Magnetic Particle Inspection (MPI) is a very popular Non-Destructive Testing process for detecting surface or sub-surface (up to 3mm deep) discontinuities in ferromagnetic materials.
A magnetic field is passed through the test component to search for the presence of a surface or subsurface discontinuity. If one is present in the material it allows the magnetic flux to leak.
As air cannot support as much of a magnetic field per unit volume as metal, magnetic particles are then applied to the test piece. If an area of flux leakage is present, the particles will be attracted to this area. The particles will build up at the area of leakage and form what is known as an indication. The indication can then be evaluated to determine what it is, what may have caused it, and what action should be taken (if any).
MPI can be completed by one person with lightweight equipment so is a relatively quick and cost effective method of inspection which can be performed in most environments.
MPI is used to inspect a variety of product forms including castings, forgings, and weldments.
Many different industries use MPI for determining a components fitness-for-use. Some examples of industries that use MPI are the structural steel, automotive, petrochemical, power generation, and aerospace industries. Underwater inspection is another area where MPI may be used to test items such as offshore structures and underwater pipelines.
MPI requires the use of aerosols in most cases however dry powders can be used in their place in some instances.
IACS NDT use PCN level 2 qualified personnel to undertake magnetic particle inspection.
All inspections are carried out with client-approved procedures which follow the most recent international British Standards and/or client specifications and are submitted to the client with the relevant risk assessment and COSHH data sheets.