Electromagnetic Inspection of Outer Side Defect on Steel Tube With Steel Support Using 3-D Nonlinear FEM Considering Non-Uniform Permeability and Conductivity

Steel tubes are used in the heat exchanger in the petrochemical plant. Since these steel tubes are grouped in a bundle by the support steel plate (the baffle), it is necessary to inspect the existence of defects from the inside of each tube. In these steel tubes, the corrosion or the defects are generated by the friction with baffle at the outer side of steel tube. In this paper, problems in applying the ac flux leakage testing method using an inner coil of low exciting frequency (about 60 Hz) for the inspection of the outer side defect on steel tube with baffle are examined using 3-D nonlinear finite element method (FEM). Moreover, the detecting property of the magnetic noise is investigated by 3-D FEM considering the non-uniformity of the permeability and conductivity in the steel tube and the baffle.