How to identify a Luxfer 6351 tank?

[JDMerk]

Yes sorry about that. I just get my information from the DOT and PSI/PCI, the organizations that train and legislate your industry. I guess I should ignore them as you do and get my psuedofacts from the National Enquirer.

You have every right to express your "opinion" on the subject but don't be surprised when others contradict it based on "fact". When you get some "facts" that indicate that the DOT and PSI/PCI position is wrong... let me (and them) know.

What your doing is interpreting what you have read about PSI/DOT etc on the internet and applying it to the best of your abilities(however inaccurately), which is fine...i guess. But there is a reason PSI does not teach their cylinder inspection program online. You can NOT effectively convey the necessary information through pictures and text that is required to produce a quality cylinder inspector. Otherwise you end up with armchair professionals who have no experience but lots of loud opinions...enter DaleC

 

[Leadking]

Lee, your comment regarding other 6351 cylinders that are in usage today for other applications other than scuba but without the required additional eddy current testing is something I have wondered about. For instance, I have a CO2 cylinder in my basement that was made by WK using 6351. The WP for it is 1800 psi. Now my understanding is that SLC does not appear to occur with lower rated cylinders. Not sure what the upper/lower pressure limit is but to the best of my knowledge this issue is related mostly to the scuba industry because of the WP being around 3000psi.

Oh and for giggles when my cylinder needed to be requaled I had the hydro station also do a eddy current test as well.

It's an interesting question so I looked it up at:
Part 180: Continuing qualification and maintenance of packagings - Federal Motor Carrier Safety Administration
From the website;
(f)(4) In addition to other requirements prescribed in this paragraph (f), each specification cylinder manufactured of aluminum alloy 6351-T6 and used in self-contained underwater breathing apparatus (SCUBA), self-contained breathing apparatus (SCBA), or oxygen service must be inspected for sustained load cracking in accordance with Appendix C of this part at the first scheduled 5-year requalification period after January 1, 2007, and every five years thereafter.

CO2 cylinders seem to be exempt but ALL oxygen cylinders are included in the eddy current testing protocol.

p.s. to readers-I consider myself a professional in the scuba industry. I have taken the PSI course. Sold in excess of 100,000 scuba cylinders. Had a close working relationship with professional engineers in the cylinder and valve business. Whenever I had a question presented to me in my business, and did not have, or was unsure of the answer I went to the most professional source available to me and provided that to my customers. After retiring after 30 years in the business, I still have customers calling me for information on scuba cylinders because they know I will provide real meaningful information. To all my old friends-Thanks

 

[DaleC]

What your doing is interpreting what you have read about PSI/DOT etc on the internet and applying it to the best of your abilities(however inaccurately), which is fine...i guess. But there is a reason PSI does not teach their cylinder inspection program online. You can NOT effectively convey the necessary information through pictures and text that is required to produce a quality cylinder inspector. Otherwise you end up with armchair professionals who have no experience but lots of loud opinions...enter DaleC

All that is required to convince me of your position is some fact based directive that supercedes those quoted by the organizations that legislate SCUBA cylinder use and who train those that handle SCUBA cylinders. You're the "supposed" professional with training and access to all the info; why can't you do that? You say I'm looking at old data etc... why not show us something more recent and contradictory from DOT or PSI/PCI then. For a guy that keeps claiming some superior educational advantage the facts just seem to elude you.

Instead, you keep attacking those who choose not to succumb to unreasonable fears or who use facts to make decisions. I, for one, am not apologising for not being a lemming.

BTW, Just for the record. You seem to be expressing the opinion that all 6351 cylinders should be taken out of service irregardless of their servicable condition. How do you explain that in regards to this statement by Bill High?

...Others state that the cylinder must be condemned outright. Such statements border on fraud and it is illegal to condemn a cylinder without proof that it is damaged beyond allowable limits.

Are you speaking as a professional representing your shop and the industry or just as an individual expressing his opinion on the net like everybody else?

And, how do you square it with this little tidbit from an earlier thread on the subject:

"I can tell you that 80-90% of all 6351 alloy tanks that we send off for hydro fail the VE test before they even get wet..."

I did the math BTW way and here's what you would end up with in that scenario. It takes 9 cycles to wind up with 12.8 tanks worldwide. Considering that many shops include eddy testing with their annual vis's is this what you really see happening or could it be a case of improperly trained testers or the unneccisary culling of servicable tanks?

25,000,000 6351 tanks reduced by 80%:

25,000,000
5,000,000
1,000,000
200,000
40,000
8,000
1,600
320
64
12.8

Again, in an article by Bill High:

"Sadly, this writer is aware of many instances in which the instruments have been improperly used.
Eddy current devices can give “false positive” readings when improperly operated or
when the cylinder thread areas being tested have been inadequately cleaned. For
example, in January 2000, Luxfer reported that fully 50% of the cylinders returned
because of alleged thread cracks were not cracked at all."

 

[DaleC]

As for how I access my out of date inaccurate info:

I type psicylinders.com in the search engine.
I press enter.
The home page for psi cylinders comes up.
I click on library.
All the info is there.

Here's a tidbit from the library:

"DOT also states, the PSI, Inc. and Luxfer Guides contain valuable information regarding cylinder inspections and recommended inspection intervals. DOT writes in this official safety alert, "For additional information on SCUBA cylinders, PSI, Inc. may be contacted". The PSI address, telephone number and web site are listed. We at PSI, Inc. are extremely proud that DOT recognizes our commitment to cylinder safety through visual inspection and safety awareness."

Under links I click on Dale Fox's (PSI instructor trainer) website.
I select facts and fiction. http://www.adalefox.com/fact_&_fiction.htm
About half way down the page more info is there.

If the official website for psi contains inaccurate information please indicate a more relevant, source.

 

[WD8CDH]

Lee, your comment regarding other 6351 cylinders that are in usage today for other applications other than scuba but without the required additional eddy current testing is something I have wondered about. For instance, I have a CO2 cylinder in my basement that was made by WK using 6351. The WP for it is 1800 psi. Now my understanding is that SLC does not appear to occur with lower rated cylinders. Not sure what the upper/lower pressure limit is but to the best of my knowledge this issue is related mostly to the scuba industry because of the WP being around 3000psi.

Oh and for giggles when my cylinder needed to be requaled I had the hydro station also do a eddy current test as well.

CO2 tanks usually are seeing under 1/2 of their rated service pressure thru out most of their life (~900psi @ 70F) so they are much less stressed than SCUBA tanks. That's probably why the DOT thought the VE test was not needed.

 

[evensplit]

Just for the sake of argument:

Why would Luxfer offer to buy back the 6351 tanks, and then why did they stop?

I know of at least one that blew up during hydro after passing VE test. On more than one occasion I've had them crack and leak after hydro and VE. I have had to evacuate the building while we "disarmed" one that began leaking out of a cracked neck at 2500psi on the fill whips.

I have also had engineers tell me it didn't really happen and that I was mistaken.

If 50% of the returned cylinders weren't cracked, then wouldn't that mean that 50% were? Pretty significant failure rate in my book.

Why would PSI press so hard to keep these cylinders in operation after they have clearly been identified by DOT, Luxfer, and the SCUBA Industry as being a safety risk?

Who makes and sells the VE machines?

I haven't sold more than 100,000 cylinders, but have probably filled more than that.

 

[mkutyna]

Just to be clear. Are you asking if cracks in the walls of a pressure vessel are a problem or stating that they are not?
Because saying they aren't a problem is just plain silly. Try saying it out loud a couple times, you'll have a laugh...I did.

Visible cracks or any cracks at all? Because just about any material will have micro cracks on the surface that would eventually lead to larger cracks when put under stress for a long enough period of time.

I'm not saying that I disagree with your sentiment on the 6351 tanks but I don't think they necessarily need to be condemned 100% as long as they are properly and thoroughly inspected such as the visual inspections where the VE can't test.

Granted, given the opportunity, I probably wouldn't buy a 6351 cylinder.

 

[Scared Silly]

Why would Luxfer offer to buy back the 6351 tanks, and then why did they stop?

PR - The cylinders were getting lots of bad press so while there was no recall Luxfer did the program so that people with concerns could trade-in their cylinder. People who new about it were happy and Luxfer was doing their part. (It also gave them a huge number of cylinders which to inspect and get data on the significance of the problem).

They stopped cause they were losing money on the deal.

I know of at least one that blew up during hydro after passing VE test. On more than one occasion I've had them crack and leak after hydro and VE. I have had to evacuate the building while we "disarmed" one that began leaking out of a cracked neck at 2500psi on the fill whips.

This is what they are suppose to do crack and and leak - not explode. Same as what 6061 are suppose to do. That said cracking and leaking is damn scary.

I have also had engineers tell me it didn't really happen and that I was mistaken.

What did not happen??

If 50% of the returned cylinders weren't cracked, then wouldn't that mean that 50% were? Pretty significant failure rate in my book.

The failure criteria can be subjective. Cracks could be there but are not of significance. Here is another example of where cracks can be catastrophic - dams. Concrete cracks, that in itself is the nature of the material. The problem is judging when the cracks are significant enough to cause concern. Interestingly there are people who are crack checkers for the major dams.

Why would PSI press so hard to keep these cylinders in operation after they have clearly been identified by DOT, Luxfer, and the SCUBA Industry as being a safety risk?

Cars are safety risk - for that matter people are a safety risk. The question becomes when does the risk outweigh the costs-benefits? I do not think it is PSI who is trying to keep these cylinders in operation - they are just saying if properly inspected the risk can be minimized. It is Luxfer who is trying to keep them in operation because if there is a recall they are going to be holding the bag for the cost of replacing the cylinder. IMHO The problem is the scuba industry's inability to properly inspect. Not saying all just some. But like with any bad apple it has the affect of tainting all.

Who makes and sells the VE machines?

I know Luxfer sells one. There are one or two others made by another mfg.

I haven't sold more than 100,000 cylinders, but have probably filled more than that.

BTW - Just curious what did you have to do to become a fill operator?

 

[WD8CDH]

Just for the sake of argument:

Why would Luxfer offer to buy back the 6351 tanks, and then why did they stop?

I know of at least one that blew up during hydro after passing VE test. On more than one occasion I've had them crack and leak after hydro and VE. I have had to evacuate the building while we "disarmed" one that began leaking out of a cracked neck at 2500psi on the fill whips.

I have also had engineers tell me it didn't really happen and that I was mistaken.

If 50% of the returned cylinders weren't cracked, then wouldn't that mean that 50% were? Pretty significant failure rate in my book.

Why would PSI press so hard to keep these cylinders in operation after they have clearly been identified by DOT, Luxfer, and the SCUBA Industry as being a safety risk?

Who makes and sells the VE machines?

I haven't sold more than 100,000 cylinders, but have probably filled more than that.

Here are some facts.

Cracks and catastrophic failure are not mutually inclusive.

Luxfer offered a buy-back purely for marketing reasons. Luxfer stopped the buy-back knowing it really wasn't a significant safety risk. (no worse than a steel tank)

Leaking at failure is exactly what a tank is designed to do.

DOT and Luxfer determined that when properly tested, they WEREN'T a significant safety risk. If they were, they would have been subject to a mandatory recall.

Several companies sell VE equipment. PSI is NOT one of them.

 

[Leadking]

BTW - Just curious what did you have to do to become a fill operator?

I am willing to bet that 99% of the fill operators at dive stores are not professionally trained and are in violation of state and federal regulations. There is a misunderstanding that the DOT is the only regulatory agency involved. Someone should point out the there is another agency called OSHA that has a lot to say about high pressure air among other things. We used to shut down our plant the first working day of every year just to go over all the training and have employees sign off on it. New employees spent half their first day going through training. Saved my butt many time with OSHA.

Running off to Isle Royale, can't play this game for a few days. Enjoy the long weekend!!