Intuitive Physical Model for Pulsed Eddy Current Inspection Techniques.

摘要

In a typical oil refinery hundreds of kilometers of insulated pipes and numerous insulated vessels are present. Because of safety and cost reasons it is not acceptable to remove the insulation from these pipes and vessels, thus seriously hampering the non-invasive inspection of the insulated objects. A screening technique for the detection of corrosion under insulation would therefore be a great asset. At Shell Research and Technology Centre in Amsterdam, such an inspection tool based on eddy currents is now under development. Because of the complexity of this inspection technique, mathematical models are needed to predict the response of the tool and for calibration purposes. Besides a computational model, there is a need for a simple physical model that gives better insight in the electromagnetic diffusion process at hand. For that purpose, an intuitive physical model is introduced in which the induced current-carrying rings in a test wall are modeled as coupled coils. This (new) model results in a better understanding of the working principles of the pulsed eddy current inspection technique, allowing fast and accurate computation of the tool response for various relevant parameters: with the introduced physical model the physical principles of the diffusion process in a test wall will be discussed, as well as the influence of various parameters on the total response. Finally, numerical results will be presented to validate the performance of the model.