Virtual Positioning and Shaping of Source Fields for ECT of Tubes

Purpose – The purpose of this paper is to present a new approach to drive the excitation field sources in the eddy current testing (ECT) of tubular conductive structures. Design/methodology/approach – The magnetic field used for ECT is generated by pairs of counter-series connected coils, driven by AC currents. The phase and amplitude of the currents is electronically controlled in order to shape the primary field map, allowing circumferential sweeps until the presence of defects is detected, and then “focusing” the field on the defective section of the tube, increasing in this way the sensibility of the ECT probes in the targeted area, in order to determine with higher precision, the position, and the shape of the defect. Findings – If suitably designed, the field measurement system allows to enable/disable a number of probes to enhance the resolution in the defect area while keeping low the number of required data channels. Research limitations/implications – The analyzed geometry is limited to circular-shaped tubes, of infinite extent. Future work should be on the extension of the methodology to general shapes, and to finite length cylinders. Practical implications – The proposed method allows to enhance resolution in ECT of tubes at the end of production lines, guaranteeing a first, simple yet effective quality assessment of tubes in industrial environments. Originality/value – The paper presents a new technique to test conductive tubes using fixed excitation system, but allowing to focus magnetic field in defective regions. The method could be helpful for industrial diagnostics.