Visual Plus for aluminum tanks

[jar546]

Spoke with a few s Florida dive shops and none use visual plus and don't plan on anytime soon. Seems to me they all talked bad about the usefulness and cost of the equipment. I was surprised that this is not a standard in S Fl.


what is the story with the negative attitude toward the Visual Plus system for al tanks?

 

[tomfcrist]

Could have to do with the fact that it is not needed for modern tanks except after hydro. Modern aluminum tanks are not susceptible to sustained load cracking.

 

[jar546]

When a shop that does not do their own hydros (most) does the hydro company or the shop do the vis? I am assuming the shop does as I am accustom to seeing. Do those that do the hydro perform a visual plus of the threads?

 

[bletso]

Eddy current testing of aluminum cylinders is only required by law at hydro on cylinders manufactured with 6351 material. Those are most cylinders manufactured before 1990 by all manufacturers except Catalina as they never used that material. The SCUBA industry was overreactive in this, but it appears the pendulum is starting to swing the other way.

I still find the occasional neck cracking in older cylinders, most of them medical O2 cylinders. They are never visually inspected except at hydro. IMO it is less of a problem in SCUBA cylinders as they are, or should be given a visual annually by industry standards. In medical field, I have stopped testing they and have informed my customers so. Cracks will grow to very dangerous sizes in less than the 5 year interval that the manufactures have convinced the DOT of.

Something to ponder.... A bad eddy current inspection will lead to a good cylinder being condemned, but a bad visual can lead to a dangerously cracked cylinder being accepted!

Eddy current inspection was put in place due in part to the poor implementation of visual inspection practices, but there are visual tools available today which will enable the inspector to see areas of the cylinder an eddy current inspection can't test. Eddy current will only find a crack once it has migrated into the threads but cracks start in the crown and work up. I have seen cracked cylinders leak air in the crown and were fine in the threads!

Dale
Engineeredinspection.com

 

[Wookie]

For me, the negative attitude comes from the cost of the equipment, the lack of requirements to test 6061T6 cylinders, and the lack of need to perform the test. I spent my money replacing my 6351 cylinders rather than take a chance on poorly performing a test on an admittedly older cylinder anyway.

 

[DA Aquamaster]

Eddy current was "the" method 12 or so years ago when SLCs in 6351-T6 tanks became a concern to the point that Luxfer recommended eddy current inspection of those tanks.

But as a poster noted above, it does not detect cracks in the crown and the hydro test facility I worked with had more than one cylinder leak through a crack in the crown during a hydro test after passing an Eddy Current inspection. My take away from that was a) do any visual plus testing after the hydro test as the test itself seems to propagate cracks, and b) you need a better tool to closely inspect the area just below the threads and in the crown.

The Optical Plus tool does that very well, and it has enough magnification that it will identify any crack found with an eddy current inspection.

Thus, unless there is a legal requirement to use an Eddy Current inspection (only required as part of the 5 year re-qualification on 6351 T-6 alloy tanks), you are far better off with a visual inspection with an Optical Plus.

Eddy Current machines run between $1800 and $2500. In comparison an Optical Plus will cost you a lot less - although there is now some serious price gouging on them. Two years ago you could get one for about $300. Now the cheapest price I can find is $399 through a hydro test equipment supplier and most scuba related websites are charging $499 with some of the greedier sites charging more. The most egregious I found in a short search was these folks at $658:

XS Scuba/Highland Tank Optical Plus Instrument AccessoriesBuy Scuba Equipment Online, Scuba Gear - Houston Texas, Gigglin' Marlin Dive & Swim

We need a wall of shame for shops like this.

Another option is the Flare Optical Viewer. It's not quite in the same class as the Optical Plus and there's no video capability, but it's effective and the street price is around $180, so it's in the realm of the realistic for any small volume shop or for a diver doing his own VIPs.

In any event, Eddy current inspection is not needed on 6061-T6 tanks and an Optical Plus is a much better approach anyway as it allows a more thorough inspection of both the threads and the crown.

 

[akdeepdiver]

Its cheaper for shops just to say they wont fill a tank made before 1989, then to invest in the equipment and proper training.

 

[Dr. Lecter]

Its cheaper for shops just to say they wont fill a tank made before 1989, then to invest in the equipment and proper training.

If only that's what they did. I have run across at least one shop on Oahu that refused to fill any AL cylinder without a Visual Plus inspection. That the cylinder in question was a brand new 20cf pony made no difference to them.

 

[tomfcrist]

Some shops have staff and policy with not factual knowledge of anything. They base their policy's off of ignorance, and then can't understand why educated divers won't use their shop. Love it.

 

[jar546]

Decided to pass on the eddy current training but certainly see the value in it, especially for 6351 tanks. The Optical Plus is definitely a must though. I found it to be extremely useful. I just don't see the eddy current equipment paying for itself due to the attitude and unofficial consensus of most SoFlo dive shops with 6351 tanks.

I was surprised to find a 1990 Catalina 6061 aluminum tank with 3 cracks in the neck. I can only assume the tank may have been abused to cause such damage. There were cracks not visible with the naked eye and a 2x mirror, but easily found with the Optical Plus.

PSI puts on a pretty solid visual cylinder inspection course.


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