| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and an apparatus which accurately detect degradations due to corrosion, erosion or the like and occurring inside steel pipes made of iron, nickel, cobalt or alloys including these ferromagnetic elements, and which can precisely and quantitatively detect the degradations, even when the degraded portion extends over a wide region of the inner surface of the pipe member, or when the degradation is uniform or planar and has no local variation, or when the degradation is a slight corrosion degradation having very few cracks or cavings. SOLUTION: In a condition where exciting current is applied to an exciting means disposed at the steel pipe made of a ferromagnetic alloy or an alloy, including a ferromagnetic element, in order to produce a magnetically saturated state where magnetic permeability is made approximately uniform, permeable magnetic fluxes are produced in the steel pipe, and induced voltage at a prescribed position is detected by a detection means arranged so as to wind the steel pipe. Reference information which includes relational data between the steel pipe cross section values and the induced voltage values, are acquired from the same steel pipe or an equivalent steel pipe and are stored; and then, the cross section of the steel pipe is obtained by comparing the detected induced voltage with the reference information, thereby detecting the degradation of the inner surface of the steel pipe. COPYRIGHT: (C)2006,JPO&NCIPI
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