The objective of the present paper is to propose a method for detecting inside corrosions at actual finned tubes in air-cooled heat exchanger by applying an Electro-Magnetic Acoustic Transducer(EMAT),where axial shear resonance waves using electromagnetic acoustic resonance (EMAR) in EMAT can detect the corrosions. The accuracy for measuring the corrosions in the finned tubes with the nominal diameter of 1 inche in which artificial flaws have been fabricated is investigated. Furthermore, the measurements in site are carried out and comparison is made between the measured results and the actual situations. As the result, (1) It is shown that an artificial flaw (slit 2mm in width, 10mm in length, 0.7mm in depth) is able to be detected clearly at the finned tubes. (2)It is shown that the artificial flaws can be detected even though the filling rate of the probe of EMAT is around 87%. (3) From the measurement results, it is found that corroded parts which is located far from the EMAT can be detected and the location of the flaw also be detected. It is can be conclude that the present method is an outstanding inspection method for detecting inside corrosions at actual finned tubes.
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