Pipeline internal corrosion sensor based on fiber optics and permanent magnets

A corrosion sensor utilizing fiber optics and the magnetic attraction force is proposed. The sensor aims to detect the internal corrosion of pipelines that are made of ferromagnetic materials. Its components include a beam made of a non-magnetic material, a strong permanent magnet, and a Fiber Bragg Grating (FBG) sensor that is very sensitive to strain changes. The sensor is based on the assumption that the magnetic attraction force generated between a magnet and a ferromagnetic material decreases if the thickness of the ferromagnetic material is decreased. To generate this force between the sensor and the pipe, the beam is positioned in a way that the magnet is only few millimeters away from the pipe. The internal corrosion causes a reduction in the thickness of the interior pipe wall, which according to the assumption should reduce the attraction force. As a result, the strain measured by the optical fiber will be affected as it is directly related to the variations in force. We present an initial numerical investigation of the feasibility of the proposed working principle utilizing a Finite Element Analysis (FEA) simulation tool. Simulation results show that the attraction force first increases then saturates with the increase in wall thickness. The change in force becomes significant once the thickness reduces to a threshold value. We also investigate the effect of changing the magnet size, magnetic permeability of pipe material, separation distance between pipe and magnet, and the magnetic flux density of the magnet.