一种采用仰角交叉点的金属管道涡流测厚方法

The deflection of the coil placed outside the pipeline will seriously affect the performance of pipeline eddy current testing. In this paper, the analytic solution of the pipe eddy current field excited by a coil placed outside the pipe was used to analyze the influence of the excitation solenoid coil deflection on the relative impedance change of the coil and then relative impedance change curves of the excitation coil with different rotation angles and tilt angles were gained, respectively. By analyzing relative impedance changes curves of the excitation coil with different tilt angles, it was found that the relative impedance increment of the coil intersects in pairs within a small range under different tilt angles. This small range was defined as the tilt angle intersection domain, where the intersection point was the tilt angle intersection point. In the domain, the coil impedance increment was little affected by the change of the vertical tilt of the coil, so it could be used for eddy current detection of pipeline. In this paper, the characteristic equation between the frequency of the tilt angle intersection point and the thickness of pipeline with the tilt angles of 0° and 90° was fitted to measure the thickness of non-ferromagnetic metal pipe. Finally, the thickness measurement method was verified by experiments. The relative error of measurement results is 2.08%, which verifies the high precision of the method.