Bought two AL80 tanks filled with 34% Nitrox

[agesilaus]

OK I just qualified OW around Christmas. Some guy was selling 3 AL 80 tanks for $65 each. I have been looking at these for the last couple of weeks, he had a photo of the tanks on craiglist and I moved it into Photoshop and enlarged it a bit and could read the dates on one of the tanks. It looked like 1984.

When we were taking our OW the instructor told us that NO Al tanks more than 17 years old could be hydroed. Asking around and looking on the web it seemed like this was bogus info. A couple of other dealers denied it for one thing.

My understanding (if I'm wrong please correct me) is that tanks made before 1990 may be made of the unsafe alloy. Luxifer stopped using that alloy in 1989 but some other companies didn't stop until 1990. Therefore post 1990 AL tanks are probably OK barring other problems. Is that correct?

Anyway I went over to look at the tanks and one was dated Luxifer 1984--> no good in other words. The other two Nitrox tanks are dated Luxifer 1999. So they should be OK. They were last hydroed in 2007.

So these tanks are Nitrox filled. Should I dump the tanks or is it safe to dive in shallow dives with them (max 70 feet). I suspect the answer is dump them. I'll get them hydroed after that.

The fellow told me to take the old tank as a freebie saying that maybe I could use the valve. It's filled with air. Is there anything to do with it except bleeding the air off, pulling the valve, and selling the tank to a scrap yard?

Thanks BK

 

[ScubaAl]

Luxfer stopped using 6351 Jan.1988. As far as the two tanks with 34% goes, they need to be hydroed so will need to be dump anyway.

Al

 

[Scared Silly]

You have a done a good job of educating yourself on the scuba industry BS. Here is a bit more:

Is my cylinder made from the "bad" alloy aka AL6351?

As for the other two cylinders filled with 34% NITROX. Using a PPO2 of 1.2 the maximum operating depth (MOD) would be 83 feet. Some may say the MOD could be deeper based on a higher PPO2. But I will stay on the shallow end. Seems like you may have already figured it out.

So here is my suggestion. You could go dive them as if they were air and not go below the 70 feet you mention. Many do just that for extra safety. Or in case the scuba police are around you could do a on-line NITROX course and then you will qualified to dive yer new cylinders. Just make sure the on-line is from a qualified representative of the agency.

 

[rhwestfall]

if you didn't verify the tank contents at the time of filling (or verify through your own testing), I sure wouldn't dive them....

 

[crosshairs]

if you didn't verify the tank contents at the time of filling (or verify through your own testing), I sure wouldn't dive them....

+1...

I would dump them and have them filled with whatever gas you choose, but at the minimum, you need to analyze them before you even think about diving them.

 

[agesilaus]

OK that's something I didn't know about. There is a paper stick on label on the tanks with 34.2 marked on it, but I don't even know if that was the last fill.

BK

---------- Post added January 27th, 2014 at 07:34 PM ----------

I have never heard of online EAN classes, makes sense since it's just a classroom session anyway.

BK

 

[scubastingray]

Congrats on the new tanks. Use this site to find places that can hydrotest near you:
PHMSA - Cylinders - Authorized DOT Cylinder Retesters: Domestic

Fire testing services are pretty awesome usually. If you are in jacksonville I'd advise against first coast fire safety as they were pretty unprofessional, quoted me a price on the phone, changed it, and were unclear about the timeline (before changing it anyway).

 

[Bob DBF]

First, you can hydro any tank, whether anyone will fill it for you after is another question. There are places that will fill 6351 alloy if properly tested, I didn't need the problems so I retired my tanks and moved on.

I have been known to breathe very old air, however it has been out of tanks I have filled. If they were filled in the last six months, I'd probably have the gas tested and dive them.



Bob
---------------------------------
... you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?
Harry Calahan

 

[scubastingray]

First, you can hydro any tank, whether anyone will fill it for you after is another question. There are places that will fill 6351 alloy if properly tested, I didn't need the problems so I retired my tanks and moved on.

I have been known to breathe very old air, however it has been out of tanks I have filled. If they were filled in the last six months, I'd probably have the gas tested and dive them.



Bob
---------------------------------
... you've got to ask yourself one question: Do I feel lucky? Well, do ya, punk?
Harry Calahan

Given that the hydro expired in 2012 I'd be surprised if it were filled in 2013.

Also, the issue isn't that the tanks aren't safe, it's that shops (particularly those in S FL) will refuse to fill them out of ignorance.

 

[agesilaus]

OK to wrap this up, I took the two tanks in for hydro today after bleeding off the gas. And the third out of date tank went to the recycle yard for $20. Thanks for all the pointers and tips here.