ASME B16.47 Series B Class 150 Flange Dimensions (NPS 26 to NPS 60)

Reference manual hosted for technician access. 1 pages.

Brand

ASME B16.47 Series B

Equipment

Class 150 compact large-diameter weld-neck flange

Document type

Dimensional reference

Revision

ASME B16.47

Issued

2026-06-16

Pages

Format

PDF (application/pdf)

ASME B16.47 Series B Class 150 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 60 — the compact companion to Series A, carrying more, smaller bolts on a smaller bolt circle. Includes NPS 30 (846.1 mm bolt circle, 44 studs), NPS 36 (1009.6 mm, 44 studs) and NPS 48 (1335.1 mm, 44 studs). Series B is NOT interchangeable with Series A, and neither mates to an ASME B16.5 flange. Values cross-checked across two independent reference tables (mm and inch), which agree on outside diameter, bolt circle and bolt count for every NPS.

ASME B16.47 Series B Class 150 flange dimensions (NPS 26 to NPS 60)

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. The values below are the Series B Class 150 dimensions for the weld-neck flange, cross-checked across two independent reference tables.

NPS	Flange OD (mm)	Bolt circle (mm)	No. of bolts	Bolt hole (mm)	Stud size
NPS 26	785	744.5	36	22.2	3/4 in
NPS 28	835	795.3	40	22.2	3/4 in
NPS 30	885	846.1	44	22.2	3/4 in
NPS 32	940	900.1	48	22.2	3/4 in
NPS 34	1005	957.3	40	25.4	7/8 in
NPS 36	1055	1009.6	44	25.4	7/8 in
NPS 38	1125	1070.0	40	28.6	1 in
NPS 40	1175	1120.8	44	28.6	1 in
NPS 42	1225	1171.6	48	28.6	1 in
NPS 44	1275	1222.4	52	28.6	1 in
NPS 46	1340	1284.3	40	31.8	1 1/8 in
NPS 48	1390	1335.1	44	31.8	1 1/8 in
NPS 50	1445	1385.9	48	31.8	1 1/8 in
NPS 52	1495	1436.7	52	31.8	1 1/8 in
NPS 54	1550	1492.2	56	31.8	1 1/8 in
NPS 56	1600	1543.0	60	31.8	1 1/8 in
NPS 58	1675	1611.3	48	34.9	1 1/4 in
NPS 60	1725	1662.1	52	34.9	1 1/4 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 22.2 mm (7/8 in) hole takes a 3/4 in stud, the 28.6 mm (1 1/8 in) hole a 1 in stud and the 34.9 mm (1 3/8 in) hole a 1 1/4 in stud. The bolt count steps DOWN at NPS 34, 38, 46 and 58 where the stud size steps up — a larger stud spaced a little wider needs fewer holes. The two tables agree exactly on the outside diameter, bolt circle and bolt count for every NPS.

Reading the dimensions

Flange OD — the overall diameter of the flange disc; sets the space the flange occupies. Series B is smaller in outside diameter than Series A at the same NPS and rating.
Bolt circle — the diameter of the circle through the bolt-hole centres, also called the PCD. This is the figure to lay out or check the drilling against and the single most important number for matching a mating flange.
Number of bolts — equally spaced; both mating flanges share the same count. Series B Class 150 carries 36 to 60 studs across the range — many more than Series A, which is the defining feature of the compact series.
Bolt hole — the drilled hole diameter; the clearance over the stud lets two flanges line up.
Stud size — the diameter of the stud bolt (these flanges are bolted with stud bolts and two nuts, not through-bolts). Series B keeps the studs small (3/4 in to 1 1/4 in) and uses more of them. Use the full set.

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 table or the flange maker’s data sheet.

Selecting and matching

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. Because Series B uses more, smaller studs, the bolting and the spanner work differ from Series A even at the same NPS and rating. The rating (Class 150 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 150 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.

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Reference compiled for identification and cross-reference. Dimensions are nominal; confirm against the controlling ASME B16.47 Series B ASME B16.47 revision and the specific component data sheets before manufacture or procurement. All trademarks are the property of their respective owners.