AWS Certified Welding Inspector — FundamentalsNondestructive Examination (NDE)Easy
A CWI is performing a visual inspection (VT) on a newly fabricated pressure vessel weld. The CWI observes a surface discontinuity that appears as an open, crater-like depression at the end of a weld bead. What type of discontinuity is this most likely to be?
- ACrater pipe
- BIncomplete fusion
- CUndercut
- DOverlap
Show answer & explanationAnswer & explanation
Correct answer: A. Crater pipe
A crater pipe is a common visual discontinuity found at the termination of a weld bead, characterized by a distinct depression. Undercut is a groove along the toe, overlap is excess metal over the base, and incomplete fusion is a subsurface condition not visible on the surface.
Why the other options are wrong
- B. Incomplete fusion is a discontinuity between the weld metal and the base metal or between adjacent layers of weld metal that is not visible on the surface.
- C. Undercut is a groove melted into the base metal adjacent to the toe or root of a weld and left unfilled by weld metal.
- D. Overlap is a weld bead that extends beyond the toe or root of the joint without fusing to the base metal.
Crater Pipe
A shrinkage cavity in a weld bead, typically occurring at the termination of the weld.
- Forms when the welding arc is broken too quickly.
- Appears as a circular or elongated depression.
- Can be a source of crack initiation.
Memory trick: Weld craters are like volcanic peaks, but inverted at the end.