API 653 Documentation 4 — Questions and Answers
Question 1: When a tank undergoes a change of service to a more corrosive product, what documentation action is required under API 653?
- No documentation is needed if the tank dimensions remain unchanged
- The change must be recorded in the tank history file and may trigger a new fitness-for-service evaluation (Correct answer)
- Only the product SDS needs to be updated
- The tank must be repainted before documentation is updated
Correct answer: The change must be recorded in the tank history file and may trigger a new fitness-for-service evaluation
A change to a more corrosive service requires updating the tank history and likely re-evaluating corrosion allowances and inspection intervals based on the new service conditions.
Question 2: What is the function of the calculated corrosion rate in API 653 inspection documentation?
- It is used to price tank cleaning contracts
- It determines the next inspection date by predicting when remaining thickness will reach the minimum allowable (Correct answer)
- It establishes the required coating thickness
- It sets the maximum operating temperature
Correct answer: It determines the next inspection date by predicting when remaining thickness will reach the minimum allowable
The measured corrosion rate, combined with remaining thickness above the minimum allowable, is used to calculate how long before the tank reaches its fitness-for-service limit and must be inspected again.
Question 3: Under API 653, which statement is correct regarding documentation of foundation inspections?
- Foundation inspections are outside the scope of API 653 and require no documentation
- Foundation condition, including settlement, cracks, and drainage issues, must be documented as part of the inspection record (Correct answer)
- Foundation documentation is only required for tanks larger than 50,000 barrels
- Foundation data is recorded only when the tank is empty for cleaning
Correct answer: Foundation condition, including settlement, cracks, and drainage issues, must be documented as part of the inspection record
API 653 includes foundation assessment as part of the overall tank inspection, and any deficiencies in settlement, bearing capacity, or drainage must be documented and evaluated.
Question 4: What does API 653 require the inspector to document when evaluating a tank roof for fitness for service?
- Only the roof color and last painting date
- Thickness measurements, condition of roof-to-shell welds, vent and drain condition, and any observed defects (Correct answer)
- Only the structural load rating of the roof
- The date of the last rainstorm to assess pooling
Correct answer: Thickness measurements, condition of roof-to-shell welds, vent and drain condition, and any observed defects
Roof documentation must include thickness measurements, weld integrity, accessory condition, and all defects observed so that a complete fitness-for-service determination can be made.
Question 5: In API 653, what is required when an out-of-service tank is placed back into service after an extended idle period?
- Only visual inspection by any plant employee
- A formal inspection per API 653 criteria with updated documentation before returning to service (Correct answer)
- A letter from the tank manufacturer confirming fitness for service
- Only a hydrostatic test with no additional documentation
Correct answer: A formal inspection per API 653 criteria with updated documentation before returning to service
Extended idle periods can allow corrosion and other degradation to occur, so API 653 requires a formal documented inspection before returning the tank to service.
Question 6: According to API 653, when a tank is taken out of service permanently, what documentation action is recommended?
- All records can be immediately discarded since the tank is no longer in service
- Final inspection results and the basis for decommissioning should be documented and retained (Correct answer)
- Only the regulatory permit needs to be cancelled
- The tank number should be removed from the facility plot plan
Correct answer: Final inspection results and the basis for decommissioning should be documented and retained
Retaining decommissioning documentation protects the owner from future liability and provides a complete life-cycle record if the tank is ever repurposed or sold.
Question 7: What information must be included in the documentation when a tank's maximum allowable working pressure (MAWP) or maximum fill height is revised?
- Only the new value needs to be posted on the tank nameplate
- The engineering basis for the change, including new calculations, and the identity of the qualified engineer or inspector approving the revision (Correct answer)
- Only verbal notification to the control room operator
- The change must be approved by the local fire marshal before documentation is created
Correct answer: The engineering basis for the change, including new calculations, and the identity of the qualified engineer or inspector approving the revision
Revisions to MAWP or maximum fill height are engineering changes that require documented calculations and approval by a qualified individual to ensure continued structural integrity.
API 653 Documentation 4
When a tank undergoes a change of service to a more corrosive product, what documentation action is required under API 653?