Inspection of a pipeline is essential for the safe use of such facilities. A trial\nsensor using an electromagnetic acoustic transducer (EMAT), which can\ngenerate the SH-mode plate wave propagating in the circumferential direction,\nhas been developed to realize this objective. It consists of a circulating\nelectromagnetic induction coil around the pipe and many permanent magnets\narranged on the surface of the pipe in the circumferential direction. It is\npostulated that the intensity of the SH-mode plate wave propagating in the\ncircumferential direction is dependent on any defects in the circumferential\ndirection. A resonance method was then utilized to obtain a stronger received\nsignal. As a result, it was confirmed that the resonance status can be detected.\nThe relationship between the signal intensity and the pipe thickness was then\nevaluated. It was confirmed that the wall thickness of about 20% can be detected\nunder a static condition. Finally, a moving test has been executed by\nusing an axially traveling device manufactured by trial. The test pipes with\ndifferent sizes of drilled holes were prepared. The change in the received signal\nintensity according to different sizes of the drilled holes was successfully\ndetected.
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