How to identify a Luxfer 6351 tank?

[Leadking]

Here, have an interesting read!!!
http://www.phmsa.dot.gov/staticfiles/PHMSA/DownloadableFiles/Files/3al3000.pdf

Quotes from report;

Measurement of the largest crack at the neck (Figure 17) results in a sub-critical crack extent or
“length” of at least 51.7 mm. Using a mean propagation rate of 0.61 x 10-3 mm/hr [10], the time
to develop the longest observed crack is estimated to be 9.7 years. A similar calculation
performed for the other crack length results in an estimate of 8.3 years. These estimates are a
significant fraction of the roughly 13 years that the cylinder was in service, following its first
hydrostatic test in 1987.

• Estimates of the time-to-rupture, based on measurements of the crack lengths and on
published crack-growth rate data, indicate that the neck cracks would have required at least 8
to 9 years prior to rupture to develop based on SLC propagation alone.

The issue is not, do 6351 tanks crack, because they do, but do they catastrophically fail (fragment)?
The DOT report documents that the dynamics for the few catastrophic failures that have occurred were in place for YEARS before the final event. If this industry (scuba) is so unsure of itself and its' abilities to deal with this, it is time to close the doors. How is it that the carbon dioxide and oxygen cylinders that are in service are not catastrophically failing? The amount of these cylinders in service, and the frequency of fills make the scuba industry pale in comparison. A little inward reflection may be called for here.

This debate should deal with facts! I have provided fACTS time and again to those who offer OPINION.

So give me FACTS.

 

[JDMerk]

The issue is not, do 6351 tanks crack, because they do, but do they catastrophically fail (fragment)?

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.

 

[Leadking]

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.

I'll answer a question with a question. "Do steel tanks rust?"

OMG steel tanks do rust.

You are trying to make this a one sentance debate. Surely your attention span is greater than that.

 

[Scared Silly]

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.

 

[JDMerk]

I'll answer a question with a question. "Do steel tanks rust?"

OMG steel tanks do rust.

You are trying to make this a one sentance debate. Surely your attention span is greater than that.

You can tumble out rust but you can't very well tumble out cracks can you?
But that wasn't my question at all. I was asking you to clarify your statement on cracks.

BTW I counted four sentences in my last post. How has this become a one sentence debate?

 

[Leadking]

You can tumble out rust but you can't very well tumble out cracks can you?
But that wasn't my question at all. I was asking you to clarify your statement on cracks.

Simply put, 6351 cylinders do have a tendancy to crack, and of the mutliple millions made some have fragmented. The same is true of steel.

If these cylinders are the bombs everyone says they are, the world would sound like popcorn.

 

[JDMerk]

Simply put, 6351 cylinders do have a tendancy to crack, and of the mutliple millions made some have fragmented. The same is true of steel.

If these cylinders are the bombs everyone says they are, the world would sound like popcorn.

That might be true, but the SCUBA industry has been actively eliminating these tanks for quite some time to stem that very scenario.

I think what I was asking before what under what circumstances is a crack in a pressure vessel acceptable. It seems to me that cracks are NEVER acceptable under any circumstances. I don't see how that can be brought into question here and I wanted clarification on your position.

Do you believe cracks in pressure vessels are acceptable?

 

[Leadking]

Last reply to JDMERCK unless you can come up with a logical argument.

I have NEVER said a tank with cracks was acceptable. What I said was;
"That is what confuses me!!! An industry that will overfill a steel by 1000 psi but will not fill a properly inspected 6351 to fill pressure."

Please don't put words in my mouth.

 

[DaleC]

Exactly...you didn't bother to educate yourself on the issue.

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.

 

[JDMerk]

The issue is not, do 6351 tanks crack, because they do, but do they catastrophically fail (fragment)?

This is the statement I was referring to. Perhaps you worded it wrong or you didn't efficiently transmit your thoughts to type. From my view however it seems as if you are trying to say that tank cracks and catastrophic failures are mutually exclusive. Begging the question that if 6351 tanks crack as you admit, is it OK if they do not fail? I just want clarifications on this statement...the one right here. No words put in your mouth, you typed them right here.

BTW there is no need to change the font color...we all learned to do that in 5th grade and thought it was pretty cool back then too.