NBBI NB-23 ( PART 1, 2, 3 & 4 ) : 2025

The National Board of Boiler and Pressure Vessel Inspectors Codebook, popularly known as the NBIC (National Boiler Inspection Code), has a long history of setting jurisdictional Standard Details in North America; and, it is the only standard recognized worldwide for in-service inspection, repairs and alterations of boilers and pressure vessels.

It is divided into four volumes or parts.

The parts of NBIC 2025 are listed below.

Part 1:

• Form I-1, Boiler Installation Report, has been revised.
• A new requirement for air intake installation in sealed combustion systems has been added to section 1.6.6.
• New requirements have been added to sections 2.8.5 and 3.8.1.5 for low-water fuel cutoffs that are installed external to the boiler.
• New drain system requirements have been added to section 3.6.3.
• Sections 3.8.2.2 and 3.8.2.3 have new requirements for thermometers and temperature-sensing elements installed on hot-water heating and hot-water supply boilers.
• Requirements in section 3.9.3 for set pressure and capacity for pressure relief valves on hot-water heating and hot-water supply boilers were updated to better align with ASME Section IV.

Part 2:

• Requirements have been updated in section 1.4 regarding owners’ or users’ responsibility for addressing safety exposure for an inspector.
• Several updates have been made to section 2.3.6.5 to revise inspection requirements for pressure vessels with quick-actuating closures.
• Recommended inspection type/frequency for thermal fluid heaters was added to Table 2.5.8.
• Several revisions were made to section 4.2 to better align the section with NBIC Part 3.
• New inspection requirements for staybolts on historical boilers were added to section S2.10.4.1.
• New sections S2.10.4.3 and S2.10.4.4 have been added to address maximum allowable working pressure (MAWP) calculations for curved stayed surfaces subjected to internal or external pressures in historical boilers.
• Table S6.13.6 has been revised to match the latest U.S. Department of Transportation standards.
• Supplement 14, Low-Pressure Boiler External Inspection List, is a new document.

Part 3:

• Requirements for temporary locations have been added to section 1.4.1.
• Paragraph j) in section 3.3.3 has been revised to clarify requirements for nozzle placement.
• New requirements for flush patches have been added to section 3.3.4.6.
• Welding requirements for plugging firetubes have been added to section 3.3.4.9.
• Several updates and revisions have been made to section 4.2.
• Section 5.2.2 has been updated to add guidance for “R” Certificate Holders with the “Design Only” scope.
• Sections 5.2.5 and 5.2.6 have been revised to provide clarification on “NR” Certificate Holder responsibilities when completing Form NR-1 and Form NVR-1.
• A new requirement has been added to section 5.7.1 to waive stamping or nameplate attachment requirements due to personnel safety or potential contamination risks.
• Section S2.4.1 has been added to address reusing parts or attachments on historical boilers.
• Section S2.13.4.1 has been added to address the replacement of through stays on historical boilers.
• Several revisions have been made to the list of graphite pressure vessel routine repairs in section S3.3.
• Section S3.5.4 has been revised to address block holes as well as tubes in graphite pressure vessels.
• Section S3.5.6 has been added to provide a repair procedure for cross-drilled blocks on graphite pressure vessels.
• Supplement 6, Repair, Alteration, and Modification of DOT Transport (Cargo) Tanks, has been updated to reflect the latest U.S. Department of Transportation requirements.
• Supplement 10, Classifying Repairs and Alterations, has been added to provide a flowchart for determining if an activity would be considered a repair or alteration.
• Supplement 11, Engineered Repairs and Alterations, has been added to provide a specific location for repair and alteration methods that require additional engineering considerations. The following methods have been relocated to this supplement:

  • External Weld Metal Buildup
  • Repair of Pressure-Retaining Items Without the Complete Removal of Defects
  • Repair of ASME Section VIII, Division 2 or Division 3 Pressure Vessels
  • Encapsulation
  • Alteration of ASME Section VIII, Division 2 or Division 3 Pressure Vessels

Part 4:

• Sections 2.5.1.6 and 3.8.2.3 have new requirements for thermometers and temperature sensing elements installed on hot-water heating and hot-water supply boilers.
• Recommended inspection type/frequency for thermal fluid heaters was added to Table 3.2.6.
• Section 3.3.4.1 has been deleted, and a new section 3.4, Annual Audits, has been added to replace 3.3.4.1.
• Section 4.2.2 has been revised to clarify how ASME Code Cases are applied to the repair and conversion of pressure relief devices.