Pipefitter Welding and Joining Techniques 5 — Questions and Answers
Question 1: When qualifying a welding procedure specification (WPS) under ASME Section IX, changing the base metal P-Number typically requires:
- Updating the WPS document only
- Requalification of the procedure with a new PQR (Correct answer)
- Notifying the owner in writing
- Increasing the preheat temperature by 50°F
Correct answer: Requalification of the procedure with a new PQR
Under ASME Section IX, a change in base metal P-Number is an essential variable that requires requalification of the welding procedure through a new Procedure Qualification Record (PQR).
Question 2: In GTAW (TIG) pipe welding, the high-frequency arc start is preferred over scratch start primarily because:
- It produces higher amperage output
- It prevents tungsten contamination of the weld pool (Correct answer)
- It increases travel speed
- It eliminates the need for shielding gas
Correct answer: It prevents tungsten contamination of the weld pool
High-frequency arc starting allows the arc to initiate without touching the tungsten to the base metal, preventing tungsten inclusions in the weld and preserving electrode geometry.
Question 3: What is the correct root opening (gap) typically used when fitting up Schedule 40 carbon steel pipe for SMAW butt welding without a backing ring?
- 0 inches (tight fit)
- 1/16 to 3/32 inch (Correct answer)
- 3/16 to 1/4 inch
- 5/16 to 3/8 inch
Correct answer: 1/16 to 3/32 inch
A root opening of 1/16 to 3/32 inch allows full penetration of the root pass in open-root SMAW pipe welding without excessive burn-through.
Question 4: During pipe welding inspection, a 'hi-lo' gauge is used to measure:
- The temperature differential across the weld joint
- The mismatch (internal misalignment) between pipe ends (Correct answer)
- The width of the weld bead crown
- The hardness of the heat-affected zone
Correct answer: The mismatch (internal misalignment) between pipe ends
A hi-lo gauge measures the internal offset between two pipe ends being joined; excessive hi-lo creates stress concentrations and is limited by welding codes.
Question 5: Which NDE method is most effective for detecting lack-of-fusion defects in a pipe weld that is inaccessible from the inside?
- Magnetic particle testing (MT)
- Liquid penetrant testing (PT)
- Phased array ultrasonic testing (PAUT) (Correct answer)
- Visual examination (VT)
Correct answer: Phased array ultrasonic testing (PAUT)
Phased array ultrasonic testing (PAUT) can detect internal volumetric defects including lack of fusion from the pipe's outer surface without requiring internal access.
Question 6: When making a socket weld connection, AWS D10.11 recommends that the pipe be inserted into the fitting and then pulled back approximately:
- Flush with the bottom of the socket
- 1/16 inch before welding (Correct answer)
- 1/4 inch before welding
- 1/2 inch before welding
Correct answer: 1/16 inch before welding
Pulling the pipe back 1/16 inch from the socket bottom allows for thermal expansion during welding and prevents crevice corrosion from a zero-gap fit.
Question 7: What is the maximum allowable undercut depth on a completed pipe weld per most ASME B31.3 process piping requirements?
- 1/64 inch or 10% of wall thickness, whichever is less
- 1/32 inch or 10% of wall thickness, whichever is less (Correct answer)
- 1/16 inch or 12.5% of wall thickness, whichever is less
- No undercut is permissible under any circumstances
Correct answer: 1/32 inch or 10% of wall thickness, whichever is less
ASME B31.3 limits undercut to 1/32 inch or 10% of the nominal wall thickness, whichever is less, to preserve the structural integrity of the pipe wall.
Pipefitter Welding and Joining Techniques 5
When qualifying a welding procedure specification (WPS) under ASME Section IX, changing the base metal P-Number typically requires: