Part B: Practical
Part B is the hands-on practical exam, where the candidate applies inspection tools and acceptance criteria to a set of weld replicas and specimens. It tests the disciplined use of gauges, accurate measurement of weld features and discontinuities, and correct accept/reject decisions against a specimen book. Success depends on method and consistency rather than memorized facts.
The Specimen Book and Acceptance Criteria
The Part B specimen book (Book of Specifications) is the rulebook for the practical, containing the acceptance criteria, definitions, and requirements the inspector must apply. For each weld replica, the candidate measures the relevant feature and compares the result to the stated criteria to decide accept or reject. Because the criteria are provided, the challenge is applying them accurately and consistently, not recalling them. Reading the criteria carefully, including which weld type and condition they govern, prevents avoidable errors.
Inspection Gauges and Replicas
Inspectors use a family of gauges to convert visual observations into measured values. Fillet weld gauges check leg size and whether the profile is convex or concave; other gauges measure reinforcement height, undercut depth, and misalignment. Weld measuring gauge sets and replicas provide standardized reference dimensions for direct comparison. Selecting the correct, undamaged gauge for the feature being measured is essential, because a wrong or bent tool yields invalid readings and bad decisions.
Measuring and Judging Discontinuities
The heart of Part B is measuring discontinuities such as undercut, porosity, overlap, and reinforcement, then comparing each to its allowable limit. A discontinuity that measures at or below the maximum allowable value conforms and is accepted; it becomes a rejectable defect only when it exceeds the limit. Inspectors must work under adequate lighting, measure each specimen individually rather than sampling, and never alter the weld to fit a tool. This disciplined, criteria-based approach produces repeatable, defensible results.
Limits of Visual Inspection
Part B is fundamentally a visual inspection exercise, so candidates must know what the eye and gauges can and cannot reveal. Surface-breaking cracks, undercut, overlap, weld size, and profile are all detectable visually. Internal flaws such as buried slag, subsurface lack of fusion, or dissolved gases are not visible and would require volumetric NDT like RT or UT. Respecting these limits keeps the inspector from claiming more than the visual evidence supports and reinforces honest reporting.