NBBI Inservice Inspector (IS) key terms

A consensus code that sets rules for inservice inspection, repair, alteration, and pressure relief device servicing of boilers and pressure vessels after they enter service, organized into Parts RB, RC, RD, and RA appendices.

The state, province, or municipal government body that legally regulates boilers and pressure vessels in a given location and adopts or amends the code editions it enforces.

An inspector holding a National Board commission who is employed by an authorized inspection agency and performs code-required inspections, including verifying repairs and alterations for code compliance.

A credential issued by the National Board to an individual who passes written and practical examinations, demonstrating competence to inspect boilers and pressure vessels under the NBIC.

An organization, typically an insurance company or jurisdictional body, that employs commissioned inspectors and is accredited by the National Board to provide code inspection services.

A standardized National Board form (such as R-1, R-2, or R-4) on which the inspector records details of a repair, alteration, or pressure relief device servicing and certifies code compliance.

The National Board report used to document and certify a repair or alteration performed on a boiler or pressure vessel, signed by the repair organization and the authorized inspector.

The National Board report used to document alterations to boilers or pressure vessels that change the pressure-retaining boundary or require recalculated maximum allowable working pressure.

The National Board report used to record the servicing, repair, or adjustment of a pressure relief device, including set pressure verification and valve identification data.

A credential the National Board issues to a qualified organization permitting it to perform code repairs or alterations and to apply the corresponding R symbol stamp to the component.

The National Board symbol stamp authorizing a qualified organization to service, repair, and test pressure relief valves and to certify them for return to service.

The highest pressure at which a boiler or pressure vessel is permitted to operate under its design and code rules, based on the strength of the pressure-retaining components at the design temperature.

The pressure used in the original design calculations to establish the required wall thickness of pressure-retaining parts, typically equal to or above the intended operating pressure.

The lowest temperature at which a pressure vessel may operate without risk of brittle fracture, established during design and tied to material toughness and impact-testing requirements.

A pressure test in which the vessel is filled with water and pressurized, usually to 1.5 times the maximum allowable working pressure, to verify structural integrity and leak tightness.

A pressure test using air or another gas instead of water, permitted only when hydrostatic testing is impractical and with additional safety precautions because of stored energy release.

A material test measuring resistance to brittle fracture by striking a notched specimen, used to qualify steels for low-temperature service or thick sections per code rules.

A controlled heating of a completed weldment to a specified temperature and time, then cooling, to relieve residual stresses and reduce hardness in the heat-affected zone.

The region of base metal adjacent to a weld that was not melted but whose microstructure and properties were altered by the welding heat.

A written document describing the welding variables and technique qualified by testing, which a welder must follow to produce a weld meeting code requirements.

The documented record of the test weld made to qualify a welding procedure, including measured variables and mechanical test results supporting the WPS.

A record certifying that an individual welder produced test welds meeting code acceptance criteria for a given process, position, and thickness range.

Work that restores a boiler or pressure vessel to a safe condition without changing its design parameters, such as replacing a wasted area with like material per code rules.

A change to a boiler or pressure vessel that affects its pressure-retaining capability or design, such as changing the MAWP, dimensions, or service, requiring engineering review and recertification.

A company holding a National Board certificate of authorization that is qualified to perform code repairs or alterations and to certify the work on the appropriate data report.

The permanent metal tag attached to a boiler or pressure vessel bearing identification, design data, and code stamping, which must remain legible and be updated when alterations change ratings.

An automatic device that opens at a preset pressure to discharge fluid and protect a boiler or pressure vessel from overpressure, then recloses as pressure falls.

The inlet pressure at which a pressure relief valve is adjusted to begin opening under operating conditions, typically at or below the maximum allowable working pressure.

The pressure increase above the maximum allowable working pressure that a vessel may experience while a relief device discharges at its rated capacity, limited by code rules.

The pressure difference between the set pressure at which a relief valve opens and the lower pressure at which it reseats and stops discharging.

The mass or volumetric flow rate a pressure relief device can discharge at specified conditions, which must equal or exceed the required capacity for the protected equipment.

A non-reclosing pressure relief device containing a frangible membrane that bursts at a predetermined pressure to vent overpressure and must be replaced after actuation.

A pressure relief valve actuated by direct spring loading and used primarily on steam boilers, characterized by rapid full-opening action with minimal overpressure.

A pressure relief valve that may be used in either steam or liquid service, opening with a pop action for compressible fluids or proportionally for liquids.

A pressure relief valve in which a small pilot mechanism senses pressure and controls the opening of a larger main valve, allowing high capacity and closer set pressure control.

Periodic examination of a boiler or pressure vessel during operation or shutdown to detect deterioration such as corrosion, cracking, or deformation and to determine fitness for continued service.

Inspection of accessible surfaces by eye, sometimes aided by mirrors, borescopes, or lighting, to identify leaks, corrosion, cracking, or other visible defects.

Testing methods such as radiography, ultrasonic, magnetic particle, and liquid penetrant that reveal internal or surface flaws without damaging the component being inspected.

Determination of remaining wall thickness, usually by ultrasonic instruments, to evaluate corrosion or erosion losses against code minimums and determine remaining life.