Training

Magnetic particle inspection (MPI) is a Non Destructive NDT Technique that is used for the detection of surface and near-surface flaws in ferromagnetic materials.

A magnetic field is applied to the surface of the specimen, either locally or overall, using either a permanent magnet, an electromagnet, flexible cables or hand-held prods. If the material is in good condition and defect free, the majority of the magnetic field is concentrated below the material's surface. However, if a flaw is present, such that it interacts with the magnetic field, the flux is distorted locally and 'leaks' from the surface of the specimen in the region of the flaw. Fine Metallic Particles, applied in solution to the surface of the specimen, are attracted to the area of ‘flux leakage’, and a visible indication is detected. The materials commonly used for this purpose are black iron particles and red or even yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material which enables them to be viewed under a Ultraviolet Lamp in a darkened area.

Eddy Current Inspection is a Non Destructive NDT Technique that is used for the detection of surface and near-surface flaws in conductive materials.

The basis of Eddy Current Inspection: To undertake Eddy Current Inspection a circular coil carrying an AC current is held adjacent to an electrically conductive specimen. The alternating current in the coil generates a magnetic field, which interacts with the test object and induces ‘eddy currents’ within the test pieces, They get their name from “eddies” that are formed when a liquid or gas flows in a circular path around obstacles when conditions are right. These eddy currents in return send returning eddy currents back to the receiving probe. Fluctuation in this returning ‘signal’ are monitored and measured, Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current flow and a corresponding change in the phase and amplitude of the measured current. This is the basis of standard (flat coil) eddy current inspection, the most widely used eddy current technique.