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

Why can a coarse water spray be used to flush a surface without removing penetrant?

1. The water droplets are too small

2. The penetrant is too viscous

3. The water droplets are relatively large

4. The surface is oily

The correct answer is: The water droplets are relatively large

A coarse water spray can effectively flush a surface without removing the penetrant because the relatively large water droplets hit the surface with a sufficient force that may not dislodge the penetrant trapped within surface discontinuities. The larger droplets have more momentum and can displace dirt or debris without dislodging the penetrant, which is designed to adhere to surface flaws. Moreover, penetrants are formulated to have good adhesion properties, allowing them to remain in cracks and pores even when subjected to some water flow. This characteristic is crucial during the cleaning phase before the developer is applied in the penetrant testing process. Understanding the physical interaction between the size of the water droplets and the penetrant can clarify why this method is effective. In contrast, smaller water droplets might not provide enough force to clean the surface effectively, and factors like the viscosity of the penetrant or the presence of oil on the surface do not directly relate to the efficacy of using a coarse spray.