Penetrant testing (PT)

Penetrant method of non-destructive testing is dedicated to detecting surface defects invisible to the naked eye. It is based on use of capillary properties of liquids (namely, on capillary penetration of special indicator liquids inside defects).

This method reveals defects by forming an indication patterns on the surface of tested items. These patterns have high optical (luminance and color) contrast and width exceeding width of the defect opening.

When performing testing a special wetting liquid (penetrating liquid, penetrant) is applied on the surface of the tested item. By impact of capillary forces this liquid fills cavities of surface defects and then it is removed from the tested area. Defects are detected already by applying a developer to the surface of the tested area. The developer absorbs penetrant remaining in cavities of defects. As a result of this process, there is either a red indication pattern appears on the developer's white background (dye penetrant testing) or a luminescent indication pattern appears in ultraviolet rays (luminescent penetrant testing).