NDT Liquid Penetrant Testing Process 3 — Questions and Answers
Question 1: What is the primary purpose of a penetrant sensitivity level designation (e.g., Level 1/2, Level 1, Level 2, Level 3, Level 4)?
- To indicate the required dwell time for each penetrant
- To classify the penetrant's ability to detect very fine discontinuities (Correct answer)
- To specify which developer must be paired with the penetrant
- To define the maximum inspection temperature for the product
Correct answer: To classify the penetrant's ability to detect very fine discontinuities
Sensitivity level ratings classify how well a penetrant system detects fine discontinuities, with higher numbers indicating greater sensitivity.
Question 2: At what minimum UV-A irradiance (black light intensity) should the inspection surface be maintained when performing fluorescent penetrant testing per ASTM E1417?
- 100 µW/cm²
- 1,000 µW/cm² (Correct answer)
- 2,000 µW/cm²
- 5,000 µW/cm²
Correct answer: 1,000 µW/cm²
ASTM E1417 requires a minimum UV-A irradiance of 1,000 µW/cm² at the inspection surface to ensure adequate fluorescence of indications.
Question 3: Which type of developer is prohibited for use on parts with blind holes or keyways?
- Dry powder developer
- Aqueous developer (wet) (Correct answer)
- Non-aqueous wet developer
- All developer types are equally suitable
Correct answer: Aqueous developer (wet)
Aqueous (wet) developers can become trapped in blind holes, making complete removal after inspection very difficult and potentially leaving harmful residues.
Question 4: What happens to liquid penetrant viscosity as the part temperature INCREASES above the normal operating range?
- Viscosity increases, improving capillary action
- Viscosity decreases, which may reduce dwell time effectiveness (Correct answer)
- Viscosity is unaffected by temperature changes
- Viscosity increases until the penetrant solidifies
Correct answer: Viscosity decreases, which may reduce dwell time effectiveness
Higher temperatures lower penetrant viscosity and increase evaporation, potentially causing the penetrant to dry in the discontinuity before developer can draw it out.
Question 5: The term 'bleeding' in liquid penetrant testing refers to:
- Loss of penetrant from the storage container
- Migration of penetrant from a discontinuity into the developer coating (Correct answer)
- The dilution of penetrant by water during washing
- Overapplication of penetrant causing surface flooding
Correct answer: Migration of penetrant from a discontinuity into the developer coating
Bleeding describes the migration of penetrant out of a discontinuity into the developer layer, forming a visible indication.
Question 6: Which penetrant method is MOST suitable for large structural components in the field where water rinsing facilities are not available?
- Post-emulsifiable hydrophilic (Method D)
- Water-washable (Method A)
- Solvent-removable (Method C) (Correct answer)
- Post-emulsifiable lipophilic (Method B)
Correct answer: Solvent-removable (Method C)
Solvent-removable penetrants (Method C) require only solvent and cloths for excess removal, making them ideal for field inspections without water access.
Question 7: When interpreting liquid penetrant indications, a linear indication is generally defined as one whose length is at least how many times its width?
- 1:1
- 2:1
- 3:1 (Correct answer)
- 5:1
Correct answer: 3:1
A linear indication is typically defined as having a length-to-width ratio of 3:1 or greater, suggesting a planar or elongated discontinuity.
NDT Liquid Penetrant Testing Process 3
What is the primary purpose of a penetrant sensitivity level designation (e.g., Level 1/2, Level 1, Level 2, Level 3, Level 4)?