Problem is 6351-T6 Alloy.
Potentially Affected Cylinders:
Any cylinder manufactured before 1990 marked 'DOT-3AL'
Exemption Numbers: Seamless Aluminum: 6498, 7042, 8107, 8364, 8422
Link to DOT Advisory:
http://www.sounddivecenter.com/3al_advisory.pdf
Thank you very much for the sensationalist pictures. There were a few nasty death and dismemberment incidents involving 6351-T6 alloy tanks before the Sustained Load Cracking issue was fully understood.
What the pictures and the advisory above do not say is that there are still millions of 6351-T6 Aluminum alloy scuba, SCBA, and medical O2 (not even counting CO2 tanks) tanks in service and that there have been exactly ZERO failures of 6351-T6 alloy tanks related to SLC issues since eddy current/visual plus inspection protocals were implemented prior to the above advisory circular that required them.
Now, over 6 years later the SLC issue is fully understood and it is also known that cracks propogate slow enough that eddy current/visual plus inspections completed as part of the tank's requalification (the hydro test is another part of this process) every 5 years is sufficient to identify any cracks before they can progress to the point of catastrophic failure.
On top of this, the dive industry standard requiring eddy current/visual plus inspections with every annaul VIP pretty much insures that 5 out of the 6 inspections occuring during that 5 year period can be screwed up by the tester and a tank with an SLC would still be pulled from service before it would fail.
The problem is there is much hysteria over the issue - promoted by things like posting pictures and 6 year old circulars without addressing the other side of the coin and in effect ignoring all the reasearch, operational experience and legislation that has occurred since then. The end result of that type of disinformation is that shops and insurance companies operate in a state of fear where there is nothing to fear and divers with properly inspected and legally certified tanks cannot get them filled in some shops.
What's worse is that the prohibition has taken the form of a blanket refusal to fill any scuba tank made prior to 1990, even though the most common scuba tanks encountered (Luxfer AL 80's) were made from 6061-T6 alloy after December 1987 and the next most commonly encountered tanks (Catalina tanks of any capacity) have always been made from 6061-T6 aluminum alloy and are not subject to SLC issues.
