How to identify a Luxfer 6351 tank?

[mtndew2112]

my 6061 tanks are only 5 and half yrs old. Far from end of their lifespan.
Are working PSI is 2216

 

[WD8CDH]

If filled to it's service pressure once per day, an aluminum cylinder's service life would be about 274 years based on fatigue.

 

[WD8CDH]

<snip>So I call vendor and ask directly for the tech.Tech claims they changed testing due to a new DOT requirement using visual eddy current.<snip>Please Advice

Ask the tech for the specific new DOT requirement.

(hint: there is no DOT requirement for testing 6061 cylinders with the Visual Eddy at all. 2nd hint: They are required by law to have a copy of the regs.)

 

[WD8CDH]

<snip>
My dept had sent in 8 bottles to be checked and all 8 come back condemned for sustained-load cracking ( SLC ).This bottles are made of 6351 alloy and have has been known to develop cracking in the threads.
May all have had cracks, but I would not have been surprised if only some had cracks.
After the bottles were returned I sent in 4 of my newer bottles and they also come back condemned for SLC failures. Now these bottles are made of 6061 alloy and have no known problems for SLC.
I am extremely surprised at this.
Luxfer recommended taking bad bottles in for a 3rd party test.Which is were they are now at a scuba shop in des moines.When I dropped them off this tech stated that there is no way other vendor could of have done test as dirty as the threads were and spent 5 minutes cleaning one bottle that had 12 cracks in the threads as reported from other vendor.When he was done his white rag looked like he had just changed his motor oil.
This might be an entirely different issue. The threads shouldn't be that dirty.
If these 6351 were actually good they are not now due to dot #'s being stamped out and can never be refilled giving us no choice but to buy replacement bottles.

I think that the problem is in the software and that vendor had not kept up with updates thus creating 100's of bottles being placed out of service for SLC within our state with no reimbursement or credit.
If this is the case we would have many departments with no bottles or funds to purchase new bottles ($450.00) each thus creating a safety issue.

Please Advice

Sounds like either incompetence or fraud. If either is true, they should owe you replacement cost, at least on the 6061 tanks.

 

[mtndew2112]

Well my 2nd test results from 3rd party tester came back tonight on my 2 condemned 6351 bottles and show no cracks using VP 3.

 

[marchand]

If filled to it's service pressure once per day, an aluminum cylinder's service life would be about 274 years based on fatigue.

That's a pretty vague statement... is this figure based on calculations or tests and which alloy? If calculations; were they based on an ideal, average, or bottom of the line cylinder? If it was a test, how many different batches did the samples come from, and is that the #of cycles for the first tank to fail, half of them to fail, the last one to fail, or is it the average? Were hydrostatic tests factored in?

That figure is pretty worthless without parameters and the rest of the data...

Also, I don't know about the rest of the world, but aluminum tanks around here tend to get filled to 3200 - 3300psi. I know 300psi doesn't sound like much, but depending on where 3000psi rests on the curve it could have a significant impact on the life of the cylinder.

 

[Scared Silly]

Well my 2nd test results from 3rd party tester came back tonight on my 2 condemned 6351 bottles and show no cracks using VP 3.

I would take them back to the first vendor and complain especially because they failed so many. If the first vendor XXXX out the DOT stamp I would be talking with the owner and discussing replacement cylinders at their cost.

 

[mtndew2112]

I would take them back to the first vendor and complain especially because they failed so many. If the first vendor XXXX out the DOT stamp I would be talking with the owner and discussing replacement cylinders at their cost.

Vendor already said the would demand bottles be tested a 3rd time from another tester.
I'm leaving it up to Luxfer now as it is their product and name.

 

[WD8CDH]

That's a pretty vague statement... is this figure based on calculations or tests and which alloy? If calculations; were they based on an ideal, average, or bottom of the line cylinder? If it was a test, how many different batches did the samples come from, and is that the #of cycles for the first tank to fail, half of them to fail, the last one to fail, or is it the average? Were hydrostatic tests factored in?

That figure is pretty worthless without parameters and the rest of the data...

Also, I don't know about the rest of the world, but aluminum tanks around here tend to get filled to 3200 - 3300psi. I know 300psi doesn't sound like much, but depending on where 3000psi rests on the curve it could have a significant impact on the life of the cylinder.

Sorry, I left out 6061 alloy. Otherwise, it's in the 3AL spec, 100,000 cycles to service pressure without any failure from fatigue.

I was just trying to get a reality check data point. 100,000 fills to service pressure at one per day is 274 years.

 

[DaleC]

Oh come on Ron, don't start trying to inject reality into the conversation

FWIW: When I log 100,000 dives on my 6351 tanks I promise I'll retire them (even if they still pass hydro and Vis).