PROGRESS IN THE EDDY CURRENT INSPECTION OF TUBES: THE NEW BREED OF FAST, COMPUTER BASED SYSTEMS FOR THE IN-SERVICE INSPECTION OF TUBES

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WCNDT '96 - New Delhi
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Electrical and Electromagnetic Testing Techniques

PROGRESS IN THE EDDY CURRENT INSPECTION OF TUBES: THE NEW BREED OF FAST, COMPUTER BASED SYSTEMS FOR THE IN-SERVICE INSPECTION OF TUBES

D. S. Dulay, C. Galsworthy, D. J. Lovejoy
NDT Consultants Ltd., United Kingdom

Keywords: Eddy current, Tube inspection, Data analysis, Computer, Rapid

ABSTRACT

Eddy current inspection of tubes, both ferrous and non-ferrous is well established in the in-service inspection of heat exchangers and other plant where the tubes are used extensively. The major problems with such inspection are well known; these being the time taken to obtain the information required and to a much greater extent the time needed to analyse the data once it has been obtained. Modern computers can help us to acquire the information from the tubes at around twice the rate which conventional systems perform however the great advantage of such computer driven eddy current systems is the speed at which the data can be analysed and displayed in an accessible way. It is difficult to compare the almost instantaneous availability of the status of tubes from the new equipment with the time taken to analyse hard copy charts by visual comparison. This enormous advantage is achieved by the application of on line signal analysis with intelligent amplitude and phase analysis coupled to an integrated signal data manager and documentation system. In this paper depth and sizing methods are discussed with reference to the application of multi-frequency, multi-mode detection and evaluation. The use of flux leakage, magnetic biased eddy current techniques, and remote field methods for the inspection of ferro-magnetic tubes is also examined. Specifically methods for estimating tube thinning in such materials is discussed. The importance of and recent advances in the documentation capabilities offered by this approach are discussed with respect to each of the techniques and applications. In conclusion the paper presents a practical approach to achieving the advantages offered by the application of modern computer technology to the problems of tube inspection.

Electrical and Electromagnetic Testing Techniques

Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 3, pages 1705 - 1708
Publisher: Ashgate Publishing Company