MPI – how does it work?

During the process of Magnetic Particle Inspection, the specimen is magnetised either locally or overall depending on the size of the specimen and a magnetic field is induced in the component. The testing process analyses the magnetic flux around the tested component. If the tested material is sound, then the magnetic flux will predominantly remain inside the material. However, if there is a surface-breaking flaw during the Magnetic Particle Inspection then the magnetic field will be distorted, causing local magnetic flux leakage around the flaw on the surface. This leakage can be detected by dusting the surface of the specimen with fine magnetic particles such as ferrous iron filings. The particles will then be attracted to the area of the flux leakage, creating a visible indication of the defect. The indication is then noted and evaluated by the operator to determine what might have caused the flaw and suggest action to take. There are two methods of Magnetic Particle Inspection. The first is white colour contrast, which is ideal for daylight and site work. the other makes use of Ultra Violet light. Here at Capital NDT, we provide both an ultraviolet method as well as the black and white contrast method.

For more information on MPI – how does it work? talk to Capital NDT Limited