What are the primary types of penetrants used in PT?

In Liquid Penetrant Testing (PT), the primary types of penetrants are categorized into fluorescent and visible dye penetrants. This classification is based on the means of detection and the characteristics of the penetrant materials used during the inspection process.

Fluorescent penetrants contain additives that fluoresce (glow) under ultraviolet (UV) light, making them especially sensitive and effective for detecting very fine discontinuities in materials. This enhances the inspector's ability to locate defects that might be missed with natural lighting. On the other hand, visible dye penetrants are colored liquids that can be readily seen with normal light, making them suitable for various applications where UV light is either unavailable or impractical.

Understanding these types is crucial for selecting the proper penetrant based on the specific requirements of the inspection task, such as the material being tested, the type of defects sought, and the inspection environment. This distinction directly influences the effectiveness and reliability of the testing process.