API 510 Inspection Methods & Nondestructive Testing 2 — Questions and Answers
Question 1: When performing wet fluorescent magnetic particle testing (WFMT) on a pressure vessel weld, what is the primary advantage over dry magnetic particle testing?
- Higher sensitivity for detecting fine, shallow surface cracks (Correct answer)
- Ability to detect subsurface discontinuities up to 1 inch deep
- No requirement for a UV light source
- Applicability to austenitic stainless steel
Correct answer: Higher sensitivity for detecting fine, shallow surface cracks
WFMT uses fluorescent particles suspended in liquid, providing higher sensitivity for fine cracks compared to dry MT methods.
Question 2: During radiographic testing of a pressure vessel shell, which IQI (image quality indicator) placement is preferred per ASME Section V?
- Source side of the weld, adjacent to the area of interest (Correct answer)
- Film side of the weld, adjacent to the area of interest
- Centered on the weld crown
- Anywhere on the radiograph as long as it is visible
Correct answer: Source side of the weld, adjacent to the area of interest
ASME Section V requires IQIs to be placed on the source side to demonstrate the minimum detectable flaw size at the most critical location.
Question 3: An API 510 inspector uses time-of-flight diffraction (TOFD) ultrasonics on a thick-walled vessel. What is a known limitation of TOFD near the scanning surface?
- Dead zone near the surface due to lateral wave interference (Correct answer)
- Inability to detect volumetric flaws
- Requires ferromagnetic material
- Cannot be used on welds wider than 2 inches
Correct answer: Dead zone near the surface due to lateral wave interference
TOFD has a near-surface dead zone caused by the lateral wave masking reflections from shallow defects.
Question 4: Which eddy current technique is most effective for detecting corrosion and pitting on the inner surface of non-ferromagnetic heat exchanger tubes from the outside?
- Remote field eddy current (RFEC) (Correct answer)
- Conventional eddy current (ET)
- Magnetic flux leakage (MFL)
- Pulsed eddy current (PEC)
Correct answer: Remote field eddy current (RFEC)
Remote field eddy current (RFEC) penetrates the full wall of ferromagnetic tubes; for non-ferromagnetic tubes, conventional ET from inside or RFEC from inside is used, but pulsed eddy current from the outside detects wall loss through insulation.
Question 5: When applying liquid penetrant testing (PT) to an austenitic stainless steel pressure vessel nozzle, which post-emulsifier type requires the most careful control of emulsification time?
- Lipophilic (oil-based) emulsifier (Correct answer)
- Hydrophilic (water-based) emulsifier
- Water-washable penetrant system
- Solvent-removable penetrant system
Correct answer: Lipophilic (oil-based) emulsifier
Lipophilic emulsifiers work by diffusion, so over-emulsification can remove penetrant from true defects if contact time is not carefully controlled.
Question 6: Per API 510, what is the primary purpose of performing a hydrostatic test after repairs to a pressure vessel?
- To verify structural integrity and leak-tightness after repair (Correct answer)
- To calibrate ultrasonic thickness gauges
- To satisfy corrosion allowance requirements
- To confirm that new nozzle reinforcement pads are properly welded
Correct answer: To verify structural integrity and leak-tightness after repair
A hydrostatic test after repair confirms the vessel can safely contain pressure and is leak-tight under test conditions.
Question 7: Which NDE method is most suitable for detecting hydrogen-induced cracking (HIC) in the base metal of a pressure vessel operating in a sour service environment?
- Straight-beam ultrasonic testing (UT) (Correct answer)
- Dye penetrant testing (PT)
- Eddy current testing (ET)
- Visual testing (VT)
Correct answer: Straight-beam ultrasonic testing (UT)
HIC creates internal planar defects parallel to the surface, which are best detected by straight-beam UT that can identify laminar-type reflectors within the wall.
API 510 Inspection Methods & Nondestructive Testing 2
When performing wet fluorescent magnetic particle testing (WFMT) on a pressure vessel weld, what is the primary advantage over dry magnetic particle testing?