Outside inspection and quantitative evaluation of pipe defects based on pulsed remote field eddy currents
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TH878; TG115.28

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    Abstract:

    The remote field eddy current (RFEC) technique is widely applied for defect inspection in the wall of metallic pipes. However, it is difficult to identify the defect’s specific location because this technique has the same sensitivity to inner diameter (ID) and outer diameter (OD) defects. To meet the demand of inservice inspection for pressure piping, this paper presents an outside inspection method based on pulsed remote field eddy current (PRFEC) for pipe defects and makes a contribution on depth quantification and location identification of ID and OD defects. First, based on the characteristic of magnetic field propagation, the principles of inside and outside RFEC inspection were compared and analyzed. Afterwards, the repetitive frequency and duty cycle of the excitation pulse were optimized by using finite element simulation. Then, the magnetic perturbations caused by ID and OD defects and their response signals were studied, and meanwhile the correlations of signal peak and time of zerocrossing (TZC) with the defect depth and location were revealed. Finally, a PRFEC system was set up and experiments were carried out on a carbon steel pipe with prefabricated ID and OD defects. The results show that: i) the peak value of defect signal increases monotonically as the defect depth increases, which can be used to quantify defect depth; ii) the signals’ TZCs of ID defects are always greater than those of OD defects with the same depths, and therefore, by using this feature, the defect location can be identified.

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  • Received:
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  • Online: January 04,2024
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