The surface to be inspected is cleaned thoroughly to remove all traces of dirt and grease
A brightly coloured or fluorescent liquid is then applied liberally to the component surface and allowed to penetrate any surface-breaking cracks or cavities. Application of the penetrating liquid can be done by brushing, spraying or dipping.
The time the liquid is allowed to soak into the material’s surface is normally about 20 minutes
After soaking, the excess liquid penetrant is wiped from the surface and a developer applied. The developer is usually a dry white powder, which draws penetrant out of any cracks by reverse capillary action to produce indications on the surface. These (coloured) indications are broader than the actual flaw and are therefore more easily visible.
Dye Penetrant and Fluorescent Penetrant Inspection techniques differ in that Fluorescent Penetrant Inspection utilizes a fluorescent dye and a black light to perform the inspection.
