| 摘要 |
PURPOSE:To detect with high accuracy the defect of a steel pipe by providing an exciting coil and a detecting coil on the outer periphery of a steel pipe, detecting the electromotive voltage due to the defect in a steel pipe and by finding the correlation between the electromotive voltage and distortion of the diameter of a steel pipe. CONSTITUTION:A sensor 2 is constituted of an exciting coil 2a and a detecting coil 2b. An eddy current is generated by placing the exciting coil 2a vertically on the outer periphery of a steel pipe 1 and the induction magnetic field induced to the steel pipe 1 is detected by the detecting coil 2b. At this moment, an electromotive voltage Zi with respect to a measuring point Pi is detected by the sensor 2 by rotating the steel pipe 1 by a certain angle theta. For instance the electromotive voltage Zi is detected at thirty-six places per one rotation of the steel pipe. The defect of the steel pipe is also calculated and determined quantitatively by the signal processing part 4 from the electromotive voltage Zi of detecting coils based on the relation found in advance on the correlation between the electromotive voltage characteristic and the steel pipe distortion. Since the correlation between the distortion of steel pipe and the depth of the defect is utilized, therefore, a steel pipe can be diagnosed with high accuracy. |
