| 摘要 |
<p>Provided is an eddy current examination method for an internal fin tube, which can detect a minute defect having appeared in the valley portion of the inner face of the tube even in case this inner face is heterogeneous in the tube circumference direction. The eddy current examination method is characterized by arranging a differential coil (2), which is so sized as can be arranged in the valley portion of the tube (P) and which is composed of a pair of coils (21 and 22) spaced in an axial direction (X), along the extending direction of the valley portion of the tube (P), and by moving the differential coil (2) relatively in the extending direction of the valley portion of the tube (P), thereby to detect the defect existing in the valley portion of the tube (P).</p> |
