Abstract: In order to solve the problem in defect distribution mapping for the current tank
floor testing system, a method is developed based on the magnetic flux leakage (MFL) technique for
generating defect distribution maps automatically for floor inspection. Firstly, the initial scanning
position of the first channel sensor in MFL detector is chosen as reference point, and the single
scanning region can be defined by sensor channel numbers and sampling interval; then the vertex
coordinates of rectangle block diagonal are calculated by the sensor channels and sampling points of
defect signals involved, a block can be drawn to characterize the defect and the single defect
distribution map is generated. And after the reference point coordinates are normalized under an
unified coordinate system, blocks characterized the same defect, which are drawn in two adjacent
scanning, are merged into a new one by combing operation. Finally, the map to show defects
distributed on the whole tank floor are joined by single defect distribution maps. The experimental
results indicate that the proposed methods can generate the defect distribution map of tank floor
automatically, provide defect reports for tank floor inspection intuitively, and improve the efficiency,
practicality and reliability of the tank floor inspection system.

Key words: tank floor, defect distribution map, coordinates normalized, magnetic flux
leakage