| NPS | O | tf | X | Ah | Y (THD) | Y (Lap) | Y (WN) | T | B (SO) | B (WN) | r | Q | Bolt Circle Dia. | Bolt Qty | Bolt Hole Dia. | Bolt Dia. |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2 | 133 | 30.2 | 43 | 21.3 | 40 | 40 | 73 | 28 | 22.9 | 3 | 23.6 | 88.9 | 4 | 7/8 | 3/4 | |
| 3/4 | 140 | 31.8 | 51 | 26.7 | 43 | 43 | 79 | 32 | 28.2 | 3 | 29 | 95.2 | 4 | 7/8 | 3/4 | |
| 1 | 159 | 35.1 | 57 | 33.5 | 48 | 48 | 89 | 35 | 35.4 | 3 | 35.8 | 108.0 | 4 | 1 | 7/8 | |
| 1 1/4 | 184 | 38.1 | 73 | 42.2 | 52 | 52 | 95 | 38 | 43.7 | 5 | 44.4 | 130.0 | 4 | 1 1/8 | 1 | |
| 1 1/2 | 203 | 44.4 | 79 | 48.3 | 60 | 60 | 111 | 44 | 50 | 6 | 50.5 | 146.0 | 4 | 1 1/4 | 1 1/8 | |
| 2 | 235 | 50.8 | 95 | 60.5 | 70 | 70 | 127 | 51 | 62.5 | 8 | 63.5 | 171.4 | 8 | 1 1/8 | 1 | |
| 2 1/2 | 267 | 57.2 | 114 | 73.2 | 79 | 79 | 143 | 57 | 75.4 | 8 | 76.2 | 196.8 | 8 | 1 1/4 | 1 1/8 | |
| 3 | 305 | 66.5 | 133 | 88.9 | 92 | 168 | 91.4 | 10 | 228.6 | 8 | 1 3/8 | 1 1/4 | ||||
| 4 | 356 | 76.2 | 165 | 114.3 | 108 | 190 | 116.8 | 11 | 273.0 | 8 | 1 5/8 | 1 1/2 | ||||
| 5 | 419 | 91.9 | 203 | 141.2 | 130 | 229 | 144.5 | 11 | 323.8 | 8 | 1 7/8 | 1 3/4 | ||||
| 6 | 483 | 108 | 235 | 168.4 | 152 | 273 | 171.4 | 13 | 368.3 | 8 | 2 1/8 | 2 | ||||
| 8 | 552 | 127 | 305 | 219.2 | 178 | 318 | 222.2 | 13 | 438.2 | 12 | 2 1/8 | 2 | ||||
| 10 | 673 | 165.1 | 375 | 273 | 229 | 419 | 277.4 | 13 | 539.8 | 12 | 2 5/8 | 2 1/2 | ||||
| 12 | 762 | 184.2 | 441 | 323.8 | 254 | 464 | 328.2 | 13 | 619.3 | 12 | 2 7/8 | 2 3/4 |
| NPS | O | tf | X | Ah | Y (THD) | Y (Lap) | Y (WN) | T | B (SO) | B (WN) | r | Q | Bolt Circle Dia. | Bolt Qty | Bolt Hole Dia. | Bolt Dia. |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1/2 | 5.25 | 1.19 | 1.69 | 0.84 | 1.56 | 1.56 | 2.88 | 1.12 | 0.9 | 0.12 | 0.93 | 3.5 | 4 | 7/8 | 3/4 | |
| 3/4 | 5.5 | 1.25 | 2 | 1.05 | 1.69 | 1.69 | 3.12 | 1.25 | 1.11 | 0.12 | 1.14 | 3.75 | 4 | 7/8 | 3/4 | |
| 1 | 6.25 | 1.38 | 2.25 | 1.32 | 1.88 | 1.88 | 3.5 | 1.38 | 1.38 | 0.12 | 1.41 | 4.25 | 4 | 1 | 7/8 | |
| 1 1/4 | 7.25 | 1.5 | 2.88 | 1.66 | 2.06 | 2.06 | 3.75 | 1.5 | 1.72 | 0.19 | 1.75 | 5.12 | 4 | 1 1/8 | 1 | |
| 1 1/2 | 8 | 1.75 | 3.12 | 1.9 | 2.38 | 2.38 | 4.38 | 1.75 | 1.97 | 0.25 | 1.99 | 5.75 | 4 | 1 1/4 | 1 1/8 | |
| 2 | 9.25 | 2 | 3.75 | 2.38 | 2.75 | 2.75 | 5 | 2 | 2.46 | 0.31 | 2.5 | 6.75 | 8 | 1 1/8 | 1 | |
| 2 1/2 | 10.5 | 2.25 | 4.5 | 2.88 | 3.12 | 3.12 | 5.62 | 2.25 | 2.97 | 0.31 | 3 | 7.75 | 8 | 1 1/4 | 1 1/8 | |
| 3 | 12 | 2.62 | 5.25 | 3.5 | 3.62 | 6.62 | 3.6 | 0.38 | 9 | 8 | 1 3/8 | 1 1/4 | ||||
| 4 | 14 | 3 | 6.5 | 4.5 | 4.25 | 7.5 | 4.6 | 0.44 | 10.75 | 8 | 1 5/8 | 1 1/2 | ||||
| 5 | 16.5 | 3.62 | 8 | 5.56 | 5.12 | 9 | 5.69 | 0.44 | 12.75 | 8 | 1 7/8 | 1 3/4 | ||||
| 6 | 19 | 4.25 | 9.25 | 6.63 | 6 | 10.75 | 6.75 | 0.5 | 14.5 | 8 | 2 1/8 | 2 | ||||
| 8 | 21.75 | 5 | 12 | 8.63 | 7 | 12.5 | 8.75 | 0.5 | 17.25 | 12 | 2 1/8 | 2 | ||||
| 10 | 26.5 | 6.5 | 14.75 | 10.75 | 9 | 16.5 | 10.92 | 0.5 | 21.25 | 12 | 2 5/8 | 2 1/2 | ||||
| 12 | 30 | 7.25 | 17.38 | 12.75 | 10 | 18.25 | 12.92 | 0.5 | 24.38 | 12 | 2 7/8 | 2 3/4 |
| NPS | THD | LAP | BL | WN |
|---|---|---|---|---|
| 1/2 | 7 / 3.18 | 7 / 3.18 | 7 / 3.18 | 8 / 3.63 |
| 3/4 | 9 / 4.08 | 8 / 3.63 | 10 / 4.54 | 9 / 4.08 |
| 1 | 12 / 5.44 | 12 / 5.44 | 12 / 5.44 | 13 / 5.90 |
| 1-1/4 | 18 / 8.16 | 17 / 7.71 | 18 / 8.16 | 20 / 9.07 |
| 1-1/2 | 25 / 11.34 | 24 / 10.89 | 25 / 11.34 | 28 / 12.70 |
| 2 | 38 / 17.24 | 37 / 16.78 | 39 / 17.69 | 42 / 19.05 |
| 2-1/2 | 55 / 24.95 | 53 / 24.04 | 56 / 25.40 | 52 / 23.59 |
| 3 | 83 / 37.65 | 80 / 36.29 | 86 / 39.00 | 94 / 42.64 |
| 4 | 127 / 57.61 | 122 / 55.34 | 133 / 60.33 | 146 / 66.22 |
| 5 | 210 / 95.25 | 204 / 92.53 | 223 / 101.15 | 244 / 110.68 |
| 6 | 323 / 146.51 | 314 / 142.43 | 345 / 156.49 | 378 / 171.46 |
| 8 | 485 / 219.99 | 471 / 213.64 | 533 / 241.77 | 576 / 261.36 |
| 10 | 925 / 419.57 | 897 / 406.33 | 1025 / 464.94 | 1068 / 484.13 |
| 12 | 1300 / 589.67 | 1262 / 572.50 | 1464 / 664.22 | 1608 / 729.73 |
Note: The above data is for reference only. Please refer to the ASME B16.5 standard for design and production.
ASME B16.5 Class 2500 flange dimensions refer to the standardized geometric measurements defined by the ASME B16.5 specification for flanges with a pressure rating of Class 2500.
This is the highest pressure class included in ASME B16.5 for NPS ½” to 24″ flanges.
The geometry of Class 2500 flanges remains exactly the same regardless of material, including:
- Carbon Steel
- Stainless Steel
- Duplex & Super Duplex
- Inconel, Hastelloy, Monel (Nickel Alloys)
- Copper Nickel (CuNi)
- Titanium, Alloy Steel, and more
Material only affects the pressure–temperature rating, not the actual dimensional values.
What Is ASME Class 2500?
Class 2500 is the highest standard pressure rating under ASME B16.5 and provides extremely high pressure containment capability.
It is significantly stronger than lower classes:
- ~2× Class 1500
- ~3.5× Class 900
- ~6× Class 600
- ~12–16× Class 150
Class 2500 flanges are designed for critical high-pressure and high-temperature services.
Common Applications of Class 2500 Flanges
These flanges are used where extreme pressure and temperature conditions demand the highest reliability:
- High-pressure steam systems
- Offshore subsea wellheads
- High-pressure natural gas transmission
- Petrochemical reactors
- High-temperature cracking units
- Power plant high-pressure lines
- Boiler and furnace superheater piping
Class 2500 flanges are commonly found in critical and hazardous services.
ASME B16.5 Class 2500 flanges represent the highest pressure rating within the ASME B16.5 standard. With extremely thick construction, large bolting, RTJ sealing, and strict dimensional control, they are engineered to perform reliably in the harshest industrial environments.
Their dimensions are material-independent, globally standardized, and widely used in oil & gas, petrochemical, offshore, high-pressure steam, and energy applications.
For any system requiring maximum strength, Class 2500 flanges are the preferred choice.
