NDTnet 1998 Aug, Vol.3 No.8

Abstract

A new probe has been developed to reduce the inspection time of SG areas usually inspected by rotating probes. Its acronym is SET which stands for Sonde a Excitation Tournante (rotating excitation probe). The SET probe is made of 16 Transmit/Receive units located on a single section of its body. This configuration was chosen to overcome any disturbing effect on EC data due to speed variations of the probe. The main challenge with a reduced number of data collected per turn (16) compared to more conventional EC rotating probes (easily 200) is to obtain a good detection efficiency for small flaws and especially for small longitudinal cracks. The transversal configuration of the coils is clearly more suited for circumferential cracks. To overcome this limitation and to extend the spatial range of the conventional impedance coils, we have used additional transmit/receive modes. Three modes of operation have been selected.

Fig.

Mode 1 is similar to the conventional impedance probe mode but is more convenient for our electronic equipment and our double windings coils.
Mode 2 looks like a basic transmit/ receive mode with 2 transmitters to enlarge the sensitive area.
Mode 3 is a mixed of mode 1 and mode 2 and gives some additional information. For example, the orientation of a crack can be obtained from a comparative phase analysis: longitudinal cracks are detected with a 180° phase shift between mode 2 and mode 3.
Those three modes are simultaneously active and produce a pattern electronically switched over the circumference of the probe.

The SET has been operated at a translation speed of 200 mm/s and is excited with two frequencies simultaneously. Preliminary results demonstrate the soundness of the SET concept through a comparison with commercial rotating probes. Experimental results obtained both on longitudinal and on transversal defects will be thoroughly presented. This first prototype of SET proves the feasibility of using electronic scanning probe instead of rotating probe for the inspection of critical areas in so tubing.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

Publication Contact:
7th ECNDT, Park Alle 345, DK-2605 Broendby, Denmark, Fax: +45 46 26 70 11, Email: 101373.3414@compuserve.com