Eddy current examination method for internal fin tube, differential coil for eddy current examination, and probe for eddy current examination

Abstract

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).

Description

technical field [0001] The present invention relates to an eddy current flaw detection method for a tube with cooling fins on its inner surface, a differential coil for eddy current flaw detection, and a probe for eddy current flaw detection. In particular, the present invention relates to the ability to reliably detect minute cracks generated in valleys (or both valleys and peaks) on the inner surface of a pipe even when the shape of the inner surface of the pipe is uneven along the circumferential direction of the pipe. An eddy current testing method for tubes with fins on the inner surface of defects (crack-like minute defects), a differential coil for eddy current testing, and a probe for eddy current testing. Background technique [0002] As steel pipes used in ethylene manufacturing equipment, there is known a so-called finned pipe on the inner surface, which has a cross-sectional shape (a cross-sectional shape perpendicular to the pipe axis direction) on its inner sur...

AI Technical Summary

Problems solved by technology

[0019] The present invention is made to solve the problems of the prior art described above, and its object is to provide a reliable solution even when the shape of the inner surface of the tube with fins on the inner surface is uneven in the circumferential direction of the tube. The eddy current flaw detection method of the tube with fins on the inner surface, the differential coil for eddy current flaw detection, and the probe device

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