Residual magnetic flux leakage: A possible tool for studying pipeline defects

Simulated defects of different shapes and sizes were created in a section of API X70 steel line pipe and were investigated using a residual magnetic flux leakage (MFL) technique. The MFL patterns reflected the actual shape and size of the defects, although there was a slight shift in their position. The defect features were apparent even at high stresses of 220 MPa when the samples were magnetized at those particular stresses. However, unlike the active flux technique, the residual MFL needs a sensitive flux detector to detect the comparatively weaker flux signals.