This non-destructive testing technique, also known as liquid penetrant inspection (LPI), is a cost-effective method used to locate surface breaking flaws such as cracks, porosity, laps, seams and other surface discontinuities. Dye penetrant inspection can be applied to both ferrous and non-ferrous materials and all non-porous materials (metals, plastics or ceramics).
Penetrant testing is commonly used to detect defects in castings, forgings and welds and is a key quality control step to assuring structural integrity of metal parts. Commonly, DPI is used to detect cracks, surface porosity, lack of penetration in welds and defects resulting from in-service conditions (e.g. fatigue cracks of components or welds) in castings, forgings, and welding surface defects. Some of the most demanding applications include nuclear plants, aerospace, turbine casings and blades, mining and refineries.
The penetrant may be applied to all non-ferrous materials and ferrous materials, but for inspection of ferrous components magnetic-particle inspection may be preferred for its subsurface detection capability. Dye penetrant testing offers the advantage as an all purpose, low-cost technique since the only requirement is a set of chemical reagents and in some cases a UV flashlight.
Liquid penetrant testing is useful for testing on-site as it is portable, and when applying certain techniques such as visible color contrast there is no need for additional resources such as electricity or water. This makes it a highly convenient for inspecting surface discontinuities.
Novaflour Yellow 131SC - yellow-green UV fluorescent dye
Novaslve Red Red 564 - solvent based visible red dye for use with a white developer