Magnetic particle inspection (MT)
How to do a magnetoscopic inspection
The instrumentation for nondestructive testing using the magnetoscopic method
Fixed-bed plant - General Industry - Accredited ACCREDIA 17025 in accordance with UNI EN ISO 9934-1 specification
Portable wheeled generator - General Industry
In the case of components having dimensions too large for the fixed bench, or in the case where it is necessary to have a system that generates high values of current and magnetic field at the customer’s site, TEC Eurolab has a wheeled generator, which can be used either by means of test leads or by means of coil windings. All techniques can be combined, depending on the type of component being inspected, with controls using colored or fluorescent magnetic particles.
Portable Electromagnets - General Industry
Specific for the inspection of welded joints or specific areas of large components or complex geometries, portable electromagnet inspection allows the requirements of UNI EN ISO 9934-1 to be met either on site or at the customer’s site, and can be combined with fluorescent magnetic particles (in the case of machined components) or colored magnetic particles (in the case of raw components).
What does the magnetoscopic method (MT) consist of?
Magnetic particle inspection (identified by the acronym MT or MPI) has the function of detecting surface and sub-surface discontinuities in ferromagnetic components.
The working principle of the method is based on theapplication of a magnetic field to the sample (or a current in turn generating an induced field). The field lines, normally lying within the sample, near open discontinuities on the surface or just below it, escape from the sample, polarizing the walls of the defect.
The application of magnetic particles (colored or fluorescent depending on the application) results in their localization near the polarization, allowingthe discontinuity to be detected by the operator.
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When and where is magnetoscopic method (MT) inspection applied?
Magnetic particle control needs to be applied to ferromagnetic components. For this reason, it finds its main application in transmission components, shafts, gears and welded joints in weakly alloyed steels.
In addition, the physical principle of the method favors thedetection of linear indications over nonlinear indications, which is why it is applied on components resulting from the molding/forging process, on mechanically machined components or components on which heat treatment has been performed, and on welded joints to search for linear discontinuities.
As with liquid penetrants, depending on the type of component and its surface condition there are different techniques that can be applied. In particular, it is possible to perform:
- Controls with color-contrasting magnetic particles, specifically for components with high surface roughness, rough or semi-finished components, or welded joints on site
- Controls with fluorescent magnetic particles, specific to machined or heat-treated components
The application of fluorescent particles in a darkened environment allows in the case of the presence of the indication, a higher contrast than the background, and a consequent better probability of detecting the discontinuity itself.
Depending on the type of process carried out on the component, the discontinuity detected may also be very small.