How do you know a tank is 6531 aluminum

[fringefan]

I bought a Aqua Lung/ US divers aluminum tank that was hydro in 02 stored with air and has the numbers Marked CTC DOT E6498-3000 885. The tank looks almost new

I was curious by looking at these numbers how you know that?

When a tank hydro is done is it common to do eddy current testing on them or is something I should ask for? I just bought this tank so I hate to scrap it.

 

[rjack321]

The exemption number (E...) is the big giveaway

The second is the original hydro date of 8/85.

Good luck finding a shop to fill this tank

 

[Stu S.]

The "6498" is the government approval to use 6351 aluminum. the "885" is probably the date of manufacture August 1985. I have been using one of these for years, it is a 1973. A correct 6351 alloy is little different from the 6061 alloy that is used to make these cylinders today. There was some bogus alloy used with a higher lead content around 1982 that caused some failures. Yours is probably not one of those.

The correct inspection is hydro and a visual-eddy current VIP. This costs no more than the standard VIP where I live. My cylinder has always passed just fine. You may encounter some dive shops that are either itchy about filling your cylinder, or itchin' to sell you a new one. If you are in an area where this is the prevailing practice, you may wish to sell it to someone elsewhere.

My brother, daughter, and I have all used our 1973 cylinder with no problems. Hopefully, yours checks out fine and you have many happy dives with it.

Stu

 

[mike_s]

A couple months ago the DOT released new guidelines on how to inspect 6351 tanks. however, you'll still find some shops not to fill them, especiall if an "unkown" shop did the visual.

I've found Florida shops to be the most discriminating against these tanks, but that's just what I've seen. Most inland shops will fill them, but they know their customer better and don't have as many transit tourist divers (in my opinin).

 

[Scared Silly]

Yup the cylinder is a 6351 cylinder the "E6498" is the exemption.

As others have said the tank will need to be hydro'ed next year and after 1 Jan 2007 it will also require a visual eddy current test. Make damn sure the hydro lab marks it not only with its normal stamp but also with a "VE" to show that a visual eddy test was done. The visual eddy test is required only at the time of hydro (i.e. every five years). However, I would probably have the visual eddy done each year. This will at least make some of the dive shops more inclined to fill your cylinder. That said it has been reported that there are shops that will not fill 6351 cylinders nor Aluminum cylinders that are more than 15 years old. There is no maximum service life for Al cylinders and if a cylinder is properly inspected and passes it should be used. So my feeling is that any shop doing this should be skipped.

 

[Jorbar1551]

just buy a new tank. I know my shop wont fill the tanks. we have a big sign that says: dont fill tanks with these alloys

 

[JahJahwarrior]

two out of three local shops won't fill. One of them seems to hate the idea of people thinking anything or doing anything for themselves....the other I don't know much about, but I don't like them. (got a reg overhauled by them, when it was touchy and freeflowed too much after the second dive they wanted me to pay them to readjust it when they didn't adjust it very well originally. fat chance. screw them.) The last shop overcharges by a ton for everything but is nice and understanding of people doing work themselves and learning more than the textbooks teach and all. They failed my tank but took the time to teach me about alloys and things (I already knew a good deal and had a great chat with the guy there about this stuff) and showed me the small scratch which failed the tank, they were worried that while it only looked like a scratch that it could be a mild crack and over time it could explode. No place around here willf ill old tanks, and I have this feeling it's becuase most of them have never read or have the capability to understand anything about physics, metals or air pressure. They know that anything old is bad and that anything without "3al" (or inthe case of steel, 3aa, I think) is bad and cannot be filled or the world will stop turning and everyone will die. Sadly, due to human ignorance, depending on where you live the tank is worthless. Then again, depending on where you live, you can use it! Don't be too upset if it fails hydro or vip though, from what I understand more old tanks fail than new ones: they've been filled more often and beaten up over the years, regardless of their alloy they are more like to be too abused for use.