Monitoring of Corrosion in a Flange Connection under Salt Production Environment using Acoustic Emission Technique

Abstract

This study aims to detect and monitor the initiation and progression of corrosion that occurs at a flange connection using an acoustic emission technique, and to investigate the correlation between acoustic emission parameters such as hit rate and frequency component of AE and the corrosion progression. We first monitor AE from the corrosion in a crevice of an assembled flange under corrosion potential control in order to investigate the feasibility of AE monitoring for corrosion detection. Many burst type AE waves were detected during testing and most of the AE source locations agreed fairly with the corrosion area. Next, AE monitoring for corrosion at a flange connection under a continuous flow of artificial concentrated sea water was performed with four PZT-type AE sensors. The AE generation rate during testing equaled 10 to 30 events / hour. Peak frequency of detected AE shifted higher to 300 kHz with the progression of corrosion. Using an optical fiber AE monitoring system developed in-house, the AE from corrosion in a crevice was also monitored. This system can monitor AE for three flanges with one optical fiber. These sensors detected AE from corrosion at an individual flange under continuous flow test. As a result, it was found that the AE method is a potential tool for monitoring corrosion at a flange connection in salt product plants.