API 653 Inspection Planning 5 — Questions and Answers
Question 1: API 653 states that inspection intervals may be extended beyond standard limits when which condition is met?
- The tank owner submits a written request to the API
- A documented RBI program demonstrates acceptable risk at extended intervals (Correct answer)
- The tank has never experienced any leaks
- The stored product has been classified as non-hazardous
Correct answer: A documented RBI program demonstrates acceptable risk at extended intervals
API 653 allows extended inspection intervals when a formal risk-based inspection program with documented analysis demonstrates that risk remains acceptable.
Question 2: When planning the scope of a tank inspection, API 653 requires the inspector to consider the potential for which damage mechanism in tanks storing crude oil with high water content?
- Stress corrosion cracking from hydrogen sulfide exposure
- Microbiologically influenced corrosion (MIC) at the water-oil interface (Correct answer)
- High-temperature hydrogen attack
- Caustic stress corrosion cracking
Correct answer: Microbiologically influenced corrosion (MIC) at the water-oil interface
Tanks storing crude oil with water bottoms are susceptible to MIC at the water-oil interface, which can cause rapid localized corrosion of the tank bottom.
Question 3: According to API 653, which item should be included in the written inspection plan to ensure inspector and worker safety during an internal inspection?
- The tank owner's preferred insurance carrier contact information
- Confined space entry procedures and atmospheric monitoring requirements (Correct answer)
- A list of nearby restaurants for the inspection crew
- The tank's original purchase invoice
Correct answer: Confined space entry procedures and atmospheric monitoring requirements
Written inspection plans must include confined space entry procedures, atmospheric monitoring for oxygen deficiency and flammable/toxic vapors, and rescue provisions.
Question 4: In API 653, the maximum internal inspection interval for a tank in non-corrosive service with known corrosion rates is limited to what fraction of the remaining corrosion life?
- One-quarter of remaining life or 10 years, whichever is less
- One-half of remaining life or 20 years, whichever is less (Correct answer)
- Three-quarters of remaining life or 15 years, whichever is less
- Full remaining life or 25 years, whichever is less
Correct answer: One-half of remaining life or 20 years, whichever is less
API 653 limits the internal inspection interval to one-half of the calculated remaining corrosion life or 20 years, whichever is less.
Question 5: When preparing an inspection plan for a tank that has undergone a change in service, API 653 requires the inspector to evaluate:
- Only the external condition since the product has changed
- New corrosion rates, damage mechanisms, and suitability of existing materials for the new product (Correct answer)
- Only the paperwork changes needed for the operating permit
- Whether the tank color needs to be updated for product identification
Correct answer: New corrosion rates, damage mechanisms, and suitability of existing materials for the new product
A change in service requires re-evaluation of corrosion rates, applicable damage mechanisms, and compatibility of tank materials and coatings with the new stored product.
Question 6: API 653 requires that inspection findings be documented in a formal inspection report that includes which critical element?
- The inspector's personal opinion on tank aesthetics
- The measured thickness data, corrosion rates, and fitness-for-service assessment (Correct answer)
- A summary of the weather conditions during inspection only
- The contact information for the tank's original manufacturer
Correct answer: The measured thickness data, corrosion rates, and fitness-for-service assessment
The formal inspection report must document all thickness measurements, calculated corrosion rates, remaining life, and a fitness-for-service determination.
Question 7: When planning inspections for a tank farm with multiple tanks, API 653 recommends that the inspection program be managed using:
- A single inspection date for all tanks to minimize disruption
- Individual inspection schedules for each tank based on its own corrosion history and risk (Correct answer)
- A random selection process to determine which tanks are inspected each year
- The oldest tank's inspection schedule applied uniformly to all tanks
Correct answer: Individual inspection schedules for each tank based on its own corrosion history and risk
API 653 requires individual inspection scheduling for each tank because corrosion rates, service history, and risk factors vary between tanks even in the same facility.
API 653 Inspection Planning 5
API 653 states that inspection intervals may be extended beyond standard limits when which condition is met?