Modelling of pulsed eddy current testing of wall thinning of carbon steel pipes through insulation and cladding

Abstract

Conventional eddy current techniques have been used to a great extent for detection of surface breaking defects in conductive materials. Pulsed Eddy Current (PEC) techniques excite the probe’s driving coil with a repetitive broadband pulse, usually a square wave, instead of sinusoidal wave. The resulting transient current through the coil induces transient eddy currents in the test piece, these pulses consist of a broad frequency spectrum, and the reflected signal contains important depth information. Surface pancake type pulsed eddy current probes have been used for wall thinning and corrosion detection but these methods can be slow. In order to increase the scanned area, an encircling coil has been proposed, with a view to inspect a complete circumference with a single pulse. The work presented in this paper employs COMSOL Multiphysics finite element (FE) modelling software, to further investigate the behaviour of an encircling probe design as a part of the development work. This work involves modelling of an encircling coil around a steel pipe with insulation and cladding of different materials. Pulsed eddy current testing of wall‐thinning through cladding and insulation was studied for various wall thinning situations. The simulation results show the capability of this system in pipe wall thinning detection.