API Inspection and Maintenance 3 — Questions and Answers
Question 1: In API risk-based inspection (RBI) methodology, what two primary factors determine the risk ranking of equipment?
- Age of equipment and original design pressure
- Probability of failure and consequence of failure (Correct answer)
- Corrosion rate and wall thickness
- Inspection interval and operator experience
Correct answer: Probability of failure and consequence of failure
RBI risk ranking is determined by the combination of probability of failure (PoF) and consequence of failure (CoF), allowing prioritization of inspection resources.
Question 2: What type of corrosion is characterized by localized attack that penetrates deeply while the surrounding metal remains relatively unaffected?
- General or uniform corrosion
- Pitting corrosion (Correct answer)
- Galvanic corrosion
- Erosion corrosion
Correct answer: Pitting corrosion
Pitting corrosion creates deep, localized cavities in the metal surface and is particularly dangerous because it can cause through-wall penetration with minimal overall metal loss.
Question 3: Under API 653, what is the recommended approach when a tank floor scan reveals extensive corrosion exceeding acceptable limits?
- Continue operating with increased inspection frequency
- Perform a hydrostatic test to confirm structural integrity
- Replace or repair the corroded floor plates before returning to service (Correct answer)
- Apply protective coating and re-evaluate in 6 months
Correct answer: Replace or repair the corroded floor plates before returning to service
When floor corrosion exceeds minimum thickness limits, API 653 requires repair or replacement of the affected floor plates before the tank can safely return to service.
Question 4: Which NDE method is most effective for detecting surface-breaking cracks in ferromagnetic materials?
- Ultrasonic Testing (UT)
- Radiographic Testing (RT)
- Magnetic Particle Testing (MT) (Correct answer)
- Eddy Current Testing (ET)
Correct answer: Magnetic Particle Testing (MT)
Magnetic Particle Testing (MT) is highly effective for detecting surface and near-surface discontinuities in ferromagnetic materials by revealing disruptions in magnetic field lines.
Question 5: What does IDMT stand for in the context of API inspection records?
- Internal Dimensional Measurement Technique
- Inspection Data Management Technology (Correct answer)
- Interval Determination and Monitoring Threshold
- Integrated Defect Mapping Tool
Correct answer: Inspection Data Management Technology
IDMT refers to Inspection Data Management Technology, systems used to store, retrieve, and analyze inspection findings and equipment history.
Question 6: According to API 571, which damage mechanism is most commonly associated with wet hydrogen sulfide environments in refinery equipment?
- High-temperature oxidation
- Hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) (Correct answer)
- Thermal fatigue
- Microbiologically influenced corrosion (MIC)
Correct answer: Hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC)
Wet H₂S environments cause hydrogen-induced cracking and sulfide stress cracking, which are among the most critical damage mechanisms in refinery processing equipment.
Question 7: What minimum documentation must be maintained for an API 510 pressure vessel inspection to be considered complete?
- Only the inspector's verbal summary
- Thickness measurements, inspection date, inspector certification number, and findings (Correct answer)
- A photograph of the vessel exterior only
- The original manufacturer's data report
Correct answer: Thickness measurements, inspection date, inspector certification number, and findings
API 510 requires inspection records to include thickness measurements, inspection date, inspector's certification, and all findings to maintain a complete equipment history.
API Inspection and Maintenance 3
In API risk-based inspection (RBI) methodology, what two primary factors determine the risk ranking of equipment?