NDT Visual Testing Fundamentals 3 — Questions and Answers
Question 1: A visual testing procedure requires 20/40 near vision acuity. What does this specification mean?
- The inspector must see at 20 feet what a normal eye sees at 40 feet (Correct answer)
- The inspector must see at 40 feet what a normal eye sees at 20 feet
- The inspector needs bifocal correction
- The inspector must use a 40x magnifier at 20 inches
Correct answer: The inspector must see at 20 feet what a normal eye sees at 40 feet
20/40 vision means the inspector sees at 20 feet what a person with normal vision sees at 40 feet, indicating reduced acuity.
Question 2: What is the primary purpose of a comparator (replica tape) in visual testing?
- To measure crack depth electronically
- To transfer and preserve a 3D impression of a surface for measurement (Correct answer)
- To compare weld color to a reference standard
- To project a magnified image of the surface
Correct answer: To transfer and preserve a 3D impression of a surface for measurement
Replica tape (such as Testex Press-O-Film) creates a physical impression of a surface profile that can be removed and measured with a micrometer.
Question 3: When using a flexible video borescope, image distortion at the edges of the field of view is typically caused by:
- Insufficient lighting power
- Wide-angle lens geometric distortion (Correct answer)
- Camera sensor overheating
- Moisture inside the insertion tube
Correct answer: Wide-angle lens geometric distortion
Wide-angle lenses used in borescopes introduce barrel or pincushion distortion, especially at field edges, which can affect dimensional assessments.
Question 4: According to SNT-TC-1A, which level of VT certification has the primary responsibility for interpreting and evaluating test results?
- Level I
- Level II (Correct answer)
- Level III
- Trainee
Correct answer: Level II
SNT-TC-1A Level II personnel are qualified to set up, calibrate, conduct, and interpret/evaluate VT results.
Question 5: Which condition would MOST adversely affect a visual inspector's ability to detect color-contrast discontinuities?
- Mild astigmatism corrected with glasses
- Red-green color vision deficiency (Correct answer)
- Slight hyperopia (farsightedness)
- 20/25 visual acuity
Correct answer: Red-green color vision deficiency
Red-green color deficiency impairs the ability to distinguish contrast between certain colors, which can mask discontinuities highlighted by color-contrast methods.
Question 6: The term 'field of view' in optical aids used for VT refers to:
- The maximum working distance of the device
- The total area visible through the device at a given distance (Correct answer)
- The magnification power of the lens system
- The depth of the cavity the device can enter
Correct answer: The total area visible through the device at a given distance
Field of view is the total area that can be observed through an optical device at a specified distance or magnification setting.
Question 7: What type of weld discontinuity is characterized by base metal that has been melted away and not replaced by weld metal, leaving a groove along the weld toe?
- Overlap
- Undercut (Correct answer)
- Incomplete fusion
- Porosity
Correct answer: Undercut
Undercut is a groove melted into the base metal at the weld toe that is left unfilled, creating a stress concentration.
NDT Visual Testing Fundamentals 3
A visual testing procedure requires 20/40 near vision acuity.
What does this specification mean?