I guess I have a different take - looking at the pictures and having
reviewed these sorts of failures for years in the aerospace industry.
The legs (not the welds) have broken at the point where the side plates
are welded to the legs. Also, the failures show no sign of ductile
deformation - note how sharp the cracks are. Also, the failures have
occurred at the point of maximum applied tensile stress to the leg
members.
This looks like a classic hydrogen embrittlement failure of the legs.
http://www.corrosion-doctors.org/Forms/embrittlement.htm
A few thoughts:
- The third leg will likely fail the same way, at any time.
- This is fixable - the legs need to be realigned and backing stock
welded in place by a professional. All three legs!
- The rest of the tower is suspect, but the failures have occurred at
the point of maximum applied tensile stress - as you move up the tower
the loads get smaller and the chances of a hydrogen embrittlement
failure go down. The rest of the tower may be okay. It should be
THROUGHLY inspected - every leg and tubing weld as a bare minimum.
- It is difficult to detect cracks with the eye and impossible to detect
hydrogen embrittlement without very sophisticated equipment. Applying
some side force with a pry bar may be the best you can do
inspection-wise.
- It is quite possible the manufacturer has seen this before. Get them
to talk to you - if they will.
Good luck -
Hal
N4GG
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