ASME B16.47 Series B Class 600 Flange Dimensions (NPS 26 to NPS 60)

Reference manual hosted for technician access. 1 pages.

Brand

ASME B16.47 Series B

Equipment

Class 600 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 600 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 higher-pressure companion to Series B Class 300 and the compact alternative to Series A. Includes NPS 30 (927.1 mm bolt circle, 28 studs), NPS 36 (1104.9 mm, 28 studs) and NPS 48 (1460.5 mm, 32 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; the relation bolt hole = stud + 1/8 in holds on every row.

ASME B16.47 Series B Class 600 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. Class 600 is the higher-pressure companion to Class 300 in Series B: a larger bolt circle, larger studs and a thicker flange for the same NPS. The values below are the Series B Class 600 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	890	806.4	28	44.5	1 5/8 in
NPS 28	950	863.6	28	47.6	1 3/4 in
NPS 30	1020	927.1	28	50.8	1 7/8 in
NPS 32	1085	984.2	28	54.0	2 in
NPS 34	1160	1054.1	24	60.3	2 1/4 in
NPS 36	1215	1104.9	28	60.3	2 1/4 in
NPS 38	1270	1162.0	28	60.3	2 1/4 in
NPS 40	1320	1212.8	32	60.3	2 1/4 in
NPS 42	1405	1282.7	28	66.7	2 1/2 in
NPS 44	1455	1333.5	32	66.7	2 1/2 in
NPS 46	1510	1390.6	32	66.7	2 1/2 in
NPS 48	1595	1460.5	32	73.0	2 3/4 in
NPS 50	1670	1524.0	28	79.4	3 in
NPS 52	1720	1574.8	32	79.4	3 in
NPS 54	1780	1632.0	32	79.4	3 in
NPS 56	1855	1695.4	32	85.7	3 1/4 in
NPS 58	1905	1746.2	32	85.7	3 1/4 in
NPS 60	1995	1822.4	28	92.1	3 1/2 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 44.5 mm (1 3/4 in) hole takes a 1 5/8 in stud, the 60.3 mm (2 3/8 in) hole a 2 1/4 in stud and the 92.1 mm (3 5/8 in) hole a 3 1/2 in stud. The bolt count in Series B Class 600 does not rise steadily with NPS — it steps up and down (24 to 32 studs) as the stud size changes, for example the count dips to 24 at NPS 34 and back to 28 at NPS 50 and NPS 60 — so confirm the exact count for the specific NPS rather than interpolating. The two tables agree 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 600 carries 24 to 32 studs across the range, and the count is not monotonic with NPS.
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). Use the full set; do not part-populate a flange.

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 600 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. The rating (Class 600 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 600 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.

Open / Download PDF

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.