The Penetrant Testing method is a development of the original oil and chalk test that has been used for many years in the detection of defects that outcrop at the surface of a component. PT can be utilized for both ferrous and non-ferrous materials but is particularly useful when components manufactured from non-ferrous materials and austenitic steels are to be examined and the more discriminating magnetic particle test cannot be employed. It can be used either in a laboratory application or on-site.
The detecting medium may be either a red dye that is visible under normal lighting conditions or a fluorescent dye which requires the use of an ultraviolet lamp. It is particularly useful in the laboratory as a cost effective method of testing small machined components in large batch quantities.
It uses simple equipment to detect flaws that are open to the surface and works on any material as long as it is not porous. The Penetrants are petroleum or water based liquids colored by a dye. Following the application to the surface, the liquid seeps into the open voids and then gets removed from the surface and replaced by a white developer. The developer acts as a blotter, drawing out the Penetrant trapped in voids. The Penetrant then stains the developer, indicating the presence and the location of the flaws/defects.
Dye Penetrant Testing is used for identifying different types of cracks such as fatigue cracks and hairline cracks as well as leaks and welding defects.