API 510 Welding Inspection 2 — Questions and Answers
Question 1: According to API 510, which welding process is most commonly specified for pressure vessel repair welds due to its controllability and low hydrogen characteristics?
- Shielded Metal Arc Welding (SMAW)
- Gas Metal Arc Welding (GMAW)
- Submerged Arc Welding (SAW)
- Low-hydrogen SMAW or GTAW (Correct answer)
Correct answer: Low-hydrogen SMAW or GTAW
Low-hydrogen processes such as low-hydrogen SMAW electrodes or GTAW are preferred for pressure vessel repair to minimize hydrogen-induced cracking.
Question 2: When inspecting a completed repair weld on a pressure vessel, which surface examination method is preferred for detecting surface-breaking cracks in ferromagnetic materials?
- Liquid Penetrant Testing (PT)
- Magnetic Particle Testing (MT) (Correct answer)
- Visual Testing (VT)
- Eddy Current Testing (ET)
Correct answer: Magnetic Particle Testing (MT)
Magnetic Particle Testing (MT) is preferred for ferromagnetic materials because it detects both surface and near-surface discontinuities more reliably than PT.
Question 3: Per API 510, what is the minimum preheat temperature requirement primarily intended to prevent in weld repairs?
- Oxidation of the weld metal
- Hydrogen-induced cracking (Correct answer)
- Porosity from moisture
- Incomplete fusion
Correct answer: Hydrogen-induced cracking
Preheat requirements are primarily designed to slow the cooling rate and allow hydrogen to diffuse out, preventing hydrogen-induced cracking.
Question 4: A weld repair is made to a pressure vessel shell that originally required PWHT. Under API 510, what is generally required for the repair weld?
- PWHT is never required for repairs
- PWHT is required unless an alternative method is approved (Correct answer)
- PWHT is optional at the inspector's discretion
- PWHT is only required if the repair exceeds 6 inches in length
Correct answer: PWHT is required unless an alternative method is approved
API 510 generally requires that repair welds on vessels that originally required PWHT also receive PWHT, unless an engineering alternative is documented and approved.
Question 5: Which document must be prepared and approved BEFORE any welding repair work begins on a pressure vessel per API 510?
- A Weld Map
- A Repair Plan or Repair/Alteration document (Correct answer)
- A Material Test Report (MTR)
- A Hydrostatic Test Procedure
Correct answer: A Repair Plan or Repair/Alteration document
API 510 requires a documented repair plan or repair/alteration document to be prepared and approved by an Inspector before repair welding commences.
Question 6: When reviewing a Welding Procedure Specification (WPS) for a pressure vessel repair, the inspector should verify that the WPS is supported by a qualified:
- Welder Performance Qualification (WPQ) only
- Procedure Qualification Record (PQR) (Correct answer)
- Mill Test Report (MTR)
- Authorized Inspection Agency (AIA) approval letter
Correct answer: Procedure Qualification Record (PQR)
A WPS must be supported by a Procedure Qualification Record (PQR) that documents the test results used to qualify the welding procedure.
Question 7: During weld repair inspection, the inspector observes undercut along the toe of the weld. Per ASME Section VIII standards referenced by API 510, undercut is most concerning because it:
- Indicates improper electrode angle only
- Creates a stress concentration that can initiate fatigue cracking (Correct answer)
- Always requires immediate rejection regardless of depth
- Only affects the cosmetic appearance of the weld
Correct answer: Creates a stress concentration that can initiate fatigue cracking
Undercut creates a mechanical notch at the weld toe that acts as a stress concentration point and can initiate fatigue cracks under cyclic loading.
API 510 Welding Inspection 2
According to API 510, which welding process is most commonly specified for pressure vessel repair welds due to its controllability and low hydrogen characteristics?