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I would like to read
that article
david
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There were some aluminum tanks manufactured (cannot recall the make) 1992 and prior which were found to be defective over time(10 years +). There were documented cases of them exploding while being re-filled. As a result of this, some shops would not refill tanks older than 10 years....
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Most of the problems with the aluminum tanks were centered around Luxfer tanks made before 1990. The alloy that was used and the one that is bad is 6351-T6. From what I heard is that hairline cracks develop and can cause issues when being filled.
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Hi Greg,
I’m a PSI/PCI inspector and all the info is within their course curriculum.
1. Is a myth as long as the tank has visible markings and can pass hydro and vis it may be put into service.
2. This applies only to Luxfer aluminum made prior to June 30 1988 and the reason is cost of upkeep. These are the only tanks that require Eddi current testing with each Visual inspection. If they pass both tests and are up to date on hydro they can be put in service. They are made with a alloy (6351) who’s molecular characteristics make them more susceptible to cracking at points of machining(the neck)
3. This refers to a spray in liner or coating that manufacturers used inside steel tanks in the past. Most will deteriorate with time and could cause regulator failure. These tanks could be tumbled with abrasive media to remove the liner but they will often deteriorate rapidly after making the effort without merit.
4. Eddi-Current testing may be used on any aluminum tank which the inspector suspects of neck fractures. There is no blanket requirement for Eddi-Current due to tank age. The only blanket requirement is due to 6351 alloy type and this is only found on the Luxfer tanks and stated above.
If you need more info you can call PSI/PCI as they are the authority on the subject
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what is Eddi current testing
tks
david
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Eddi Current testing is an electronic test for fractures in the neck of an aluminum tank. It is capable of finding cracks before they can be seen.
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much tanks! pun intended
david
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I have a set of doubles that were sold as U.S. Divers tanks pre 1993 that are lined tanks. I keep them as more of a conversation piece as they are no longer in service. But these tanks have a rubber lining which has been cracking and flaking off which could lead to plugging up the first stage of a regular. I won’t take the chance of that happening, so I have retired them.
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It depends on who owns the air pump. They can set whatever policy they want. I don’t know how common it is but I know a filler that won’t fill aluminum tanks over 20 years old. They don’t care what tests you have run on them. Right or wrong it’s their pump and they decide what tanks they will fill. I’d check on who you will expect will be filling your tanks most of the time to see if they are one of the restrictive facilities.
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In theory you are correct he who owns the pump has last say unless you want to really get involved with a battle. Those business’ that require a license and insurance are required to follow fair business practices and not discriminate against anyone in any way. They are also required to comply with CGA and DOT regulations. So in effect you could go after their business license if they refuse to fill a tank that is within compliance. Then it gets even more technical as they could claim upon external inspection of the tank they found reason to require another VIS or Hydro. It becomes a pissing contest at best. If it were my tank, in compliance and I didn’t have the ability to fill it myself I would probably just politely remind the owner that filling your tank brings you to his shop for your other diving necessities but if forced to invest in another tank before CGA/DOT regulations require it may cause you not to spend that money with that shop and instead cause you to take your business elsewhere. Even if he is the only fill station in town you can threaten to purchase your own pump and compete for business instead of being taken advantage of.
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what does a good air pump cost these days?
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#1 There is no good reason not to buy a used 72 that has been properly maintained.
#2 Luxfer and Walter Kiddy both used the 6351 alloy, Luxfer stopped using that alloy in mid 1988 and Walter Kiddy used it until they went out of business in 1990. As long as the 6351 alloy tanks can pass the eddy current or microscopic inspection every year there is no reason they can not be used either.
#3 There is no good reason not to buy a lined tank that has been properly maintained.
#4 The eddy current test is only for tanks made from the 6351 alloy. There is no reason to do an eddy test on a Catalina tank of any age as they never used this alloy.
All of these so called rules you listed were arbitrarily made up by dive shop owners. I still dive a lined 72 cu/ft tank made in 1965 that I bought used in 1970. It passed hydro a couple of years ago without any problem. The age of an aluminum tank has NO bearing on its safety, only the 6351 alloy tanks have a potential problem but even the majority of these tanks are safe. I would not patronize any shop that made up BS rules like this.
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luxfercylinders.com/support/technical-bulletins/4...-6351-aluminum-alloy
phmsa.dot.gov/pv_obj_cache/pv_obj_id_8DDCA19A9084...filename/3al3000.pdf
phmsa.dot.gov/pv_obj_cache/pv_obj_id_07162D61C544...me/3al2015_57003.pdf
ctcseminars.com/Files/Technical/3al_advisory.pdf
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Luxfer Gas Cylinders
Technical Bulliten
October 17, 2002
Dates by models when Luxfer changed the aluminum alloy in its scuba tanks from 6351-T6 to Luxfer’s proprietary 6061-T6 alloy.
Scuba tank model.................................Date of alloy change
S808.............................................. ....................5/87
S72............................................... .....................8/87
S100.............................................. ....................8/87
S80............................................... .....................1/88
S50............................................... .....................4/88
S92............................................... .....................4/88
S30............................................... .....................5/88
S63............................................... .....................5/88
S40............................................... .....................6/88
This information relates only to cylinders manufactured in the U.S. Cylinders manufactured in Australia are subject to different dates.
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Here is "The List" of scuba tanks that the DOT says are most likely made
from the :
· All DOT-3AL tanks manufactured under one of the following
exemptions or special permits: 6498, 7042, 8107, 8364, 8422
· All composite cylinders manufactured under one of the following
exemptions: 7235, 8023, 8115
· All Walter Kidde DOT-3AL scuba tanks.
· All Cliff Impact DOT-3AL scuba tanks made before July 1990.
· All Luxfer 80.8 cu. ft. scuba tanks (S80.8) made before May 1987.
· All Luxfer 72 and 100 cu. ft. scuba tanks (S72, S100) made before
August 1987.
· All Luxfer 80 cu. ft. scuba tanks (S80) made before January 1988.
· All Luxfer 50 and 92 cu. ft. scuba tanks (S50, S92) made before
April 1988.
· All Luxfer 30 and 63 cu. ft scuba tanks (S30, S63) made before May
1988.
· All Luxfer 40 cu. ft. scuba tanks (S40) made before June 1988.
· All other scuba tanks made in the US before February 1990 (except
Catalina).
· All scuba tanks not made in the US.
Unless proven otherwise, all scuba tanks in the above list should be
assumed as being made using the 6351-T6 alloy.
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I got a 1961 steel 72 just Hydro’ed and visual. passed dive shop owner - I was told that he has done steel tanks from the early 1900. don’t know if it is true but if he does that I have a long way to go on my tank
david
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1. I have two very old steel I think 63’s, great for beach dives!
2. I have a Kiddy 14cuft pony, 2015psi and still passes test. A few times tank monkies haven’t read the stamp and have filled it to 3000+ psi! It has a nice ring at that pressure! I bleed it back down before doing a hydro while wearing it :)
3. I’d always heard that if the lining flaked that could end up in the first stage (unlikely) or rust could form behind the lining and would not be seen during a VIP.
4. A LDS tried to tell me they had to do Eddi-Current testing on ALL aluminum tanks even if they had current VIP and hydros from other shops. I’m guessing this was to pay for the tester! I stopped going there for fills, there was word on a local NJ dive board that they were not keeping up on compressor servicing and pumping water. They closed shortly after that.
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Greg - 7/15/2014 3:17 PM 
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I’ve run into dive shops in the Keys that won’t fill the older aluminum tanks. Think it’s mostly because they have so much business, they can refuse. As for the 72’s. I know several guys that still use them, and am starting to think about picking a couple up myself just because of the weight. Currently using hp 119’s which I love, except for the weight. I still have a ’94 aluminum 80, and still use it on occasion. I haven’t had any problem, yet, having it filled.
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What was the name of the shop in the Keys that would not fill your tank? I always avoid shops like that.
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Wish I could remember. It was a couple of years ago. Wasn’t my tank, but a buddy had an AL80 manufactured in ’90. We were down there a week. Started at one end and went to the bottom. Wasn’t a big deal at the time, as there was another shop close by. If something jiggles my memory, I’ll update the post.
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All manufactures had stopped using the 6351 alloy by 1990 so there was no good reason to refuse to fill the tank other then to get you to buy a new one from them. Very underhanded business tactics on their part. It is not a problem for me as I do not bring my own tanks when I am in the Keys but I would still want to avoid a shop that does business like that.
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I just had a 6351 Luxfer tank hydro’d and Vis+Eddy and it passed with flying colors. I am not scared to dive this tank at all nor is my shop scared to fill it. I obtained the tank free and it cost me 32 bucks to get up to date.
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MDW - 11/12/2014 9:36 AM
I agree with RAWalker (detailed first response) and RichKeller (response to all 4 points).
I, too, and a PSI/PCI inspector and have also seen all these questions well addressed in the documentation / training.
Now for some anecdotal evidence:
1) I have 5 steel 72s, the newest of which was produced in 1976. I bought them all used (of course, since I was only 7 in 1976) and in fact, the last 2 I just picked up this year. Some are lined, some unlined. All of them still pass hydro with + rating, so I regularly get them filled to 2475-ish (really 2500). 2 are doubled up and the other 3 I use for sidemount. They work great in both configs, have good buoyancy characteristics (compared with AL80s), and can take a beating. I just stripped the paint off the doubles and cold (re)galvanized them. I did this not because they had any rust (they were clean as a whistle under there), but just so they would match and look like new (had 2 different paints on them before). These are my favorite tank size because they are big enough, small enough, and dirt cheap (I think the most I paid for one was $50).
2) About 6 years ago I bought a set of 4 AL50s that were made of 6351 for $20 each on eBay. All 4 passed hydro, but one failed Eddy and was condemned. Still a pretty good deal ($80 to buy plus $50 to ship plus $80 to hydro equals $210. That’s still just $70 each for the 3 good ones). I originally bought them for the kids to learn to dive, but they never did take OW and now they are full grown so wouldn’t need a small tank anyway. For the 5 years I had them, I used them for sidemount (2x50cf is equal to what my single backmount buddies were using, so worked well). When they came up for hydro again, I sold the 3 for $50 each on eBay and bought the last 2 72s mentioned above. So overall, these tanks cost me $4 a year each, including hydro. Sweet.
3) I have not had a problem yet with my lined tanks. A buddy of mine had one where the liner was starting to peel, so we tumbled it and then O2 cleaned and dried it. It has held up fine in the 2 years since. Still clean every time I vis it for him.
4) See Eddy comment in item 2 above.
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