Magnetic Particle Powder
A common particle used to detect cracks is iron oxide, for both dry and wet systems.
- Wet system particle range in size from less than 0.5 to 10 micrometres for use with water or oil carriers. Particles used in wet systems have pigments applied that fluoresce at 365 nm (ultraviolet A) requiring 1000 µW/cm2 (10 W/m2) at the surface of the part for proper inspection. If the particles do not have the correct light applied in a darkroom the particles can not be detected/seen. It is industry practice to use UV goggles/glasses to filter the UV light and amplify the visible light spectrum (normally green and yellow) created by the fluorescing particles. Green and yellow fluorescence was chosen because the human eye reacts best to these colors.
- Dry particle powders range in size from 5 to 170 micrometres, designed to be seen in white light conditions. The particles are not designed to be used in wet environments. Dry powders are normally applied using hand operated air powder applicators.
- Aerosol applied particles are similar to wet systems, sold in premixed aerosol cans similar to hair spray.
Read more about this topic: Magnetic Particle Inspection
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