Magnetic flux leakage (MFL) testing is widely used to inspect and characterize defects in storage tank floors, pipelines and other structures. In this paper, magnetic flux leakage testing technology is applied to the horizontal product oil underground tank wall inspection. The artificial defects were prefabricated on the tank wall such as corrosion pits, grooving and other artificial defects to simulate the corrosion, cracks and other actual defects in actual working conditions. The experimental research of the mutual influence between magnetic flux leakage and defects’ parameters were carried out, such as the depth and width of cracks, and depth and diameter of corrosion pits. Then the relationship between the defect’s parameter and magnetic field amplitude was obtained. The experimental results showed that, whether corrosion or crack, the depth is a very important factor affecting the leakage magnetic field amplitude. Especially for crack, width, length and the inclination angle between crack and magnetic field had great influence on the detection of the cracks, and too small angle to lead to misjudgment and undetected of crack. Therefore, single direction inspection may lead to undetected in engineering practice.
<i>Letter to the Editor</i> Low-frequency electric field fluctuations and field-aligned electron beams around the edge of an auroral acceleration region
