Study of a pipe inspection system using SH-surface wave travelling in the circumferential direction of a pipe by an EMAT

Speaker:
Murayama, Riichi; Fukuoka Kogyo Daigaku; Japan

Authors:
Murayama, R.; Fukuoka Institute of Technology; Japan

ID: ECNDT-0006-2018
Download: PDF
Session: Guided Waves techniques 3
Room: G3
Date: 2018-06-15
Time: 09:00 - 09:20

Evaluation of the residual wall thickness distribution of a pipeline and other facilities is essential for the safe use of such facilities. For this purpose, various approaches have been carried out by many researchers. Although there have been many inspection instruments using ultrasonic waves for this objective, there is currently no equipment that can solve these problems.
In this study, our objective is to evaluate the average residual wall thickness in the circumferential direction of a pipe using an SH surface wave propagating in the circumferential direction of the pipe. It is postulated that the intensity of the SH surface wave propagating in the circumferential direction is relevant to the average residual thickness of the circumferential direction. Next objective is to evaluate the average residual thickness distribution along the axis direction using a mechanical scanner that can move carrying the sensor system to the axis direction.
With respect to the SH surface wave propagating in the circumferential direction, the trial sensor was fabricated using the drive principle of an electromagnetic acoustic transducer (EMAT). That is, the EMAT has been made of a circulating electromagnetic induction coil around the pipe and many permanent magnets arranged on the surface of the pipe in the circumferential direction. Next, a resonance method has been utilized to obtain a stronger received signal. The electromagnetic induction coil-shape of the receiver has been devised so as not to detect the guide wave propagating in the axis direction of the pipe which was generated based on the principle of the electromagnetic ultrasonic sensor.
Finally, it was confirmed that the change in the wall thickness of about 20% can be detected as the circumferential wall thickness average by combining with the axially traveling device manufactured by trial. Although this ability is not sufficient to apply the system under actual field conditions, it is indicated that the system could be useful for the inspection of a pipeline by adding this improvement.