Magnetic Particle Inspection (MPI) is an extension of visual inspection. This critical technique for non-destructive testing (NDT) is used for the detection of surface and near-surface flaws (discontinuities) in ferromagnetic materials.
A magnetic field is applied to the test piece, either locally or overall, using a permanent magnet, electromagnet, flexible cables or hand-held prods. If the material is sound, most of the magnetic flux is concentrated below the material’s surface. However, if a flaw is present, such that it interacts with the magnetic field (disturbs it), the flux is distorted locally and “leaks” from the surface of the specimen in the region of the flaw.
We can detect this leak by applying fine magnetic particles to the surface of the specimen. These particles are attracted to the area of the “flux leakage” creating a visible indication that there is a flaw. The materials commonly used for this purpose are black iron particles and red or yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material enabling them to be easily viewed under an ultraviolet lamp (black light) in darkened conditions.
Our portable power packs, yokes and equipment provide the foundation for SEQ Inspections to provide fast and reliable magnetic particle examinations with a multitude of approved techniques. These include visible and fluorescent in both wet & dry formats and can be performed just as easily in a fabrication shop or out in the field.