The field AE test results of a repaired toluene storage tank
showed that significant genuine emissions related to weld like defects and the mechanical noise signals of inordinate
emission bursts. The genuine emissions resulting from weld
defect areas appeared as a band pattern in which the value of
event counts was approximately proportional to peak amplitude, whereas the mechanical noise resulting from valve
shut-off was characterized by a high event rate, high count
and low amplitude signals.
Some of the genuine emissions were related to structural
weld defects, but other emissions appeared to be unrelated
to any detected defects. The weld defects observed by the
follow-up RT were a through-wall weld crack of 1.5 cm
length and a round individual porosity of 0.5 cm diameter,
respectively. The defect emissions observed during the
110% maximum operating load conditions of the repaired
storage tank were active but not characteristic of defect
growth. In the repaired storage tank, the 110% load level
was not sufficient to cause structural defect growth during
the AE test. Consequently, some differences between the
AE test and the follow-up RT results of the repaired storage
tank will be improved through further considerations for
field test procedure in excess of 110% maximum operating
load.