With magnetic particle inspection, defects can be detected at the surface. Unlike with dye penetrant testing, flaws can be detected even when the direct surface is intact or sealed, e.g. with grease, etc. The typical flaws to be expected are hairline cracks. Magnetic particle inspection (MPI for short) is used with metals that can be magnetized.
Through magnetization, a so-called magnetic leakage flux occurs around the cracks in the surface of the material, which allows for the test medium to stick and form a contrast to the metal. During the process of magnetic particle inspection, fluorescently coloured iron powder or black iron powder on a white background (known as the black-and-white test) is dispersed, after which it accumulates in the area of the material defect (crack).
The magnetic particle inspection is a wet method, with either oil or water being the powder carrier.
The ability to quickly make any flaws visible is another advantage. The area in question can be subjected to grinding and then be re-examined immediately.
We check our fluorescing testing system against the reference standard Type 1. Included in the equipment are a UVA-Lux Check as well as a field intensity meter.
Die MPI test is a popular second test procedure, e.g. with connectors to gas pipes, but it is also on shafts, rails, wheel rims, in engine manufacturing and flying constructions that are more heavily strained due to movement. Other areas of application include turbine housing, turbine blades, containers, mass-produced parts, and in any location where cracks may appear and the material can be magnetized.
In our laboratory, we can conduct MPI tests with a hand yoke, a high-voltage generator, prods, as well as a test bench.
The test bench is ideal for all components from a minimum size of 3-4 cm up to 105 cm. The component is fixed and a magnetic field is created. After extensive spraying, UV-lamps that are suspended above the components now make any flaws visible.
With this process, large quantities can be inspected very quickly!
All of our lab vehicles, as well as our workshop van, contain transportable MPI equipment, comprised of a hand yoke, UV lamp, field intensity meter, lux meter, a test body, and the suitable test equipment.
For components that are a bit more challenging to test, we have a high-voltage generator and consumable electrodes at our disposable. They operate similar to the hand yoke, but with the addition that they are significantly better suited for testing corners, for example.