Magnetic Particle Testing

Magnetic Particle Inspection (MPI) is a form of Non-destructive Testing (NDT) and is used to detect surface and sub-surface discontinuities and differences, such as a break or crack, in ferromagnetic materials, such as nickel and iron. It cannot be used for non-ferromagnetic materials, such as stainless steel. MPI is considered by many industries as being affordable and faster in comparison to other NDT methods.

The MPI method of application first involves preparing the material for testing by cleaning it of oil and other contaminates. Once the material has been prepared it is magnetised, with the most common method for this generating a magnetic flow by using electromagnetic yoke. When the material is magnetised, iron powder is then applied to it. If there is a surface or sub-surface discontinuity or difference in the material then a magnetic flux will leak, the result of magnetic particles being attracted by the surface field. If this is the case, the iron powder will adhere to the link of the magnetic flux leakage, revealing discontinuities such as a crack.

As a very sensitive analysis method, MPI is used for testing cam shafts, connecting rods, threaded bars, piping points, engine blocks, washers, etc. MPI is most commonly used for both raw material testing and product inspection in the aerospace, automotive, power generation, nuclear, and petrochemical industries.