Penetrant testing (PT) also known as dye penetrant inspection (DPI), or liquid penetrate inspection (LPI) is a cost effective testing method. It is used to detect surface-breaking defects in non-porous materials.
Penetrant testing relies on the physics of “capillary action” to enhance surface and slightly sub surface defects in parent and weld metal.
Defects such as cracks and porosity are easily detected. They are detected by providing a “bleed though” colour contrast between the red dye penetrant and the developer white background.
The liquid penetrant inspection process is relatively quick and simple. Equipment generally is simpler and less expensive than most other NDT methods. When used on ferromagnetic steels, in some instances, the sensitivity of liquid penetrant test is better than that of magnetic particle testing.
The method is used to inspect a variety of product forms. These include but are not limited to castings, forgings, and weldments. Weldtest New Zealand also uses magnetic particle inspection for determining a component’s fitness-for-use.