API 653 Code Requirements 2 — Questions and Answers
Question 1: According to API 653, what is the minimum thickness requirement for a tank bottom when it is being evaluated for continued service?
- 0.05 inches regardless of tank size
- Determined by the corrosion rate and remaining service life calculation (Correct answer)
- Always 0.10 inches for all tank sizes
- Equal to the original design thickness minus 10%
Correct answer: Determined by the corrosion rate and remaining service life calculation
API 653 requires that minimum acceptable bottom thickness be determined by calculating remaining corrosion life versus required inspection intervals.
Question 2: Under API 653, which standard governs the design requirements referenced for new shell plates used in tank repair?
- API 650 (Correct answer)
- API 620
- ASME Section VIII
- NFPA 30
Correct answer: API 650
API 653 references API 650 as the governing design standard for new materials and welding requirements used in repairs and alterations.
Question 3: What does API 653 define as a 'reconstruction' of a tank?
- Any repair costing more than 50% of replacement value
- Relocation of a tank to a new site with reassembly (Correct answer)
- Replacement of more than half the shell plates
- Any work requiring a welding inspector
Correct answer: Relocation of a tank to a new site with reassembly
Reconstruction under API 653 specifically refers to disassembling and relocating a tank to a new site, which triggers additional requirements.
Question 4: Per API 653, when must an authorized inspection agency be involved during tank repair or alteration work?
- Only when the owner requests it
- For all alterations and major repairs as defined in the standard (Correct answer)
- Only when the tank is over 500,000 barrels capacity
- Only when a regulatory agency requires it
Correct answer: For all alterations and major repairs as defined in the standard
API 653 requires that an authorized inspection agency be involved in all alterations and repairs classified as major under the standard.
Question 5: Which API 653 section addresses requirements for tanks storing products at temperatures above 200°F?
- Section 4 — Inspection
- Section 7 — Alterations
- Section 5 — Materials
- Appendix provisions for high-temperature service (Correct answer)
Correct answer: Appendix provisions for high-temperature service
High-temperature service requirements in API 653 are addressed in appendix sections that supplement the main body requirements.
Question 6: What is the purpose of the fitness-for-service (FFS) assessment referenced in API 653?
- To determine if a tank needs repainting
- To evaluate whether a tank with damage or deterioration can continue to operate safely (Correct answer)
- To assess contractor qualifications
- To establish inspection personnel certification levels
Correct answer: To evaluate whether a tank with damage or deterioration can continue to operate safely
FFS assessments evaluate whether degraded or damaged tanks can continue operating safely within defined limits.
Question 7: Under API 653, what action is required if an inspector finds a tank shell with a vertical crack?
- Monitor the crack and re-inspect in 12 months
- The crack must be repaired before the tank returns to service (Correct answer)
- Reduce operating level by 10% as a precaution
- Apply a weld repair overlay without removing the crack
Correct answer: The crack must be repaired before the tank returns to service
Vertical cracks in tank shells are not acceptable for continued service and must be repaired before the tank is returned to operation.
API 653 Code Requirements 2
According to API 653, what is the minimum thickness requirement for a tank bottom when it is being evaluated for continued service?