NDTnet 1998 Aug, Vol.3 No.8

Full-Text -Abstract

The Remote Field Eddy Current (RFEC) Technique is a new method for the inspection of ferromagnetic and non-ferromagentic heat exchanger and boiler tubes. While there is extensive experience about conventional eddy current probes for heat exchanger tubes and other applications, the development of RFEC probes requires still a high experimental efford.

Fig. Basic Sketch of RFEC Probe

There are two main difficulties for the probe design. One problem is the very complicated magneticfield distribution, which must be considered. While in conventional eddy current technique only conductive parts in the vicinity of the coils have an influence on the probe signal, in RFEC a much larger area must be observed. Mainly tube support plates in heat exchangers cause a very large field disturbation. The second problem is the high dependency from the magnetic permeability of the tube material which is characteristic to the method. An evaluation of the tube properties is therefore essential for probes with a high detectability.

The conventional probe development requires the design and manufacturing of a first RFEC probe for the required application. The detection capability has to be found out with machined reference defects. After analyzing this probe a new improved probe will be designed and manufactured with the experience made with the first one. This procedure will be repeated until the optimum probe is found.

A minimization of this development work can be achieved by a combined addpoach of precalculation and experimental evaluation. The tools for this approach are now additionally to high resolution RFEC equipment the computer simulation and animation. The complicated interaction between an arbitrary probe and a modelled defect can be visualized, so that probe response are known before production of the probe. By this approach the cost and time expensive manufacturing work can be reduced to a minimum.

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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