NDT Penetrant Testing 2 — Questions and Answers
Question 1: What is the primary purpose of the dwell time in liquid penetrant testing?
- To allow the developer to absorb excess penetrant
- To allow the penetrant to seep into surface discontinuities by capillary action (Correct answer)
- To dry the surface before developer application
- To activate the fluorescent dye in the penetrant
Correct answer: To allow the penetrant to seep into surface discontinuities by capillary action
Dwell time allows the penetrant to remain on the surface long enough for capillary action to draw it into any open discontinuities.
Question 2: Which type of penetrant system uses an emulsifier applied after penetrant to make excess penetrant water-washable?
- Type 1 fluorescent penetrant
- Post-emulsifiable penetrant system (Correct answer)
- Solvent-removable penetrant system
- Water-washable penetrant system
Correct answer: Post-emulsifiable penetrant system
Post-emulsifiable (PE) systems require a separate emulsifier step after penetrant dwell to render the surface penetrant removable with water.
Question 3: According to ASME standards, what is the minimum dwell time for penetrant when testing for lack of fusion in welds at room temperature?
- 1 minute
- 5 minutes
- 10 minutes (Correct answer)
- 30 minutes
Correct answer: 10 minutes
ASME standards typically specify a minimum 10-minute dwell time for most weld discontinuities under standard temperature conditions.
Question 4: What type of discontinuity CANNOT be detected by liquid penetrant testing?
- Surface cracks
- Subsurface voids (Correct answer)
- Porosity open to the surface
- Cold shuts
Correct answer: Subsurface voids
LPT relies on capillary action into surface-open discontinuities; subsurface defects with no opening to the surface cannot be detected.
Question 5: What is the function of the developer in liquid penetrant testing?
- To clean the surface before penetrant application
- To emulsify the excess penetrant for easy removal
- To draw penetrant back out of discontinuities and provide a contrasting background (Correct answer)
- To increase the viscosity of the penetrant
Correct answer: To draw penetrant back out of discontinuities and provide a contrasting background
Developer acts as a blotter to pull entrapped penetrant out of discontinuities and provides a white background that enhances contrast of the indication.
Question 6: Which lighting condition is required when examining parts with fluorescent penetrant?
- Bright white light above 1000 lux
- Ultraviolet (black) light in a darkened area (Correct answer)
- Infrared light at 940 nm
- Daylight or equivalent ambient lighting
Correct answer: Ultraviolet (black) light in a darkened area
Fluorescent PT indications are only visible under UV-A (black) light in a darkened inspection booth, typically less than 2 fc ambient light.
Question 7: What does the term 'false indication' mean in penetrant testing?
- An indication caused by a real but acceptable discontinuity
- An indication produced by poor technique or contamination rather than a true discontinuity (Correct answer)
- A fluorescent glow from the base metal
- An indication that disappears before it can be recorded
Correct answer: An indication produced by poor technique or contamination rather than a true discontinuity
A false indication results from improper cleaning, poor rinsing, or contamination and does not represent an actual discontinuity in the material.
NDT Penetrant Testing 2
What is the primary purpose of the dwell time in liquid penetrant testing?