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

Reference manual hosted for technician access. 1 pages.

Brand

ASME B16.47 Series A

Equipment

Class 150 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 A Class 150 large-diameter flange dimensions: flange outside diameter O, bolt-circle diameter, number of bolts, bolt-hole size and stud size for weld-neck flanges from NPS 26 through NPS 60 — the range above the NPS 24 ceiling of ASME B16.5. Includes NPS 30 (914.4 mm bolt circle, 28 studs), NPS 36 (1085.8 mm, 32 studs) and NPS 48 (1422.4 mm, 44 studs). Series A is not interchangeable with Series B. Values cross-checked across two independent reference tables.

ASME B16.47 Series A 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 with more, smaller bolts). 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 A Class 150 dimensions for the weld-neck flange, cross-checked across two independent reference tables.

NPS	Flange OD O (mm)	Bolt circle (mm)	No. of bolts	Bolt hole (mm)	Stud size
NPS 26	870	806.4	24	35	1 1/4 in
NPS 28	925	863.6	28	35	1 1/4 in
NPS 30	985	914.4	28	35	1 1/4 in
NPS 32	1060	977.9	28	41.3	1 1/2 in
NPS 34	1110	1028.7	32	41.3	1 1/2 in
NPS 36	1170	1085.8	32	41.3	1 1/2 in
NPS 38	1240	1149.4	32	41.3	1 1/2 in
NPS 40	1290	1200.2	36	41.3	1 1/2 in
NPS 42	1345	1257.3	36	41.3	1 1/2 in
NPS 44	1405	1314.4	40	41.3	1 1/2 in
NPS 46	1455	1365.2	40	41.3	1 1/2 in
NPS 48	1510	1422.4	44	41.3	1 1/2 in
NPS 50	1570	1479.6	44	47.6	1 3/4 in
NPS 52	1625	1536.7	44	47.6	1 3/4 in
NPS 54	1685	1593.8	44	47.6	1 3/4 in
NPS 56	1745	1651.0	48	47.6	1 3/4 in
NPS 58	1805	1708.2	48	47.6	1 3/4 in
NPS 60	1855	1759.0	52	47.6	1 3/4 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 35 mm (1 3/8 in) hole takes a 1 1/4 in stud, the 41.3 mm (1 5/8 in) hole a 1 1/2 in stud and the 47.6 mm (1 7/8 in) hole a 1 3/4 in stud. The two reference tables agree on the bolt circle and bolt count for every NPS.

Reading the dimensions

Flange OD O — the overall diameter of the flange disc; sets the space the flange occupies.
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 A Class 150 runs from 24 studs at NPS 26 to 52 at NPS 60.
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.

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 A 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 A flange will not mate to a Series B flange of the same NPS and rating — the outside diameter, bolt circle and bolt count differ — and neither mates to an ASME B16.5 flange. Series A is the common choice where a Series A flange is already installed or where the heavier flange suits the duty; Series B saves weight and bolt-up effort where the line and the mating equipment are built to Series B throughout. 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 A Class 150 share the same outside diameter, bolt circle, bolt hole, bolt count and stud size.

Dimensions are nominal ASME B16.47 Series A 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 A ASME B16.47 revision and the specific component data sheets before manufacture or procurement. All trademarks are the property of their respective owners.