In boiler heat transfer tubes for thermal power plants, corrosion thinning caused by caustic gouging may occur on the tube inner surface. Mitsubishi Heavy Industries, Ltd. and Mitsubishi Hitachi Power Systems, Ltd. have established inner UT technologies using the ultrasonic method for continuous thickness measurement of heat transfer tubes, but they are affected by scale which is comprised of rust and deposits produced by corrosion, resulting in difficulty in the detection of thinning of the tube inner surface. The author et al. studied the application of ECT (Eddy Current Testing) as a method of inspecting the overall length/circumference of the tube without being affected by scale, extracted the flaw detection conditions for detecting thinning parts through electromagnetic field simulation and developed a special ECT probe.
