MFL - Magnetic Flux Leakage tube testing technique utilizes strong permanent magnets to magnetize conductive tubes, e.g. Carbon steel tubes. When discontinuities such as corrosion and material loss are located between the magnets, the magnetic field in the tube material is disturbed and a small amount of flux leaks which is detected by the sensors. The variation of flux leakage induces current in the detector coils that is converted into output signals.
MFL is most ideal for rapid inspection of Aluminum finned tubes and all ferromagnetic heat exchanger tubes, ideal for detecting corrosion, erosion, pitting and circumferential cracks, is optimized for internal and external discontinuities.