The Influence of the Elbow Surface of Boiler Tube on Eddy Current Probe′s Impedance

The complex structure of elbow surface is the main difficulty which hampers eddy current technique being conducted on boiler tube elbow. Therefore, in order to improve the detection accuracy, it is of great significance to study the influence of the elbow surface on probe’s impedance. In this paper, the finite element model of a pancake probe-coil over a stainless steel tube elbow was established. Influences of the variations of the pipe’s curvature radius and the probe′s circumferential detecting position on the probe’s reflected impedance were respectively studied. Also, an experiment validation of the simulation was conducted. The results are as follows: (i) as the radius of curvature increases, the variation of the reflected impedance amplitude increases but the impedance phase decreases. (ii) as the probe is moved from the inner side of the elbow to the outer side, the variation of the reflected impedance amplitude decreases but the impedance phase increases.