Liquid Penetrant Examination is an excellent method used for locating discontinuities that are open to the surface. This examination can be used on almost any material. The technique is very simple and with trained technicians, reliable and consistent results can be obtained. The examination is carried out by first pre-cleaning the part, spraying a visible or fluorescent dye over the area to be examined and allowing it to stand (dwell) on the area being examined. After the dye has set on the part for a satisfactory amount of time, the capillary action takes place.
This pulls the surface dye into any discontinuities open to the surface by capillary action. All of the surface dye is then removed. Once the part is dry, the developer is sprayed on the part. This developer will absorb and bring to the surface dye which remains in the discontinuities and provide a white background for viewing. Any indications are then evaluated to the proper code or specification.
Liquid Penetrant Testing (PT)