Dimensional standard
ASME B16.47
Large Diameter Steel Flanges (NPS 26 through NPS 60)
ASME B16.47 defines large diameter steel flanges above the range of B16.5, in two dimensional series: Series A (formerly MSS SP-44) and Series B (formerly API 605).
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What it covers
- Sizes NPS 26 through NPS 60.
- Classes 75, 150, 300, 400, 600 and 900 depending on series.
- Series A flanges are heavier with larger bolting; Series B flanges are lighter with more, smaller bolts.
Practical notes
Points to specify
- Series A and Series B flanges of the same size and class are not interchangeable — the bolt circles differ.
- Always state the series along with size, class and facing when enquiring for large diameter flanges.
Common questions about ASME B16.47
- Can Series A and Series B flanges be bolted together?
- No. Their bolt circle diameters and bolt counts differ, so the series must be matched across the joint.
- Does Omegha Steel supply flanges above NPS 24?
- Yes — large diameter flanges are part of the range, with size, series, class, facing and material confirmed per enquiry.
More references
General guidance only. Work from the current published edition of the standard and your project specification; sizes, grades, classes and documentation are confirmed per enquiry.