NDT Visual Testing Fundamentals 2 — Questions and Answers
Question 1: What is the minimum illuminance level (in foot-candles) required for general visual inspection per ASME standards?
- 25 fc
- 50 fc (Correct answer)
- 100 fc
- 150 fc
Correct answer: 50 fc
ASME standards require a minimum illuminance of 50 foot-candles (540 lux) for general visual inspection.
Question 2: During remote visual inspection (RVI), which tool is best suited for inspecting internal bores of small-diameter tubing?
- Rigid borescope (Correct answer)
- Flexible fiberscope
- Video borescope
- Dental mirror
Correct answer: Rigid borescope
Rigid borescopes provide superior image quality and are ideal for straight, small-diameter bores where flexibility is not required.
Question 3: What does the term 'depth of field' mean in the context of visual testing optics?
- The maximum magnification achievable
- The range of distances over which objects appear acceptably sharp (Correct answer)
- The field of view angle of a lens
- The minimum defect size detectable
Correct answer: The range of distances over which objects appear acceptably sharp
Depth of field is the range of distances within which objects remain in acceptable focus without readjusting the optic.
Question 4: Which discontinuity type is MOST likely to be missed during a direct visual inspection of a weld surface?
- Surface porosity
- Undercut
- Subsurface lamination (Correct answer)
- Overlap
Correct answer: Subsurface lamination
Subsurface laminations are internal discontinuities not visible at the surface, making them undetectable by direct visual methods.
Question 5: A pit gauge is used during visual testing primarily to measure:
- The length of a surface crack
- The depth of a corrosion pit (Correct answer)
- The width of a weld bead
- The height of a reinforcement
Correct answer: The depth of a corrosion pit
A pit gauge (or depth gauge) is specifically designed to measure the depth of corrosion pits and similar surface depressions.
Question 6: In visual testing, 'raking light' technique is most effective for detecting:
- Subsurface voids
- Surface roughness and shallow surface irregularities (Correct answer)
- Internal porosity
- Material composition changes
Correct answer: Surface roughness and shallow surface irregularities
Raking (oblique) light cast at a low angle creates shadows that highlight subtle surface irregularities and shallow discontinuities.
Question 7: Which personal protective factor is MOST critical when performing visual inspection inside a confined space vessel?
- Wearing anti-static gloves
- Atmospheric testing and continuous air monitoring (Correct answer)
- Using polarized lenses
- Applying sunscreen for UV exposure
Correct answer: Atmospheric testing and continuous air monitoring
Confined space entry requires atmospheric testing for toxic gases, oxygen deficiency, and flammable vapors before and during entry.
NDT Visual Testing Fundamentals 2
What is the minimum illuminance level (in foot-candles) required for general visual inspection per ASME standards?