Liquid Penetrant Testing (PT):
Liquid Penetrant Testing is a test method which reveals discontinuities in materials which are open to the surface. This method is based on the phenomenon of capillarity or capillary action.
The method involves applying penetrant to a precleaned surface. The penetrant is allowed to enter into possible discontinuities through capillarity, dwelling for an appropriate period of time. After this time has elapsed, the excess penetrant on the surface is removed and a developer is applied. The developer allows the penetrant in possible discontinuities to blot to the surface, signalling a bleed out. This condition is observed, interpreted and evaluated based on the part history and criteria applied. As with other NDE methods, suitably qualified individuals are allowed to conduct these tests in accordance with written procedures.
Test materials for this method are quite common and portable including being readily available for immediate inspection.