The ultrasonic wave is applied as an inspection method for the gas-holder and the pipeline in service. In such an inspection, the application of an automatic inspection system is desirable, because a manual inspection is difficult to accomplish perfectly and exactly due to its enormity, a so-called nondestructive inspection robot is then preferable. However, an ultrasonic nondestructive inspection robot with a piezoelectric oscillator needs to directly touch the material surface to be inspected using the coupling medium. Therefore, a mechanism where the coupling medium is spread thoroughly between the sensor and the material surface and where the sensor is always held at a constant pressure in the same direction on the material side to be inspected, are performances requested for the inspection robot. Actually, it is difficult to overcome this problem and the ultrasonic inspection robot could not be applied widely. We then tried to develop an ultrasonic inspection robot with an electromagnetic acoustic transducer (EMAT) which did not require the coupling medium, which inspected the circumferential parts in the pipe. We especially developed the EMAT to transmit and receive a S0-mode with high sensitivity and a SH0-mode plate wave without the influence of the welding bead alternately as the sensor parts. The fixed method between the pipe and the inspection robot was not especially fabricated, because the magnetic force of the EMAT was very strong and was sufficient for attaching the inspection robot on the surface of the steel pipe. The method in which the inspection robot turned around in the direction of the steel pipe surroundings was executed by observing the tape pasted in the direction of the steel pipe surroundings with an installed CCD camera. In this study, the basic mechanisms of this inspection robot and the examination results are described.
Time of flight diffraction (TOFD), an advanced non-destructive testing technique for inspection of welds for heavy walled pressure vessels
Laufzeitbeugung (TOFD), ein modernes zerstörungsfreies Prüfverfahren zur Untersuchung von Schweißverbindungen in dickwandigen Druckbehältern
2004
8 Seiten, 8 Bilder, 17 Quellen
(Nicht paginiert)
Conference paper
Storage medium
English
Inspection and testing of welds in ships and pressure vessels
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