This paper presents the 2D axi-symmetric finite element modeling and experimental studies carried out towards estimation of thickness of ferritic steel tube using sweep frequency remote field eddy current (RFEC) technique. The inductive reactance component of the impedance of the RFEC receiver coil as a function of frequency was predicted and analyzed to arrive at a unique value of frequency called as the peak frequency. A perfect linear relationship was observed between this peak frequency and thickness of the tube. The peak frequency variation for thickness reduction in the tube arising due to extended and localized corrosion type of degradation was analyzed in detail and results are presented. An attempt was also made to size the remaining wall thickness of the tubes from the peak frequency parameter. Experimental measurements were also found to be in good agreement with the model predictions. Studies are promising for accurate and absolute thickness estimation of ferritic steel tubes using sweep frequency RFEC technique.
Thirunavukkarasu et al. (Thu,) studied this question.