Pipelines transport valuable energy resources such as oil and natural gas, keeping substantial utilities in service. A continuous supply is then necessary, while ensuring the integrity of the piping system in terms of safety of the process. Steel pipes are prone by time to defects like corrosion that attacks the wall and may have brutal impacts on both economic and environmental aspects. Hence, pipeline inspection is of great importance to prevent catastrophic failures. The diagnosis of pipelines can be performed using nondestructive testing techniques that evaluate the properties of a material without causing damage. Magnetic flux leakage (MFL) is one method that uses powerful magnetic field which can be generated by portable permanent magnets to locally magnetize and saturate a portion of the pipe under examination. Large wall thinning defects are serious problems threatening thousands of kilometers of aging pipelines around the world. This work follow a numeric approach to measure the wall thickness of a pipe specimen, resulting in a calibrated curve serving as a reference to estimate with a good precision the pipe wall thickness in the real applications. The proposed technique is generic and can be applied systematically for a pipe with specific size and material property. It represents an enhancement over the current practices by avoid doing multiple physical experiments. The method is implemented and simulated using the finite element method package ANSYS. The MFL sensing system is designed for scanning external pipes, crawling smoothly on top of the outer surface by a robotic platform and carrying magnets that generate a strong axial magnetic field. At areas where there is metal loss, the magnetic flux flowing in the pipe leaks from the steel. The leaking flux is then captured by a Hall effect sensor and the wall thickness is estimated by referring to the calibrated curve.
