I did some research. In the US, the sole regulation of pressure cylinders
is by the Dept. of Transportation. That only covers movement of such on
roads/aircraft etc. They must be tested every five years.

Now, if they NEVER leave the plant, there's no regulation. But they
can not have a DOT sticker if it's not up to date.

The safety engineer I spoke two was not aware of any history of body
failures such as it appears Qantas/JB experienced. Some SCUBA tanks of
one aluminum alloy were infamous for splitting, but other than that....

I also asked about acetylene cylinders exploding on shock input [such as
dropping five stories..] but that person knew of no such cases.... but
then wouldn't unless it happened in transit.

In short, I bet lots of folks are rather PO'd that the pieces are
not available for examination.