Damage Detection on Invisible Reverse Side of Planar Steel Using Disturbance Measurement of Magnetic Flux

Steel materials are used at many aspects in the oil and gas plants and easily result in corrosion defects caused by anode/cathode effects on the side of contact to the surrounding materials. We need to detect these defects to prevent the production from decreasing caused by the work of maintenance and to obviate the pollution to the environment by the leakage of hydrocarbon. However, it is in general difficult to detect backside defects using conventional methods such as eddy current testing, etc. even though they are useful for detecting surface defects. In this research, we propose a new non-destructive inspection method using magnetic field permeable to steel materials from which the disturbance of the flux occurs where the homogeneity of the materials breaks up even on the other side of the measurements. We hypothesize that the location of defects on the reverse side could be detected with the measurements of leaked magnetic field induced by the circumvention of magnetic flux on the visible surface side. We employ a numerical experiment to test our hypothesis and confirmed the possibility to estimate not only the location but also the physical dimensions of defects on the invisible reverse side of metal plate.