This is due to the generated eddy currents in the conducting permeable specimens due to a moving magnet. It should be noted that the MFL inspection process is a transient process and the leakage signal is influenced by the scanning velocity. This leakage signal is usually used to predict the defect features: the defect characteristics, such as shapes, dimensions and locations, can be determined by the leakage signals. The main reason for the leakage is due to the difference of the magnetic permeability of the mediums at the interface. The principle of the MFL method is based on the following: when a magnetic field is applied to a ferromagnetic material, the discontinuity of the geometry (ferromagnetic material) causes the leakage of the magnetic field and this leakage can be captured by magnetic sensors, such as Hall probe etc. However, it is worth pointing out that sometimes the magnet and sensors are sensitive to lift off variations from the settlement and construction of the tank floor which is a consequence of the environment. MFL systems have many advantages including their speed of operation. MFL systems are suitable for the detection of material losses which are as small as a few millimetres in diameter in areas which typically exceed 100 m \(^2\). For such inspection, MFL systems are employed to detect and record locations of material losses normally due to corrosion. Here, we only focus on the magnetic flux leakage (MFL) method, as applied to the inspection of bulk liquid storage tank floors. Non-destructive testing (NDT) covers a whole range of techniques that can help prevent disasters similar to the Buncefield incident.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |