Liquid Penetrant Testing Level 1 (PT-1) Practice Exam

Which of the following types of discontinuities would not be detectable by liquid penetrant examination?

1. Surface cracks

2. Subsurface porosity

3. Open fissures

4. Pinholes

The correct answer is: Subsurface porosity

Liquid penetrant testing is specifically designed to detect surface discontinuities that are open to the surface. The method involves applying a penetrant to a material's surface, allowing it to seep into any surface-breaking flaws, and then drawing the penetrant out using a developer, which highlights these discontinuities. Subsurface porosity refers to voids or cavities that are located beneath the surface of the material. These types of defects do not break the surface, meaning that the penetrant cannot reach them. As a result, subsurface porosity remains undetectable using liquid penetrant examination. This is why the identification of subsurface porosity makes it the correct choice in this context. On the other hand, surface cracks, open fissures, and pinholes are discontinuities that break the surface, allowing the penetrant to infiltrate and subsequently be identified during the examination process.