Eddy current testing of Luxfer tanks made of 6061 alloy

[akdeepdiver]

luxfer just released the official position statement that their cylinders made of 6061 alloy do not require eddy current testing.

Luxfer does not require or recommend eddy-current testing of Luxfer scuba cylinders made from aluminum alloy 6061

 

[guruboy]

Nice to have an official position from the manufacturer. Whether or not LDS will follow it is another matter...

 

[JackD342]

Nice to have an official position from the manufacturer. Whether or not LDS will follow it is another matter...

I think if you are running into a shop that is mandating eddy current test on 6061, they are very much in the minority. And personally I would only care if they are charging extra for it over and above the visual inspection.

In case anyone reading lost track or confused the two, eddy current is the testing used on the older 6351 alloy that is subject to sustained load cracking. DOT requires this test every 5 years, while Luxfer requires it (yes, they say "require" and not "recommend") every 2.5 years. I don't know about other manufacturer requirements/recommendations, but most of them out there are Luxfer, including Dacor and US Diver branded tanks. (look for Luxfer stamped on the bottom edge under the tank boot)
A tester may apply their own stricter standards if they so choose, and many shops now refuse to touch these tanks regardless. I for one will continue to inspect and fill these tanks, but I do enforce an annual eddy current test at time of visual inspection. Failures are most likely to occur at the fill station and not while diving, so I make that choice to err on the side of caution while continuing to provide support to those cylinder owners. (and let's be real, no one has a separate 2.5 year sticker for eddy current testing)

 

[rjack321]

I don't know about other manufacturer requirements/recommendations, but most of them out there are Luxfer, including Dacor and US Diver branded tanks.

I can't think of another manufacturer that has approved 6351 tanks in 2018? I'm pretty sure Walter Kidde's, and Norris' SPs expired. There was another minor manufacturer, Kaiser I think, but that SP is gone too. So if you see anything besides Luxfer it should be condemned. Knowing several 6351 cylinders have passed hydro and VE and then leaked on the first fill, I would suggest you just require customers to recycle theirs. The annual VE is proving to be marginally adequate to prevent explosions, but these are all 30+ years old at this point.

Locally (Seattle area) the cost of hydro and the actual 5 yr VE stamp by the requalifier far exceeds these cylinder's value. Last time I checked total combined price was $35 + $20 ($55) * 10% in state and local sales taxes. ~$60 to keep a 30+yr old cylinder in service that cost under $120 new is crazy.

 

[JackD342]

I don't have the cylinder in front of me, but my records show I had one WK cylinder from a customer in the past couple of years I listed as 3AL. Couldn't say if it started with a Special Permit, of if 3AL was the original stamp. I think I saw one other one recently, but the customer didn't leave it.

Looks like Walter Kidde SP7042 can be re-stamped at hydro with 3AL, so no need to actually renew the permit. Which was my understanding before I searched today.
https://www.phmsa.dot.gov/approvals...ile-serve/offer/SP7042.pdf/offerserver/SP7042

Yeah, when a customer finds a 6351 in their garage or a yard sale and wants to put it back into service, I vigorously encourage scrapping it. But when a customer has been continuously using a cylinder and has a valve that I can service with OEM parts, the added cost of annual eddy current testing is rarely a show stopper for them.

 

[Bob DBF]

The annual VE is proving to be marginally adequate to prevent explosions, but these are all 30+ years old at this point.

Locally (Seattle area) the cost of hydro and the actual 5 yr VE stamp by the requalifier far exceeds these cylinder's value. Last time I checked total combined price was $35 + $20 ($55) * 10% in state and local sales taxes. ~$60 to keep a 30+yr old cylinder in service that cost under $120 new is crazy.

Although I'm in agreement in recycling to reduce recurring costs, although there are a lot of those cylinders in use in this area, I would like to know more about the ongoing explosions.


Bob

 

[JackD342]

I am also very curious about those "several 6351 cylinders have passed hydro and VE and then leaked on the first fill." While a leaking cylinder is possible, I have never heard of it being a common problem, nor particular to 6351 alloy. My 1st thought on a leak at first fill after service it to check the valve, which should have been serviced at hydro. Also my 2nd and 3rd thought...

 

[Diving Dubai]

The annual VE is proving to be marginally adequate to prevent explosions, but these are all 30+ years old at this point.

This is no surprise. My opinion as someone who once held a Level III cert in Eddy Current (amongst others) it that this test is performed by a sub standard piece of equipment, by poorly trained operators who are using a poorly written procedure.

The fact that any defect indication must be confirmed by a visual backs this up.

Eddy Current will detect both surface breaking and sub surface defects. Tight fatigue cracks will be easily detected by Eddy current but not seen with a visual.

The fact that the critical size of the defect (the largest it can get before the cylinder goes bang) is of a size that you can clearly see means this test is frankley worthless in its present form

 

[rjack321]

I am also very curious about those "several 6351 cylinders have passed hydro and VE and then leaked on the first fill." While a leaking cylinder is possible, I have never heard of it being a common problem, nor particular to 6351 alloy. My 1st thought on a leak at first fill after service it to check the valve, which should have been serviced at hydro. Also my 2nd and 3rd thought...

They were described by a shop owner in NC years ago on decostop. I don't recall his name (so it would be hard to find the thread and I hate that board) but after the 3rd or 4th 6351 leaker he quit filling them completely.

 

[rjack321]

Although I'm in agreement in recycling to reduce recurring costs, although there are a lot of those cylinders in use in this area, I would like to know more about the ongoing explosions.

Bob

There was one posted on facebook in Jim Lapenta's accidents group last week.