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Publication: e-Journal of Nondestructive Testing (NDT) ISSN 1435-4934 (NDT.net Journal)
Technical guide “Alternatives to penetrant testing and magnetic particle testing”COFREND21, Paris, France
The technical guide “Alternatives to penetrant and magnetic testing” will be published at the beginning of the second semester 2018. The COFREND working group which produced it was created at the end of 2013. The topic, a large one, brought together participants from various sectors. The first question we had to answer was: alternatives to MT and PT, for what?
The members of the WG, from left to right: Hervé Trétout (Dassault Aviation), Robert Lévy, Matthieu Taglione (Framatome), Patrick Bouvet (CTIF). « So goes NDE: methods “live” together, their fields of application overlap and very often several solutions exist for one problem. »
The first interchanges ended with the conclusion that, in the current conditions, MT and PT are reference methods, universally used. They do have challenges to face but strengthened with more than a century of feedback from industry and, regularly taking advantage from improvements, they are still relevant in the current and future industrial landscape.
The question is then to know the place of so called “alternative” techniques. Indeed, MT and PT being reference surface methods, the other methods are often proposed as an alternative, meaning that the user expects to find there his preferred characteristics of the reference method. But the alternative implies making a choice, creating a contrast between a historical method and the “replacement” method. Our roadmap was based on the idea that it must be applied to an application and not to the general case. It may be very pertinent to use penetrant testing for one case and eddy current testing for another or to use magnetic particle testing for an application and thermographic testing for another. So goes NDE: methods “live” together, their fields of application overlap and very often several solutions exist for one problem.
That is why this guide aims to enlighten the technical choice that must be made when defining a test, with a presentation of the state-ofthe art of penetrant testing magnetic particle testing and the other testing methods that can replace them. This collaborative work gathers the knowledge, ideas, interchanges of the participants in the working group. It is not intended to be exhaustive; its purpose is to propose elements making it possible to define the methods which can offer today acceptable alternatives to reference methods such as MT and PT. These alternatives can only be linked to an application, an industrial need: indeed, to assess the pertinence of choosing one method instead of another, a large number of elements must be considered: the nature of the defects sought, the cost of the inspection, Health, Safety and Environmental factors, the acceptance level of the methods proposed by the customer.
This guide includes a first part, in which the two reference methods MT and PT are described, with their interest, their limitations but also their future changes. Indeed, without doubt, these methods will continue to offer to the industrialists innovations that will have limited influence on the operator and on the environment while showing reduced dependence on human factor.
The second part describes the methods presented as acceptable alternatives. They were “dissected” by the experts and their advantages and limitations with respect to MT and PT are presented. If many methods may often solve the same problem, some are better adapted than others to each specific problem: the working group therefore chose to put forward thermography, eddy currents, ACFM (Alternating Current Field Measurement) and surface ultrasounds. Indeed, we find there all the elements which make it possible in most cases to solve a problem that could have been solved by MT or PT; these alternative methods are better suited for reasons of sensitivity, human factor, cost, security, or environmental factors. Elements enabling a first level choice to be made between these alternatives are presented in conclusion. A third part briefly describes the various approaches that an industrialist may use once he has decided to replace MT or PT in an application by another NDE. This part is intended to calculate rapidly the effort to be deployed for this transition, using the available elements (mock-ups, knowledge of the application, knowledge of the discontinuity sought…) and the industrial constraints (delays, budget).
Finally, a fourth part synthetises the results of our interchanges as it presents examples of successful alternatives, for different applications, with different choices of the technique or the equivalence approach. It ends the guide and enables the reader to consider an actual implementation of the conclusions of our work and to address the effect of the introduction of alternative methods in industrial applications.
The whole guide is illustrated with application examples in which are recalled the technical issue, the detection sensitivity obtained, the TRL (Technology Readiness Level) and the inspection speed.
Matthieu TAGLIONE (Framatome), convenor of COFREND’s WG on Alternatives to PT & MT