An accurate localization method for subsea pipelines by using external magnetic fields

Accurate localization of subsea pipeline is the prerequisite of pipeline maintenance, reinforcement and tracking inspection. Via finite element simulations and experiments, this paper reveals the distribution characterizations of the total magnetic flux density (MFD) and the reduced MFD near the steel pipeline, and demonstrates a method for accurately positioning subsea pipeline by using the external magnetic field. The characteristic peak position of the total and reduced MFDs' components are all susceptible to the radial magnetization direction, except for the reduced MFD's norm whose peak always overlaps the projection of the pipeline axis on the magnetic measurement plane. The norms of the total and reduced MFDs are used to determine the pipeline orientation and axis position, respectively. For an 8 m long steel pipe with diameter of 8 in., when the measurement plane is 1.5 times the diameter away from the pipe, the positioning error is around 2 cm. (C) 2019 Elsevier Ltd. All rights reserved.