Combining eddy current and magnetic flux leakage for tank floor inspection

Magnetic flux leakage (MFL) test technology has been applied to the inspection of aboveground storage tank (AST) bottoms since the late 1980s, when it was demonstrated that corrosion in flat carbon steel tank floor plates up to 10 mm (0.4 in.) thick could be detected using MFL techniques. This article will discuss a method that combines eddy current and MFL methods into one test probe design. This design not only detects discontinuities on the top and bottom sides of the tank bottom, but also discriminates between them.