Optimization of Excitation Coil in Pulsed Eddy Current Testing of a Pipe Based on the Incident Field

Abstract

Pulsed eddy current testing (PECT) is widely used to detect corrosion in industrial pipelines with coatings; however, the energy dissipation caused by liftoff limits the detection capability for small-sized pipes, especially the non-ferromagnetic pipes recently installed in various industrial scenarios. Since the magnetic field is not concentrated within non-ferromagnetic pipes due to their low permeability, energy dissipation is particularly large, which makes the PECT challenging. Aiming at such energy dissipation problem, this article investigates the excitation process of PECT and proposes an optimization method for excitation coils. The proposed optimization aims to increase the incident field intensity, which is then decoupled from the PECT analytical solution, thereby allowing the solution to have only electromagnetic coupling relationship between the excitation coil and the specimen. Theoretical calculations are verified by the finite-element method (FEM) simulations, followed by the experimental validation of optimized coils, which verified their advantages in enhancing the specimen-related components in signals. Furthermore, the PECT performance improvement is also discussed when the average incident field of different surfaces is enhanced. Results show that the coils designed based on the average incident field of modified footprint have good performance.