Augmenting ILI tools to assess external coatings

THE COATINGS USED TO protect oil and natural gas pipelines can degrade over time, enabling corrosion and stress-corrosion cracks to initiate and grow. Pipeline companies use in-line inspection (ILI) tools to detect these anomalies, and repair methods to mitigate the result of a failed coating. This project developed inspection sensors that could prevent these anomalies from occurring in the first place by monitoring the integrity of the external protective coating of the pipeline. This coating assessment, which could be performed during a typical ILI, could help pipeline owners assess the general health of the coating protecting their pipeline system. A goal of the design was to keep these sensors simple so that an implementation would not add substantial cost or complexity to a typical magnetic-flux leakage (MFL) or caliper survey.