The MPT machine, or Magnetic Particle Testing machine, is one of the non-destructive testing (NDT) methods that allow the detection of flaws and imperfections located on or just below the surface of the magnetic materials such as iron, steel, and some alloys without damage. Its working principle is based on simple magnetic concepts.

The testing process consists of two main operations. The first takes place when the component is subjected to magnetism that can be done by either applying the electrical current through it or creating an external magnetic field. The second step is applying very fine iron particles on the surface. The application of the iron particles could be through a liquid carrier (wet method) for better coverage or could be done dry. If the object is free of defects, the magnetic field propagates steadily throughout. But, if a flaw such as a crack, an inclusion, or a lack of fusion occurs, it disturbs this field and as a result, some of the magnetic flux gets "leaked" at the defect site.

The leakage of this flux produces local magnetic poles that have a very strong attraction for the iron particles and thus, they are held firmly. This leads to the formation of a clear and visible defect indication that shows the size and shape of the flaw. For the purpose of making the detection more sensitive, the use of fluorescent particles is very common and they are examined under ultraviolet (UV-A) light in a dark environment.

Due to the attributes of high speed, easy portability, and very good detection of the extremely small surface cracks, mpt is a must-have in the aerospace, automotive, oil & gas, and heavy fabrication industries. It is applied in manufacturing as quality control, maintenance of in-service, and failure analysis playing a major role in sustaining structural integrity, safety, and reliability by averting the occurrence of potential disastrous failures.