Liquid Penetrant Testing (PT) is one of the most common methods of surface crack detection used in not destructive testing (NDT). There are two popular methods of testing, Color Contrast and Fluorescent Dye. Both of these methods use the same basic procedures.
1. The application of a penetrant to the surface of the weld to be tested, followed by a soaking stage to allow enough penetration of the liquid penetrant into any surface breaking discontinuities.
2. Requires the careful removal of any excess penetrant, usually by means of a special weld crack detection cleaner.
3. Applying a developer to extract penetrant left behind within any discontinuity.
These three steps are then followed by the evaluation and interpretation of the test results. This involves the detection of penetrant bleed-out from within any surface discontinuity.