EXC — Execution Class
The class (EXC1 to EXC4) that sets how strictly a welded steel structure must be made and proven — how much is inspected, at what NDT extent, and how much of the record is kept.
The execution class is chosen from the consequence of failure and the type of loading, and it drives everything downstream: welder and procedure qualification requirements, the extent of visual and volumetric NDT, and the depth of the documentation. EN 1090-2 ties the required welding quality level (ISO 3834 part) to the class — EXC1 to 3834-4, EXC2 to 3834-3, EXC3 and EXC4 to 3834-2.
The recurring mistake
Deciding the NDT extent job by job from memory. As the class rises the required coverage rises with it, and hand-picking the percentage is where inspection quietly drifts below what the class demands — a finding that should never have been a finding.