CWI Welding Inspector Certification: Part B Visual Exam Breakdown
Pass the AWS CWI Part B visual exam with this complete breakdown of weld inspection criteria, tools, discontinuities, and the most-missed acceptance tests.
What the CWI Part B Visual Exam Actually Tests
Part B is a timed, hands-on practical examination. Candidates receive a set of weld specimens — typically fillet welds, groove welds, or both — and must evaluate them against the applicable acceptance criteria. The exam is closed-book, which means you cannot reference AWS D1.1 or any other code during the test. It evaluates three core competencies: weld discontinuity identification (you need to recognize and correctly categorize common discontinuities including porosity, undercut, overlap, cracks, incomplete fusion, and surface irregularities), dimensional measurement (using fillet weld gauges, the Bridgecam gauge, the Hi-Lo gauge, and scale rules accurately), and accept/reject judgment (applying the correct acceptance criteria to make a final call).
The Most Common Weld Discontinuities Tested — and Where Candidates Miss
Undercut is the most commonly missed measurement call. Many candidates identify undercut correctly but misjudge its depth. AWS D1.1 allows undercut up to 1/32 inch (0.8 mm) for most structural applications. Porosity trips candidates who don't distinguish between individual, cluster, and piping porosity — cluster porosity is often held to stricter limits. Overlap is often confused with excessive convexity: overlap is weld metal that rolls over the base metal without fusing (a reject on virtually every code), while convexity is acceptable within limits based on fillet leg size. Cracks of any length are reject conditions under AWS D1.1 without exception — don't try to categorize or measure them. Weld profile issues require knowing the convexity limit formula: 1/8 inch plus 0.07 × fillet leg size, rounded to the nearest 1/16 inch.
Tools You Must Know Cold Before Part B
You are permitted to bring specific inspection tools into the Part B exam. Fillet weld gauges (set of 6–10) are go/no-go gauges for measuring fillet weld leg size and throat. The Bridgecam gauge is the most important multi-function tool: it measures undercut depth, weld reinforcement, hi-lo root opening alignment, and fillet leg dimensions. Practice until you can read it accurately in under 10 seconds per measurement. The Hi-Lo gauge measures root opening and root face mismatch in joint fit-up. Bring a 6-inch scale rule for general linear measurements. Practice with physical tools before the exam — not just photos or videos. Tactile repetition builds the muscle memory you need when you're nervous and on a clock.
Common Mistakes That Cost Candidates Their CWI Score
Going too fast produces sloppy measurements. Budget roughly 2–3 minutes per specimen and use remaining time to re-check calls you weren't confident about. Skipping the full surface scan is another costly mistake — candidates who lock onto the first discontinuity they see often miss a second issue on the same specimen. Develop a systematic scan pattern (left to right, start of weld to crater, face to toe to root) and stick to it. Confusing inspection criteria across codes is also a frequent error: Part B uses a specific code scenario, so read the setup instructions carefully. Applying D1.1 criteria to a scenario governed by D1.3 or D1.5 is an automatic error. Finally, under-practicing with actual weld samples has no shortcut — purchase CWI practice weld specimen kits or arrange lab time through your local AWS Section.
How many specimens are in the CWI Part B exam?
The number of specimens can vary by exam administration, but candidates typically evaluate between 5 and 10 weld samples. Each sample may require multiple measurements and accept/reject determinations. AWS does not publish the exact specimen count in advance.
Can I bring my own inspection tools to the CWI Part B exam?
Yes. Candidates are responsible for bringing their own inspection tools, including fillet weld gauges, a Bridgecam gauge, and a scale rule. AWS publishes the approved tool list in the CWI candidate handbook — review it before your exam date and bring everything on the list, even tools you think you won't need.
What is the minimum passing score for CWI Part B?
Candidates must score at least 72% on each of the three parts (A, B, and C) to earn the CWI credential. A high score on Part A or Part C does not compensate for a failing score on Part B — each part must be passed independently.