Luxfer Aluminium Tank, pre 1980

[Elkfriend]

Hello Folks,

I have tank with J valve that I am planning to use diving! Its a Luxfer Aluminium, but other than that, the numbers are just hieroglyphs to me..

There are some extremely knowledgable people on this forum and I am blown away by Luis H. quick tank analysis in previous post.

Any chance that someone could help me understand what I got please?

On the tank shoulder, it reads:

CTC - SP922 - 3000
P10562
USD 2119 99
3 (arrow up) 78
611998

Not even sure what the size is!

thanks a lot
Chris

 

[fppf]

Me personally, I would just scrap it, but that is me.

It was made under a CTC Special permit 922, which is still listed on the Canadian Transportation site. It is a 3000 PSI cylinder. If there are no other stamps in it, the tank needs to be hydro tested. After that it will need a visual inspection and very possible a mandatory eddy current test. Before doing a hydro on it, the facility must contact the CTC to get a copy of the permit for testing proccedures.

Even if it passes all the tests, there are many dive shops out there that are refusing to fill older 6351 cylinders.

 

[Slonda828]

It all depends on where you live man, but down here in the south nobody will fill 6351 alloy tanks. If it were a steel tank, I'd tell you to keep it until you grow old and crotchety. I'm pretty adventurous and I will not use 6351 alloy tanks. There's plenty of other aluminum tanks around for good prices. I picked up a 90's aluminum tank the other day for 30 bucks. I'd scrap it, or make wind chimes out of it.

 

[jbrians]

I have 4 AL tanks that are of 6351 alloy. All are in current hydro and viz and I'll take my chances as long as someone will fill them. I believe there have been something like 34 tanks out of 20,000,000 that have failed. When they fail a hydro, I'll stop using them...or when they are refused at the shops I deal with...
Having said that, I'm only using them now because they are my double 50's which I dive vintage with.
I wouldn't buy them now for anything above scrap value.

 

[elan]

So far I know that G&S at Tobermory refuses filling them (Al tanks older than 89) I have not been to many shops here but I have not seen any other refusing older ones.

 

[Luis H]

I have 4 AL tanks that are of 6351 alloy. All are in current hydro and viz and I'll take my chances as long as someone will fill them. I believe there have been something like 34 tanks out of 20,000,000 that have failed. When they fail a hydro, I'll stop using them...or when they are refused at the shops I deal with...
Having said that, I'm only using them now because they are my double 50's which I dive vintage with.
I wouldn't buy them now for anything above scrap value.

Make sure they are also eddy current tested (Visual Eddy or Visual Plus). A hydro test only detects the metal elasticity. It does not detect cracks. Many aluminum tanks will pass hydro test perfectly fine with very visible cracks on the neck.

The statistic you quoted is correct but it can be very misleading. The reason more are not failing is because they are being pulled out of service (in very large numbers yearly). Many cracked tanks are constantly being detected by the inspection methods that have being put in place.

Obviously, not all tanks that are pulled out of service have crack, but the percentage of aluminum 6351 tanks that will end up developing cracks eventually (even according to Luxfer) is kind of high for my comfort.

They are fine to use as long as they are carefully inspected to confirm that there are no cracks, but personally I prefer to just avoid them if possible. That is just a personal choice.

Again don’t get a false sense of security from passing a hydro test... it doesn’t test for cracks at all. The hydro will expand the cracks and make them easier to detect after the hydro, but it can pass hydro perfectly fine.

 

[jbrians]

Make sure they are also eddy current tested (Visual Eddy or Visual Plus). A hydro test only detects the metal elasticity. It does not detect cracks. Many aluminum tanks will pass hydro test perfectly fine with very visible cracks on the neck.

The statistic you quoted is correct but it can be very misleading. The reason more are not failing is because they are being pulled out of service (in very large numbers yearly). Many cracked tanks are constantly being detected by the inspection methods that have being put in place.

Obviously, not all tanks that are pulled out of service have crack, but the percentage of aluminum 6351 tanks that will end up developing cracks eventually (even according to Luxfer) is kind of high for my comfort.

They are fine to use as long as they are carefully inspected to confirm that there are no cracks, but personally I prefer to just avoid them if possible. That is just a personal choice.

Again don’t get a false sense of security from passing a hydro test... it doesn’t test for cracks at all. The hydro will expand the cracks and make them easier to detect after the hydro, but it can pass hydro perfectly fine.

I hear and agree with what you are saying. The shop does an eddy current vis and passes the tank. The guy that does the vis also fills the tanks, so he knows he is in the line of fire!
At some point, I won't be willing to spend the money to get them tested anymore as the eddy current vis can only go up in price. Maybe by then I'll have a steel set of vintage doubles? Besides, I'd far sooner dive steel. AL just doesn't work for me as well for weight reasons.

 

[jbrians]

So far I know that G&S at Tobermory refuses filling them (Al tanks older than 89) I have not been to many shops here but I have not seen any other refusing older ones.

Just got back from Toby. Friday and Sat were amazing weather but rain on Sunday...what is it about me that I hate getting wet before I get into the water??? LOL. 7 dives in 3 days. Water temp was 46F and pine tree pollen had been stirred into the water so the vis was down to only 60 feet or so.

About G&S...they won't fill any AL tank older than 1990...same with the other 2.
On the other hand, they will all fill 72's in date. Matter of fact, they give you really good fills if they are distracted. I put the gauge on mine when I picked them up saturday morning and one was sitting at 4000psi. If the burst disc had of let go, someone would be needing to change!

 

[WD8CDH]

My personal opinion of 6351 alloy tanks is while they are safe if properly tested, I would only keep VIS and eddy current testing current until next hydro is needed and then retire them. The cost of the hydro just doesn't seem to justify the LDS hassle.

 

[Luis H]

About G&S...they won't fill any AL tank older than 1990...same with the other 2.
On the other hand, they will all fill 72's in date. Matter of fact, they give you really good fills if they are distracted. I put the gauge on mine when I picked them up saturday morning and one was sitting at 4000psi. If the burst disc had of let go, someone would be needing to change!

If you had a steel 72 filled to 4000psi, you should at least have the burst disk replaced... and maybe even have it rehydroed... hopefully it will do well on the next hydro... it probably will, but this is not a good habit.
That tank was taken a bit beyond its elastic limit (or yield strength).