[3B3] PECT through steel covers: mitigating vibration and signal distortion via magnetic saturation
J Salas¹, Z Chen¹, G Finch² and L Wright²
¹MAIERIC Ltd, UK
²National Physical Laboratory, UK
Pulsed eddy current testing (PECT) is a leading technique for detecting corrosion under insulation (CUI) in steel pipes and structures, offering advantages such as minimal surface preparation and rapid scanning. While PECT excels at inspecting through thick non-conductive insulation layers and conductive cladding, steel cover sheeting presents challenges due to signal distortion and vibration.
Steel cover sheeting directly interferes with pulsed eddy current electromagnetic mechanisms, causing signal distortion and attenuation of both the excitation pulse and the secondary field. The cover’s own magnetic decay introduces measurement errors, especially significant for thin samples at high lift-off. Additionally, PECT’s pulsed excitation induces vibration in loose sheeting, complicating reliable testing and requiring manual intervention. In many cases, the removal of the steel cover sheeting is required before inspection.
This work reports the results of a novel probe design incorporating magnetic saturation to mitigate these issues. Similar to eddy current testing (ECT), magnetic saturation reduces measurement sensitivity to the magnetic permeability of the steel cover, minimising signal distortion and attenuation. Moreover, the constant magnetic field stabilises the steel cover sheeting, effectively reducing vibration. This innovation enables more reliable and efficient PECT inspections through steel covers, enhancing CUI detection in challenging conditions.
Steel cover sheeting directly interferes with pulsed eddy current electromagnetic mechanisms, causing signal distortion and attenuation of both the excitation pulse and the secondary field. The cover’s own magnetic decay introduces measurement errors, especially significant for thin samples at high lift-off. Additionally, PECT’s pulsed excitation induces vibration in loose sheeting, complicating reliable testing and requiring manual intervention. In many cases, the removal of the steel cover sheeting is required before inspection.
This work reports the results of a novel probe design incorporating magnetic saturation to mitigate these issues. Similar to eddy current testing (ECT), magnetic saturation reduces measurement sensitivity to the magnetic permeability of the steel cover, minimising signal distortion and attenuation. Moreover, the constant magnetic field stabilises the steel cover sheeting, effectively reducing vibration. This innovation enables more reliable and efficient PECT inspections through steel covers, enhancing CUI detection in challenging conditions.
