Flange Pressure Rating Chart (ASME B16.5, A105)
Find the maximum allowable working pressure of a carbon steel (Group 1.1, A105) ASME B16.5 flange at your design temperature, with linear interpolation between table points.
Class 300 rating, Group 1.1 (bar g)
| Temperature (°C) | Max pressure (bar g) |
|---|---|
| −29 to 38 | 51.1 |
| 50 | 50.1 |
| 100 | 46.6 |
| 150 | 45.1 |
| 200 | 43.8 |
| 250 | 41.9 |
| 300 | 39.8 |
| 325 | 38.7 |
| 350 | 37.6 |
| 375 | 36.4 |
| 400 | 34.7 |
| 425 | 28.8 |
| 450 | 23.0 |
| 475 | 17.4 |
| 500 | 11.8 |
| 538 | 5.9 |
How Flange Ratings Work
Values are for ASME B16.5 Material Group 1.1 (A105 forgings, A216 WCB castings, A515/A516 Gr 70 plates) from the B16.5 rating tables, cross checked with published copies. Other materials (stainless steel groups 2.x) have different ratings.
Worked example
Class 300 at 180 °C: between 150 °C (45.1 bar) and 200 °C (43.8 bar), so the rating is about 44.3 bar g.
Frequently Asked Questions
What is the pressure rating of a Class 150 flange?
19.6 bar g at −29 to 38 °C for Group 1.1 carbon steel, falling with temperature.
What is the pressure rating of a Class 300 flange?
51.1 bar g at ambient for Group 1.1, about 43.8 bar g at 200 °C.
Can I interpolate between temperatures?
Yes, ASME B16.5 allows linear interpolation between tabulated temperatures.
Learn more on the blog
Control valve sizing rules
A practical, field focused guide on instrumentationblog.in that explains the theory behind this tool and how engineers apply it on real plants.
Read Full Article