Visual Welding Inspection Fundamentals
What the visual inspector must control
Visual inspection is the most-used and least-forgiving NDT method: it happens before, during and after welding, and it either catches a defect or lets it enter the finished joint. A Level 1 inspector must know the discontinuities that are visible to the eye or a low-power aid: porosity, undercut, overlap, incomplete fusion, incomplete penetration, slag inclusion, spatter, arc strikes, cracks, excessive reinforcement and misalignment. Learn to separate discontinuity (any interruption in the joint) from defect (a discontinuity that exceeds the acceptance criteria of the applicable code).
Conditions that make a visual result valid
Lighting, access, cleanliness and angle of view decide whether a visual result means anything. Rule of thumb: illumination at the weld surface should be at least about 500 lux, with roughly 1000 lux recommended for detailed work, and the surface must be dry, clean and free of slag, spatter or paint that could mask indications. The viewing angle should be within about 30 degrees of perpendicular to the surface being examined, and the eye should be within roughly 600 mm (about 24 in) of the area. A common exam trap is a question that describes a perfect inspection technique but ignores lighting or access; the correct answer is usually that the examination is invalid.
Traps and worked example
Watch for questions that confuse a size limit with a type prohibition: some codes prohibit cracks outright regardless of length, whereas undercut is judged by depth and length. Also expect questions on when visual inspection must occur: root pass before capping, each layer where specified, and final. Worked example: a fillet weld leg measures 6 mm against a specified 8 mm; the size is under by 25 percent, so it fails regardless of how smooth the profile looks. Measure, compare to the drawing and the code, then record.
Recording what you see
Notes must identify the joint, location, size and type of each indication, plus the standard used. Never write "weld looks good"; write what was measured and against which criterion.