DIVISION-TYPE FLAW-DETECTING SENSOR AND FLAW DETECTING METHOD FOR CONDUCTIVE TUBE

摘要

PROBLEM TO BE SOLVED: To obtain a division-type flaw-detecting sensor in which the influence of a tube sheet is eliminated and in which a flaw generated in the circumferential direction of a tube near the mounting part of the tube sheet can be detected with good accuracy by a method wherein gaps are formed between cross sections of a plurality of magnetic-substance cores arranged in a circular shape and a primary coil and a secondary coil are wound so as to be piled up on the respective cores. ;SOLUTION: A primary coil 4 and a secondary coil 5 are wound so as to be piled up on two semicircular magnetic-substance cores 3, sensor divided bodies 2 are formed, the sensor divided bodies 2 are arranged so as to form a nearly circular shape by keeping respective gaps at prescribed distances G (1mm or higher) between both opposite edges of the cores 3, and a division-type flaw-detecting sensor 1 is constituted. Then, a sensor assembly provided with the flaw detecting sensor 1 is inserted into a tube 200 to be inspected, a square-wave current, e.g. at a frequency of 100Hz to 10kHz and a current of 0.1 to 0.5A is supplied to the primary coil 4, the pulse width of pulse waveform voltage which is output from the secondary coil 5 is measured, and a flaw such as a crack, a thickness reduction or the like which is generated in the circumferential direction of the tube 200 is measured.;COPYRIGHT: (C)1998,JPO