6531 tanks? Are they worse than Luxfers?

I was unable to determine what kind of alloy my old US Divers Aluminum 50 is made from. Once again it says: USD R19220, SP 6498-3000, 6<74, and is overstamped with the 3AL. Is this one probably OK? I guess I'll go back and read the posts again.

What's the best new tank to buy? Aluminum or steel?

 

[DaleC]

I've noticed that paranoia about this depends on how close you were to an incident. Shops in B.C. and Florida seem to be quite sensitive about it, California not so much.

Anyone who tells you SLCs can be picked up reliably during a normal visual inspection has never seen the real thing. Some may be obvious but others are very difficult to see even when the eddy current test has told you where to look. If the threads aren't properly cleaned before inspection they're even harder to find.

Back in 1999 when an incident happened near us I had 20+ 6351 tanks in my inventory. One of the local shops bought an eddy current test machine and I took them all in for testing. They came back with an 80% failure rate. Luxfer indicated this was far too high and probably operator error so I sent four of them to another agency that had the machine but didn't have a vested interest in selling equipment. Of this batch two passed, one was suspect, and the fourth had multiple cracks forming in the neck .

Not a good feeling.

I took a cold chisel to all the tanks and took them to recycling. Was this a rational decision? Probably not. The risk is something happening to a particular tank is like 2 million to one, but in the end I decided I needed to be willing to sit on each cylinder while it was filling and I wasn't comfortable with that idea.

Rationally, if you know the history of the cylinder, have it hydro tested every 5 years and VIP'd by a well trained, knowledgeable inspector who uses an eddy current tester as part of his kit and takes the time to clean and inspect properly there should be minimal risk.

The fact that the shops in your area aren't insisting on eddy current tests for these particular cylinders makes me wonder how knowledgeable and up to date they're keeping their staff. But I guess the risk is minimal and there's a ready supply of 17 year olds if that one in a million does happen.

More homework:

Neck Cracks

Delta, I live in BC and the paranoia seems to be centered in the okanogan as far as I can tell. And I do say paranoia. When I was up there I had a shop flat out refuse to fill a 6061 cylinder because it was over 20 years old. No rationale explanation to it at all. The LFS staff member I spoke to acted very smug about his decision but all I could think was "retard". I also call BS to the claim of an 80% failure rate, just do the math; 12 or 13 failures in 25 million but you happen to have 16 out of 20 fail??? This reminds me of the loosy goosy facts being bantied about by another poster in yet another 6351 thread I once participated in. My reading of the available data indicates that SLC can be detected years befor it becomes a problem by a compitent tester. If the LFS isn't picking up cracks because of dirty threads its a tester problem, not a cylinder problem.

Having said that I just did my last dives on my Al80 6351's (born 1976). I always said I would take them out of rotation when I "naturally" gained replacement cylinders. I am swapping them with two Voit ST72's though (born 1970, 1971) so... I don't know what that means.

 

[captain]

If most of your diving is with heavy exposure protection such as a 5 or 7 mill wet suit or dry suit steel would be a better choice because you would not need as much weight as with aluminum. The down side is steel is significantly more expensive. Service life of either should not be an issue with proper care.

 

[Delta_P]

I also call BS to the claim of an 80% failure rate, just do the math; 12 or 13 failures in 25 million but you happen to have 16 out of 20 fail??? This reminds me of the loosy goosy facts being bantied about by another poster in yet another 6351 thread I once participated in. My reading of the available data indicates that SLC can be detected years befor it becomes a problem by a compitent tester. If the LFS isn't picking up cracks because of dirty threads its a tester problem, not a cylinder problem.

Sorry if I wasn't clear - that was my point. I just had 4 re-tested so I don't know what the real rate was, but as Luxfer indicated it most certainly was not 80%. The problem was I then knew I didn't have a reliable testing service nearby and wasn't comfortable continuing to use the tanks while they sorted things out.

Delta, I live in BC and the paranoia seems to be centered in the okanogan as far as I can tell. And I do say paranoia. When I was up there I had a shop flat out refuse to fill a 6061 cylinder because it was over 20 years old. No rationale explanation to it at all. The LFS staff member I spoke to acted very smug about his decision but all I could think was "retard".

I haven't been inside an Island shop with a tank for years, so I don't know what the situation here is like. Hopefully a bit saner. What got me out completely was an incident where my 6061 tanks were tested with a 6351 eddy tester. The false positive rate drops to a mere 25% when they do that.

All you can do is refer them to Luxfer's materials. It's not like Luxfer or PSI hide any of this stuff, so I really don't understand why fill station operators and testers don't haul it out when something like this comes up. If a shop isn't doing this I'd be worried they aren't reading and following their compressor's operating manual either, so maybe I don't want to breath their air...

 

[duckbill]

If a shop isn't doing this I'd be worried they aren't reading and following their compressor's operating manual either, so maybe I don't want to breath their air...

LOL! Good point.

 

[JamesBon92007]

Where are you reading this stuff? I assume you mean "hydro" and not "VIP".

http://www.luxfercylinders.com/downloads/docs/scubaguide.pdf

Minimum for a VIP (as per the manufacturer) is annually, more often under heavy use.

This is from a Luxfer VIP Guide from 1972-1987 so yes, it is out-of-date.

>>The frequency of inspection for an SCBA cylinder is determined by the type of cylinder,
how often it is used22 and the care4 it has received.
Aluminum Cylinders and Hoop-Wrapped Composite Cylinders
Luxfer has identified three levels of service: Normal, Heavy and Unusual Treatment,
Accident or Condition (UTAC). They are defined as follows:
A. NORMAL SERVICE. These cylinders are well cared4 for and maintained and are filled
or ‘topped off’ three or four times22 a week or less. Every SCBA cylinder in good condition
should be visually inspected no less than every 30 months for all-aluminum
and every 18 months for hoop-wrapped composite cylinders and at any opportune
time before that point.15
B. HEAVY SERVICE: “Heavy service” means any one or more of the following:
1. Cylinders being filled or ‘topped off’ five or more times per week; and/or
2. Cylinders used wherever damage is more likely than in normal use or where the
care and/or maintenance is below recommended care;4 and/or
3. Normal Service Cylinders that have been repaired (defined below).
If the cylinder is used in Heavy Service, it should be inspected every twelve months<<


However, this is not the document that I read--I'm sure it was fairly recent. I just can't find the one I read but I recall it said 2 1/2 years as opposed to 30 months and was regarding the alloys under discussion. I'll keep looking...

I don't necessarily agree with this, but it does not agree with the required frequency of VIPs, even at the time it was written. As I recall, in the late 80s and early 90s some dive shops required a VIP annually and other dive shops did not require a VIP at all.

As dive shop owners, how often does a scuba tank (either steel or aluminum) NOT pass a hydro test, VIP, or eddy test and become condemned?