Pipeline Welding (API 1104): Girth Welds and Acceptance
What the candidate must understand
API 1104 covers welding of pipelines and related facilities, focusing on girth welds in transmission lines. Candidates should know the qualification of welding procedures, the qualification of welders and operators, and the acceptance standards for nondestructive testing. Understand the essential variables for procedure qualification, including pipe grade, diameter, wall thickness, filler, and position. Know the production welding requirements and the acceptance criteria for radiographic and other examinations, including the treatment of cracks, incomplete fusion, and porosity. Familiarity with the distinction between transmission and distribution work and the role of the company specification is useful.
Traps in questions
A frequent trap is assuming any crack is acceptable if small; under API 1104, cracks are generally rejectable. Another is confusing welder qualification ranges with procedure ranges. Watch for questions on whether a change in pipe diameter or wall thickness requires requalification, and on the difference between radiographic and ultrasonic acceptance. Answers that apply structural steel criteria are wrong.
Worked example / rule of thumb
Rule of thumb: cracks reject; size the rest against the standard. Worked example: a stem describes a girth weld with a small crack and asks for disposition. The correct answer is rejection and repair, not acceptance based on length, because the standard treats cracks as unacceptable regardless of size. For porosity, by contrast, acceptance depends on size and distribution per the standard.
Study approach
Study the qualification and acceptance clauses together, then compare procedure and performance ranges. Practice classifying defects as rejectable or size-dependent.