API 653 Code Requirements 4 — Questions and Answers
Question 1: Per API 653, when is a hydrostatic test required after repairs to a tank?
- After any repair, regardless of scope
- Only when required by local regulations
- After repairs to the shell or bottom that affect structural integrity as defined in the standard (Correct answer)
- Hydrostatic testing is never required for repairs, only for new construction
Correct answer: After repairs to the shell or bottom that affect structural integrity as defined in the standard
API 653 requires hydrostatic testing after certain shell and bottom repairs that could affect the tank's structural integrity, as specified in the standard.
Question 2: What does the term 'alteration' mean under API 653, as distinct from a 'repair'?
- Any work performed by a contractor rather than the owner
- A physical change to a tank component that affects its design, capacity, or operating conditions (Correct answer)
- Replacement of corroded shell plates with identical material
- Any work requiring welding on the tank shell
Correct answer: A physical change to a tank component that affects its design, capacity, or operating conditions
An alteration under API 653 is a physical change that affects the tank's design configuration, capacity, or operating conditions, distinguishing it from like-for-like repair.
Question 3: According to API 653, what is the minimum preheat temperature required for welding on tank shell plates with carbon equivalent (CE) above 0.43?
- No preheat is required for API 653 tank repairs
- Minimum 50°F (10°C)
- As required by applicable welding procedures per AWS or ASME standards (Correct answer)
- Exactly 300°F (149°C) for all high-CE materials
Correct answer: As required by applicable welding procedures per AWS or ASME standards
API 653 requires preheat to be as specified in the applicable welding procedure standard, such as AWS D1.1 or ASME Section IX, based on material CE.
Question 4: Under API 653, what is the minimum overlap required when installing a new bottom lap-welded to an existing bottom?
- 1 inch
- 1.5 inches (Correct answer)
- 2 inches
- 3 inches
Correct answer: 1.5 inches
API 653 specifies a minimum 1.5-inch overlap for new bottom plates installed over existing bottom plates using lap-welded construction.
Question 5: Per API 653, what action must be taken when the remaining corrosion allowance on the tank shell is insufficient to last until the next scheduled internal inspection?
- Increase the inspection interval to match the remaining life
- Repair, rerate, or take the tank out of service (Correct answer)
- Apply an external coating to slow corrosion
- Document the condition and continue monitoring
Correct answer: Repair, rerate, or take the tank out of service
When corrosion allowance is insufficient for the next inspection interval, API 653 requires the tank to be repaired, rerated to a lower operating level, or removed from service.
Question 6: Which API 653 provision addresses the installation of new nozzles in existing tank shells?
- New nozzles are prohibited in existing tank shells
- New nozzles must meet API 650 requirements for reinforcement and welding (Correct answer)
- New nozzles only require owner approval, no engineering review
- Nozzle installation is covered exclusively by local piping codes
Correct answer: New nozzles must meet API 650 requirements for reinforcement and welding
API 653 requires that new nozzles installed in existing shells comply with API 650 design and reinforcement requirements.
Question 7: What does API 653 require regarding documentation of tank inspection and repair records?
- Records must be kept for the life of the tank (Correct answer)
- Records need only be kept for 5 years after each inspection
- Records are optional and left to owner discretion
- Records must be submitted to API upon completion
Correct answer: Records must be kept for the life of the tank
API 653 requires that inspection and repair records be maintained for the life of the tank to support future fitness-for-service evaluations.
API 653 Code Requirements 4
Per API 653, when is a hydrostatic test required after repairs to a tank?