"Michael A. Terrell" fired this volley in
m:


It was on the neck. Just a few inches of metal that wasn't under
water. It turned out the inside of the tank was quite rusty, which
wasn't visible before it blew.

Well... "sitting on empty" and "empty, and open to the air" for two years
are two different things.

I assume (unless welding gasses were the culprit) that there had not been
adequate ventilation of the tank.

I've modified numerous "pulled from service" gasoline and propane tanks
(of course, emptied, dried, purged, and filled with inert stuff before
work), and not had any even _minor_ malfunctions. And usually, all that
folderol takes longer than the modifications do.

I deal with a surprisingly high-tech welding/cutting shop in our little
town of 2000 that welds repairs on RV gas tanks as a regular part of
their business, and they don't have those problems, either.

If it's gasses that are your problem, a _slightly_ oxidizing flame is
your friend -- no free fuel, either in the form of gas or air-suspended
particulate carbon, gets into the tank by accident.

As part of my practice on propane tanks, I also wash out the mercaptan,
which _can_ form an explosive mixture. (household lye converts it to
other stuff which can be washed out with water)

LLoyd