API 510 Inspection Planning and Scheduling 2 — Questions and Answers
Question 1: Under API 510, which factor is MOST important when establishing the next inspection interval for a pressure vessel?
- The vessel's original construction date
- The remaining corrosion allowance divided by the corrosion rate (Correct answer)
- The date of the last external inspection
- The operating temperature only
Correct answer: The remaining corrosion allowance divided by the corrosion rate
The next inspection interval is primarily determined by dividing the remaining corrosion allowance by the measured corrosion rate to predict when the minimum required thickness will be reached.
Question 2: When a pressure vessel is placed in a Risk-Based Inspection (RBI) program, which output is used to drive inspection planning decisions?
- Maximum allowable working pressure recalculation
- Risk ranking combining probability and consequence of failure (Correct answer)
- Hydrostatic test frequency schedule
- Weld joint efficiency factor
Correct answer: Risk ranking combining probability and consequence of failure
RBI programs rank vessels by combining the probability of failure with the consequence of failure, and this risk ranking drives the inspection planning priorities.
Question 3: API 510 allows an inspector to extend the internal inspection interval beyond the normal limit under which condition?
- The vessel has never experienced overpressure
- On-stream inspection techniques are used and the risk is acceptable (Correct answer)
- The vessel is less than 10 years old
- The owner-user has never had a prior incident
Correct answer: On-stream inspection techniques are used and the risk is acceptable
API 510 permits extension of internal inspection intervals when appropriate on-stream inspection techniques demonstrate acceptable integrity and risk.
Question 4: A pressure vessel has a measured corrosion rate of 0.010 in/yr and a remaining corrosion allowance of 0.125 in. What is the calculated remaining life?
- 10 years
- 12.5 years (Correct answer)
- 15 years
- 8 years
Correct answer: 12.5 years
Remaining life = remaining corrosion allowance ÷ corrosion rate = 0.125 ÷ 0.010 = 12.5 years.
Question 5: Per API 510, the maximum internal inspection interval for a pressure vessel in normal service is:
- 5 years
- 10 years (Correct answer)
- 15 years
- 20 years
Correct answer: 10 years
API 510 sets the maximum internal (or on-stream equivalent) inspection interval at 10 years for pressure vessels in normal service.
Question 6: Which document is MOST critical to review when planning an internal inspection of a pressure vessel?
- The original purchase order for the vessel
- The vessel's inspection history, prior thickness data, and last inspection report (Correct answer)
- The plant's annual capital expenditure budget
- The operator's personal safety record
Correct answer: The vessel's inspection history, prior thickness data, and last inspection report
Prior inspection reports, thickness measurements, and inspection history are essential inputs for planning the scope and focus areas of an upcoming internal inspection.
Question 7: If a pressure vessel's calculated inspection interval based on corrosion rate would exceed the API 510 maximum allowable interval, which interval governs?
- The calculated interval, since it is based on actual data
- The API 510 maximum allowable interval (Correct answer)
- An interval agreed upon between owner-user and contractor
- The interval specified in the original design documents
Correct answer: The API 510 maximum allowable interval
API 510 maximum allowable intervals are absolute limits; even if the calculated corrosion-based interval is longer, the code maximum governs.
API 510 Inspection Planning and Scheduling 2
Under API 510, which factor is MOST important when establishing the next inspection interval for a pressure vessel?