ASME B16.5 class 400 (400 lb) flange: dimensions, bolt pattern and weight
All class 400 flange types on one page: weld neck, slip-on, socket weld, threaded, lap joint and blind. Dimensions in millimeters per ASME B16.5 2020 edition, bolts in inches.
Up to NPS 3½, ASME B16.5 requires class 400 to use the same dimensions as class 600. In the tables these rows appear with "= 600" next to the NPS.
General dimensions and weld neck (WN) flange
| NPS | DN | O | tf | R | X | Ah | Y WN | B WN | WN weight* | Blind weight* |
|---|---|---|---|---|---|---|---|---|---|---|
| ½" = 600 | 15 | 95 | 14.2 | 35.1 | 38 | 21.3 | 52 | customer | 0.9 | 0.8 |
| ¾" = 600 | 20 | 117 | 15.7 | 42.9 | 48 | 26.7 | 57 | customer | 1.5 | 1.3 |
| 1" = 600 | 25 | 124 | 17.5 | 50.8 | 54 | 33.5 | 62 | customer | 1.8 | 1.6 |
| 1¼" = 600 | 32 | 133 | 20.6 | 63.5 | 64 | 42.2 | 67 | customer | 2.5 | 2.2 |
| 1½" = 600 | 40 | 155 | 22.4 | 73 | 70 | 48.3 | 70 | customer | 3.5 | 3.3 |
| 2" = 600 | 50 | 165 | 25.4 | 91.9 | 84 | 60.5 | 73 | customer | 4.3 | 4.1 |
| 2½" = 600 | 65 | 190 | 28.4 | 104.6 | 100 | 73.2 | 79 | customer | 6.3 | 6.1 |
| 3" = 600 | 80 | 210 | 31.8 | 127 | 117 | 88.9 | 83 | customer | 8.5 | 8.5 |
| 3½" = 600 | 90 | 229 | 35.1 | 139.7 | 133 | 101.6 | 86 | customer | 10.7 | 11 |
| 4" | 100 | 254 | 35.1 | 157.2 | 146 | 114.3 | 89 | customer | 13.3 | 13.8 |
| 5" | 125 | 279 | 38.1 | 185.7 | 178 | 141.2 | 102 | customer | 17.5 | 18.4 |
| 6" | 150 | 318 | 41.1 | 215.9 | 206 | 168.4 | 103 | customer | 22.9 | 25.5 |
| 8" | 200 | 381 | 47.8 | 269.7 | 260 | 219.2 | 117 | customer | 36.1 | 42.8 |
| 10" | 250 | 444 | 53.8 | 323.8 | 321 | 273.0 | 124 | customer | 50.4 | 64.2 |
| 12" | 300 | 521 | 57.2 | 381 | 375 | 323.8 | 137 | customer | 72.6 | 94.6 |
| 14" | 350 | 584 | 60.5 | 412.8 | 425 | 355.6 | 149 | customer | 99.7 | 124.8 |
| 16" | 400 | 648 | 63.5 | 469.9 | 483 | 406.4 | 152 | customer | 123.4 | 161.7 |
| 18" | 450 | 711 | 66.5 | 533.4 | 533 | 457.2 | 165 | customer | 150.5 | 204.2 |
| 20" | 500 | 775 | 69.8 | 584.2 | 587 | 508.0 | 168 | customer | 179.1 | 254.3 |
| 22" | 550 | 838 | 73.2 | 641.4 | 641 | 558.8 | 171 | customer | 210.5 | 311.8 |
| 24" | 600 | 914 | 76.2 | 692.2 | 702 | 609.6 | 175 | customer | 258.2 | 385.8 |
Slip-on, socket weld, threaded and lap joint
| NPS | Y SO / SW / TH | B SO / SW | D socket | T thread | Q counterbore | Y LJ | B LJ | r LJ | SO weight* |
|---|---|---|---|---|---|---|---|---|---|
| ½" = 600 | 22 | 22.4 | 10 | 16 | 23.6 | 22 | 22.9 | 3 | 0.7 |
| ¾" = 600 | 25 | 27.7 | 11 | 16 | 29.0 | 25 | 28.2 | 3 | 1.2 |
| 1" = 600 | 27 | 34.5 | 13 | 18 | 35.8 | 27 | 35.1 | 3 | 1.5 |
| 1¼" = 600 | 28 | 43.2 | 14 | 21 | 44.4 | 28 | 43.7 | 5 | 2 |
| 1½" = 600 | 32 | 49.5 | 16 | 22 | 50.5 | 32 | 50.0 | 6 | 3 |
| 2" = 600 | 37 | 62.0 | 18 | 28 | 63.5 | 37 | 62.5 | 8 | 3.6 |
| 2½" = 600 | 41 | 74.7 | 19 | 32 | 76.2 | 41 | 75.4 | 8 | 5.2 |
| 3" = 600 | 46 | 90.7 | 21 | 35 | 92.2 | 46 | 91.4 | 10 | 7 |
| 3½" = 600 | 49 | 103.4 | – | 40 | 104.9 | 49 | 104.1 | 10 | 8.8 |
| 4" | 51 | 116.1 | – | 37 | 117.6 | 51 | 116.8 | 11 | 11.1 |
| 5" | 54 | 143.8 | – | 43 | 144.5 | 54 | 144.5 | 11 | 13.8 |
| 6" | 57 | 170.7 | – | 46 | 171.4 | 57 | 171.4 | 13 | 18.2 |
| 8" | 68 | 221.5 | – | 51 | 222.2 | 68 | 222.2 | 13 | 28.5 |
| 10" | 73 | 276.4 | – | 56 | 276.4 | 102 | 277.4 | 13 | 38.8 |
| 12" | 79 | 327.2 | – | 60 | 328.7 | 108 | 328.2 | 13 | 56.8 |
| 14" | 84 | 359.2 | – | 64 | 360.4 | 117 | 360.2 | 13 | 78.7 |
| 16" | 94 | 410.5 | – | 68 | 411.2 | 127 | 411.2 | 13 | 100.6 |
| 18" | 99 | 461.8 | – | 70 | 462.0 | 137 | 462.3 | 13 | 121.7 |
| 20" | 102 | 513.1 | – | 73 | 512.8 | 146 | 514.4 | 13 | 145.9 |
| 22" | 108 | 564.4 | – | – | – | 152 | 565.2 | 13 | 174.1 |
| 24" | 114 | 616.0 | – | 83 | 614.4 | 159 | 616.0 | 13 | 217.5 |
Y = overall length without raised face · B = minimum bore · D = socket depth · T = minimum thread length · Q = thread counterbore diameter · r = lap joint bore radius. "–" = type not covered by the standard at this diameter.
Bolt pattern and bolting
| NPS | O | W (bolt circle) | No. of holes | Hole Ø | Bolt Ø | Stud bolt, RF | Stud bolt, RTJ |
|---|---|---|---|---|---|---|---|
| ½" = 600 | 95 | 66.5 | 4 | ⅝" | ½" | 75 | 75 |
| ¾" = 600 | 117 | 82.6 | 4 | ¾" | ⅝" | 90 | 90 |
| 1" = 600 | 124 | 88.9 | 4 | ¾" | ⅝" | 90 | 90 |
| 1¼" = 600 | 133 | 98.6 | 4 | ¾" | ⅝" | 95 | 95 |
| 1½" = 600 | 155 | 114.3 | 4 | ⅞" | ¾" | 110 | 110 |
| 2" = 600 | 165 | 127.0 | 8 | ¾" | ⅝" | 110 | 110 |
| 2½" = 600 | 190 | 149.4 | 8 | ⅞" | ¾" | 120 | 120 |
| 3" = 600 | 210 | 168.1 | 8 | ⅞" | ¾" | 125 | 125 |
| 3½" = 600 | 229 | 184.2 | 8 | 1" | ⅞" | 140 | 140 |
| 4" | 254 | 200.2 | 8 | 1" | ⅞" | 140 | 140 |
| 5" | 279 | 235.0 | 8 | 1" | ⅞" | 145 | 145 |
| 6" | 318 | 269.7 | 12 | 1" | ⅞" | 150 | 150 |
| 8" | 381 | 330.2 | 12 | 1⅛" | 1" | 170 | 170 |
| 10" | 444 | 387.4 | 16 | 1¼" | 1⅛" | 190 | 190 |
| 12" | 521 | 450.8 | 16 | 1⅜" | 1¼" | 205 | 205 |
| 14" | 584 | 514.4 | 20 | 1⅜" | 1¼" | 210 | 210 |
| 16" | 648 | 571.5 | 20 | 1½" | 1⅜" | 220 | 220 |
| 18" | 711 | 628.6 | 24 | 1½" | 1⅜" | 230 | 230 |
| 20" | 775 | 685.8 | 24 | 1⅝" | 1½" | 240 | 250 |
| 22" | 838 | 743.0 | 24 | 1¾" | 1⅝" | 255 | 260 |
| 24" | 914 | 812.8 | 24 | 1⅞" | 1¾" | 265 | 280 |
Stud bolt length in mm, excluding the ends. Ring type joints (RTJ) use a longer stud in almost all diameters.
Allowable pressure of class 400 (bar)
| Material (group) | −29 to 38 °C | 100 °C | 200 °C | 300 °C | 400 °C |
|---|---|---|---|---|---|
| Carbon steel A105 / A350 LF2 (1.1) | 68.1 | 62.1 | 58.4 | 53.1 | 46.3 |
| Stainless F304 / F304H (2.1) | 66.2 | 54.5 | 46.0 | 41.2 | 37.9 |
| Stainless F316 / F316H (2.2) | 66.2 | 56.3 | 47.6 | 42.2 | 39.3 |
| Duplex F51, super duplex F53 / F55 (up to 315 °C), 6Mo F44 (2.8) | 68.9 | 67.5 | 56.9 | 51.8 | 48.9 |
| Inconel 625, Incoloy 825, Hastelloy C-276 / C-22 (3.8) | 68.9 | 68.7 | 64.5 | 57.0 | 48.9 |
Values from ASME B16.5 tables 2-1.1 to 2-3.8. "–" = material outside the standard's temperature range. For other groups and temperatures, consult engineering.
Table notes
- Dimensions without the raised face: add 6.4 mm to the thickness (tf) and length (Y) of raised-face flanges.
- "= 600" next to the NPS: up to NPS 3½, class 400 uses the same dimensions as class 600, as the standard requires.
- * Weight estimated from geometry in carbon steel, with STD bore when the customer does not state the schedule. Stainless weighs about 1 % more; nickel alloys 7 % to 13 % more.
- "customer" = the WN bore follows the pipe schedule stated in the order.
Frequently asked questions
What does class 400 flange (400#, 400 lb) mean?
It is the ASME B16.5 pressure class. It is not the pressure in psi: it defines an allowable pressure vs. temperature curve for each material group. In A105 carbon steel, class 400 allows 68.1 bar from −29 to 38 °C and less as the temperature rises.
Which flange types exist in class 400?
Weld neck (WN): NPS ½ to 24; Slip-on (SO): NPS ½ to 24; Socket weld (SW): NPS ½ to 3; Threaded (TH): NPS ½ to 24; Lap joint (LJ): NPS ½ to 24; Blind (BL): NPS ½ to 24.
Do the thickness (tf) and length (Y) include the raised face?
No. Since the 2017 edition, tf and Y are measured without the raised face. In class 400 the standard raised face is 6.4 mm, which is added to the table thickness.
What is the bore (B) of the weld neck flange?
The WN bore follows the pipe wall thickness (schedule). The standard gives the standard-wall (STD) bore only for classes 150 and 300 up to NPS 12; in the other cases the customer states the schedule in the order.
