API 510 API 510 Welding Procedures and Qualifications 2 — Questions and Answers
Question 1: What is the primary purpose of post-weld heat treatment (PWHT) in pressure vessel repairs?
- Stress relief and improved resistance to stress corrosion cracking (Correct answer)
- Increasing hardness of the weld
- Eliminating the need for radiographic testing
- Satisfying hydrostatic test requirements
Correct answer: Stress relief and improved resistance to stress corrosion cracking
PWHT is primarily performed to relieve residual welding stresses and improve resistance to stress corrosion cracking and hydrogen embrittlement.
Question 2: According to ASME Section VIII Div. 1, PWHT is mandatory for carbon steel welds when the nominal thickness of the base metal exceeds what value?
- 1-1/2 inches (38 mm) (Correct answer)
- 1 inch (25 mm)
- 2 inches (51 mm)
- 3/4 inch (19 mm)
Correct answer: 1-1/2 inches (38 mm)
ASME Section VIII Div. 1 requires mandatory PWHT for P-1 carbon steel when base metal thickness exceeds 1-1/2 inches.
Question 3: Which type of weld joint is used when only one side of a pressure vessel shell is accessible for repair welding?
- Single-welded butt joint with backing strip (Correct answer)
- Double-welded butt joint
- Full penetration groove weld from both sides
- Fillet weld only
Correct answer: Single-welded butt joint with backing strip
When access is limited to one side, a single-welded butt joint with a backing strip is commonly used to achieve full penetration and adequate root quality.
Question 4: Under API 510, an authorized inspector must review and accept which document before repair welding begins on a pressure vessel?
- The repair plan and applicable WPS/PQR (Correct answer)
- The insurance renewal certificate
- The vessel's original hydrostatic test record only
- The welder's employment contract
Correct answer: The repair plan and applicable WPS/PQR
The authorized inspector must review and accept the repair plan and applicable Welding Procedure Specifications (WPS) and Procedure Qualification Records (PQR) prior to commencing repair work.
Question 5: When performing a temper bead welding technique, what is its primary advantage over conventional PWHT?
- It refines the heat-affected zone grain structure without furnace PWHT (Correct answer)
- It eliminates the need for filler metal qualification
- It reduces weld hardness by increasing heat input only
- It avoids the need for a WPS
Correct answer: It refines the heat-affected zone grain structure without furnace PWHT
Temper bead welding uses controlled deposition of successive weld beads to refine and temper the heat-affected zone, achieving stress relief without furnace PWHT.
Question 6: A change in base metal P-number is considered what type of variable in ASME Section IX welding procedure qualification?
- Essential variable (Correct answer)
- Supplementary essential variable
- Non-essential variable
- Informational variable
Correct answer: Essential variable
A change in base metal P-number is an essential variable requiring requalification of the welding procedure because it affects the metallurgical properties of the weld.
API 510 API 510 Welding Procedures and Qualifications 2
What is the primary purpose of post-weld heat treatment (PWHT) in pressure vessel repairs?