Warnings about 6351 tanks on CL

[vjanelle]

RE: Aluminum 80 Dive Tank - $150 (East Georgia )

This is in general goes for anything on craigslist, so YMMV... Especially since he's asking $150, wtf?

(A lot of shops won't fill AL tanks over 20 years old, 6061 or not.)

No, I wasn't the person that posted this on CL originally, I can read tank necks . Anything with a "604 808 xxxx" # in it is this guy though.

ATTN:

This guy [mod edit- name removed] is not giving the full information on these tanks he is selling. They do not have the required TC label needed to fill these tanks in Canada, don't let him tell you otherwise.
Save yourself the headaches, I called 4-5 different shops and they refuse to fill these tanks, even though they have been hydro'd. Also these tanks are made of 6531 T6 alloy, which are know to crack
and potentially harm. The only label on the tank is DOT-SP6498 ) 03@73 which indicates that these tanks were made with a weaker aluminum alloy, know crack (SLC) over time and potentially blow up. Also, most shops will not fill tanks over 30 years old due to the weaker alloy used. He is totally un-reasonable and is out to rip people off!! BEWARE! Do your research! check out this website
Beaver Aquatics -SCUBA tank explosion
these are the same tanks he is selling!! Luxfer 80ci same year..

DON'T LET THIS GUY RIP YOU OFF!! DON'T DEAL WITH HIM!!
He will not refund your the money..

 

[DaleC]

Isn't it nice when some who doesn't disclose all the information meets up with someone who resorts to hyperbole. Almost as good as reality TV!

BTW; I must be out of the loop. Which shops in the lower mainland won't fill 20 year old tanks, 6061 or not?

 

[vjanelle]

IDC won't touch AL tanks over 20 years old. They'll do steel.

Flicking over to the tanks forum shows this isn't uncommon(the basis for my "a lot of tanks" statement), wether it extends from catching bad alloy tanks or not or just the way AL handles the stress of being filled and drained... Basically though, it's their compressor, their rules. I read the catalina VIP manual and they suggest VIS every 3-5 months and hydro every 3 years for tanks that experience heavy duty cycles such as being in a rental fleet...

Mostly though, selling tanks made of alloys people won't fill, that're over 20 years old (and that people won't fill), without tc stamps, for $10 less than new online? C'mon.

A new AL80 costs $160-$200 online in canada without a valve, and you can probably get a fill card or two out of the deal if they don't give them to you for buying them new anyways... Online in the US they're even cheaper and come with TC stamps.

As for SLC, 1m+ tanks, 1.25% known to have issues.. 10,000 tanks out there. Just sayin'.

 

[bighiller]

The missus and I bought two of these tanks before we knew about this. Luckily OceanQuest will fill them. I think that if you bring the tank to the LDC and they hydro it and viz it then, I assume, they are pretty much obliged to fill it.

I only learned about this when I tried to trade one of my 80s for a 40cf pony... would have been a great trade, but that when i learned my tanks were crap now.

Such is life and thank god for steel!

 

[DaleC]

I'm pretty sure Les at Langley Diving will fill them as he was doing the vis plus and filling mine. When I hear of shops not filling 6351's I say OK as they have the right to assess their own risk levels and there is a (slight) risk associated with SLC in 6351 alloy tanks. When I hear of a shop not filling 6061 tanks I just shake my head. Might as well throw out those old lead weights too by that logic.

The scary stories we tell ourselves to make ourselves feel safer because we do things differently...

 

[vjanelle]

Stupid correlation... Lead doesn't undergo expansion/contraction stresses, but I don't know of any real metallurgy studies done on 20+year old tanks. It'd be more akin to throwing away regulators because they're old (apart from the fact that sometimes its hard to get kits for them).

In the tanks forum, there were people claiming their dive shop required doing eddy tests on steel tanks and getting mighty confused about it. Some places do it for any AL tank, etc.. In 20 years though, god knows how many overfills/hotfills those tanks have received.

Ask Les what his position would be on a 20+ year old tank brought in that he or his staff hadn't done a VIP on?

 

[DaleC]

I don't think it's a stupid correlation. Either we base our actions on some sort of scientific understanding or we base them on our "feelings" (or voodoo or tarot cards, rolls of the dice etc...). With 6351 alloy there is a demonstrated risk of SLC (although very very slight) so I think it is reasonable to either not want to fill them or fill them only if the shop does the vis itself. I don't know what Les's take is (and I don't care any more as I have taken my 6351's out of circulation) but I have always stated that I think wanting to do the vis is a reasonable degree of risk mitigation.

With the case of 6061 alloy tanks however there is no evidence of SLC (or any other defect that would affect integrity) so rejecting them for reasons other than failed vis or hydro's falls under the heading of "feeling" not science. A properly inspected and maintained 20 year old 6061 tank has less chance of harming someone (from a spontaneous catastrophic failure) than ones lead weights. Lead is toxic, and many older weights are uncoated and leach lead oxide. Is it not reasonable to replace those old lead weights with newer, coated ones? They don't put lead in paint any more because of its risk.

As kooky as it sounds there is more scientific evidence involved in that decision than in not filling older 6061 alloy tanks. And there are shops that council customers to throw out those old regs too, even though many of them are of a higher quality than the plastic regulators of today and have easily accessible rebuild kits.

If one wants to argue that older tanks have an unknown history and cannot be trusted then that argument must be carried across the board; steel as well as aluminum. Damage due to overfills falls primarily upon LP steel tanks yet nobody seems too concerned about them. I would be much more concerned about a 20 year old LP 108 coming out of Florida than I would about an old Al 80 (especially if it had double or triple bust discs installed).

Where are the threads about that practice?

Yes steel and aluminum have different metallurical properties true, but these are accounted for in lifecycle and hydro test parameters. As long as a tank falls within those parameters it should be considered safe (or we should resort to casting magical spells before hooking them up for filling).

All those threads where people are confused about doing eddy tests on steel tanks etc... are there because the SCUBA industry itself has intentionally chosen to ignore educationing themselves on the real vs perceived risks involved in this issue and have chosen to resort "peicemeal" with a variety of arbitrary, emotionally based criterion.

 

[mustang_5l]

Dale... my 2 x aluminum 72's last hydro'd in 1972 and vis'd in Ontario thank you! The VIS is not mandated as "mandatory" by any agency in Canada. It is a simple "rule" that "most" shops follow. You learn this in the Gas Blender course.

 

[tregrrr]

Dale... my 2 x aluminum 72's last hydro'd in 1972 and vis'd in Ontario thank you! The VIS is not mandated as "mandatory" by any agency in Canada. It is a simple "rule" that "most" shops follow. You learn this in the Gas Blender course.

right. It is an industry practice put in place to conform to recommendations made by the CGA and to appease DOT (and TC vicariously) and contend with the issue of tank failures **WITH** visible precursory indicators such as SLC development in threads or neck folds. If we did not have the industry policing itself such as it is, there is always big brother willing to step in and implement another AirCare or similar program which with their bureaucratic largess and our small numbers would wind up costing 150$++ per annum.

To each compressor operator their own rules fine. Make those rules based on BS, or in such a way that we (the diving population) can interpret them as unreasonable or collusion aimed at forcing unnecessary purchases, and expect to lose face. If you are going to plunk down a company rule for certain cylinders, base it on FACT, not convenience. DOT advisory clearly lays out which tanks are rightfully subject to extra scrutiny.

Right now I have a friend's tank in my truck which is a Luxfer from October 88. It was hydro tested 3 months ago. It is 6061-T6.

Please tell me how Hydro Testing and thus what regulatory standards do apply to our industry are WRONG??!!?? Okay, then why is it not safe to fill it?? There would be some awfully irate people out there if some gas stations decided that they would not sell fuel to people with cars older than 19XX because they MAY have a bad metal gas tank that might leak. There is more potential energy in a tank of gas than there ever will be in a scuba cylinder.

SOME shops will refuse to fill it based on the previously mentioned company rule. It is in their rights to make any rule they want to make, Just don't expect someone with both principles and a spine to spend a lead cent buying a new tank in your store if you have arbitrarily SXXT-LISTED their perfectly serviceable one.

Dive and Sea in New West will fill tanks that have been properly tested and certified and which have current VIP from a reputable shop (not so keen on 'generic' stickers with no store affiliation).

 

[sablefish]

Thanks for the OP, because this CL response has been deleted without a trace. The thread has turned into alloy talk, but what irks me is the time i'd waste responding to a local ad only to find out it had no TC numbers.

It doesn't matter if the tank walls are pure rubidium; if it doesn't have TC# it's an extra hoop to jump through to get them filled around here.