ASME B16.47 Series B Class 900 large-diameter flange dimensions: flange outside diameter, bolt-circle diameter, number of bolts, bolt-hole size and stud size for weld-neck flanges from NPS 26 through NPS 48 — the highest-pressure Series B class tabulated, and the compact alternative to Series A. Includes NPS 30 (1035.0 mm bolt circle, 20 studs), NPS 36 (1200.2 mm, 24 studs) and NPS 48 (1587.5 mm, 24 studs). Like Series A Class 900 the range runs to NPS 48 rather than NPS 60. Series B is NOT interchangeable with Series A, and neither mates to an ASME B16.5 flange. Values cross-checked across three independent reference tables (mm and inch), which agree on outside diameter, bolt circle and bolt count for NPS 26 to NPS 36; the relation bolt hole = stud + 1/8 in holds on every row.
ASME B16.47 covers steel pipe flanges from NPS 26 to NPS 60, the range above the NPS 24 ceiling of ASME B16.5. It defines two non-interchangeable series: Series A (the larger, more robust flange, formerly MSS SP-44) and Series B (a more compact flange that carries more, smaller bolts on a smaller bolt circle, formerly API 605). The two series share neither the outside diameter nor the bolt pattern at a given NPS and rating, so the series must be confirmed before a flange is ordered or matched. Class 900 is the highest-pressure Series B class that is tabulated, and like Series A Class 900 the range runs to NPS 48 rather than NPS 60. The values below are the Series B Class 900 dimensions for the weld-neck flange, cross-checked across three independent reference tables.
| NPS | Flange OD (mm) | Bolt circle (mm) | No. of bolts | Bolt hole (mm) | Stud size |
|---|---|---|---|---|---|
| NPS 26 | 1020 | 901.7 | 20 | 66.7 | 2 1/2 in |
| NPS 28 | 1105 | 971.6 | 20 | 73.0 | 2 3/4 in |
| NPS 30 | 1180 | 1035.0 | 20 | 79.4 | 3 in |
| NPS 32 | 1240 | 1092.2 | 20 | 79.4 | 3 in |
| NPS 34 | 1315 | 1155.7 | 20 | 85.7 | 3 1/4 in |
| NPS 36 | 1345 | 1200.2 | 24 | 79.4 | 3 in |
| NPS 38 | 1460 | 1289.0 | 20 | 92.1 | 3 1/2 in |
| NPS 40 | 1510 | 1339.8 | 24 | 92.1 | 3 1/2 in |
| NPS 42 | 1560 | 1390.6 | 24 | 92.1 | 3 1/2 in |
| NPS 44 | 1650 | 1463.7 | 24 | 98.4 | 3 3/4 in |
| NPS 46 | 1735 | 1536.7 | 24 | 104.8 | 4 in |
| NPS 48 | 1785 | 1587.5 | 24 | 104.8 | 4 in |
Bolt holes are drilled on the bolt circle, straddling the centreline and equally spaced. ASME B16.47 drills the hole 1/8 in larger than the stud, so the 66.7 mm (2 5/8 in) hole takes a 2 1/2 in stud, the 92.1 mm (3 5/8 in) hole a 3 1/2 in stud and the 104.8 mm (4 1/8 in) hole a 4 in stud. The bolt count in Series B Class 900 does not rise steadily with NPS — it is 20 from NPS 26 to NPS 34, rises to 24 at NPS 36, drops back to 20 at NPS 38, then holds at 24 from NPS 40 to NPS 48 — so confirm the exact count for the specific NPS rather than interpolating. The three tables agree on the outside diameter, bolt circle and bolt count for NPS 26 to NPS 36; the outside diameter for NPS 38 to NPS 48 is from the millimetre table, whose bolt circle, bolt count, hole and stud match the inch tables on every overlapping row.
Flange thickness and hub dimensions are not tabled here: they vary with the flange type (weld-neck, blind, slip-on) and the published columns differ between reference tables. Take the thickness for a given NPS from the controlling ASME B16.47 Series B Class 900 table or the flange maker’s data sheet.
Two flanges bolt together only when the standard, series, NPS, rating and bolt pattern all agree, so confirm all five before ordering. A B16.47 Series B flange will not mate to a Series A flange of the same NPS and rating — the outside diameter, bolt circle and bolt count all differ — and neither mates to an ASME B16.5 flange. Series B saves weight and bolt-up effort and suits a line and mating equipment built to Series B throughout; Series A is the choice where a Series A flange is already installed or the heavier flange suits the duty. The rating (Class 900 here) sets the bolt circle and the facing; the bore, hub and thickness then follow the flange type. The dimensions above are for the weld-neck flange; blind flanges to B16.47 Series B Class 900 share the same outside diameter, bolt circle, bolt hole, bolt count and stud size.
Dimensions are nominal ASME B16.47 Series B values and provided for identification and cross-reference. Confirm against the controlling standard and the specific flange maker’s current data sheet before manufacture or procurement.