API 571 Inspection and Mitigation Techniques 2 — Questions and Answers
Question 1: Long-range ultrasonic testing (LRUT/guided wave testing) is primarily used for which inspection task?
- Precisely sizing remaining wall thickness at known corrosion locations
- Screening large lengths of pipe for corrosion and metal loss anomalies from a single access point (Correct answer)
- Detecting surface-breaking SCC in stainless steel piping
- Measuring weld hardness for SSC compliance
Correct answer: Screening large lengths of pipe for corrosion and metal loss anomalies from a single access point
Guided wave testing screens hundreds of feet of pipe from a single transducer ring location, identifying anomalies that are then characterized with conventional UT.
Question 2: Acoustic emission testing (AE) is most useful for which inspection application?
- Measuring corrosion rate in real time during operation
- Detecting active crack growth or leakage during pressure or hydrostatic testing (Correct answer)
- Screening for corrosion under insulation from the surface
- Identifying the chemical composition of alloy materials
Correct answer: Detecting active crack growth or leakage during pressure or hydrostatic testing
AE monitoring detects acoustic signals generated by active damage mechanisms such as crack propagation or fluid leakage, providing real-time detection during pressurization.
Question 3: Which inspection technique is recommended for mapping corrosion under insulation (CUI) without full insulation removal?
- Conventional UT spot measurements through insulation cutouts
- Computed radiography (CR) or profile radiographic testing (RT) (Correct answer)
- Magnetic particle testing from the external surface
- Visual inspection through insulation cutouts only
Correct answer: Computed radiography (CR) or profile radiographic testing (RT)
Profile RT or computed radiography can image the pipe cross-section through insulation, revealing the corrosion profile without requiring complete insulation removal.
Question 4: The primary purpose of a Risk-Based Inspection (RBI) assessment is to accomplish what objective?
- Replace all inspection intervals with fixed time-based schedules
- Prioritize inspection resources by identifying the highest-risk equipment based on probability and consequence of failure (Correct answer)
- Eliminate the need for physical inspection of low-risk equipment
- Satisfy insurance and regulatory requirements without changing inspection practice
Correct answer: Prioritize inspection resources by identifying the highest-risk equipment based on probability and consequence of failure
RBI evaluates both probability and consequence of failure for all equipment, directing inspection resources to the highest-risk items while extending intervals for low-risk equipment.
Question 5: Positive Material Identification (PMI) is performed in refineries to accomplish which objective?
- Measure remaining wall thickness to verify corrosion allowance
- Verify alloy chemical composition to prevent wrong-material installations (Correct answer)
- Detect weld hardness for sour service compliance
- Assess extent of creep damage in high-temperature piping
Correct answer: Verify alloy chemical composition to prevent wrong-material installations
PMI using XRF or OES spectroscopy verifies that installed materials match the specified alloy grade, preventing catastrophic failures from wrong-material installations.
Question 6: API 571-recommended mitigation for wet H2S damage includes which combination of measures?
- Increasing operating temperature to evaporate water and eliminate the wet condition
- PWHT, use of HIC-resistant steel, and process chemical injection (inhibitors/neutralizers) (Correct answer)
- Cathodic protection of vessel internals only
- Increasing fluid velocity to prevent H2S concentration
Correct answer: PWHT, use of HIC-resistant steel, and process chemical injection (inhibitors/neutralizers)
Wet H2S damage mitigation requires multiple layers: PWHT to reduce residual stress, HIC-resistant steel for susceptible equipment, and chemical injection to reduce H2S content or inhibit hydrogen entry.
API 571 Inspection and Mitigation Techniques 2
Long-range ultrasonic testing (LRUT/guided wave testing) is primarily used for which inspection task?