Magnetic Particle Inspection (MPI or MT) is a NDT method for checking the surface integrity of ferromagnetic materials. The material is magnetised using a handheld yoke or a horizontal MPI bench setup.
This method is used to test welds, castings, and forgings for defects. Identity of a leak, ferrous particles are applied to an object, these are attracted to an area of flux leakage and form what is known as an indication. Indications are evaluated to determine its nature and cause.
For high sensitivity, a fluorescent liquid and backlight can be used. This requires a dark testing environment.
- The method can be adapted for site or workshop use.
- It shows surface and near surface defects.
- It is quick and relatively uncomplicated.
- It gives immediate indications of defects.
- Large or small objects can be examined.
- Cannot be used if thick paint coating is present.
- Restricted to ferromagnetic materials.