Eddy Current Sensor Arrays for Pipeline Inspection With and Without Coatings

Abstract

Coatings are used on pipelines throughout the oil and gas industry for a variety of applications including corrosion protection, temperature maintenance, and weight control. These coatings also present a barrier to inspections for damage and typically need to be removed prior to inspection with nondestructive evaluation (NDE) methods. This has led to the development of improved NDE methods for detection and characterization of damage without removing the coatings or insulation. This paper describes adaptations of JENTEK’s Meandering Winding Magnetometer (MWM®)-Array technology for improved NDE in pipelines, including rapid and reliable imaging of damage, such as external corrosion, external mechanical damage, and stress corrosion cracking (SCC). The MWM-Array technology uses magnetic field-based sensor arrays and model-based inverse methods to determine electromagnetic and geometric properties of the pipeline material, which are then related to specific damage conditions of interest. This technology has been successfully applied in the aerospace and manufacturing industries and provides substantially improved performance for imaging surface and buried damage through coatings and for curved surfaces compared to conventional NDE methods. Several representative applications are described. These include: 1) imaging of near surface material loss through moderate thickness coatings (less than 1.5-in. (38 mm)); 2) imaging of mechanical damage through thin (less than 0.25-in. (6.35 mm)) coatings; 3) imaging of SCC through very thin (less than 0.030-in. (0.76 mm)) and thin (less than 0.25-in. (6.35 mm)) coatings. For SCC, digital imaging of damage regions and automated analysis tools for assessing individual cracks has the potential to be a replacement for magnetic particle inspection (MPI). Initial work has demonstrated these capabilities in a laboratory environment with some field testing and ongoing work is transitioning this technology into field environments.