Liquid Penetrant Test
Penetrant testing (PT) is one of the most widely used nondestructive testing methods for the detection of surface discontinuities in nonporous solid materials. It is almost certainly the most commonly used surface NDT method today because it can be applied to virtually any magnetic or nonmagnetic material. PT provides industry with a wide range of sensitivities and techniques that make it especially adaptable to a broad range of sizes and shapes. It is extremely useful for examinations that are conducted in remote field locations, since it is extremely portable. The method is also very appropriate in a production type environment where many smaller parts can be processed in a relatively short period of time.
Fluorescent or dye penetrant, developers, cleaners (solvents, emulsifiers, etc.). Suitable cleaning gear. Ultraviolet light source if fluorescent dye is used.
Weld discontinuities open to surface, i.e., cracks, porosity.
Portable, relatively inexpensive equipment. Expedient inspection results. Results are easily interpreted. Requires no electrical energy except for light sources.
Surface films such as coatings, scale, smeared metal mask or hide rejectable defects. Seepage from weld porosity at the surface can also mask indications. Parts must be cleaned before and after inspection.
Source: American Welding Society Inc., The McGraw-Hill Companies Inc.