Risk with 1972-1988 AL80 Tanks ?

[DaleC]

every fill operator has a right to decline to fill a tank.

Risk is a personal thing - just don't disguise it as an absolute truth.

These two statements express my sentiments exactly.

I have always said that the one with the compressor gets to make the rules (same with the boat), regardless of whether I might agree or disagree with their reasoning. Just don't suggest that a personal interpretation of risk is inviolate fact. The closest I feel I can come to fact on this matter is the recommendations put forth by DOT.

My question to those that reject the DOT stance on 6351 cylinders is whether they fill all cylinders to the prescribed max pressure or not and whether they go along with 1 year vis's and 5 year hydros? Why not go 1000psi over or insist on 1000psi under or insist on yearly hydros etc... if they believe that DOT specifications can be wrong? Why go along with 99% of the specs but then reject 1% when an error with any of them can result in catastrophic failure?

I personally assess this risk based on the best information possible. Both regulatory and inspection bodies have studied the issue and tabled their guidelines. At some point I have to either accept their expertise or reject it. They have all told me I have a perfectly servicable cylinder.

I really don't have a personal opinion on the subject. My opinion is DOT, Luxfers and PSI's. If theirs changes, so will mine.

 

[rjack321]

Actually, you are undone by your own logic. There is a very simple way to mitigate the risk from a 6351 cylinder. Do a proper Visual inspection. There has not been a single reported case of catastrophic failure in such a case.

Read the thread I linked. In it you will find all the supporting data. It's funny that so many people know someone who was right there when the 6351 tank exploded yet there have only been a few actual cases (pre VE testing), and each one has been well documented.

Dale,
Do you actually own a dive shop or fill station?

Would you trust your competitor to always do a proper inspection?

How about the monkey at the hydro station making minimum wage who was trained on the eddy machine by his friend?

Maybe you shouldn't tell fill station operators what is and isn't acceptable to them until you stand in their shoes next to 20, 30, 70, 100 tanks of sometimes dubious origin a day?

The "risk" of an improper or incomplete visual inspection is very high when it comes to 6351 cylinders. Most of these won't fail. But occasionally one will and it will almost always kill or maim and pretty much destroy the shop space in the process. All for a 20yo cylinder that can be replaced via ebay or craigslist for $80.

 

[rjack321]

Just don't suggest that a personal interpretation of risk is inviolate fact.

This is where you're wrong. "Risk judgements" not fact in the first place. They might be influenced or modified by facts but they are not facts.

 

[PhilEllis]

My question to those that reject the DOT stance on 6351 cylinders is whether they fill all cylinders to the prescribed max pressure or not and whether they go along with 1 year vis's and 5 year hydros? Why not go 1000psi over or insist on 1000psi under or insist on yearly hydros etc... if they believe that DOT specifications can be wrong? Why go along with 99% of the specs but then reject 1% when an error with any of them can result in catastrophic failure?

I will take a crack at this one. If you read through the final recommendations from the PHMSA on this issue, you wouldn't have a clue if 6351T6 cylinders are safe or unsafe. (Well, actually there are clues that they are unsafe. There are no clues that they are safe) You would see a bureaucratic agency compromise decision to allow the use of the cylinders for a "limited remaining service life" based on public comments from a very large number of "respondents" who have a pretty big financial vested interest in seeing that these cylinders WERE NOT removed from service. The manufacturers (they represented about 25% of all respondents) argued that they should remain in service. A person could make a pretty good guess that any other action might have well provided pretty good legal fodder for anyone making a claim that a decision to remove them from service recognized a manufacturing problem. I don't blame them for fighting any action to remove them from service. Certain users of 6351T6 cylinders argued that taking them from service would be a gigantic financial burden to small companies and organizations using them for various purposes. Their arguments were all COMPLETELY FINANCIAL arguments. Some manufacturers (two of them) argued that there were SPECIFIC non-destructive testing methods that could be used to "eliminate from use any cylinders that posed a danger to the public". Would it surprise you to know that BOTH of these happen to manufacture machines designed to do eddy current testing on threaded tank necks. If the cylinders are removed from service completely, I would suspect there would be a limited market for the machines designed to detect the problem.

So, what ACTUALLY did the PHMSA say about 6351T6 cylinders? Well, they certainly never said they were safe. They never said they were just as safe as other alloys. In fact, they specifically said that the argument for leaving them in service was purely based on the economic burden that would be imposed if they took other action. To quote the PHMSA final report.....

"The commenters state that SLC is a
manufacturing problem, and no level of testing will prevent future
incidents. These commenters assert that the only way to prevent future
SLC incidents is to prohibit the use of all aluminum alloy 6351-T6
cylinders. They also assert that the safety benefits outweigh the costs
involved in removing these cylinders from service and express concern
that the SLC problem will only get worse if the cylinders remain in
service. We agree. However, the original economic evaluation showed
immediate removal of these cylinders from service would place an undue
economic burden on the affected industries. Although the economic
burden of immediate removal is not justified, a gradual phase out of
these cylinders over time will address the safety issue, and limit the
costs associated with removal of these cylinders."

They did give a little hint in the convoluted decision to leave these cylinder in service. They imposed an "operational control" for the filling of 6351T6 cylinders that does not exist for ANY OTHER TYPE OF CYLINDER filling operation. To quote....

"F. Operational Controls for Filling Aluminum Alloy Cylinders

In the NPRM, we proposed to add operational controls during the
filling of cylinders constructed of aluminum alloy 6351-T6. The
proposed operational controls included a provision requiring the
cylinder filler to allow only those individuals essential to the
filling process to be in the vicinity of the cylinder during the
filling process.

Commenters generally support this requirement. One commenter
suggests the term ``vicinity'' is not clearly defined and could lead to
wide interpretation. The commenter requests we clarify the area that is
intended to be covered by the term ``vicinity.''

We recognize the term vicinity could be widely interpreted. The
intent of this requirement is to protect non-essential personnel and
innocent bystanders from injury if a cylinder were to rupture during
filling. For purposes of this requirement, vicinity means a location
near or around the filling operation that would impose an unreasonable
risk of injury to an individual if the cylinder were to rupture during
the filling process. The actual distance could vary broadly depending
upon the type of safety mechanisms in place and the actual square
footage of a particular filling location."

In other words, when filling 6351T6 cylinders, get everyone who isn't essential out of the "vicinity". And "vicinity" means that blast zone of un-described and un-defined area, best determined after an explosion happens. Now, this might seem like common sense, but they don't ask for this "clear-out" for filling operations with any other type of cylinder construction.

Anyway just my reading of the final report. I could be wrong.

Phil Ellis
www.divesports.com

 

[Scared Silly]

Phil, like many things, things do not happen until there is enough of a financial burden. I remember a road near my Grandparents that was notorious for accidents. My Grandfather said the state DOT would not do anything until there was a death. A few years later a relative of Frank Sinatra was killed - and sure enough a new overpass.

 

[DaleC]

Dale,
Do you actually own a dive shop or fill station?

No, are they the only ones allowed to comment in this thread? I do have a perfectly servicable 6351 alloy tank though that some would condemn without reasonable justification IMO (hence my participation and interest in the discussion).

Would you trust your competitor to always do a proper inspection?

No. And I said in the thread I linked and other such threads that I thought it was a perfectly reasonable assertion that a fill operator be able to do a VE test on an unfamiliar tank. I do not hold as much of an extremist view on the subject as you might suppose.

How about the monkey at the hydro station making minimum wage who was trained on the eddy machine by his friend?

If you can't trust them in this regard how do you trust them with every other aspect of your cylinder? How do you know if they did a proper hydro?

Maybe you shouldn't tell fill station operators what is and isn't acceptable to them until you stand in their shoes next to 20, 30, 70, 100 tanks of sometimes dubious origin a day?

I don't recall telling any operators what to do or what should be acceptable to them. If you reread my post above I think I explicitly said each person could do what they wanted. I am just defending my reasoning.
Some say A. Some say B. Both provide reasons for their position. I'm pretty sure that's how it works.

The "risk" of an improper or incomplete visual inspection is very high when it comes to 6351 cylinders. Most of these won't fail. But occasionally one will and it will almost always kill or maim and pretty much destroy the shop space in the process. All for a 20yo cylinder that can be replaced via ebay or craigslist for $80.

The risk is about 12 in 25 million or so for cylinders that are not VE tested. The odds are 0 for a properly inspected cylinder. The guy that does the VE testing at my LDS (who also fills the tanks) accepts those odds. I (who am usually standing right beside him during the fill) accept those odds. Your suggestion that it is a $80 ebay fix is ridiculous. It is a multi billion dollar fix. Unless you think 25 million used cylinders will pop up on ebay cheap soon. Of course, many of those same fill operators who won't fill 6351 tanks won't also fill 20yr old tanks either so the used tank you just bought off ebay to solve the problem probably won't help you anyways.

However, if anyone wants to sell me two newer cylinders that are currently vis'd and hydroed for $80 each we could take two 6351's out of circulation right now.

This is where you're wrong. "Risk judgements" not fact in the first place. They might be influenced or modified by facts but they are not facts.

I'm not sure what you mean by this? If it's important for you to express perhaps you could rephrase it.

I will take a crack at this one. If you read through the final recommendations from the PHMSA on this issue, you wouldn't have a clue if 6351T6 cylinders are safe or unsafe. (Well, actually there are clues that they are unsafe. There are no clues that they are safe) You would see a bureaucratic agency compromise decision to allow the use of the cylinders for a "limited remaining service life" based on public comments from a very large number of "respondents" who have a pretty big financial vested interest in seeing that these cylinders WERE NOT removed from service. The manufacturers (they represented about 25% of all respondents) argued that they should remain in service. A person could make a pretty good guess that any other action might have well provided pretty good legal fodder for anyone making a claim that a decision to remove them from service recognized a manufacturing problem. I don't blame them for fighting any action to remove them from service. Certain users of 6351T6 cylinders argued that taking them from service would be a gigantic financial burden to small companies and organizations using them for various purposes. Their arguments were all COMPLETELY FINANCIAL arguments. Some manufacturers (two of them) argued that there were SPECIFIC non-destructive testing methods that could be used to "eliminate from use any cylinders that posed a danger to the public". Would it surprise you to know that BOTH of these happen to manufacture machines designed to do eddy current testing on threaded tank necks. If the cylinders are removed from service completely, I would suspect there would be a limited market for the machines designed to detect the problem.

So, what ACTUALLY did the PHMSA say about 6351T6 cylinders? Well, they certainly never said they were safe. They never said they were just as safe as other alloys. In fact, they specifically said that the argument for leaving them in service was purely based on the economic burden that would be imposed if they took other action. To quote the PHMSA final report.....

"The commenters state that SLC is a
manufacturing problem, and no level of testing will prevent future
incidents. These commenters assert that the only way to prevent future
SLC incidents is to prohibit the use of all aluminum alloy 6351-T6
cylinders. They also assert that the safety benefits outweigh the costs
involved in removing these cylinders from service and express concern
that the SLC problem will only get worse if the cylinders remain in
service. We agree. However, the original economic evaluation showed
immediate removal of these cylinders from service would place an undue
economic burden on the affected industries. Although the economic
burden of immediate removal is not justified, a gradual phase out of
these cylinders over time will address the safety issue, and limit the
costs associated with removal of these cylinders."

They did give a little hint in the convoluted decision to leave these cylinder in service. They imposed an "operational control" for the filling of 6351T6 cylinders that does not exist for ANY OTHER TYPE OF CYLINDER filling operation. To quote....

"F. Operational Controls for Filling Aluminum Alloy Cylinders

In the NPRM, we proposed to add operational controls during the
filling of cylinders constructed of aluminum alloy 6351-T6. The
proposed operational controls included a provision requiring the
cylinder filler to allow only those individuals essential to the
filling process to be in the vicinity of the cylinder during the
filling process.

Commenters generally support this requirement. One commenter
suggests the term ``vicinity'' is not clearly defined and could lead to
wide interpretation. The commenter requests we clarify the area that is
intended to be covered by the term ``vicinity.''

We recognize the term vicinity could be widely interpreted. The
intent of this requirement is to protect non-essential personnel and
innocent bystanders from injury if a cylinder were to rupture during
filling. For purposes of this requirement, vicinity means a location
near or around the filling operation that would impose an unreasonable
risk of injury to an individual if the cylinder were to rupture during
the filling process. The actual distance could vary broadly depending
upon the type of safety mechanisms in place and the actual square
footage of a particular filling location."

In other words, when filling 6351T6 cylinders, get everyone who isn't essential out of the "vicinity". And "vicinity" means that blast zone of un-described and un-defined area, best determined after an explosion happens. Now, this might seem like common sense, but they don't ask for this "clear-out" for filling operations with any other type of cylinder construction.

Anyway just my reading of the final report. I could be wrong.

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

Lots to chew over there Phil and I respect the effort you put into the response so I'll take some time to digest it.

 

[DaleC]

Just a thought but while talking about financial contributors to the decision making process how many LDS's refuse to fill 6351 tanks because they don't want to invest in a VE device or pay for proper training for their employees? Can anyone also ignor the fact that those who would condemn the tanks are also the ones who will sell the new ones?

The fiscal knife can cut both ways.

To me this discussion is about checks and balances. Does anyone simply want to give one viewpoint carte blanche over the usage of cylinders regardless of what the regulatory agencies involved say. I don't believe they have my best interests at heart. Would it stop there. We hear about shops that will also refuse to fill older 6061 Al tanks and some who will even refuse to fill ST 72's. One poster said he would require a vis and hydro of older tanks before filling them (even when the hydro was not up). Another claimed 80-90% failed their vis's. 80-90%.
Who holds the industry accountable for their decisions.
I am a reasonable guy (IMO) and will respond to a reasonable argument. But I won't be swayed by emotional appeals, being called cheap, told I have no respect for human life or other guilt tactics.

 

[PhilEllis]

Just a thought but while talking about financial contributors to the decision making process how many LDS's refuse to fill 6351 tanks because they don't want to invest in a VE device or pay for proper training for their employees? Can anyone also ignore the fact that those who would condemn the tanks are also the ones who will sell the new ones?

I will guarantee you that there are dive stores that exactly match the description you give. People do things and businesses make decision for a vast number of reasons...and financial considerations often come into play. To be honest, I would make more net revenue from the hydro, inspection and filling of a 6351T6 cylinder than I make on the sale of a brand new 6061T6 cylinder, which includes a VIP and first fill at no charge. My decision not to fill these cylinders has nothing to do with financial matters.

In my case, I have an eddy current machine, and when I was using it routinely, I was absolutely confident in my ability to properly use the machine. It has been put away for several years now, for the reasons I state below. I also use a hydro facility that properly follows the DOT recommendations. They perform a VE test on all cylinders made from 6351T6 alloy.

I have recounted this story other places here on ScubaBoard, but I will repeat the important details here again.

We brought a customer cylinder back from hydro several years ago that had been properly visually inspected by the retester prior to the hydro, had been properly hydo tested, and was subjected to a VE test and properly stamped prior to returning it to me. When we received the cylinder, we cleaned it internally and did a through inspection of the thread area. We saw NO evidence of a crack anywhere in the neck area and I am confident that the visual inspection was both complete and proper.

Less then 15 minutes later, upon reaching a pressure of about 2000 PSI in the filling operation, a rather large crack formed in the neck and the tank began an active and rather robust leak. Now, this failure clearly conformed to the LLB failure requirement of any 3AL cylinder, and we are fortunate that it exhibited this failure mode instead of the alternative.

The point is.....REGARDLESS of what the DOT and the manufacturer says about SLC, I experienced a cylinder that failed in a very unpredictable way. There was no easily recognizable evidence of SLC in the cylinder, the exact opposite of what everyone claims will be the case. Now, I can allow for the possibility that I was having a bad day and I simply failed to detect a crack that had been there for years and years. But that is not the evidence. No crack was detected by the visual inspector at the hydro facility, no leak was detected during the hydro expansion, it was not detected by the VE inspection at the hydro facility, and it was not detected by ME during a rather through visual inspection, a process that we follow about 10 times per day.

My stores policy of filing properly inspected 6351T6 cylinder ended that very day at about 4:30 PM in the afternoon. Why? I have limited confidence in the ability of inspection methods alone to successfully correct a clear manufacturing problem. I think it was said well by a responder prior to the PHMSA final report......

"This is a manufacturing problem. No amount of inspection can be thoroughly trusted to eliminate the poor choice of materials in this product. They only remedy to eliminate this risk is the immediate disqualification of these cylinders from commerce".

With regard to this statement, the PHMSA said some simple words....."We agree, but our mandate under the various acts which prohibit the unnecessary transfer of unfunded mandates requires that we look at economic issues as well".

ADDED NOTE: All of the quotes I have used in these several posts are taken from a WordPad document created through clip and paste, and that I saved several years ago to save quotes that interested me in the reading the Federal Register. Unfortunately, I did not save page number references along with these quotes, and the comments in the Federal Register jump around from page to page, and go on for pages and pages and pages. I will attempt to search and find an online source link and will post it on this thread.

Phil Ellis
www.divesports.com

 

[Davidstealey3]

then why dont we do this, if the tanks are going to fail

figure out a way to provide a decent buyback program. we know this debate will not go away untill all the tanks are gone.

it is aluminum, and there has to be a use for it in another type of manufactoring process. i dont know what the diference is in price between the two types of ALM but it cant be much.

the scuba manufactors have buy back programs on old gear, so why cant the tanks? figure out the cost to make a new tank over the price to melt down and reuse the old tanks and add 10% to the cost. then luxfer wont lose money, and the buyer wont get raped over a new tank.

or after XXX years of service, render the 6351 tanks unuseble and implment the above idea.
maybe even the next hydro.

if they were to sit down and come up with a idea how to do this and be cost effective it would work. there is no reason to render them obbsoleate and pull them from service yet, but they are heading in that direction.

 

[PhilEllis]

...figure out a way to provide a decent buyback program. we know this debate will not go away untill all the tanks are gone.

Luxfer operated just such a program for nearly three years. Thousands of these cylinders were removed from service under program. It is reasonable to believe that some of the cylinders removed with this program might have otherwise exhibited this problem, at a later date, and that exhibition might have been disastrous.

or after XXX years of service, render the 6351 tanks unuseble and implment the above idea. maybe even the next hydro.

That was exactly what the PMHSA was counting on when they issued their final ruling on these cylinders. They expected that they would be removed from service after a reasonable service life, through a voluntary program by the scuba industry.

there is no reason to render them obbsoleate and pull them from service yet, but they are heading in that direction.

If you read the ACTUAL REPORT on these cylinders issued by the PMHSA, you might conclude that there are ample reasons to remove these cylinders from service. In fact, the UNILATERAL actions taken by many fill operations are IN FACT removing them from service, just as anticipated by the DOT.

Phil Ellis
www.divesports.com