Development of a High-Sensitive Dual Frequency Remote Field Eddy Current Instrument for Inspection of Ferromagnetic Steam Generator Tubes

摘要

This paper presents the development of a high-sensitive remote field eddy current (RFEC) instrument for detection of flaws in ferromagnetic steel tubes. The instrument is capable of simultaneously driving the exciter coil of the RFEC probe with two different frequencies and measuring the phase lag of the receiver coil using software-implemented lock-in amplifier. The performance of this high-sensitive RFEC instrument has been demonstrated by detecting a variety of localised flaws in a modified 9Cr-1Mo steel tube used in steam generators. The instrument is sensitive to detect localised flaws of depth, 20% of the wall thickness of 17.2-mm diameter, 2.3-mm thick ferromagnetic steel tubes.