ANSI Buttweld Fittings – Dimensional Tolerances

Cross-sectional tolerances for all buttwelding fittings (ASME/ANSI B16.9 and B16.28)

Nominal Pipe Size (NPS)All Fittings
OD at BevelID at Bevel ±Wall thickness
inmminmm
½ to 2½+0.06, -0.03+1.6, -0.80.030.8Not less than 87.5% of nominal wall thickness
3 to 3½±0.6±1.60.061.6
4±0.6±1.60.061.6
5 to 6+0.09, -0.06+2.4, -1.60.061.6
8+0.09, -0.06+2.4, -1.60.061.6
10+0.16, -0.12+4.0, -3.20.123.2
12 to 18+0.16, -0.12+4.0, -3.20.123.2
20 to 24+0.25, -0.19+6.4, -4.80.194.8
26 to 30+0.25, -0.19+6.4, -4.80.194.8
32 to 48+0.25, -0.19+6.4, -4.80.194.8

Tolerances for Specific Fittings

Dimensional tolerances for elbows and returns (ASME/ANSI B16.9 & B16.28)

Nominal Pipe Size (NPS)90° & 45° Long Radius Elbows 90° Short Radius Elbows
and Tees
180° Returns
Centre-to-End Dimension ±
A, B
Centre-to-Centre Dimension ±
B (=2 x A)
Back-to-Face Dimension ±
C
inmminmminmm
½ to 2½0.0620.2560.256
3 to 3½0.0620.2560.256
40.0620.2560.256
5 to 60.0620.2560.256
80.0620.2560.256
100.0920.38100.256
12 to 180.0920.38100.256
20 to 240.0920.38100.256
26 to 300.123
32 to 480.195

Dimensional tolerances for reducers, caps and stub ends (ASME/ANSI B16.9)

Nominal Pipe Size (NPS)Reducers & Lap Joint
Stub Ends
CapsLap Joint Stub Ends
Overall Length ±
A
Overall Length ±
A
OD of Lap
B
Fillet Radius of Lap
B
inmminmminmminmm
½ to 2½0.0620.123+0+0, -1+0+0, -1
3 to 3½0.0620.123+0, -0.03+0, -1+0, -0.03+0, -1
40.0620.123+0, -0.03+0, -1+0, -0.06+0, -2
5 to 60.0620.256+0, -0.03+0, -1+0, -0.06+0, -2
80.0620.256+0, -0.03+0, -1+0, -0.06+0, -2
100.0920.256+0, -0.06+0, -2+0, -0.06+0, -2
12 to 180.0920.256+0, -0.06+0, -2+0, -0.06+0, -2
20 to 240.0920.256+0, -0.06+0, -2+0, -0.06+0, -2
26 to 300.1950.3810
32 to 480.1950.3810

Alignment Tolerances

Alignment tolerances are concerned with the way that the ends of a fitting are cut. Exaggerated distortions are shown for clarity in the diagram below.

Alignment Tolerances (ASME/ANSI B16.9)

Nominal Pipe Size (NPS)Off Plane Tolerances, ±
A
Off Angle Tolerances, ±
B
Alignment of Ends, ±
C
inmminmminmm
½ to 40.0620.0310.031
5 to 80.1240.0620.031
10 to 120.1950.0920.062
14 to 160.2560.0930.062
18 to 240.38100.1240.062
26 to 300.38100.195
32 to 420.50130.195
44 to 480.75190.195

Dimensional Tolerances for reducers, caps and stub ends (ASME/ANSI B16.9)

Dimensions and Tolerances MSS SP-43

MSS SP-43 only covers buttweld fittings made for use with Schedule 5S and 10S pipe as defined in ANSI/ASME B36.19M (plus short pattern stub ends suitable for use with Schedule 40S pipe). The dimensions and tolerances defined in MSS SP-43 are substantially the same as those in ASME/ANSI specifications (½ to 24 in).

  • MSS SP-43 tolerances (including alignment tolerance) are the same as for ASME/ANSI B16.9 and B16.28 except with regard to the outside diameter at the bevel:
  • Tolerance of OD at Bevel =

± 0.03 in for NPS ½ to 4

+0.06, -0.03 in for NPS 5 to 8

+0.09, -0.03 in for NPS 10 to 18

+0.12, to -0.03 in for NPS 20 to 24