API 653 Repair and Alteration 2 — Questions and Answers
Question 1: According to API 653, which organization must authorize a repair organization to perform repairs on aboveground storage tanks?
- The tank owner/operator (Correct answer)
- A National Board-authorized inspection organization
- The local fire marshal
- The original tank manufacturer
Correct answer: The tank owner/operator
API 653 requires the tank owner/operator to authorize repair organizations and ensure repairs meet the standard's requirements.
Question 2: When welding a flush-type cleanout fitting to a tank shell as a repair, what is the minimum shell plate thickness that must be maintained after the repair?
- The original nominal thickness minus any corrosion allowance
- The minimum thickness required for the design conditions per API 653 (Correct answer)
- 0.25 inches regardless of design pressure
- The thickness specified by the original construction standard
Correct answer: The minimum thickness required for the design conditions per API 653
API 653 requires that after any repair, the resulting wall thickness must meet the minimum thickness required for the current design conditions.
Question 3: A tank shell plate shows a horizontal crack. Per API 653, what is the preferred repair method?
- Grinding the crack flush and applying a weld overlay
- Removing the cracked plate section and installing a flush patch (Correct answer)
- Applying an external reinforcing plate over the crack
- Peening the crack edges to close the gap
Correct answer: Removing the cracked plate section and installing a flush patch
API 653 recommends removing cracked material entirely and replacing with a flush patch rather than attempting crack repairs that may not address root cause.
Question 4: What is the minimum overlap distance for a lap-welded shell repair patch per API 653?
- 1 inch
- 2 inches (Correct answer)
- 3 inches
- 4 inches
Correct answer: 2 inches
API 653 requires a minimum overlap of 2 inches (50 mm) for lap-welded repair patches on tank shells.
Question 5: Under API 653, an alteration to a storage tank that increases the maximum fill height requires which of the following?
- A re-rating calculation and engineer approval (Correct answer)
- Notification to the local fire department only
- A new API 650 nameplate
- Visual inspection only
Correct answer: A re-rating calculation and engineer approval
Increasing fill height is an alteration that requires engineering calculations to verify structural and design adequacy under API 653.
Question 6: When installing a new nozzle in a tank shell as a repair alteration, what additional reinforcement may be required per API 653?
- A reinforcing pad if the nozzle opening exceeds allowable limits (Correct answer)
- A full encirclement band around the shell
- External gussets welded to the nozzle neck
- A doubler plate on the inside of the tank only
Correct answer: A reinforcing pad if the nozzle opening exceeds allowable limits
API 653 requires reinforcing pads for nozzle openings that exceed the limits allowable by the tank shell thickness and design conditions.
Question 7: Which type of repair is specifically prohibited on tank shells operating above what API 653 considers a critical stress level without special engineering review?
- Hot tapping
- Flush patch installation
- Lap patch installation (Correct answer)
- Weld overlay repair
Correct answer: Lap patch installation
Lap patch installation is restricted or requires special engineering review on highly stressed shell areas due to the secondary stress introduced by the lap joint geometry.
API 653 Repair and Alteration 2
According to API 653, which organization must authorize a repair organization to perform repairs on aboveground storage tanks?