- What This Cheat Sheet Covers (and What It Doesn't)
- Exam Snapshot: The Facts You Can Rely On
- The Reference Stack You Must Know
- The Nine Headings at a Glance
- Deterioration Mechanisms: The Recognition List
- Calculation Quick-Reference
- NDE and Pressure Tests Side by Side
- Relief Devices and Controls: Inspector Checklist
- Installation: What the Inspector Verifies
- Sequencing Your Review by Heading
- Where NBII Holders Work
- Frequently Asked Questions
- The NBII content outline is NB-331-IS Revision 7, organized into nine detailed headings with no published percentage weights.
- The exam is 85 questions administered in one day; confirm the timer, fee and pass mark with the National Board directly.
- Required references include NBIC Parts 1, 2 and 3 context, RCI-1/NB-263, ASME Sections I, IV and VIII Division 1, B31.1 and CSD-1.
- Deterioration, code calculations and relief devices reward memorized formulas and mechanism names, so build a personal one-page sheet for each.
What This Cheat Sheet Covers (and What It Doesn't)
This page condenses the National Board Inservice Inspector Commission (NBII) outline into a single scannable review. It is built from the issuer's own body-of-knowledge document, NB-331-IS Revision 7, which is the authoritative list of what a candidate can be tested on. If you want the long-form walk-through of each area, our complete guide to all 9 NBII content areas goes deeper; this sheet is the fast refresher you reread in the final days.
One honest limitation up front: the issuer does not publish percentage weights for the nine headings, so no cheat sheet can legitimately tell you "Domain 5 is X percent of the exam." Anything claiming otherwise is guessing. Use this sheet to confirm you can recall the content under every heading, not to gamble on which ones to skip.
Exam Snapshot: The Facts You Can Rely On
Here is what the issuer's examination information confirms, and, just as important, what remains unverified in the sources we rely on.
| Item | What Is Confirmed |
|---|---|
| Governing body | The National Board of Boiler and Pressure Vessel Inspectors |
| Content outline | NB-331-IS Revision 7 (hosted as NB-331I), nine detailed headings |
| Question count | 85 questions |
| Administration | Completed in one day |
| Domain weights | Not published |
| Exact timer, current fee, pass mark | Unverified here; confirm with the National Board before scheduling |
Notice the caution on timing. The issuer says the exam is administered in one day, but that does not tell you the length of the clock, so do not assume a specific number of hours. For the practical questions of cost, scoring and scheduling, see our breakdowns of NBII certification cost, the NBII passing score and NBII exam dates and scheduling, and verify every figure with the National Board's current published information.
The Reference Stack You Must Know
The outline names the documents that the questions draw on. An NBII candidate is effectively being tested on how well they can work between these sources, so know which book answers which kind of question.
- NBIC Part 1: installation requirements, including jurisdictional considerations.
- NBIC Part 2: inservice inspection, including internal and external inspections and inspection practices.
- NBIC Part 3: repairs and alterations, including welding-related methods.
- RCI-1 / NB-263: the required reference for the credential's rules and procedures.
- ASME Section I: power boilers.
- ASME Section IV: heating boilers.
- ASME Section VIII, Division 1: pressure vessels.
- ASME B31.1: power piping.
- CSD-1: controls and safety devices for automatically fired boilers.
The Nine Headings at a Glance
These are the nine headings in the issuer's outline, in the issuer's order, with the high-value items under each.
Domain 1: Inservice Inspection
The heart of the commission: how an inspector actually examines equipment in service.
- NBIC Part 2 internal and external inspections
- Safety and confined-space entry
- Venting and fuel supply
- Deterioration and hazards found during inspection
- NBIC Part 3 repair and alteration methods, including welding
Domain 2: Boiler and Pressure Vessel Types and Terminology
Vocabulary is a scoring tool. Identify the types of boilers and vessels and name their parts correctly, because later questions assume you already speak the language.
Domain 3: Conditions Causing Deterioration or Failures
Covered in detail in the next section because it is the longest list on the outline.
Domain 4: Installation
NBIC Part 1 and jurisdictional requirements across steam and hot-water heating boilers, hot-water supply boilers, potable-water heaters, vessels, piping, welding, venting and fuel systems.
Domain 5: Code Calculations
Thickness and pressure math plus remaining-life reasoning, detailed below.
Domain 6: Nondestructive Examination
Requirements and principles for radiography, ultrasonic, magnetic-particle, liquid-penetrant and visual examinations.
Domain 7: Pressure Testing
Liquid, pneumatic, initial-service leak and vacuum tests.
Domain 8: Pressure Relief Devices
Application, limitations, sizing, set pressures, failure causes, inspection and test procedures.
Domain 9: Controls and Safety Devices
Fuel, waterside and fireside controls, limit switches, device types and level indicators.
Deterioration Mechanisms: The Recognition List
Domain 3 is where a memorized checklist pays off, because the outline names the specific mechanisms. Be able to recognize each by cause and appearance, not just by name.
Corrosion forms named in the outline
- Uniform corrosion
- Galvanic corrosion
- Erosion
- Crevice corrosion
- Pitting
- Line corrosion
- Exfoliation
- Selective leaching
- Grooving
- Stress-corrosion cracking
Other damage and degradation mechanisms
- Chemical attack
- Creep
- Fatigue
- Fracture
- Thermal aging
Assessment concepts that go with them
- Corrosion rate and averaging of metal loss
- Local metal loss
- Weld joint efficiency
- Corrosion in the central portions of formed heads
- Remaining life
Key Takeaway
For each mechanism, prepare a three-part card: what causes it, where in a boiler or vessel you would expect to find it, and what the inspector would see or measure. The assessment concepts (rate, averaging, weld joint efficiency, remaining life) connect straight into Domain 5, so study them together.
Calculation Quick-Reference
Domain 5 is where candidates either gain or lose steady points. The outline specifies the categories; the exact formulas come from the code books you are expected to know, so memorize them from those sources rather than from a third-party sheet.
- Minimum thickness and MAWP for tubing, piping, drums, shells, headers and heads.
- MAWP differences between a vessel and its components, the weakest-component idea.
- Static head and total pressure considerations.
- Metal loss and averaging to evaluate corrosion.
- Corrosion rates and remaining service life.
- Inspection intervals derived from remaining life.
NDE and Pressure Tests Side by Side
Domains 6 and 7 are compact and highly memorizable, which makes them good places to bank points.
| Topic | Items to Know |
|---|---|
| Radiography | Requirements and principles per the outline |
| Ultrasonic | Requirements and principles per the outline |
| Magnetic particle | Requirements and principles per the outline |
| Liquid penetrant | Requirements and principles per the outline |
| Visual examination | Requirements and principles per the outline |
| Liquid pressure test | Purpose, conditions, safety considerations |
| Pneumatic pressure test | Purpose, conditions, added hazards of stored gas energy |
| Initial-service leak test | When and why it is used |
| Vacuum test | Where it applies and what it demonstrates |
For each NDE method, be ready to answer three things: what the method physically relies on, what kinds of flaws it is suited to find (surface versus subsurface), and what its limitations are. For each pressure test, know when it is chosen over the alternatives and what makes it more or less hazardous.
Relief Devices and Controls: Inspector Checklist
Domains 8 and 9 are safety-critical, and the outline's wording suggests the questions are practical rather than purely theoretical.
Pressure Relief Devices (Domain 8)
Know why the device exists, how it is chosen, and how it is checked.
- Application and limitations of each device type
- Pressure and capacity sizing
- Set pressures and permitted deviations
- Causes of poor performance
- Reasons for inspection and how often
- Inspection and test procedures
- Maintenance safety
Controls and Safety Devices (Domain 9)
Trace the logic from fuel to flame to water level.
- Fuel controls
- Waterside controls
- Fireside controls
- Limit switches and device types
- Level indicators
Installation: What the Inspector Verifies
Domain 4 spans many equipment types, so organize it by checkpoint rather than by boiler category.
- Equipment covered: steam and hot-water heating boilers, hot-water supply boilers, potable-water heaters and vessels.
- Systems: piping, welding, venting and fuel systems.
- Source and discharge requirements: particularly for power and heating boilers.
- Operating systems: controls, gages and relief devices on the installed unit.
- Governing rules: NBIC Part 1 together with jurisdictional requirements, so remember that the local jurisdiction can add to the base code.
The overlap with Domains 8 and 9 is intentional. An installation question may be answered by recalling a relief-device or controls fact, so review these three headings together.
Sequencing Your Review by Heading
This is the one study-method section on the page, and it is tied to the outline rather than to generic advice. Because no weights are published, spread effort across all nine headings, but order them so concepts build on each other.
Vocabulary and Foundations
- Domain 2 types and terminology so every later question reads clearly
- Domain 1 inspection basics and confined-space safety
Failure and Math
- Domain 3 mechanism cards
- Domain 5 formulas, starting with thickness, MAWP and corrosion rate
Examination and Testing
- Domain 6 NDE methods
- Domain 7 pressure tests
Safety Hardware and Installation
- Domain 8 relief devices
- Domain 9 controls
- Domain 4 installation, then full mixed review
Adjust the pacing to your background: someone who already runs boiler inspections daily may compress Weeks 1 and 4, while a candidate new to code math should expand Week 2. For a fuller plan, see our NBII study guide, and check NBII requirements so you know you qualify before you invest weeks of prep.
Where NBII Holders Work
The commission is aimed at people who inspect boilers and pressure vessels once they are in service, so the work is tied to the organizations responsible for that equipment's safety. Typical employers include jurisdictional inspection departments, insurance and inspection companies, and owner-user organizations that maintain their own pressure equipment. The specifics of any given role vary by employer and by jurisdiction, so read job postings carefully for the credentials they actually require.
For a closer look at the market, see our pages on NBII jobs and NBII salary, and our ROI analysis if you are weighing the investment. We deliberately avoid quoting pay figures on this one-page sheet, since earnings depend heavily on employer, region and experience.
Key Takeaway
Keep your final-week routine simple: reread this sheet, rebuild each list from memory, then take timed mixed sets on the practice test site to find the headings where recall is still shaky. Rework the weak ones from the primary references, not from summaries.
Frequently Asked Questions
The issuer's examination information confirms 85 questions administered in one day. The exact timer, current fee and pass mark should be confirmed directly with the National Board, since those details are not verified here.
The NB-331-IS Revision 7 outline lists nine detailed headings but publishes no percentage weights. Plan to be competent in all nine rather than betting on a subset.
The outline names RCI-1/NB-263, NBIC Parts 1 and 2, ASME Sections I, IV and VIII Division 1, B31.1 and CSD-1, with Part 3 repair and alteration methods appearing under inservice inspection. Learn what each document is used for and where to find answers in it.
The named deterioration mechanisms and the calculation categories. Both are enumerated explicitly in the outline, so you know exactly what the issuer expects you to recognize and compute. See the NBII pass rate page for what is and isn't known about outcomes.
No. It is a recall aid built on the issuer's outline. Use it alongside the primary code references and realistic practice questions, and read what NBII certification is if you need background on the credential itself.