National Board of Boiler and Pressure Vessel Inspectors

Inspection Authority The National Board of Boiler and Pressure Vessel Inspectors is composed of the chief inspectors of states and municipalities in the United States and Canadian provinces which have made any pari of the Boiler and Pressure Vessel Code a legal requirement. This board promotes uniform enforcement of boiler and pressure-vessel rules. One of the board s imporiant activities is providing examinations for, and commissioning of, inspectors. Inspeciors so qualified and employed by an insurance company state, municipality, or Canadian province may inspect a pressure vessel and permit it to be stamped ASME—NB (National Board). An inspector employed by a vessel user may authorize the use of only the ASME stamp. The ASME Code Committee authorizes fabricators to use the various ASME stamps. The stamps, however, may be apphed to a vessel only with the approval of the inspector. 

The National Board Inspection Code, published by the National Board of Boiler and Pressure Vessel Inspectors, Columbus, Ohio, is helpful. Any repair, however, is acceptable if it is made in accordance with the rules of the Pressure Vessel Code. 

NBIC. National Board Inspection Code. ANSI/NB-23. National Board of Boiler and Pressure Vessel Inspectors, USA, 1998. 

Combination capacity factors that have been determined by test and are acceptable to use are compiled by The National Board of Boiler and Pressure Vessel Inspectors in the Pressure Relief Device Certifications publication, NB-18 or the so-called Red Book. This publication lists the combination capacity factors to be used with a specific rupture device and relief valve by manufacturer rupture device/valve models. 

National Board of Boiler and Pressure Vessel Inspectors. 1992. 

In spite of some of the most rigorous, well-conceived safety rules and procedures ever put together, boiler and pressure vessel accidents continue to occur. In 1980, for example, the National Board of Boiler and Pressure Vessel Inspectors reported 1972 boiler and pressure vessel accidents, 108 injuries and 22 deaths. The pressure vessel explosions are of course rare nowadays and are often caused by incorrect operation or poorly monitored corrosion. Safety in boiler and pressure vessels can be achieved by ... 

Since that time, organizations such as the National Board of Boiler and Pressure Vessel Inspectors and the Technical Association of the Pulp and Paper Industry have issued warnings to plant operators, and these have resulted in the formation of inspection programs for evaluating the integrity of deaerator tanks. As a result, many operators have discovered serious cracking problems. The following example illustrates the problem. 

Kc equals to 1.0 for a PRV without a rupture disk. Kc equals to 0.9 for a PRV with a rupture disk at its inlet (0.9 is uncertified Kc certified Kc available from the National Board of Boiler and Pressure Vessel Inspectors). 

Kc equals 1.0, if there is no rupture disk at PRV inlet. Kc equals 0.9, if there is a rupture disk at PRV inlet. (0.9 is uncertified Kc certified Kc is available from the National Board of Boiler and Pressure Vessel Inspectors). Kv is viscosity correction factor. At initial orifice area calculation (Eq. (9a)), let Kv equal to 1.0. Based on calculated orifice area, select a PRV orifice. Based on this orifice area, recalculate Re, kv, and A using Eq. (9c), Eq. (9b), and Eq. (9a). Repeat these calculations until selected PRV orifice doesn t change anymore. 

To be authorized to perform repairs, a repair company must hold an "R" stamp issued by the National Board of Boiler and Pressure Vessel Inspectors. In all cases, the owner and the repair company must consult an inspector before a repair is begun. The completed repair is subject to the inspector s acceptance. 

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