In heat transfer tubes of combined cycle Heat Recovery Steam Generators (HRSG) for thermal power plants, corrosion thinning caused by caustic gouging may occur on the tube inner surface. Mitsubishi Heavy Industries, Ltd. (MHI) and Mitsubishi Hitachi Power Systems, Ltd. (MHPS) developed the Pneumatic transfer Eddy Current Testing (ECT) inspection system as a technology which allows corrosion-thinned parts of heat transfer tubes to be measured without removing scale. In addition, to evaluate the performance of this technology, a verification test was conducted using the HRSG at Sendai Thermal Power Station No. 4 of Tohoku Electric Power Co., Inc. and satisfactory results were obtained.
