Pressure Classes Reference
Comparison of ANSI/ASME pressure classes and PN ratings — pressure-temperature ratings for flanges, valves, and fittings.
Pressure Class Systems
Two main pressure class systems exist worldwide: ANSI/ASME Class (150, 300, 600, 900, 1500, 2500) used primarily in North America, and PN (Pression Nominale: 6, 10, 16, 25, 40, 63, 100, 160, 250, 400) used in Europe and international (ISO) standards. Both define the pressure-temperature rating of flanges, valves, and fittings.
ANSI/ASME B16.5 Ratings (Carbon Steel)
| Class | Rating at 38°C (bar) | Rating at 200°C (bar) | Rating at 400°C (bar) |
|---|---|---|---|
| 150 | 19.6 | 13.8 | 5.5 |
| 300 | 51.1 | 43.9 | 30.9 |
| 600 | 102.1 | 87.9 | 61.9 |
| 900 | 153.2 | 131.6 | 92.8 |
| 1500 | 255.3 | 219.6 | 154.6 |
| 2500 | 425.5 | 366.4 | 257.6 |
PN Ratings (EN 1092)
| PN | Rating at 20°C (bar) | Rating at 200°C (bar) | Rating at 400°C (bar) |
|---|---|---|---|
| PN6 | 6 | 5 | 3 |
| PN10 | 10 | 9 | 6 |
| PN16 | 16 | 14 | 9 |
| PN25 | 25 | 22 | 15 |
| PN40 | 40 | 35 | 24 |
| PN63 | 63 | 55 | 38 |
| PN100 | 100 | 87 | 60 |
| PN160 | 160 | 140 | 96 |
| PN250 | 250 | 219 | 150 |
| PN400 | 400 | 350 | 240 |
Temperature derating is critical
Flange ratings drop significantly with temperature. A Class 150 flange rated at 19.6 bar at 38°C drops to 5.5 bar at 400°C. Always check the pressure-temperature rating at your operating temperature, not just the ambient rating.
How CHI can help
Ask CHI about pressure class ratings and to recommend the correct class for your pressure and temperature. The CHI assistant can look up specific values, explain what each table entry means, and help you cross-reference between different standards and unit systems.