Dye Penetrant Testing
Dye penetrant testing / Liquid penetrant inspection is the most reliable method of finding defects and discontinuities opened on the surface especially in all non-porous materials. This method is widely used for testing of non-magnetic materials.
In PT method, a liquid/dye penetrant is applied to the surface of the product for a certain predetermined time specified by codes, standards or specifications, after which the excess penetrant is removed from the surface. The surface is then dried and a developer is applied to it.
The penetrant which remains in the discontinuity is absorbed by the developer to indicate the presence as well as the location, size and nature of the discontinuity. Penetrants used are either visible dye penetrant or fluorescent dye penetrant. The inspection for the presence of visible dye indications is made under white light while inspection of presence of indications by fluorescent dye penetrant is made under high intensity ultraviolet (or black) light under darkened conditions.