Old steels denied fills due to store "policy"

[Diving Dubai]

Some of us hope that the market forces are based on good solid evidence of safety

You should be open to questioning. What we "knew" yesterday might not be valid "tomorrow"

Look at SLC (or more correctly Solid metal induced embrittlement SMIE) on Ali Cylinders ask anyone on SB and they will tell you that it only applies to cylinders made from 6351. Except they've found the SMIE defects present on 6061 alloys. And its not well understood. It was thought to be lead content but the same defects were found in cylinders with less than 10ppm suggesting SMIE may not sufficiently explain the failure mechanisms i.e. other causes not understood

Cracking in Aluminum Gas Cylinders: A Review of Causes and Protection Measures
J.W.H. Price and R.N. Ibrahim 2003

No-one bats an eyelid for not using 6351 and yet statistically there were very few failures relative to the number of cylinders in service. And the same problems manifest themselves in modern 6061 Alloys


Science keeps getting quoted:

The US requires Annual Vis, 5yr Hydro
The UK requires 2.5yr Vis, 5yr Hydro
Australia & New Zealand require Annual Vis, Annual Hydro

All based on the same evidence (science) all with different interpretations - Who's right?

 

[kelemvor]

No-one bats an eyelid for not using 6351

Actually, in threads about 6531 there will always be some people who show up and post in favor of continuing to use 6531 tanks. Personally, I don't own a 6531 tanks, and I don't own a fill station so it doesn't matter much to me.

It's worse than fill stations refusing to fill 6531 tanks. Many just implement a blanket policy that they won't fill aluminum tanks older than some year that 6531 ceased to be used regardless of the actual metal used.

How did we digress into aluminum tank discussion? I thought we were talking about a shop refusing to fill perfectly good steel tanks based only on age of the tank.

 

[Sam Miller III]

This thread is becoming serious- very serious !

The chairman has posted, Boulder John came out of retirement and posted and Marie 13 posted
Like a holy trinity The father , the son and Marie 13 --GOK where she fits in ?

Can any one recall a documentation of when the first SCUBA tank exploded ?
Where did it occur ?
Who was injured ?

I can only recall of documentation of three SCUBA tanks exploding
There certainly must be more
list them ?????

What single individual was responsible for VIP= inspection of SCUBA cylinders ?
What national program initiated the VIP program ?
When was it initiated ?

Why and when did PSI begin ?

Maybe some can come up with the answers ????

The sun is up the air is warm - I going down the hill to the beach to walk my little Tibetan Terrier Lucky

Samuel Miller, III

 

[Diving Dubai]

How did we digress into aluminum tank discussion?.

I used it as an example of "accepted science" to illustrate how little we sometime understand about failure mechanics. I could have given an example of Intergranular corrosion of nimonic alloys on the Harrier Aircraft- but people can't relate to that.

Many just implement a blanket policy that they won't fill aluminum tanks older than some year

Yes blanket policies are troubling, although they're generally implemented to make life simple rather than someone havign to actually identify if a cylinder is 6351 or 6061 etc.

In the UK there appears to be an accepted practice - more like an unwritten but informally accepted convention that Steel cylinders over 40 years would be considered at the end of their life. How that came into place I don't yet know (hunting for that info) It's probable accepted because there are very few cylinders being used in the UK of that aged, many having deteriorated before that so the "economic cost" impacts very few.

I have a query in with a couple of Steel tank manufacturers about paint specifications and accepted refinishing processes, and have also asked the question on their thoughts on the accepted life of steel cylinders, I'll let people know when I get an answer.

 

[txgoose]

You should be open to questioning. What we "knew" yesterday might not be valid "tomorrow"

All based on the same evidence (science) all with different interpretations - Who's right?

And yet the thread is still waiting on a single post outlining the failure of a steel tank in hydro not due to abuse. Please provide that information so that we can question the validity of our assertions. Steel.

 

[Eric Sedletzky]

Overeating is why I have gut!

Yeah, no kidding!
We have a great burrito place around here where the food is delicious and the burrito’s are huge. I trusted my gut and look what happened!

 

[Manatee Diver]

Yes blanket policies are troubling, although they're generally implemented to make life simple rather than someone havign to actually identify if a cylinder is 6351 or 6061 etc.

That is pretty simple, if it isn't a Catalina and is older than 1990 it is highly likely to be a 6351 tank there may be some edge cases as didn't didn't wholesale switch production at once that you can note in a more detailed document.

 

[Diving Dubai]

And yet the thread is still waiting on a single post outlining the failure of a steel tank in hydro not due to abuse. Please provide that information so that we can question the validity of our assertions. Steel.

What am I? Your research B1tch?

 

[Bob DBF]

In the UK there appears to be an accepted practice - more like an unwritten but informally accepted convention that Steel cylinders over 40 years would be considered at the end of their life. How that came into place I don't yet know (hunting for that info) It's probable accepted because there are very few cylinders being used in the UK of that aged, many having deteriorated before that so the "economic cost" impacts very few.

It could be as simple as the manufacturing specs, material used, and conditions of use combine to give a shorter life. The 2.5 year interval visual itself could give more than enough time to ruin a tank. Also, it has been overlooked in this discussion that a lot of old steel 72s have gone to scuba gear heaven over the decades, and we are left with the ones that have been treated well.


Bob

 

[Jiminy]

That is pretty simple, if it isn't a Catalina and is older than 1990 it is highly likely to be a 6351 tank there may be some edge cases as didn't didn't wholesale switch production at once that you can note in a more detailed document.

The interview said there must be a press release somwhere
Aluminium tanks - what every diver should know

Sustained load cracking is a defect that appears in some cylinders made from 6351 alloy. In the USA, this alloy was used by Luxfer Gas Cylinders from 1971 through to 1987. All Walter Kidde scuba cylinders were also made from 6351.

But wait there is more

Alert Diver | Are 6351-T6 Alloy Scuba Cylinders Safe to Use?

• Eddy-current testing is required of 6351-T6 alloy cylinders at the time of hydrostatic testing (per federal regulations) and at the time of visual inspection (by the manufacturers). This generally adds $15-$25 to the cost of the visual inspection and hydrostatic test.
  
  [*]We know of 31 ruptures of 6351-T6 alloy cylinders out of more than 50 million manufactured. (Note, however, that sustained load cracking occurs over time, and many of these cylinders, which stopped being produced in 1989, might have been retired before a problem occurred.)