Magnetic Particle Inspection (MPI), or Magnetic Particle Testing (MPT), is a highly efficient, cost effective non destructive testing (NDT) method used extensively throughout many industries to enable the detection of surface and slightly sub-surface defects within ferro-magnetic materials.
The process is relatively versatile as it can be performed using hand-held equipment, which is particularly suited to on-site applications as well as employing more substantial equipment, which would typically be installed in a laboratory or test house environment.
Whilst magnetic particle inspection can detect near surface faults, its ability to do this is greatly dependent upon the magnetic field applied and the preparation that is carried out on the item under test. It is therefore generally accepted that components and/or structures need to be presented with any surface coating removed in the area(s) under inspection. Most on-site testing is performed using an AC Yoke which applies a magnetic field to the ferro-magnetic item/component. This method is primarily used for the detection of surface breaking faults only although it can have a limited capability to perform the de-magnetisation of small components and/or local inspection areas.
MPI is similar to Dye Penetrant Inspection in that there are two different viewing methods available – Colour Contrast and Fluorescent, and each method has succinct applications. As its name implies, the Fluorescent method is carried out under ‘darkened’ conditions utilizing UVa (black light) and is more sensitive to the detection of small, fine defects than its ‘Colour Contrast’ counterpart. It is generally the preferred option for test house applications.
The Colour Contrast method is carried out under good daylight (white light) conditions and is therefore more suited to site environments. Whilst not as effective as the Fluorescent method for detecting minute defects, nevertheless it is widely recognised and accepted as a highly effective inspection system that can provide demonstrable results quickly and reliably.
Caparo Testing Technologies will be pleased to advise the most appropriate MPI inspection method for your particular requirement and our skilled and highly experienced staff will be pleased to discuss things with you. Call the number listed above or email enquiries@caparotesting.com for further information.