API 510 Non-Destructive Examination Methods 4 — Questions and Answers
Question 1: What does the term 'sensitivity' mean in the context of liquid penetrant testing?
- The ability of the penetrant to wet and enter tight discontinuities (Correct answer)
- The time required for the penetrant to fully cure on the surface
- The resistance of the penetrant to high-temperature degradation
- The viscosity of the developer when applied to the test surface
Correct answer: The ability of the penetrant to wet and enter tight discontinuities
In liquid penetrant testing, sensitivity refers to the penetrant system's ability to enter and be retained in fine, tight discontinuities, ultimately producing visible or fluorescent indications.
Question 2: Which phase of the eddy current signal is most useful for characterizing the depth of a defect in a pressure vessel tube wall?
- Amplitude only, since deeper defects produce larger signals
- Phase angle, since deeper defects cause greater phase lag in the eddy current response (Correct answer)
- Frequency, since higher frequencies penetrate deeper into the material
- Impedance magnitude at the reference standard frequency
Correct answer: Phase angle, since deeper defects cause greater phase lag in the eddy current response
Phase angle in eddy current testing is used to characterize defect depth because eddy currents at greater depths experience more phase lag, allowing differentiation of ID and OD defects and depth estimation.
Question 3: During magnetic particle testing, demagnetization is required after inspection. Which of the following situations most critically requires demagnetization?
- Vessels used in high-temperature steam service above 800°F
- Components that will be welded after MT inspection (Correct answer)
- Vessels in cyclic service with pressures below 100 psi
- Components subject to future liquid penetrant testing only
Correct answer: Components that will be welded after MT inspection
Demagnetization is most critical when components will be welded after MT inspection, because residual magnetism can cause arc blow, which deflects the welding arc and leads to poor weld quality.
Question 4: In UT shear wave (angle beam) examination of a pressure vessel weld, what is the significance of the 'dead zone' near the entry surface?
- The dead zone is where the transducer cannot detect defects due to the main bang pulse width (Correct answer)
- The dead zone represents the area where the beam is at maximum intensity
- The dead zone is a region of higher sensitivity near the examination surface
- The dead zone defines the maximum depth the beam can penetrate
Correct answer: The dead zone is where the transducer cannot detect defects due to the main bang pulse width
The dead zone in pulse-echo UT is the region immediately below the examination surface where the initial pulse (main bang) masks detection of near-surface defects, limiting the method's near-surface resolution.
Question 5: When performing visual inspection of the internal surface of a pressure vessel, which lighting condition is specified by ASME Section V for direct visual examination?
- A minimum of 50 foot-candles (540 lux) at the examination surface (Correct answer)
- Natural daylight only, supplemented by portable white LED lights
- A minimum of 100 foot-candles (1076 lux) at the examination surface
- Any adequate illumination as judged by the inspector
Correct answer: A minimum of 50 foot-candles (540 lux) at the examination surface
ASME Section V, Article 9 requires a minimum illuminance of 50 foot-candles (540 lux) on the examination surface for direct visual examination to ensure adequate defect visibility.
Question 6: What is the primary reason for using tandem ultrasonic scanning on thick-wall pressure vessels?
- To increase the scanning speed on large vessel shells
- To detect vertically oriented planar flaws that would not reflect energy back to a single transducer (Correct answer)
- To reduce the need for calibration blocks during examination
- To eliminate the need for couplant on rough surfaces
Correct answer: To detect vertically oriented planar flaws that would not reflect energy back to a single transducer
Tandem UT uses separate transmitter and receiver transducers to detect vertically oriented planar discontinuities (such as lack-of-fusion in heavy welds) that reflect sound away from the transmitting transducer.
Question 7: In radiographic testing of pressure vessel welds, which type of IQI placement provides the most conservative (strictest) sensitivity demonstration?
- Source-side placement of the IQI on the surface closest to the radiation source (Correct answer)
- Film-side placement of the IQI on the surface closest to the film
- IQI placed on the weld crown directly over the weld reinforcement
- IQI placement is irrelevant as long as it is within the area of interest
Correct answer: Source-side placement of the IQI on the surface closest to the radiation source
Source-side IQI placement is more conservative because the IQI image must be visible even after radiation passes through the maximum material thickness, demonstrating higher technique sensitivity than film-side placement.
API 510 Non-Destructive Examination Methods 4
What does the term 'sensitivity' mean in the context of liquid penetrant testing?