API 510 Welding Inspection 4 — Questions and Answers
Question 1: Per API 510, a post weld heat treatment (PWHT) is performed to primarily achieve which metallurgical benefit in carbon steel welds?
- Increase the hardness of the heat-affected zone
- Relieve residual stresses and improve toughness (Correct answer)
- Eliminate all weld discontinuities
- Increase the tensile strength of the weld metal
Correct answer: Relieve residual stresses and improve toughness
PWHT in carbon steel welds primarily relieves residual welding stresses and improves the toughness and ductility of the heat-affected zone.
Question 2: An inspector reviewing NDE reports for a pressure vessel repair weld finds a linear indication reported by PT on the weld surface. Per acceptance criteria, linear indications are considered rejectable when they exceed:
- 3/16 inch (5 mm) in length
- 1/4 inch (6 mm) in length (Correct answer)
- 1/2 inch (13 mm) in length
- Any linear indication is automatically rejectable
Correct answer: 1/4 inch (6 mm) in length
Per ASME Section VIII Division 1, linear indications detected by PT or MT exceeding 1/4 inch (6 mm) in length are rejectable.
Question 3: During weld repair inspection, an inspector observes a high-low (hi-lo) misalignment at a butt weld joint. Per API 510 and ASME VIII, excessive hi-lo is primarily a concern because it:
- Makes radiographic interpretation more difficult
- Creates local bending stresses and stress concentrations at the joint (Correct answer)
- Requires automatic rejection of the joint
- Only affects weld aesthetics and is not a structural concern
Correct answer: Creates local bending stresses and stress concentrations at the joint
Excessive hi-lo misalignment creates local bending stresses and a stress concentration at the weld that can significantly reduce the fatigue life of the joint.
Question 4: Which of the following is an essential variable for a SMAW welding procedure under ASME Section IX that would require procedure requalification if changed?
- Changing the weld bead sequence
- Changing the electrode classification (e.g., E7018 to E6010) (Correct answer)
- Changing the welding position from flat to horizontal
- Changing the travel speed within the qualified range
Correct answer: Changing the electrode classification (e.g., E7018 to E6010)
A change in electrode classification (filler metal F-Number or A-Number) is an essential variable under ASME IX that requires requalification because it changes the deposited weld metal chemistry and properties.
Question 5: When inspecting a weld on an austenitic stainless steel pressure vessel, which NDE surface method should NOT be used as the primary method due to masking concerns?
- Liquid Penetrant Testing (PT)
- Magnetic Particle Testing (MT) (Correct answer)
- Visual Testing (VT)
- Eddy Current Testing (ET)
Correct answer: Magnetic Particle Testing (MT)
Austenitic stainless steel is non-ferromagnetic, making Magnetic Particle Testing (MT) ineffective and inappropriate for this material; PT or ET must be used instead.
Question 6: Per API 510, when welding repairs are made using temper bead welding technique, this technique is employed primarily to:
- Eliminate the need for a qualified WPS
- Provide post weld heat treatment in lieu of furnace PWHT by tempering the HAZ with subsequent weld beads (Correct answer)
- Allow unqualified welders to perform repairs
- Replace radiographic testing requirements
Correct answer: Provide post weld heat treatment in lieu of furnace PWHT by tempering the HAZ with subsequent weld beads
Temper bead welding uses subsequent weld beads to thermally treat and refine the heat-affected zone of previous beads, providing an alternative to furnace PWHT.
Question 7: A repair weld on a pressure vessel is rejected due to an unacceptable indication found by RT. After excavation and re-welding, what is the minimum NDE requirement per API 510?
- Visual inspection only is sufficient after re-weld
- The same NDE method that found the original indication must be repeated on the repair weld (Correct answer)
- Only a pressure test is required after repair
- MT is always required regardless of the original NDE method
Correct answer: The same NDE method that found the original indication must be repeated on the repair weld
The repair area must be re-examined using at least the same NDE method that originally identified the rejectable indication to confirm the repair is acceptable.
API 510 Welding Inspection 4
Per API 510, a post weld heat treatment (PWHT) is performed to primarily achieve which metallurgical benefit in carbon steel welds?