NDT Liquid Penetrant Testing Process 2 — Questions and Answers
Question 1: What is the minimum dwell time typically required for liquid penetrant to enter a tight fatigue crack in steel at room temperature?
- 30 seconds
- 5 minutes (Correct answer)
- 10 minutes
- 1 hour
Correct answer: 5 minutes
A minimum of 5 minutes dwell time is typically required for penetrant to enter tight fatigue cracks in steel at room temperature.
Question 2: Which surface condition would MOST adversely affect the quality of a liquid penetrant test?
- Slight surface roughness
- A thin oil film covering the part (Correct answer)
- Metallic color variation
- Slight oxidation on non-critical areas
Correct answer: A thin oil film covering the part
An oil film blocks penetrant from entering discontinuities, making pre-cleaning the most critical preparatory step.
Question 3: After applying a water-washable penetrant, what is the danger of over-washing the part?
- The developer will not adhere to the surface
- Penetrant trapped in discontinuities may be removed, causing false-negative indications (Correct answer)
- The part will become magnetized
- Excess moisture accelerates corrosion during testing
Correct answer: Penetrant trapped in discontinuities may be removed, causing false-negative indications
Over-washing can remove penetrant from shallow or wide-open discontinuities, causing relevant indications to be missed.
Question 4: A Type II penetrant system uses which fluorescent agent characteristic?
- Visible dye that fluoresces under white light
- Dye that is visible only under UV-A (black) light (Correct answer)
- Dye that changes color with temperature
- Dual-mode dye visible under both white and UV light
Correct answer: Dye that is visible only under UV-A (black) light
Type II penetrants contain fluorescent dye that glows under UV-A (ultraviolet) light, providing high contrast against the dark inspection background.
Question 5: What is the purpose of a non-aqueous wet developer in liquid penetrant testing?
- To remove excess penetrant from the surface
- To dissolve the penetrant trapped in defects
- To draw penetrant out of discontinuities and provide a contrasting background (Correct answer)
- To accelerate the drying of water-based penetrants
Correct answer: To draw penetrant out of discontinuities and provide a contrasting background
Non-aqueous wet developer uses a carrier solvent that evaporates, leaving a white powder coating that draws penetrant out and creates contrast.
Question 6: When inspecting a part using solvent-removable penetrant, the excess penetrant should be removed by:
- Spraying solvent directly onto the part until clean
- Wiping with a dry cloth first, then a cloth lightly dampened with solvent (Correct answer)
- Submerging the part in a solvent bath
- Rinsing with warm water then blotting dry
Correct answer: Wiping with a dry cloth first, then a cloth lightly dampened with solvent
The correct technique is to wipe with a dry cloth first and then use a lightly dampened cloth to avoid flushing penetrant out of discontinuities.
Question 7: In liquid penetrant testing, a 'false indication' is BEST described as:
- An indication caused by a non-relevant surface condition such as a scratch or lap
- An indication that appears in a location where no material exists
- A relevant indication that was missed by the inspector
- An indication caused by improper developer application (Correct answer)
Correct answer: An indication caused by improper developer application
A false indication results from faulty technique—such as improper developer application—rather than from an actual material condition.
NDT Liquid Penetrant Testing Process 2
What is the minimum dwell time typically required for liquid penetrant to enter a tight fatigue crack in steel at room temperature?