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RE: welding inspection

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I find it interesting that many engineers require that
only pre-qualified weld procedures can be used.  I
believe that this is an undue limitation and could
potentially create problems if none of the
pre-qualified weld procedures are applicable.

The first step is to have the WPS reviewed by somebody
familiar with the welding code.

Second and probably more important, the welding
operation needs to be visually inspected while the
welding is being performed.  Without this you do not
know what was really done.  Inspections after the fact
of completed welds cannot identify many problems.  For
example some welding practices can result in brittle
welds, yet none of the NDT methodologies in the code
will identify the  existance of this brittle material.

I fundamentally disagree with the practice of allowing
significant welding to be performed with no outside
insspection even if the plant is certified.

Thirdly supplement visual inspections with some form
of NDT.  These tests will find things that a visual
inspection will not find.  Dye penetrant and magnetic
particle testing are useful but will only find surface
defects.  If stresses are high consider UT tests to
find sub surface tests.

Fourth: use weld metal and processes that result in
decent charpy values.  No matter what form of testing
you use you will not find all defects.  Good weld
toughness helps the weld be tolerant of the inevitable
weld defects.

Mark Gilligan

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