Tolerance
ASME B16.5 flange dimensions including different pressure ratings for weld neck flange, slip on flange, blind flange, reducing flange, socket weld flange, threaded flange, view below for more details.
In order to determine compliance with this standard, where a fixed effective number is required where the limits, maximum and minimum values are specified, rounding shall be in accordance with the method defined in ASTM Practice E29.
Required tolerances for different flanges and flanged fittings elements are as follows:
Center to Contract Surfaces and Center to End Tolerances
(a). Center-to-Contract Surfaces other than Ring Joint
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | +/- 1.0 mm (+/- 0.03 in.) |
| NPS ≤ 12 | +/- 1.5 mm (+/- 0.06 in.) |
(b). Center-to-End (Ring Joint)
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | +/- 1.0 mm (+/- 0.03 in.) |
| NPS ≤ 12 | +/- 1.5 mm (+/- 0.06 in.) |
(c). Center surface-to-Contact surface other than ring joint
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | ±2.0 mm(±0.06 in.) |
| NPS ≥ 12 | ±3.0 mm(±0.12 in.) |
(d). End-to-End
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | ±2.0 mm(±0.06 in.) |
| NPS ≥ 12 | ±3.0 mm(±0.12 in.) |
Tolerances for Flange Facings
For both flange and flanged fittings facings tolerances are as follows:
(a) Inside and outside diameter of large and small tongue and groove and female, ±0.5 mm (±0.02 in.).
(b) Outside diameter,2.0 mm (0.06 in.) raised face, ±1.0 mm (±0.03 in.).
(c) Outside diameter, 7.0 mm (0.25 in.) raised face, ±0.5 mm (±0.02 in.).
(d) Ring joint groove tolerances are shown in Table 5 (Table II-5 of Mandatory Appendix II in ASME B16.5)
(e)Perpendicularity of the face with the bore as below table
| Size | Tolerance |
|---|---|
| NPS ≤ 5 | 1 deg |
| NPS ≥ 6 | 0.5 deg |
Flange thickness tolerances
| Size | Tolerance |
|---|---|
| NPS ≤ 18 | +3.0, -0.0 mm (+0.12,-0.00 in.) |
| NPS ≥ 20 | +5.0, -0.0 mm (+0.19,-0.00 in.) |
The plus tolerance is applicable to bolting bearing surfaces whether as-forged, as-cast, spot-faced, or back-faced.
Welding end flange ends and hubs
Outside Diameter
For welding ends of welding neck flanges nominal outside diameter as follows:
| Size | Tolerance |
|---|---|
| NPS ≤ 5 | +2.0, -1.0 mm (+0.09,-0.03 in.) |
| NPS ≥ 6 | +4.0, -1.0 mm (+0.16,-0.03 in.) |
Inside Diameter
Tolerances for nominal inside diameter of welding ends of weld neck flange and socket weld flange with smaller bore.
(a) For figures 7 (Bevel for wall thickness from 5 mm to 22 mm), figure 8 (greater than 22 mm) and figure 4 (Straight Hub Welding Flange) in ASME B16.5.
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | ±1.0 mm (±0.03 in.) |
| 12 ≤ NPS ≤ 18 | ±1.5 mm (±0.06 in.) |
| NPS ≥ 20 | +3.0, -1.5 mm (+0.12,-0.06 in.) |
For figure 9 (Inside Contour for Use With Rectangular Backing Ring)
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | +0.0, -1.0 mm (+0.0,-0.03 in.) |
| NPS ≥ 12 | +0.0, -1.5 mm (+0.0,-0.06 in.) |
Backing ring contact surface
| Size | Tolerance |
|---|---|
| 2 ≤ NPS ≤ 24 | +0.25, -0.0 mm (+0.01,-0.0 in.) |
Length through hub on welding neck flanges
| Size | Tolerance |
|---|---|
| NPS ≤ 4 | ±1.5mm (±0.06 in.) |
| 5 ≤ NPS ≤ 10 | +1.5, -3.0 mm (+0.06,-0.12 in.) |
| NPS ≥ 12 | +3.0, -5 mm (+0.12,-0.18 in.) |
Flange Bore Diameter
Lapped and Slip-On Flange Bores
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | +1.0, -0.0 mm (+0.03,-0.0 in.) |
| NPS ≥ 12 | +1.5, -0.0 mm (+0.06,-0.0 in.) |
Counter Bores, Threaded Flanges
| Size | Tolerance |
|---|---|
| NPS ≤ 10 | +1.0, -0.0 mm (+0.03,-0.0 in.) |
| NPS ≥ 12 | +1.5, -0.0 mm (+0.06,-0.0 in.) |
Counter Bores, Socket Welding Flanges
| Size | Tolerance |
|---|---|
| 1/2 ≤ NPS ≤ 3 | ±0.25 mm (±0.010 in.) |