Investigation of Focusing Properties of Probes for Pulsed Eddy Current Testing

Pulsed eddy current testing (PECT) for detecting localized corrosion and wall thinning in the pipeline under insulation has attracted much attention. In this paper, cylindrical and U-shaped PECT probes are used and their focusing properties are studied by simulations and experiments. In the simulations, the focusing properties of these two types of probes are compared by analyzing the gathering degree of the eddy currents, which is closely related to the detection sensitivity of a probe to localized defects. The focusing region of eddy currents of a cylindrical probe is not under the center of the probe while that of a U-shaped probe is. The power dissipated by the eddy currents is introduced to quantitatively characterize the focusing performance of the probe. The simulation results indicate that the U-shaped probe achieves a much better focusing performance of eddy currents than the cylindrical probe. The experimental results show that the two probes designed can effectively detect the localized corrosion of non-magnetic stainless-steel plates under certain lift-off distances and the U-shaped probe has higher detection sensitivity than the cylindrical probe. The research results are helpful for the optimization of the PECT probe to detect localized corrosion.