The integrity of these tubes being important for the safety of the plant, it is necessary to use really suitable tools to be sure to detect any cracks. This probe is one of this tools.
The sensor is placed on a rotating mechanism, and it is held up against the inner wall of the tube to minimize the geometric effects such as lift-off. Sensitivity remains constant during the inspection and it is suited to detect small defects in deformed areas such as the end of roll transition.
Detection performances are rather good since a 10% outer wall circumferential EDM notch (4mm long, 0.1 wide) is detected with a signal to noise ratio greater than three (3) on 22.22mm (7/8") tubing, without signal processing.
The paper discusses the choice of frequencies to reach the best performance and the operating principles to assess circumferential crack length and depth. Examples of signal processing which improve detection performances are also given.
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:
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