Evaluation methods of thickness and interfacial soundness of polymer-lining on steel substrate were developed. The dispersive Rayleigh mode wave and The leaky Interfacial Compressional Wave (LICW) propagating along the lining surface or interface of a lining/substrate were utilized. Propagation characteristics of the waves were experimentally studied. Two methods of estimating lining thickness were proposed and experimentally verified using the dispersion relation of the Rayleigh mode wave and the propagation characteristic of the LICW. Size and location of the delamination portion can be determined utilizing the propagation characteristics of the LICW and Lamb wave via the delaminated lining layer.

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On-site study for the source location of artificial acoustic sources on the floor plate of a cylindrical storage tank of 32.98 m diameter was performed. We monitored Lamb wave AEs from artificial sources on the floor plate inside the tank using four types of AE sensors with different center frequencies mounted on the terrace of the annular plate. Among the sensors, only the one with a center frequency of 30 kHz monitored the Lamb wave AEs from 15 artificial sources (slight impacts) on the one radial line and 5 sources on the annular plates along a quarter circumferential line. AE sources were located from the arrival time differences of Ao-Lamb waves using two kinds of location scheme, i.e., a virtual source scanning method developed in-house and a conventional time-of-flight method. Fifteen artificial sources on the radial line were located within 3.2 m error from the given locations. Five artificial sources along the quarter circumferential line were located within 2.9 m error. These sources, however, tend to be located toward to the tank center. Location accuracy was discussed in relation to the propagation path and attenuation of the Lamb wave.

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