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The magnetic flux leakage (MFL) technique is based on the magnetization of the material being inspected. The magnetization is provided by a strong magnet located inside the probe. As the probe encounters a wall reduction or a sharp discontinuity, the flux distribution var- ies around that area and is detected either with a Hall-effect transducer or with an inductive pickup coil.
MFL measures the magnetization of the tube to detect irregularities such as corrosion and steam erosion. MFL is recommended for the inspection of aluminum-finned carbon steel tubes because the magnetic flux is not affected by the presence of fins.
The MFL technique is also suitable for the detection of circumferential cracks: a type of flaw that is not detected by RFT or IRIS
inspec- tions. For better results, the TFB series probes should be used with the TF-ADP-001 adaptor.