Piping Pipe Welding and Fabrication 2 — Questions and Answers
Question 1: What is the difference between a socket weld and a butt weld fitting?
- Socket welds use a fillet weld at the outside of the fitting; butt welds use a groove weld joining pipe ends directly (Correct answer)
- Socket welds require PWHT; butt welds do not
- Socket welds are used only on high-pressure lines; butt welds on low-pressure lines
- There is no structural difference between them
Correct answer: Socket welds use a fillet weld at the outside of the fitting; butt welds use a groove weld joining pipe ends directly
Socket weld fittings slip over the pipe end and are sealed with a fillet weld, while butt weld fittings are beveled to match the pipe end for a full-penetration groove weld.
Question 2: According to ASME B31.3, what is the standard gap (crevice) to be left when making a socket weld?
- No gap — pipe must be fully inserted
- Approximately 1/16 inch (1.6 mm) gap before making the weld (Correct answer)
- 1/4 inch (6.4 mm) gap for thermal expansion
- The gap is at the welder's discretion
Correct answer: Approximately 1/16 inch (1.6 mm) gap before making the weld
ASME B31.3 requires approximately 1/16 inch gap in socket welds to allow for thermal expansion of the pipe end during welding and operation.
Question 3: What nondestructive examination (NDE) method is specifically used to detect surface-breaking cracks in ferromagnetic pipe welds?
- Radiographic Testing (RT)
- Magnetic Particle Testing (MT) (Correct answer)
- Ultrasonic Testing (UT)
- Penetrant Testing (PT)
Correct answer: Magnetic Particle Testing (MT)
Magnetic Particle Testing (MT) detects surface and near-surface discontinuities in ferromagnetic materials by applying a magnetic field and iron particles.
Question 4: What is the purpose of a Procedure Qualification Record (PQR)?
- To certify a welder's skill level
- To document the test results that support and qualify a WPS (Correct answer)
- To record production weld inspection results
- To list approved filler metals for a project
Correct answer: To document the test results that support and qualify a WPS
The PQR records the actual welding variables used and the mechanical test results from a test weld, demonstrating that the WPS procedure produces acceptable welds.
Question 5: In pipe fabrication, what is 'spool' fabrication?
- Manufacturing pipe in long continuous lengths
- Pre-fabricating pipe assemblies (sections with fittings and flanges) in a shop for field installation (Correct answer)
- Coiling small-diameter tubing on reels for transport
- Wrapping pipe in protective material for shipping
Correct answer: Pre-fabricating pipe assemblies (sections with fittings and flanges) in a shop for field installation
Pipe spools are pre-fabricated assemblies made in controlled shop conditions, then transported to the field and connected by field welds, improving quality and efficiency.
Question 6: What is the purpose of radiographic testing (RT) on pipe welds?
- To measure the hardness of the weld metal
- To detect internal volumetric defects such as porosity, inclusions, and lack of fusion (Correct answer)
- To check the weld bead profile and appearance
- To verify the chemical composition of the filler metal
Correct answer: To detect internal volumetric defects such as porosity, inclusions, and lack of fusion
Radiographic testing uses X-rays or gamma rays to create images of the weld interior, revealing internal discontinuities that cannot be seen from the surface.
Piping Pipe Welding and Fabrication 2
What is the difference between a socket weld and a butt weld fitting?