Advanced comparative studies between MTM-G technology and inline pipeline inspection technology

This paper discusses the comparative system and method for inspecting a carbon steel pipeline utilizing the magnetic gradient tomography method (MTM-G) and intelligent pig (IP). The data and results from both technologies complementarily identify stress-related defects, their dimensional characterization and precise orientation location effectively. The comparative studies analyze the data and results given by both systems post-inspection and are valuable in the further optimization of inspection and maintenance processes. While MTM-G measures the mechanical stress directly through magnetic field gradient of the pipeline under in situ conditions, IP, on the other hand provides the geometry and orientation location of the anomalies. In order to compare and complement the outputs, we first established a baseline from the known defects with verified dimensions on the intended pipeline for inspection. Post-inspection, the reported results from both technologies are assessed and compared accordingly by the defect matching process. Subsequently, we use a standard statistical analysis method to analyse the probability of identification (POI) and their dimensions for the comparative studies. The MTM-G technology notably determines the comparative degree of danger of anomalies by a direct quantitative assessment of the mechanical stresses reflected from the distribution of magnetic field gradient along the pipeline. Therefore, with the additional data on the geometrical parameters of the defects, subsequent calculation or correlation can be established to assess the impact of anomalies on the overall pipelines' safe operation and their constituted imminent risks. Based on these comparative studies, the probability of identification (POI) of MTM-G inspection can be confirmed, complemented and enhanced from the sizing information of the defects and their orientation location on the pipeline provided by the IP inspection technology. On the other hand, the defects' severity in terms of remaining wall thickness can be enhanced and complemented with MTM-G findings that evaluate defect stress directly from the measured magnetic field gradient of the pipeline. As a result, the aforementioned integrative and comparative studies may provide comprehensive findings that become the basis for pipeline integrity and maintenance programme enhancements. The comparative analytical studies will be a reference for pipeline asset owners to extensively explore their pipeline’s behaviour, examining its actual state and evaluating risk with increased confidence, thus improving Pipeline Integrity Management.