API 510 Repair and Alteration 3 — Questions and Answers
Question 1: When performing a weld overlay repair on a corroded vessel shell, the minimum thickness after repair must meet:
- The original nominal thickness
- The required minimum thickness per applicable code (Correct answer)
- 75% of the original wall thickness
- The thickness specified by the repair organization
Correct answer: The required minimum thickness per applicable code
Post-repair thickness must meet or exceed the calculated minimum required thickness per the applicable code, not necessarily the original nominal thickness.
Question 2: Under API 510, a pressure vessel alteration that increases the maximum allowable working pressure (MAWP) must be reviewed by:
- The repair organization's QC manager
- A pressure vessel engineer with expertise in vessel design (Correct answer)
- The original vessel manufacturer
- Only the authorized inspector
Correct answer: A pressure vessel engineer with expertise in vessel design
Alterations that affect the MAWP require engineering review by a qualified pressure vessel engineer to ensure the vessel can safely handle the new conditions.
Question 3: Hot tapping on a pressure vessel in service is considered:
- A standard maintenance activity
- An alteration requiring engineering review and inspector approval (Correct answer)
- Prohibited under all circumstances by API 510
- A repair if the vessel is not depressurized
Correct answer: An alteration requiring engineering review and inspector approval
Hot tapping is an alteration that requires engineering review for integrity and must be approved by the authorized inspector before proceeding.
Question 4: When is a pressure test required after completing a repair on a pressure vessel?
- After every repair regardless of scope
- When the repair involves welding that penetrates the pressure boundary (Correct answer)
- Only when PWHT is also performed
- Only for vessels above 300 psi MAWP
Correct answer: When the repair involves welding that penetrates the pressure boundary
API 510 requires a pressure test after repairs that penetrate the pressure boundary to verify the integrity of the weld repair.
Question 5: A vessel with a P-1 carbon steel shell requires PWHT after repair welding when the repair weld exceeds which thickness threshold per ASME Section VIII Div. 1?
- 1/4 inch (6 mm)
- 1/2 inch (13 mm) (Correct answer)
- 3/4 inch (19 mm)
- 1 inch (25 mm)
Correct answer: 1/2 inch (13 mm)
ASME Section VIII Div. 1 requires PWHT for P-1 carbon steel welds exceeding 1/2 inch (13 mm) thickness under most conditions.
Question 6: An insert plate repair used to replace a corroded section of a vessel shell must have:
- Only fillet welds connecting it to the existing shell
- Full penetration welds on all seams connecting it to the shell (Correct answer)
- A minimum of four corner attachment welds
- Plug welds at regular intervals across the patch
Correct answer: Full penetration welds on all seams connecting it to the shell
Insert plate repairs must use full penetration welds on all connecting seams to maintain full shell integrity equivalent to original construction.
Question 7: When a repair is made on a vessel without performing the normally required post-weld heat treatment, which alternative method is acceptable per API 510?
- Doubling the NDT inspection frequency
- Using a temper bead welding technique with appropriate documentation (Correct answer)
- Increasing the safety factor by reducing the MAWP by 10%
- Performing a hydrostatic test at 2.5 times MAWP
Correct answer: Using a temper bead welding technique with appropriate documentation
The temper bead welding technique can substitute for PWHT in specific cases when approved by the authorized inspector and engineering review.
API 510 Repair and Alteration 3
When performing a weld overlay repair on a corroded vessel shell, the minimum thickness after repair must meet: