NDTnet 1998 Aug, Vol.3 No.8

Abstract

Object
A new examination technique (STF) using an eddy current motorized rotating probe has been developed by Intercontrole in order to optimally characterize the degradation of the drilled 7/8" tube support plates in steam generators. This anomaly which generally occurs on the upper supports is known as support plate fragmentation.

Technique
The STF technique is based on the use of a low frequency << + point >> probe and a specific analysis software developed by Intercontrole. The frequencies used are 10 kHz and 100 kHz, with most of the information obtained from the x component of the 10 kHz signal in both differential and absolute mode.

The detection of the support plate is performed using the absolute mode as shown in figure 1. The indications reported as support plate fragmentation are detected and characterized, both from the phase angle measurement at 10 kHz differential and the x component display of the differential filtered signals as described in figure 2.

Application
Introduced on site in April 1997, this technique enables to identify precisely those tubes which are no longer adequately supported and which therefore require a maintenance intervention.

Illustrations


figure 1 shows the x component of the 10kHz absolute of the uppermost tube support plate.

figure 2 shows a drilled 7/8" tube support plate with 4 indications reported as breaches.

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