older luxfer tanks worth getting hydro'd?

[rhwestfall]

and post #6, 1(B) - [emphasis added]:

1. When storing a scuba cylinder for long periods of time, should the tank be stored full or almost empty?

b. Almost empty

Storing a cylinder almost empty helps to reduce corrosion because of the reduced oxygen partial pressure. While this is not so important with an aluminum cylinder, it can make a big difference with a steel cylinder. Also, storing a cylinder almost empty just makes sense from the perspective of reducing permanent expansion although the effects are minimal.

There is too much speculation in the crack propagation concept (so stated in the first post) as there is no idea which alloy was subject to the study. The early "bad" is known to be problematic. The other, not so.

 

[runsongas]

thanks for the clarification, I'll probably go ahead and get them hydro'd.

 

[rhwestfall]

enjoy diving them! (but do please report on the hydro outcome)

 

[teknitroxdiver]

I just finished a PSI cert class. The instructor explained there were 11 known cases of the older tanks (6561) failing. IMO, the tanks should be good to go. The issue will be finding a company who will hydro the tanks. Many companies do not want to bother. The Hydro company is also supposed to insect the threads for cracking and stamp "VE" (Visual Eddy) on the tank after the hydro date.

You should go request a refund of your course fee, or at least re-review your notes. The bad alloy is 6351. There's no such thing as 6561. And no tank made in 1994 would be made of 6351. Luxfer advises not doing the visual eddy test on 6061 tanks, which is what his is made of.

 

[fpv930]

Sorry I didn't see you stated the tanks were '94. These tanks (alloy 6061) have had no known issues with cracking. Even so much to add that the VE testing is not part of the inspection anymore. Just a visual inspection of the threads. I wouldn't worry about the tanks as they were stored full. Once they pass hydro just store with positive pressure when not in use.

 

[rhwestfall]

numbers.... so unimportant.....

what did you use? A .38? --.38. .39...what ever it took.



(welcome to SB)

 

[fpv930]

You should go request a refund of your course fee, or at least re-review your notes. The bad alloy is 6351. There's no such thing as 6561. And no tank made in 1994 would be made of 6351. Luxfer advises not doing the visual eddy test on 6061 tanks, which is what his is made of.

My mistake as I didn't read the original post correctly.

 

[teknitroxdiver]

My mistake as I didn't read the original post correctly.

Then where did 6561 come from? It doesn't exist, at all. It's not even an option. I'm not trying to run you down, but if you're going to be working with other people's tanks you need to get this stuff right. When you send a guy's tank off for additional testing because you think it's made out of something it's not, he's going to be pretty upset when he finds he actually didn't need to pay for it.

 

[Dsix36]

I have a great way to stop all this confusion.

1 - The OP will put the tanks in question at the curb with regular trash.

2 - The OP will PM his address to ME.

Problem solved. OP does not need to worry about wasting money for a hydro and VIP on the tanks, and I will suddenly have a few more tanks in my collection.

 

[Darol]

fpv930 said:

I just finished a PSI cert class. The instructor explained there were 11 known cases of the older tanks (6561) failing. IMO, the tanks should be good to go.

teknitroxdiver said:

Then where did 6561 come from? It doesn't exist, at all. It's not even an option.

This is the case with "Tank Experts", misinformation. Tek has it right, it's 6351. The new trend seems to be not filling aluminum tanks that
are over 20 years old, something to do with insurance. I made it a point recently to ask which is best, to store a tank full or with say 300
to 500 psi. Three different experts, three different answers. The worst thing you can do is a quick fill, aka a hotshot, which usually happens
to tanks used in rental service or at dive resorts. I recently had a set of older USD twin 50's that were 6351 they tested good one year,
and had cracks the next, so scrapped them out. I currently have seven tanks I dive, six Catalinas and one newer Luxfer.