API 653 Inspection Planning 4 — Questions and Answers
Question 1: In API 653, what is the purpose of determining the 'corrosion allowance' during inspection planning?
- To calculate the purchase price of replacement steel
- To establish how much metal loss can occur before minimum thickness is reached (Correct answer)
- To determine the tank's paint coating specification
- To set the product temperature operating limit
Correct answer: To establish how much metal loss can occur before minimum thickness is reached
The corrosion allowance represents the difference between current measured thickness and minimum required thickness, indicating how much additional corrosion is permissible.
Question 2: According to API 653, what is the inspection frequency for external visual inspections under normal operating conditions?
- Monthly
- Every 5 years
- Annually or as defined by the inspector based on risk (Correct answer)
- Every 10 years
Correct answer: Annually or as defined by the inspector based on risk
API 653 requires external visual inspections at least annually or at a frequency determined by the inspector based on operating conditions and risk factors.
Question 3: When planning a tank bottom replacement, the API 653 inspector must verify that the new bottom plate meets minimum thickness requirements based on:
- The original design drawings only
- API 650 requirements and the projected corrosion rate for future service (Correct answer)
- The cost of available plate material
- The opinion of the welding contractor
Correct answer: API 650 requirements and the projected corrosion rate for future service
Replacement bottom plates must satisfy API 650 design requirements and incorporate adequate thickness to accommodate future corrosion over the planned service life.
Question 4: API 653 requires that the inspection plan for a tank with a floating roof include specific attention to which component that is critical to environmental compliance?
- The tank nameplate
- The floating roof seal system (Correct answer)
- The external paint coating color
- The venting capacity calculations
Correct answer: The floating roof seal system
The floating roof seal system is critical to preventing vapor emissions and must be inspected for condition, contact with the shell, and effectiveness.
Question 5: Under API 653, which of the following is a prerequisite before any hot work is performed during a tank inspection or repair?
- Painting the tank a bright color for visibility
- Gas freeing the tank and obtaining a hot work permit (Correct answer)
- Notifying the local media
- Increasing the tank's contents level above 50%
Correct answer: Gas freeing the tank and obtaining a hot work permit
API 653 requires tanks to be gas freed and a hot work permit obtained before any welding or cutting to prevent ignition of flammable vapors.
Question 6: When reviewing inspection data for a tank with both internal and external corrosion, API 653 requires the inspector to use which corrosion rate for remaining life calculations?
- The average of internal and external rates
- The higher (more conservative) of the two measured rates (Correct answer)
- The internal corrosion rate only
- The external corrosion rate only
Correct answer: The higher (more conservative) of the two measured rates
API 653 requires using the most conservative (highest) corrosion rate when calculating remaining life to ensure safe continued operation.
Question 7: According to API 653, an inspection plan must include provisions for examining the tank foundation for which specific concern?
- The aesthetic appearance of the concrete
- Settlement, erosion, cracks, and drainage effectiveness (Correct answer)
- The foundation's original construction cost documentation
- The color uniformity of the gravel fill
Correct answer: Settlement, erosion, cracks, and drainage effectiveness
Foundation inspections must assess settlement patterns, erosion, cracking, and whether drainage prevents water accumulation under the tank.
API 653 Inspection Planning 4
In API 653, what is the purpose of determining the 'corrosion allowance' during inspection planning?