API 510 Pressure Vessel Design & Inspection Codes 4 — Questions and Answers
Question 1: According to API 510, what is the maximum interval for internal or on-stream inspection of a pressure vessel?
- 5 years regardless of corrosion rate
- 10 years or half the remaining life, whichever is less (Correct answer)
- 15 years for low-corrosion service
- The interval set by the original equipment manufacturer
Correct answer: 10 years or half the remaining life, whichever is less
API 510 limits the internal inspection interval to the lesser of 10 years or half the calculated remaining corrosion life.
Question 2: A pressure vessel inspector calculates a corrosion rate of 10 mpy (mils per year) and measures a remaining corrosion allowance of 100 mils. What is the remaining life?
- 5 years
- 10 years (Correct answer)
- 20 years
- 100 years
Correct answer: 10 years
Remaining life = remaining corrosion allowance ÷ corrosion rate = 100 mils ÷ 10 mpy = 10 years.
Question 3: Under ASME VIII Division 1, nozzle reinforcement is required to compensate for:
- The increased weight added by the nozzle flange
- The weakening effect of the opening cut in the vessel shell (Correct answer)
- Thermal expansion differences between the nozzle and shell materials
- Vibration stresses introduced by attached piping
Correct answer: The weakening effect of the opening cut in the vessel shell
Nozzle reinforcement replaces the load-carrying metal removed when an opening is cut in the shell, restoring the vessel's pressure-carrying capacity.
Question 4: According to API 510, what triggers a thickness measurement survey to establish a new corrosion rate?
- Only when visible corrosion is observed during external inspection
- When a vessel is moved to different service or when the previous corrosion rate is no longer valid (Correct answer)
- Every calendar year regardless of service history
- Only after a vessel has been in service for more than 20 years
Correct answer: When a vessel is moved to different service or when the previous corrosion rate is no longer valid
A new corrosion rate survey is triggered when service conditions change or when existing rate data is no longer representative of current service.
Question 5: In the context of API 510, what is meant by 'fitness-for-service' (FFS) assessment?
- A physical fitness test required for personnel entering confined spaces
- An engineering evaluation to determine if a vessel with known flaws can safely operate to the next inspection (Correct answer)
- A manufacturer's certification that the vessel meets original design specifications
- An OSHA-required safety audit of pressure vessel operating procedures
Correct answer: An engineering evaluation to determine if a vessel with known flaws can safely operate to the next inspection
FFS assessment is an engineering evaluation that determines whether a vessel with damage or flaws can continue safe operation until the next planned inspection or repair.
Question 6: Which ASME Section covers the welding procedure and welder qualification requirements applicable to pressure vessel repairs?
- ASME Section V — Nondestructive Examination
- ASME Section IX — Welding and Brazing Qualifications (Correct answer)
- ASME Section II — Materials
- ASME Section VI — Recommended Rules for Care and Operation of Heating Boilers
Correct answer: ASME Section IX — Welding and Brazing Qualifications
ASME Section IX governs the qualification of welding procedures (WPS/PQR) and welders used in pressure vessel fabrication and repair.
Question 7: What does ASME Section VIII Division 2 offer compared to Division 1 that allows thinner vessel walls?
- Less stringent inspection requirements
- More rigorous design-by-analysis rules and mandatory impact testing, with lower safety factors (Correct answer)
- Exemption from post-weld heat treatment requirements
- Permission to use lower-grade materials
Correct answer: More rigorous design-by-analysis rules and mandatory impact testing, with lower safety factors
Division 2 uses more rigorous analytical methods and tighter fabrication controls, permitting lower safety factors and resulting in thinner, lighter vessel walls.
API 510 Pressure Vessel Design & Inspection Codes 4
According to API 510, what is the maximum interval for internal or on-stream inspection of a pressure vessel?