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Post by technidiver on Feb 3, 2019 10:51:20 GMT -8
I picked up some Aluminum tanks from the 80s (also happen to be 80 cf). LDS will not fill them and recommends them as display pieces. Now I know that some of you have 80s Alu's as well, and some of you dive them!
These tanks have USD J valves and still have 1800 PSI pressure.
If I would like to dive them and re use them, are they save-able?
TD
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Post by cnotthoff on Feb 3, 2019 11:20:00 GMT -8
TD, We've seen this issue before. A small percentage of aluminum cylinders made prior to ~1990 have developed cracks at their neck due to sustained load. This is the best explanation of this issue I've seen. psicylinders.com/inspectors/library/18-a-short-review-of-6351-alloy-aluminum-cylindersAn electronic eddy current test is required for any of these cylinders to pass it's 5 year hydrostatic test. Even if the cylinder passes this test, your LDS can still refuse to fill it. I don't know if you have options for where to get those cylinders filled. Good Dives, Charlie |
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Post by nikeajax on Feb 3, 2019 11:51:26 GMT -8
A: find a place that will fill these tanks IF they pass the eddy-test
B: find some place that services fire extinguisher to do your testing
C: test EVERY YEAR no matter what--ZERO EXCEPTIONS--EVER!
D: after every use, dump all of the air: these micro cracks are caused by sustained loads
JB
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Post by snark3 on Feb 3, 2019 12:10:18 GMT -8
IMHO, These old aluminum tanks aren't worth taking a chance on. You can buy a new 80 for about $150 or a used later model tank for $75-$100. I'm not real computer savey so I don't know how to create a link but check out www.underseadivers.com then click on gear and aluminum tank policy. I have an old aluminum 50 I'm going to make a gas grill out of it. |
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Post by technidiver on Feb 3, 2019 12:29:39 GMT -8
I checked around and Eddy Testing is few and far apart for me, and I think it's a good idea to salvage the valves and decommission the tanks. They were used for about 15 years before being put into storage, so they have a lot of mileage on them!
I'm going to use the remaining air for testing regs (not breathing 20 year old air, don't worry!) and then remove the valves.
TD
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Post by SeaRat on Feb 3, 2019 12:55:07 GMT -8
I have two Al 80s and two Al 50, all of which I have decommissioned. I have one that I will use sometime for my Dacor Nautilus CVS, but even that system also uses a steel 72, so for all intensional purposes it too ha been decommissioned. I had one which was identical to the Al 80 used in Jaws that I sold to someone interested in it as a Jaws display. All my tanks are now steel with the exception of a set of almost new Al twin 40, which I will be using (different alloy from the old Al 80s). My reasoning was that with all that is known about these tanks, if something were to happen because of sustained load cracking (an explosion, for instance) and someone was hurt, I would not be able to forgive myself.
John
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Post by snark3 on Feb 3, 2019 13:16:36 GMT -8
TD- In another thread you were asking about J valves. If those tanks still have 1800 psi in them then those valves are probably good. The USD valves with the black knobs are my favorite. There's the valves you were looking for.
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Post by nikeajax on Feb 3, 2019 13:52:14 GMT -8
TD, there's nothing wrong with the air in those tanks, it's air fer crin' out loud, that stuff can't go stale, nope  Kinda like when they put expiration dates on bottled water, huh?  Air becomes stale when it has too much CO2 in it, most everything else becomes stale when it gets too much oxygen in it  If you get them down to around 300-500-psig you can use them to adjust the second stages on unbalanced regs like your Scuba Star-TD... JB |
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Post by cnotthoff on Feb 3, 2019 14:21:48 GMT -8
I agree with Jay, that stuff won't kill you, as long as it was a good fill to begin with.
The only danger I know about breathing old air happens with steel tanks. There was an incident many years ago where a diver died while using a tank with extensive internal rust. Rust is oxidation and locks up oxygen. There wasn't enough breathable oxygen left to maintain consciousness.
Aluminum oxidizes as well, but it's a self-limiting reaction. Give 'er a sniff and go for it.
Good Dives,
Charlie
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Post by nikeajax on Feb 3, 2019 14:50:47 GMT -8
The only danger I know about breathing old air happens with steel tanks. There was an incident many years ago where a diver died while using a tank with extensive internal rust. Rust is oxidation and locks up oxygen. There wasn't enough breathable oxygen left to maintain consciousness... Good Dives, Charlie WOW, very interesting, but sad too! I write sci-fi books/stories, this is good fodder! JB |
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Post by technidiver on Feb 3, 2019 15:48:42 GMT -8
So I hooked up my Dacor 400, only balanced reg I have right now I'm working order, and used a MR-12 second stage. Really good combo. I didn't breathe off of it, but the tank has plenty of pressure and the MR-12 worked flawlessly. A really nice second stage.
As for the tanks, I'm going to use them till their empty, salvage the valves, buy some valves for cheap on ebait and use them just for show, and make a display out of them.
My LDS has asked me to bring some of my vintage gear and double hoses, and I gratefully accepted. I could likely incorporate the tanks into a display and talk about the 6351 Alu alloy. The owner Robbin, is really nice, and she likes the vintage gear. She grew up using it and selling it. Most of the divers in southern Canada were served at this dive shop, it started out in 1953 as a Sport and Ski shop.
TD
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Post by waldenwalrus on Feb 14, 2019 9:18:00 GMT -8
I hear if you cut the bottoms off they make great wind chimes
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Kinda like when they put expiration dates on bottled water, huh? 
Air becomes stale when it has too much CO2 in it, most everything else becomes stale when it gets too much oxygen in it 
