On Thu, 21 Jun 2012 15:19:05 -0700, "Steve B"
wrote:


wrote

These tanks are welded, to begin with, they are made to be welded.
Yes, they are made to be welded - and then X-Rayed and
hydrostatically tested. Brazing, unlike welding, does not run the risk
of undercutting or "burning" the steel - it adds a ductile material
which bonds TO the surface, not menting the substrate. A GOOD welder
can weld it and pretty well guarantee the repair is as strong as, or
stronger than the base metal. Most , even on this list, can not.
With brazing, you can.

A lot has to do with what is wrong with the tank. If it is leaking because
the mount has been bent, and the wall compromised, then yes, it can be fixed
easily. But, if it is due to corrosion, then it is more difficult because
of thinner wall thicknesses, and the probability that there is more than one
site of compromise.

Steve

I believe we are talking about an almost new compressor unit with a
crack close to where the foot was welded on - considered to likely be
due to vibration (metal fatigue) which would lead me to believe the
initial welding of the foot was not stress relieved - resulting in a
crack at the edge of the heat affected zone. Welding is more likely to
make that worse, while brazing, if done correctly, is more likely to
anneal the area around the crack - and the brass will strengthen the
area, where a bead of weld is likely to make the problem worse. Of
course it IS possible to lay a few beads over the area to build it up
with a stick welder to get the same effect, more or less - but brazing
is simpler and a lot less likely to CAUSE a problem down the road.
Could even "sweat braze" a patch over the crack, depending where it
is (not applicable as I understand the failure in this case).