Fluorescent penetrant inspection probability of detection demonstrations performed for space propulsion

Fracture critical rocket hardware requires nondestructive testing for flight quality assurance. Fracture critical hardware is defined as hardware with failure modes that may endanger space systems, missions or crew. This hardware includes major housings, disks, impellers and gas path hardware. A number of these components are evaluated with fluorescent penetrant inspection for defects open to the surface. Industry data supports the conclusion that with ultra high sensitivity penetrant, defects > 0.090" in length can reliably be detected with a 90/95 probability of detection (POD). To ensure the same POD on fracture critical hardware with reject lengths < 0.090", POD demonstrations are conducted. These demonstrations are conducted on in-house inspectors and on approved external vendor's inspectors. Included in this paper are the results from over 50 of these demonstrations including results from different levels, methods and manufactures of penetrant. The paper describes: the specimens used, process used, specimen cleaning method, types of systems tested, analysis method, problem encountered and the lessons and conclusions that can be made.