NDT Nondestructive Testing Methods & Techniques 4 — Questions and Answers
Question 1: What is the function of the 'developer' step in liquid penetrant testing?
- To remove excess surface penetrant before inspection
- To draw entrapped penetrant out of discontinuities and create a visible indication (Correct answer)
- To chemically etch the surface to improve penetrant adhesion
- To neutralize the penetrant after inspection is complete
Correct answer: To draw entrapped penetrant out of discontinuities and create a visible indication
Developer acts as a blotter that draws trapped penetrant out of discontinuities by capillary action, spreading it to form a visible indication against the developer background.
Question 2: Which ASME code section specifically governs the nondestructive examination requirements for pressure vessels?
- ASME Section I — Power Boilers
- ASME Section V — Nondestructive Examination (Correct answer)
- ASME Section IX — Welding and Brazing Qualifications
- ASME Section II — Materials
Correct answer: ASME Section V — Nondestructive Examination
ASME Section V provides the methods, procedures, and requirements for NDE techniques used in pressure vessel and boiler inspection programs.
Question 3: A boilermaker inspector finds a linear indication on a weld radiograph that is parallel to the weld axis and located at the weld centerline. This is most likely indicative of:
- Slag inclusion at the weld toe
- Centerline cracking or lack of fusion along the weld root (Correct answer)
- Tungsten inclusion from GTAW process
- Undercut at the weld crown
Correct answer: Centerline cracking or lack of fusion along the weld root
A linear indication parallel to and centered on the weld axis suggests centerline hot cracking or incomplete fusion along the root, both critical planar defects.
Question 4: In ultrasonic testing, 'attenuation' refers to:
- The increase in signal amplitude as sound travels deeper into the material
- The loss of sound energy as the beam travels through the material due to absorption and scattering (Correct answer)
- The angle at which the sound beam refracts at the material interface
- The time delay between the initial pulse and the first back-wall echo
Correct answer: The loss of sound energy as the beam travels through the material due to absorption and scattering
Attenuation is the progressive reduction of ultrasonic energy as the beam travels through material, caused by absorption (heat conversion) and scattering at grain boundaries.
Question 5: What is the primary advantage of phased array ultrasonic testing (PAUT) over conventional single-element UT in weld inspection?
- PAUT uses lower frequencies that penetrate thicker materials
- PAUT can electronically steer and focus the beam without moving the probe, improving coverage and speed (Correct answer)
- PAUT eliminates the need for a couplant
- PAUT can detect chemical corrosion that conventional UT cannot
Correct answer: PAUT can electronically steer and focus the beam without moving the probe, improving coverage and speed
Phased array systems use multiple elements fired at controlled time delays to steer and focus the ultrasonic beam electronically, enabling rapid volumetric weld inspection without mechanical scanning.
Question 6: Which of the following conditions would render a magnetic particle test invalid on a boiler component?
- Testing after the component has been preheated
- Testing a component with a non-ferromagnetic weld overlay (Correct answer)
- Testing after shot blasting the surface
- Testing at ambient temperature above 50°F
Correct answer: Testing a component with a non-ferromagnetic weld overlay
Magnetic particle testing is only effective on ferromagnetic materials; a non-ferromagnetic overlay (such as austenitic stainless steel) cannot be magnetized, making MT invalid for that surface layer.
Question 7: When evaluating a radiographic film, the 'IQI sensitivity' is considered acceptable when:
- The IQI itself is not visible on the film
- The required wire or hole of the designated IQI is visible on the film (Correct answer)
- The darkest area of the film is below optical density 1.0
- The IQI is placed on the film side closest to the detector
Correct answer: The required wire or hole of the designated IQI is visible on the film
Radiographic sensitivity is verified by confirming that the essential wire (wire-type IQI) or the required hole (hole-type IQI) is visible on the processed film, demonstrating adequate contrast and definition.
NDT Nondestructive Testing Methods & Techniques 4
What is the function of the 'developer' step in liquid penetrant testing?