ACOUSTIC EMISSION EVALUATION OF CORROSION DAMAGES IN BURIED PIPES OF REFINERY

In order to investigate the applicability of AE method for the evaluation of corrosion damages in buried pipes, systematic tests have been conducted in laboratory and field. Corrosion tests in laboratory showed that steel specimens with thick oxide film generate very strong AE signals with amplitudes over 80 dB during the corrosion process in a salt water. It was also found that signals in a low frequency band (20 ‐ 80 kHz) are mainly produced during the process. Wave propagation tests using pipes under different surface and buried conditions found that source location can be applied to a buried pipe covered with protection film up to 4 m in length. Field AE measurements for 13 buried pipes in service were made in a refinery. Comparison of the AE data and UT thickness measurements and visual inspection demonstrated the potential usefulness of AE technique for evaluation of corrosion damages in buried pipes.