Experimental Research on Blind Area of Condenser Tube Sheet in Eddy Current Testing

This paper firstly shows the problem of blind area encountered in eddy current testing of heat exchanger tubes of condenser near the tube sheet area with bobbin technique. In addition, it gives the principle of blind area and experimental results with mockup tube sheet. The experiments indicate that signals of the tube sheet and expanded area have great impact on inspection ability of bobbin probes. As a result, an 8 mm length blind area outside the TTS comes. And the less the distance from TTS is, the more the influence from TTS. Finally, a CXB technique is figured out as a method to solve blind area problem.