Cracks in newer Aluminum tanks

[fppf]

I don't know anyone that has found a crack in a 6061 cylinder.
Last PSI course also indicated that they have not seen a cracked 6061 yet.

Also, there are different visual inspection plus testers for the different aluminum alloys.

 

[akscubaduck1]

There seems to be a little disbelief here.
Been inspecting tanks for over 20 years.
An eddy current wouldn't of picked the AL 80 up because the crack didn't extend in to the threads. the smaller of the two tanks the cracks did extend into the bottom two threads.
The friend that brought them in was a fellow PSI inspector.
Being newer tanks he wanted a 2nd opinion before condeming them.
Yes my friend was going to call Luxfur.
I'll ask him today about what they said.
They were not tool stop marks, or folds.
I'm 100% sure.
I just had never seen them in tanks of that vintage.
Again a ask has any body else seen this in newer AL tanks?

 

[akscubaduck1]

Thanks for your reply fppf.

 

[akdeepdiver]

This is a follow up to Terry's original post, since I am the person who inspected the cylinders. I am posting this as a lesson learned to anyone that is interested. A little about me first before I go into the cylinders. I have been involved in the diving/firefighting/HAZMAT industry for 10+ years. I currently run a hydro facility here in Anchorage AK. Additionally, I am a PSI Instructor and a PADI Divemaster. On the average, my partner and I test and VIP aprox 500 tanks a year.

This week, I was given 5 tanks to Hydro and vis. 2 were HP Steel, and three were Aluminum cylinders, all of 6061 Aluminum alloy. All passed Hydro with no issues. During visual inspection, I red flagged two aluminum tanks which had crack like features/anomalies at lower threads and in the neck area. The first one, in my best determination, started out as a fold and was either expanded, or developed into a crack due to the pressures put on it by the current hydro(and/or past hydrotests) or by pressures put on it by filling. Either way, the feature extended through two threads therefore condemning it. For those not aware, PSI states that a cylinder should be condemned if the fold extends through two threads, and Luxfer states the cylinder should be condemned if it extends through more than ONE full thread. Additionally, it was confirmed by Eddy Current that there was a anomaly in the metal.

The second cylinder had a crack like feature that extended from the bottom thread down toward the shoulder. This is the cylinder that I wanted second opinions on. I had three separate PSI trained inspectors at 3 different shops take a look at the tank. All came back with the same answer of "crack". Photos were taken and emailed to Mark Gresham at PSI and also talked to Luxfer. After examination of the pictures, the determination was that the feature was a very faint fold and to return to service. The cylinder was returned with the proper annotation about the feature and put back in service.

In closing, I wish to state the following:
1. This is why I like second opinions as to the fact that I do not like to condemn tanks for invalid reasons. Additionally, it is a good learning point for all.
2. Just because these cylinders are made of 6061 alloy, that is no reason to become complacent on checking for cracks in threads. I am sure people did not think cracks would occur in 6351 Alloy tanks before the first one was discovered. Cracks can be caused by other reasons, and if you don’t believe me ill tell you about the steel 72 I used to have with the 8 inch long crack in it caused by environmental reasons. I refuse to compromise my safety, or that of other divers by not checking something that could easily and quickly be checked and double checked.

If anyone would like to see a copy of the pictures or discuse this more in detail, I can be reached at tanktest@gmail.com

Myles

 

[WD8CDH]

You are very correct that we should not become complacent about checking threads of ANY tank material. I have also seen threads damaged by overtightening of the valve.

 

[WD8CDH]

Did Luxfer say if they would replace the tank?

 

[fppf]

Yeah, I'll third the complacent comment. This is why we hydro and visual.

I would love to see the pics for my own education. Also, was the cylinder returned to luxfer and what was there response?

 

[akdeepdiver]

The cylinder that was condemned has not been returned to Luxfer because the customer has not picked them up from the dive shop yet that they dropped them off at.

The AL60 that was condemed was manufactured in 1993. As per the luxfer website :

1. This Luxfer Limited Warranty covers all Luxfer aluminum and composite cylinders manufactured in the United States on or after November 1, 2004, for 15 years from the original hydrostatic test date on each cylinder. (On a Luxfer aluminum cylinder, the original hydrostatic test date is the earliest test date stamped on the cylinder crown. On a Luxfer composite cylinder, the original hydrostatic test date is the earliest test date either stamped on the cylinder neck or printed on a label on the cylinder body.)
2. This warranty is not retroactive to Luxfer cylinders manufactured before November 1, 2004. There are no warranties that extend beyond the exact text of the express written warranties described in this Luxfer Limited Warranty, which supersedes all previous Luxfer warranty statements.

In my paperwork provided back to the customer, I did leave POC numbers for Luxfer in the event he wants to call them, but I believe he is out of luck with them. Additionally, the cost of shipping from AK is usually somewhat prohibitive for people. But, I will say, he is not completely out of luck. When i do have a cylinder fail visual for something like this, or neck cracks, or other reasons, I usually offer to purchess the tank so I can cut the crown off and use as a teaching prop.

 

[fppf]

Yeah, I would at least like to contact them. They may want it back from service to try and do failure analysis on it.

 

[Scared Silly]

I don't know anyone that has found a crack in a 6061 cylinder.
Last PSI course also indicated that they have not seen a cracked 6061 yet.

Also, there are different visual inspection plus testers for the different aluminum alloys.

About two years ago I was down at my local hydro shop and I was shown one.