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

Which of the following is NOT a characteristic of liquid penetrant testing?

1. This method can measure the depth of a crack

2. This method can find surface discontinuities

3. This method is suitable for non-porous materials

4. This method is sensitive to small defects

The correct answer is: This method can measure the depth of a crack

Liquid penetrant testing (PT) is primarily designed to detect surface discontinuities such as cracks, porosity, and other surface faults in non-porous materials. The method relies on a liquid penetrant that seeps into surface-breaking flaws and is subsequently drawn out, revealing defects under ultraviolet or visible light. The assertion that this method can measure the depth of a crack is not accurate. Liquid penetrant testing is inherently a surface inspection technique; it reveals the presence of defects only at or near the material's surface but does not provide information about the depth of those defects. Other testing methods, such as ultrasonic testing, are required to assess the depth of cracks or flaws in materials. In summary, while liquid penetrant testing is adept at identifying surface discontinuities, is suitable for non-porous materials, and exhibits sensitivity to small defects, it does not possess the capability to measure the depth of cracks. Therefore, the characteristic related to measuring crack depth is not aligned with the fundamental principles of liquid penetrant testing.