NDT - Non-Destructive Testing Liquid Penetrant Testing Process Questions and Answers

Question 1

An NDT technician applies a visible dye penetrant to a non-porous component. After the appropriate dwell time, the excess penetrant is removed, and a non-aqueous wet developer is applied. Which of the following is the PRIMARY function of the developer in this process?

Accepted Answer

To act as a blotter, drawing the penetrant out of discontinuities to form a visible indication.

Answer

The primary function of the developer is to act like a blotter. It has a high absorbency that draws the penetrant trapped within surface-breaking discontinuities back to the surface through capillary action. This allows the small amount of trapped penetrant to spread out, creating a visible indication that is much larger and easier to see than the actual discontinuity.

Question 2

A liquid penetrant inspection is being performed on an aluminum casting. Which of the following pre-cleaning methods would be considered detrimental to the inspection's sensitivity because it might close or smear over the very discontinuities the test is designed to find?

Accepted Answer

Grit blasting

Answer

Aggressive mechanical methods like grit blasting, shot peening, or power wire brushing can smear the metal surface, closing the openings of small discontinuities. This prevents the penetrant from entering the flaws, rendering the test ineffective for detecting them. The other methods listed are generally acceptable for removing organic and other contaminants without damaging the surface.

Question 3

When comparing Type I (Fluorescent) and Type II (Visible) liquid penetrant systems, which statement is generally correct regarding their sensitivity?

Accepted Answer

Type I is more sensitive because the human eye is more readily drawn to a glowing indication against a dark background.

Answer

Type I (Fluorescent) penetrant systems are generally considered more sensitive than Type II (Visible) systems. The reason is that under proper UV-A (black light) conditions in a darkened area, the glowing fluorescent indication provides a much higher contrast against the dark background, making it easier for the human eye to detect very fine and small indications that might be missed with a visible dye.

Question 4

A technician is performing a solvent-removable visible dye penetrant test. During the excess penetrant removal step, the technician sprays the solvent remover directly onto the test surface before wiping. What is the most likely negative consequence of this action?

Accepted Answer

It can flush the penetrant out of shallow discontinuities, leading to missed flaws.

Answer

For the solvent-removable method, the correct procedure is to apply the solvent to a lint-free cloth and then wipe the surface. Spraying the solvent directly onto the part is too aggressive and can wash the penetrant out of the discontinuities it is intended to find, especially shallow ones. This results in a high probability of failing to detect existing flaws.

Question 5

After completing a liquid penetrant inspection and evaluating the results, what is the critical final step in the process before returning the component to service?

Accepted Answer

Post-cleaning the component to remove all inspection materials.

Answer

Post-cleaning is a critical final step to thoroughly remove all residual penetrant and developer materials. If left on the surface, these chemicals can sometimes interfere with subsequent manufacturing processes (like welding or painting) or could potentially cause corrosion or other adverse effects on the component during service.

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Practice Test

NDT - Non-Destructive Testing Liquid Penetrant Testing Process Questions and Answers