ASME B16.5 flange dimensions — Class 150 & 300
Outside diameter, minimum thickness, bolt circle and bolting for Class 150 and Class 300 flanges, NPS ½" to 12", in millimetres. The same outside dimensions apply to weld neck, slip-on, blind, socket weld, threaded and lap joint flanges of the same size and class.
Class 150
| NPS | Flange OD | Min. thickness | Bolt circle | No. of bolts | Bolt dia (in) |
|---|---|---|---|---|---|
| ½" | 90 | 9.6 | 60.3 | 4 | ½" |
| ¾" | 100 | 11.2 | 69.9 | 4 | ½" |
| 1" | 110 | 12.7 | 79.4 | 4 | ½" |
| 1¼" | 115 | 14.3 | 88.9 | 4 | ½" |
| 1½" | 125 | 15.9 | 98.4 | 4 | ½" |
| 2" | 150 | 17.5 | 120.7 | 4 | ⅝" |
| 2½" | 180 | 20.7 | 139.7 | 4 | ⅝" |
| 3" | 190 | 22.3 | 152.4 | 4 | ⅝" |
| 3½" | 215 | 22.3 | 177.8 | 8 | ⅝" |
| 4" | 230 | 22.3 | 190.5 | 8 | ⅝" |
| 5" | 255 | 22.3 | 215.9 | 8 | ¾" |
| 6" | 280 | 23.9 | 241.3 | 8 | ¾" |
| 8" | 345 | 27.0 | 298.5 | 8 | ¾" |
| 10" | 405 | 28.6 | 362.0 | 12 | ⅞" |
| 12" | 485 | 30.2 | 431.8 | 12 | ⅞" |
Class 300
| NPS | Flange OD | Min. thickness | Bolt circle | No. of bolts | Bolt dia (in) |
|---|---|---|---|---|---|
| ½" | 95 | 12.7 | 66.7 | 4 | ½" |
| ¾" | 115 | 14.3 | 82.6 | 4 | ⅝" |
| 1" | 125 | 15.9 | 88.9 | 4 | ⅝" |
| 1¼" | 135 | 17.5 | 98.4 | 4 | ⅝" |
| 1½" | 155 | 19.1 | 114.3 | 4 | ¾" |
| 2" | 165 | 20.7 | 127.0 | 8 | ⅝" |
| 2½" | 190 | 23.9 | 149.2 | 8 | ¾" |
| 3" | 210 | 27.0 | 168.3 | 8 | ¾" |
| 3½" | 230 | 28.6 | 184.2 | 8 | ¾" |
| 4" | 255 | 30.2 | 200.0 | 8 | ¾" |
| 5" | 280 | 33.4 | 235.0 | 8 | ¾" |
| 6" | 320 | 35.0 | 269.9 | 12 | ¾" |
| 8" | 380 | 39.7 | 330.2 | 12 | ⅞" |
| 10" | 445 | 46.1 | 387.4 | 16 | 1" |
| 12" | 520 | 49.3 | 450.8 | 16 | 1⅛" |
Dimensions in mm per ASME B16.5 (current editions): thickness excludes the 1.6 mm raised face. Bolt diameter in inches. Material is specified separately — ASTM A182 (stainless, duplex), B564 (nickel alloys) or A105 (carbon steel).
Stud bolts for these flanges
Each flange joint uses the number of bolts shown, normally as fully threaded stud bolts with two heavy hex nuts. Stud length depends on flange type, facing and gasket; B7/2H for general service, B8M/8M or duplex for corrosive service.
Stud boltsFlange dimensions — questions
Does flange thickness in ASME B16.5 include the raised face?
No. In current editions the minimum thickness tf excludes the raised face. For Class 150 and 300 the raised face adds 1.6 mm (1/16"); for Class 400 and above it adds 6.4 mm (1/4").
Are weld neck, slip-on and blind flanges the same size?
For a given size and class they share the outside diameter, bolt circle and bolting, so they bolt together. Hub length, bore and some thicknesses differ by type.
How many bolts does a 4 inch Class 150 flange have?
Eight bolts of 5/8" diameter on a 190.5 mm bolt circle.
Do ASME B16.5 and EN 1092-1 flanges fit together?
Generally no. PN flanges have different bolt circles and bolt sizes, so check both before mixing standards.