Magnetic particle testing or Magnetic particle inspection – called MPI inspection or magnetic crack detection – MPT / MT in short is one the most widely used Nondestructive testing method for inspection of ferro magnetic materials, components and structures made of Iron, Nickel and Cobalt alloys. As majority of engineering materials are predominantly made of Steel alloys this method is considered important in testing of materials in raw material, during manufacturing and in-service inspection stages. MPI testing is one of the predominantly used NDE method considering the operating cost of equipment, consumables and certified Level I / II inspectors.
Magnetic particle testing method detects surface and subsurface discontinuities. The depth of detection varies considerably from material to material based on magnetic permeability, strength of magnetic flux generated, magnetic particle properties, sensitivity desired and orientation of discontinuity with respect to the direction of magnetic field induced. Although test method can prove sensitivity up to approximately around 14mm under ideal conditions, but in actual practice the detectability or sensitivity is much lesser.