Abstract
Corrosion damage of floor plates of a naphtha storage tank was monitored by acoustic emission (AE). AEs from the fracture of rusts were monitored by AE sensors of 30 and 50 kHz resonant frequencies, mounted on the terrace of annular plates and the side wall. AE signals were separated from noise by the waveform inspection. The signal counts from the sensors on the terrace were larger than those from the side wall sensors, and submitted to the location estimation of corrosion zone. The ratio of AE signals to total AE events were as low as a few percent. Source locations of the Lamb wave AEs detected by the AE sensors on the terrace of annular plates were estimated by three methods and ranked into three levels depending on the determination accuracy of the arrival times. Four portions in the third quadrant of the tank bottom were located as corrosion zones. They appear to be spreading from the zone with relatively large reduction of wall thickness measured in 2003. This paper also discusses some future problems of condition monitoring of huge steel structures by AE.
