CWI Part B Exam Study Guide (2026)
Everything the AWS CWI Part B Practical Exam (Certified Welding Inspector) tests, topic by topic: what each section covers, the facts that come up most, and how to study it. Pair it with the free 15-question practice test.
The exam at a glance
| Questions | 46 questions on hands-on tasks with plastic weld replicas, inspection tools and a Book of Exhibits |
|---|---|
| Time | 120 minutes |
| Passing score | 72% on Part B (each of Parts A, B and C must be passed at 72%) |
| Format | Open book: the Part B Book of Specifications (2017) is provided, paper-based |
| Certifying body | American Welding Society (AWS) |
| Test provider | AWS-authorized exam sites (paper-based, usually at the end of an AWS seminar week) |
Mind map: the whole exam on one screen
Read the complete CWI Part B study notes for “Inspection Tools and Dimensional Tolerances”
Our first full set of comprehensive notes, about 15 minutes of reading: What you'll be given · What each tool is for · Decimal and fractional tolerances · Weld length, spacing and size · Shall, should and may, a worked exam example, the traps examiners use and a one-minute recap. Create a free account to read it and see how premium notes work before you decide.
1. Inspection Tools and Dimensional Tolerances
The Part B kit and the general rules of the Book of Specifications (Clause 1): which gauge measures what, how tolerances work, and the meaning of shall, should and may.
Key facts
- The kit includes fillet weld gauges, a V-WAC gauge, a dial caliper, a ruler, the C4.1 surface roughness gauge, a protractor, a hi-lo gauge, a magnifying glass, a mirror and a flashlight.
- You work on a four-piece plastic replica set: T-joint, groove, bend and pipe specimens. Ignore pinholes, seams, glue and color variations.
- Decimal tolerances (1.3.1): X.X ±0.1, X.XX ±0.01, X.XXX ±0.005.
- Fractional tolerances (1.3.2): whole numbers over 6 in. ±1/8; 1 to 6 in. ±1/16; 1/16 to under 1 in. ±1/32; 1/32 to under 1/16 in. ±1/64.
- Tolerances do not apply to test specimens, Annex IV or discontinuity limits. Fillet weld size is a minimum with no tolerance (2.4.2).
- Shall is mandatory, should is a beneficial non-mandatory practice, may means a choice of options (1.1.6).
- Calculations, formulas, definitions and material properties come from the BOS annexes (1.1.5).
Flashcards
Exam tip: Learn to zero every instrument before exam day. The BOS says you are expected to know how to use each tool in the kit.
2. Structural Steel Acceptance Criteria
BOS Clause 2 and Tables 1 to 3: base metal preparation, weld terminations, visual acceptance criteria and profile schedules for structural steel.
Key facts
- Mill-induced discontinuities (2.1.1): 1 in. or less needs no repair; over 1 in. with depth up to 1/8 in. needs no repair but explore depth; over 1/8 to 1/4 in. remove and repair; over 1/4 in. refer to the Engineer.
- Weld edge prep roughness (2.2.1): manual and semiautomatic not rougher than Sample 3, no gouges deeper than 1/16 in.; SAW not rougher than Sample 3, no gouges.
- Fillet weld terminations (2.2.4): statically loaded, hold back at least the weld size or wrap 2 to 4 times the weld size. Cyclically loaded, wrap 2 to 4 times the weld size.
- Table 1: no cracks; thorough fusion; craters filled; undersized fillets may be less than nominal by 1/16 in. (L ≤ 3/16), 3/32 in. (L = 1/4) or 1/8 in. (L ≥ 5/16).
- Table 1 undercut: material under 1 in., 1/32 in. maximum; 1 in. or more, 1/16 in. maximum. Primary members transverse to tensile stress, 0.01 in.; other primary-member cases, 1/32 in.
- Time of inspection: A514, A517 and A709 Grade 100/100W need inspection at least 48 hours after welding.
- Schedule A reinforcement (Table 3): up to 1 in., 1/16 in.; over 1 to 2 in., 1/8 in.; over 2 in., 3/16 in. Schedule B convexity: width up to 5/16 in., 1/16 in.; over 5/16 and under 1 in., 1/8 in.; 1 in. and over, 3/16 in.
Flashcards
Exam tip: Find your column first in Table 1 (statically loaded, cyclically loaded or tubular), then read across. Many wrong answers come from the wrong column.
3. Pipeline Acceptance Criteria
BOS Clause 3: workmanship and the visual acceptance limits for pipeline welds, including inadequate penetration, burn-through, porosity and undercut.
Key facts
- Offset (3.1.3): 1/8 in. maximum for same nominal thickness.
- Crown (3.1.4): not below the pipe surface and not more than 1/16 in. above the parent metal.
- IP (3.2.1): a defect if a single indication exceeds 1 in., the aggregate in any 12 in. exceeds 1 in., or the aggregate exceeds 8% of a weld shorter than 12 in.
- IPD (3.2.2): a defect if a single indication exceeds 2 in. or the aggregate in 12 in. exceeds 3 in.
- BT (3.2.4): a defect if the maximum dimension exceeds 1/4 in., or the sum exceeds 1/2 in. in 12 in. or the total weld length, whichever is less.
- Porosity (3.2.5): a defect if a pore exceeds 1/8 in. or 25% of the thinner nominal wall. Cluster porosity in the finish pass is a defect above 1/2 in. in diameter or 1/2 in. aggregate in 12 in.
- Undercut (Table 4): over 1/32 in. or 12.5% of wall is not acceptable; over 1/64 to 1/32 in. or over 6% to 12.5% is limited to 2 in. in 12 in. or one-sixth the weld length, whichever is smaller; 1/64 in. or 6% or less is acceptable.
Flashcards
Exam tip: Two limits often apply together, as with porosity. Work out both and use the smaller. The trap answer is the one that passes only the first test.
Test yourself on these topics
Take the free 15-question CWI Part B test, then save your results to unlock your Readiness Score and the mistakes bank.
4. Pressure Piping Acceptance Criteria
BOS Clause 4: workmanship, repairs and the visual acceptance limits for pressure piping welds, including reinforcement in Table 5.
Key facts
- Internal misalignment (4.1.1): 1/16 in. maximum. Internal trimming is preferred, keeping minimum allowable thickness and a contour change no more than 30°.
- Cracks, lack of fusion and incomplete penetration are unacceptable (4.2).
Flashcards
Exam tip: Pipeline and pressure piping use different numbers for the same words. Check which clause the question names before you look at the limit.
5. WPS and PQR Review
BOS Clause 5: reading a WPS and PQR from the Book of Exhibits, the qualification variables in Table 8, and the thickness limits in Table 7.
Key facts
- A change in a qualification variable requires a new or revised WPS and a new PQR. Other changes need only a revised WPS (5.2).
- Table 7 test weldment thickness: 1/16 to 3/8 in. qualifies 1/16 in. to 2T; over 3/8 and under 3/4 in. qualifies 3/16 in. to 2T; 3/4 to under 1-1/2 in. qualifies 3/16 in. to 2T; 1-1/2 to under 6 in. qualifies 3/16 in. to 8 in.
Flashcards
Exam tip: Set the WPS beside the PQR and compare line by line against Table 8. You are looking for a change the WPS made that the PQR doesn't support.
6. Welder Performance Qualification
BOS Clause 6: what a welder's test qualifies, the variables that force requalification, position limits in Table 15 and visual acceptance of test weldments.
Key facts
- Qualification on a CJP groove also qualifies PJP groove and fillet welds (6.1.4).
- Requalification variables (6.2) include process (GMAW spray and gas-shielded FCAW cross-qualify), deletion of backing, F-Number, position, vertical progression and GTAW current type or polarity.
Flashcards
Exam tip: On a WQTR question, list the test welder's position and process first, then apply Table 15 and 6.2 in that order. Most errors come from skipping a variable.
7. Mechanical Tests and NDE Exhibits
Mechanical test criteria from BOS Clause 5 and reading photographs of NDE results in the Book of Exhibits. AWS's test specification gives each of mechanical tests and NDE at least 8% of the exam.
Key facts
- Structural bend test (5.4.2.1): no surface discontinuity over 1/8 in. in any direction; the sum of those over 1/32 in. and up to 1/8 in. must not exceed 3/8 in.; corner cracks up to 1/4 in.
- Corner cracks over 1/4 in. with no slag or fusion defect: disregard the specimen and test a replacement.
Flashcards
Exam tip: On bend test questions, sort the indications by size first: anything over 1/8 in. fails it outright, then add up the rest.
How to pass
- The Book of Specifications is free to download from aws.org. Read it cover to cover before exam day: every answer comes from it, not from D1.1 or API 1104 memory.
- 46 questions in 120 minutes is about 2.5 minutes each, but measuring replicas takes time. Answer the document questions (WPS, PQR, welder qualification) quickly to save minutes for the gauges.
- Know your tools: fillet weld gauges, the V-WAC gauge, dial caliper, hi-lo gauge and the AWS C4.1 roughness gauge, including how to zero them.
- Watch which clause applies. Structural, pipeline and pressure piping each have their own acceptance criteria, and the numbers differ (pipeline offset 1/8 in., pressure piping misalignment 1/16 in.).
Frequently asked questions
How long should I study for the CWI Part B exam?
Most working candidates need 4 to 8 weeks at 45 to 60 minutes a day. Book your exam once your Readiness Score has stayed at 80 or higher for about a week.
Can I take the CWI Part B exam online?
AWS delivers Parts A and C on computer at Prometric test centers and Part B on paper at AWS-authorized exam sites. Its current guides don't describe remote proctoring. Format: open book: the part b book of specifications (2017) is provided, paper-based. Check aws.org for updates.
What score do I need to pass the CWI Part B exam?
72% on Part B (each of Parts A, B and C must be passed at 72%). The exam has 46 questions on hands-on tasks with plastic weld replicas, inspection tools and a book of exhibits and a time limit of 120 minutes.
What are the most tested topics?
The outline covers inspection tools and dimensional tolerances, structural steel acceptance criteria, pipeline acceptance criteria, pressure piping acceptance criteria, wps and pqr review, welder performance qualification, mechanical tests and nde exhibits. Use the free practice test to see which ones you need most.
The premium CWI Part B study path
Premium CWI Part B prep is studied one topic at a time. Each step starts with that topic's key notes and flashcard deck, then its own question sets of 25, so you master one topic before you move to the next. When every topic is strong, the 6 full mock exams show you're ready.
Your step-by-step study path
- 1Inspection Tools and Dimensional Tolerances9 key notes, 115 flashcards, then 450 practice questions in 18 sets of 25Notes free with an account
- 2Structural Steel Acceptance Criteria9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25Premium
- 3Pipeline Acceptance Criteria9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25Premium
- 4Pressure Piping Acceptance Criteria9 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25Premium
- 5WPS and PQR Review8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25Premium
- 6Welder Performance Qualification8 key notes, 115 flashcards, then 425 practice questions in 17 sets of 25Premium
- 7Mechanical Tests and NDE Exhibits8 key notes, 110 flashcards, then 425 practice questions in 17 sets of 25Premium
- Final step: 6 full mock exams50 questions each, timed like test day. Pass them, then book your exam.Premium
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Summarized from AWS's official candidate information and the rules cited, checked October 2026. Confirm current requirements with American Welding Society (AWS).