American national standards ASME/ANSI B16.5 and B16.47 together cover pipe flanges
up to NPS 60 (NPS 48 is the largest detailed in this summary). ASME/ANSI B16.47 covers
two series of flanges, Series A which is equivalent to MSS SP-44 (the 1996 Edition of
MSS SP-44 complies with B16.47 tolerances), and Series B which is equivalent to API
605 (API 605 is now cancelled).
Dimensions and Tolerances
Note
1 See page 8-5 for weld neck welding end dimension and tolerance data.
Tolerances on flange dimensions (ASME/ANSI B16.5 and B16.47, and MSS SP-44)
Dimension Range
Tolerance
in mm
General and Blind Flanges (For blind flange dimensions see page 8-23 for B16.5, page 8-46 for B16.47
Series A / MSS SP-44 and page 8-51 for B16.47 Series B / API 605):
G (raised face diameter)
< NPS 24 ±0.03 ±0.76
> NPS 26, with
0.06 in raised face
±0.08 ±2.03
> NPS 26, with
0.25 in raised face
±0.04 ±1.02
I (bolt hole diameter) All No tolerance in B16.5 or B16.47
J (bolt circle diameter) All ±0.06 ±1.52
Centre to centre of
adjacent bolt holes All ±0.03 ±0.76
Eccenticity of bolt circle
and machined facing
diameters
< NPS 21/2 ±0.03 ±0.76
> NPS 3 ±0.06 ±1.52
Weld Neck Flanges1 (For dimensions see page 8-10 for B16.5, page 8-46 for B16.47 Series A / MSS SP-44
and page 8-51 for B16.47 Series B / API 605):
D (overall length)
< NPS 4 +0.06 +1.52
NPS 5 to 10 +0.06, -0.12 +1.52, -3.05
NPS 12 to 24 +0.12, -0.18 +3.05, -4.57
> NPS 26 ±0.19 ±4.83
Thickness of hub All > 87.5% of pipe nominal wall thickness
Slip on (see page 8-17), Lap Joint (see page 8-32 for dimensions) and Socket Welding (see page 8-30 for
dimensions) Flanges:
B (inside diameter, or
bore)
< NPS 10 +0.03, -0.0 +0.76, -0.0
> NPS 12 +0.06, -0.0 +1.52, -0.0
Threaded Flanges (see page 8-40 for dimensions):
B (counterbore)
(Not applicable for
Class 150 lb)
< NPS 10 +0.03, -0.0 +0.76, -0.0
> NPS 12 +0.06, -0.0 +1.52, -0.0
Ring Joint Facing (See page 8-6 for dimensions; see page 8-9 for tolerances)
