Flange pressure–temperature rating chart (ASME B16.5)
Maximum non-shock working pressure for Material Group 1.1 — carbon steel A105 forgings, A216 WCB castings and A106 Gr B — by pressure class and temperature.
Working pressure in bar
| Temp °C | Class 150 | Class 300 | Class 600 | Class 900 | Class 1500 | Class 2500 |
|---|---|---|---|---|---|---|
| -29 to 38 | 19.6 | 51.1 | 102.1 | 153.2 | 255.3 | 425.5 |
| 50 | 19.2 | 50.1 | 100.2 | 150.4 | 250.6 | 417.7 |
| 100 | 17.7 | 46.6 | 93.2 | 139.8 | 233.0 | 388.3 |
| 150 | 15.8 | 45.1 | 90.2 | 135.2 | 225.4 | 375.6 |
| 200 | 13.8 | 43.8 | 87.6 | 131.4 | 219.0 | 365.0 |
| 250 | 12.1 | 41.9 | 83.9 | 125.8 | 209.7 | 349.5 |
| 300 | 10.2 | 39.8 | 79.6 | 119.5 | 199.1 | 331.8 |
| 325 | 9.3 | 38.7 | 77.4 | 116.1 | 193.6 | 322.6 |
| 350 | 8.4 | 37.6 | 75.1 | 112.7 | 187.8 | 313.0 |
| 375 | 7.4 | 36.4 | 72.7 | 109.1 | 181.8 | 303.1 |
| 400 | 6.5 | 34.7 | 69.4 | 104.2 | 173.6 | 289.3 |
| 425 | 5.5 | 28.8 | 57.5 | 86.3 | 143.8 | 239.7 |
| 450 | 4.6 | 23.0 | 46.0 | 69.0 | 115.0 | 191.7 |
| 475 | 3.7 | 17.4 | 34.9 | 52.3 | 87.2 | 145.3 |
| 500 | 2.8 | 11.8 | 23.5 | 35.3 | 58.8 | 97.9 |
| 538 | 1.4 | 5.9 | 11.8 | 17.7 | 29.5 | 49.2 |
Working pressure in psi
| Temp °C | Class 150 | Class 300 | Class 600 | Class 900 | Class 1500 | Class 2500 |
|---|---|---|---|---|---|---|
| -29 to 38 | 284 | 741 | 1,481 | 2,222 | 3,703 | 6,171 |
| 50 | 278 | 727 | 1,453 | 2,181 | 3,635 | 6,058 |
| 100 | 257 | 676 | 1,352 | 2,028 | 3,379 | 5,632 |
| 150 | 229 | 654 | 1,308 | 1,961 | 3,269 | 5,448 |
| 200 | 200 | 635 | 1,271 | 1,906 | 3,176 | 5,294 |
| 250 | 175 | 608 | 1,217 | 1,825 | 3,041 | 5,069 |
| 300 | 148 | 577 | 1,155 | 1,733 | 2,888 | 4,812 |
| 325 | 135 | 561 | 1,123 | 1,684 | 2,808 | 4,679 |
| 350 | 122 | 545 | 1,089 | 1,635 | 2,724 | 4,540 |
| 375 | 107 | 528 | 1,054 | 1,582 | 2,637 | 4,396 |
| 400 | 94 | 503 | 1,007 | 1,511 | 2,518 | 4,196 |
| 425 | 80 | 418 | 834 | 1,252 | 2,086 | 3,477 |
| 450 | 67 | 334 | 667 | 1,001 | 1,668 | 2,780 |
| 475 | 54 | 252 | 506 | 759 | 1,265 | 2,107 |
| 500 | 41 | 171 | 341 | 512 | 853 | 1,420 |
| 538 | 20 | 86 | 171 | 257 | 428 | 714 |
Group 1.1 only. Stainless, alloy and nickel material groups have different ratings — see ASME B16.5 Table 2. Read flange pressure classes explained.
Frequently asked questions
What is the pressure rating of a Class 150 flange at 200 °C?
13.8 bar (about 200 psi) for carbon steel Group 1.1 materials.
What is the rating of a Class 300 flange at ambient?
51.1 bar (740 psi) for Group 1.1 carbon steel at −29 to 38 °C.
Why does the rating fall with temperature?
The allowable stress of steel decreases as temperature rises, and above about 425 °C creep governs, so the permitted pressure drops sharply.
Last updated 2026-11-02