Penetrant Testing (PT)

Liquid Penetrant examination is used to reveal surface breaking flaws by bleedout of a colored or fluorescent dye from the flaw.

Test objects are coated with visible or fluorescent dye solution. The dye is highly penetrating and is pulled into surface defects or cracks through capillary action. After a period of time called the "dwell," excess dye is removed from the surface and a developer is applied. The developer acts as a blotter, drawing the Penetrant out of imperfections that are open to the surface . The dye used in visible dye Penetrant is usually vibrant red providing vivid contrasts between the developer and the Penetrant and making "bleedout" easy to see. With florescent dyes, ultraviolet light is used to make the bleedout fluoresce.

The advantage that a liquid penetrant inspection offers over an unaided visual inspection is that it makes defects easier to see for the inspector

Typical discontinuities detectable by this method are cracks, seams, laps, cold shuts, laminations, and porosity.

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