AL 80's Failing Hydro

[uncjump]

Group,
Wanted to get your input on a scenario I'm having.

I have 2 AL 80's that were ready for this years VIP and refilling. Thinking that they look like crap, I decided I should take them back to bare metal. I researched on here and TDS how to safely remove the paint and determined that everyone was recommending the AL Aircraft stripper which does not have any heat. So I masked everything off and gave the tanks a light coat. Stuff worked amazing. Everything bubbled up in 15-30 mins and I used a piece of plastic to remove everything. Tanks looked pretty good.

1st tank (newest) stripped perfectly clean, but had 2-3 small (1-2 inch) shiny spots on the outside. I believe others referenced those as where the manufacturer trued up the cylinder (can anyone confirm)

2nd tank (older) stripped pretty clean, but required a little scrubbing to get all spots removed. I used one of the 3m pads I clean dishes with and scrubbed the whole tank. Of course that made that tank more shiny than the other tank.

So I carry into LDS and explain what I did and everything seems cool. Few days later I get a call that they won't VIP it since it had been stripped. After discussing for a while I agree to another hydro (already had them both hydro'd in Dec 05). They send for hydro and hydro company immediately fails both tanks (apparantly without testing them) for visually having the appearance of possibly being sanded. I admit to scrubbing the crap out of the second tank with the 3m brush, but doubt my elbow can create that much heat, but the first tank had practically nothing done to it.

A) Could I have really damaged the tanks as they are indicating? I removed no actual AL and generated no heat to anneal the AL.

B) Are there any other legit options? I figure I could repaint the tanks and then see if they would be VIPed/Hydroed, but I tried doing everything the legit way and feel like I'm burned.

Thanks for letting me vent and I'm open to any suggestions.

 

[mike_s]

hmm.... stripping them shouldn't cause them to fail hydro.

sounds like to me that the LDS called or told the hydro facility that they were suspect of the tanks because they had been stripped and thought they would fail and that the hdyro facility "sided" with the LDS. I personally would be "Pissed".


I've stripped a tank before and taken it to the hydro facility right afterwards and it passed with flying colors.

I didn't use a brush or 3m pad though. I just sprayed "Aircraft Remover" on it and then wiped it off with papertowels and then cleaned up anything left scraping it off with a razor blade. (see my thread on it Recent Stripper Pics to share).

 

[truck1]

As far as damaging the tanks I honestly dont know.
I have asked a few shops about painting my cylinders and one or 2 (and I dont know if it is true or not) said if they look newly painted they will fail them on the assumption that they are heat treated even if they are not heat treated in the painting process.
As far as the hydro I would try taking them to another hydro shop and see what they say and also look up the DOT regs on hydros.

 

[bane51031]

Guess I am lucky, stripped two of my tanks and clear coated them, hydro'd no problem and when Vis. done they noted they looked to have been refinished but, still passed?
Have had no problems, maybe take them somewhere else or I'll buy them from you cheap LOL. Other than that not sure what to say.....

 

[nereas]

I have stripped several tanks with liquid paint stripper (phosphoric acid solutions), and then subsequently had them hydro-ed, with no problems. And I was not required to have them hydro-ed any earlier either.

I used a soft brass bristled brush on the difficult spots, which worked fine, except when it splashed phosphoric acid onto my arms and face. Then I got smarter and more careful.

Sounds like you need to go to another store, where the tank monkeys have better brains.

I am surprised that this is a problem for you in NC.

NC has a well established scuba industry, going out to all those shipwrecked tankers and U-boats from WW2.

 

[divenutny]

I agree, this does not sound right. I know of several people who stripped the paint without using heat and repainting the tanks without heat. They did not have any issues. There may be another concern here. Many aluminum tanks manufactured before 1988 are being considered unsafe. There is a DOT warning regarding this. This concerns aluminum tanks made from T6351 alloy. This involves over 1 million tanks. Maybe your tank is made from T6351? You can check the DOT site for the manufacture batch numbers.

If not, I would call other LDS's in your area to see if they have any issues with a stripped tank. Maybe I would call the hydro shop directly to hear their concerns. Wonder if you are getting the "complete" story.

 

[RonFrank]

Many aluminum tanks manufactured before 1988 are being considered unsafe. There is a DOT warning regarding this. This concerns aluminum tanks made from T6351 alloy.

This was the first thought that crossed my mind. However that warning has been in place for a goodly while, and these were hydro'd in 2005?

Check your tanks, make sure they were not part of the (I think Luxfer) T6351 lineup.

If not, take them to another hydro facility. This assumes they have not been condemned. If the hydro facility XXX'd your tanks, you are screwed, and you will either need to go to battle to get something out of them, or just give up and get new tanks.

I don't mess with my tanks finish, and they are UGLY! One yellow, one Blue, paint chips allover, dead vis stickers, Heck, I should put some SB and Dead stickers on those suckers! I plan on them staying that way (ugly that is)!

 

[oxyhacker]

Howeve,r You can check a tank really easily for sanding - just put a straightedge on it. Since no home sanding job can remove metal perfectly evenly, if the tank has been sanded or blasted so aggresively as to remove significant amount of wall thickness, the wall will show dips and crests quite distinct from what you'll see on a tank which has not been tampered with.

Probably too much to expect a dive shop to know this, but you'd think when you explained how and why you did it the way you did they'd realized you'd done your homework.

Did the hydro shop condemn them or just refuse to test them? If the latter, I'd call Luxfer, see what they can tell you, and try another dive shop.

BTW it is no clear from your post whether the tank needed a hydro or if the shop just sent them in for an "extra" one "just in case." if the latter, the shop had no business doing so without your authorization.

 

[uncjump]

The tanks were hydro'd in Dec 05, so they were still in date. In all fairness though, the shop was concerned and discussed re-hydroing the tanks with me before hand. I think the hydro shop just refused to test them. I'm going to call around and find some other hydro shops and see what they say. I think the shop will be ok filling for me if I can get a VALID hydro on the tank and paperwork proving the hydro. They have just been extra cautious.

 

[Scottri]

I think I'd find another dive shop as well. I've stripped tanks over the years and I've never had a problem with VIP or hydro.