What type of surface defect is Liquid Penetrant Testing designed to detect?

Liquid Penetrant Testing (PT) is specifically designed to detect surface-breaking defects in non-porous materials. This method works by applying a liquid penetrant to the surface of a test component, allowing it to seep into any cracks or flaws that are open to the surface. After a specific dwell time, the excess penetrant is removed, and a developer is applied, which draws out the penetrant from the defects, making them visible for inspection under ultraviolet light or white light.

Surface-breaking defects include issues such as cracks, laps, seams, and porosity that extend to the surface of the material. These defects can compromise the integrity of a component, making their detection crucial for quality control and safety.

In contrast, internal voids, thickness variations, and color variations are not detectable by this method. Internal defects would require other testing methods such as radiographic or ultrasonic testing, while thickness variations typically involve measuring instruments rather than visual inspection techniques. Color variations, though they may affect the appearance of a surface, do not imply the presence of a flaw that compromises structural integrity. Therefore, the focus of Liquid Penetrant Testing on surface-breaking defects makes it a vital tool in the inspection process.