API 510 Fundamentals & Core Concepts 5 — Questions and Answers
Question 1: Under API 510, who has overall responsibility for ensuring that pressure vessels are inspected in accordance with the code?
- The authorized inspector employed by the AIA
- The owner/user of the pressure vessel (Correct answer)
- The National Board of Boiler and Pressure Vessel Inspectors
- The original equipment manufacturer
Correct answer: The owner/user of the pressure vessel
API 510 places overall responsibility for a safe inspection program on the owner/user of the pressure vessel.
Question 2: When a pressure vessel is operated above its established MAWP, the immediate required action per API 510 is to:
- Document the exceedance and re-rate the vessel at the higher pressure
- Take the vessel out of service and conduct an engineering review before restart (Correct answer)
- Notify the local jurisdiction and continue operation pending review
- Increase the relief valve set pressure to match the new operating pressure
Correct answer: Take the vessel out of service and conduct an engineering review before restart
Operating above MAWP requires immediate removal from service and an engineering review to determine fitness for service before resuming operation.
Question 3: In API 510's risk-based inspection (RBI) framework, 'risk' is defined as a function of:
- Probability of failure only
- Consequence of failure only
- Probability of failure multiplied by consequence of failure (Correct answer)
- Inspection cost divided by remaining vessel life
Correct answer: Probability of failure multiplied by consequence of failure
In RBI, risk = probability of failure × consequence of failure, providing a basis for prioritizing inspection resources.
Question 4: Which of the following statements about pressure relief devices (PRDs) is correct under API 510?
- PRDs are outside the scope of API 510 and governed solely by API 520
- API 510 covers pressure vessels and considers PRDs as an integral part of the pressure-containing system (Correct answer)
- PRDs require inspection every year regardless of service
- Only rupture disks are considered by API 510; relief valves are not
Correct answer: API 510 covers pressure vessels and considers PRDs as an integral part of the pressure-containing system
API 510 recognizes pressure relief devices as part of the pressure-containing system protecting the vessel, though detailed PRD inspection guidance is in API 576.
Question 5: What is the significance of 'remaining life' in API 510 inspection interval calculations?
- It is used only for documentation; inspection intervals are fixed by the code
- Remaining life = (actual thickness − minimum required thickness) ÷ corrosion rate, and drives the maximum inspection interval (Correct answer)
- Remaining life determines when a vessel must be replaced, not when it is inspected
- It applies only to vessels older than 20 years
Correct answer: Remaining life = (actual thickness − minimum required thickness) ÷ corrosion rate, and drives the maximum inspection interval
Remaining life, calculated from corrosion rate data, is the primary driver for setting the next inspection interval under API 510.
Question 6: According to API 510, which type of weld is typically given the highest scrutiny during an internal inspection due to its stress concentration potential?
- Longitudinal seam welds only
- Nozzle-to-shell welds and other discontinuity welds (Correct answer)
- External attachment welds for insulation supports
- Overlay cladding welds on vessel heads
Correct answer: Nozzle-to-shell welds and other discontinuity welds
Nozzle-to-shell junctions and other geometric discontinuities create stress concentrations and are focal points for inspection per API 510 guidelines.
Question 7: API 510 allows inspection intervals to be extended beyond the normal limits under which condition?
- When the vessel has been in service more than 25 years without incident
- When an approved risk-based inspection (RBI) program per API 580/581 is implemented and documented (Correct answer)
- When the process fluid is classified as non-hazardous
- When the vessel operates below 50% of its MAWP
Correct answer: When an approved risk-based inspection (RBI) program per API 580/581 is implemented and documented
A documented RBI program meeting API 580/581 requirements allows the owner/user to adjust inspection intervals beyond the standard API 510 limits.
API 510 Fundamentals & Core Concepts 5
Under API 510, who has overall responsibility for ensuring that pressure vessels are inspected in accordance with the code?