ASME B16.47 covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60 (DN 650 to DN 1500), in rating class designations 75, 150, 300, 400, 600, and 900. The standard is limited to flanges made from cast or forged materials and blind flanges made from cast, forged, or plate materials. Current edition: ASME B16.47-2025 (published 30 May 2025, supersedes B16.47-2020).

Where ASME B16.5 stops at NPS 24, B16.47 takes over. The dimensional step is not a simple scale-up: bolt circles, bolt counts and handling weight all change. B16.47 defines two dimensional series, Series A (derived from MSS SP-44) and Series B (derived from API 605), which are not interchangeable.

Series A vs Series B: what actually changes

Do not mix series. Bolt circles and bolt counts differ; a Series A flange will not bolt to a Series B flange of the same size and class. Always confirm the series on the drawing, the BOM and the mating equipment before ordering.

Series A — Class 150 dimensions (mm)

Minimum thickness excludes the raised face height (1.6 mm for Class 150 and 300). Values per ASME B16.47 dimensional tables; verify against the current standard and project specification.

Series B — Class 150 dimensions (mm)

Minimum thickness excludes the raised face height (1.6 mm). Series B uses more bolts of smaller diameter than Series A at the same size.

Series A — Class 300 dimensions (mm)

For Class 400, 600 and 900 in NPS 38 and larger, Series A dimensions are the same as Series B. Full Class 400–900 tables are available on request.

Series B — Class 300 dimensions (mm)

Minimum thickness excludes the raised face height (1.6 mm).

Flange types and facings

ASME B16.47 covers only two flange types: weld neck (WN) and blind. Slip-on, threaded, socket weld and lap joint flanges are outside its scope; when those styles are needed above NPS 24, they are built to industry practice, not to B16.47 dimensions.

Both series are supplied with a raised face (RF). Ring-type joint (RTJ) facings are defined only for Series A, in Classes 300 through 900 and sizes NPS 26 through NPS 36.

Materials

Pressure-temperature ratings follow the material groups of the standard. The 2025 edition revised the rating tables and added a duplex stainless steel group; select the group, not just the class, when checking allowable pressure.

Marking and inspection

Each flange is marked with the manufacturer name or trademark, material specification, pressure class, size (NPS), and the designation B16.47. Heat number traceability links the finished flange back to the melt. For Class 600 and above, volumetric UT of the forging before machining is standard practice on critical projects, and it is far cheaper than discovering a lamination after machining.

Fabrication: forged vs plate

Above roughly NPS 36, many weld neck flanges are cut and machined from rolled plate rather than forged, which the standard permits provided the starting material is certified and dimensional control is tight. Where a project requires fully forged construction, state it in the inquiry: it affects both lead time and price.

Applications

Refinery and petrochemical large-bore process lines, gas transmission and compressor stations, power plant cooling water, desalination, water transmission mains, and API 650 tank nozzles. Series B dominates buried water and low-pressure transmission; Series A is the default in process plants and where external loads govern.

How HT PIPE supplies ASME B16.47 flanges

HT PIPE manufactures and supplies Series A and Series B weld neck and blind flanges in NPS 26 to 60, in A105, A350 LF2, A694 F52/F60/F65 and A182 stainless and alloy grades, with EN 10204 3.1 certification, full heat traceability and optional NACE MR0175 compliance. Send size, class, series, material and facing: we quote within 24 hours.

Frequently asked questions

What flange sizes does ASME B16.47 cover?

NPS 26 through NPS 60 (DN 650 to DN 1500). ASME B16.5 stops at NPS 24.

Are Series A and Series B flanges interchangeable?

No. Bolt circle diameter, bolt count and outside diameter all differ. They cannot be bolted together without modification.

Which series has more bolts?

Series B uses more bolts of smaller diameter. At NPS 26 Class 150, Series A has 24 bolts of 1-1/4 in and Series B has 36 bolts of 3/4 in.

Which pressure classes are available?

75, 150, 300, 400, 600 and 900. Class 75 is only defined for Series B.

Is RTJ available in B16.47?

Only in Series A, for Classes 300 through 900 in sizes NPS 26 to 36.

Which flange types does B16.47 cover?

Weld neck and blind only. Slip-on, threaded, socket weld and lap joint are not covered.

Dimension data is provided for reference and has been cross-checked against the ASME B16.47 dimensional tables. ASME B16.47 does not specify flange weights; weights vary by type, facing and manufacturer. Verify all values against the current standard and applicable project specifications before fabrication.