Welding Inspection & Metallurgy API ICP Self Study Notes

The quick freeze characteristic, which can result in LOF, is the reason this
process is frequently written out of purchase requisitions. GMAW in the shortcircuiting
transfer mode is of particular significance to inspectors in that many
specifications, codes and standards impose limitations or special conditions
on its use. The technique can suffer from incomplete fusion particularly in the
sidewall of steep or narrow weld preparations. This occurs as transfer of small
fast freezing droplets only occurs whilst the electrode is short circuited by
contact with the work piece. Intermittent loss of contact can leave areas of
lack of fusion. In shallow weld preparations, these are also very difficult to
detect with conventional radiographic techniques. Consequently, a higher
standard of NDE inspection is required. In pipeline welding, automated
ultrasonic has been adopted to overcome this problem. The risk of LOF
associated with GMAW-S means restrictions on qualification of welders using
radiography only and inspectors should make note of these potential
problems.