ASME B16.47 · Standard reference
ASME B16.47-2025 pressure–temperature ratings (Group 1.1)
Table 3 (SI, bar) and Table 3C (U.S. customary, psig) of ASME B16.47-2025 give the maximum working pressure of Group 1.1 flanges at design temperatures from 38 °C to 538 °C (100 °F to 1,000 °F) for Classes 75, 150, 300, 400, 600 and 900. The ratings apply to large-diameter Series A and Series B flanges alike: the allowable pressure is fixed by the pressure class and the material group, not by the flange series or the outside diameter.
The first row of each table is a floor, not an extra data point — every temperature at or below 38 °C (100 °F) takes the ambient rating. Linear interpolation is permitted between the listed temperatures, but interpolation between classes is not, and the tables must not be extrapolated above their highest listed temperature. The six notes under each table carry the material and temperature limits that go with the numbers; they are reproduced as footnotes on the tables below.
- Standard
- ASME B16.47-2025
- Tables
- 3 (bar) and 3C (psig)
- Material group
- 1.1
- Classes
- 75, 150, 300, 400, 600, 900
- Ambient rating
- 9.8 bar (Class 75) to 153.1 bar (Class 900)
- Top temperature
- 538 °C / 1,000 °F
Materials covered by Tables 3 and 3C
Group 1.1 is the carbon and carbon-manganese steel group. Table 3 and Table 3C name a nominal designation for each row and list the accepted forging, casting and plate specifications; note markers refer to the limits given under each rating table. The same group also covers the C-Mn-Si-V and 3½Ni grades listed below.
B16.47 · ASME B16.47-2025
| Nominal designation | Forgings | Castings | Plates |
|---|---|---|---|
| C-Si | A105 [Notes (1), (2)] | A216 Gr. WCB [Note (1)] | A515 Gr. 70 [Note (1)] |
| C-Mn-Si | A350 Gr. LF2 [Note (1)] | — | A516 Gr. 70 [Notes (1), (2)] |
| C-Mn-Si | — | — | A537 Cl. 1 [Note (3)] |
| C-Mn-Si-V | A350 Gr. LF6 Cl. 1 [Note (4)] | — | — |
| 3½Ni | A350 Gr. LF3 [Note (5)] | — | — |
Product forms shown exactly where the standard lists them; '—' means the standard lists no specification of that form for the row. Note markers correspond to the footnotes on the rating tables.
Table 3 — Group 1.1 working pressure in bar (SI units)
Metric table. Pressure values are bar; temperatures are degrees Celsius. The 538 °C row is the last tabulated condition.
B16.47 · ASME B16.47-2025
| Temperature °C | Class 75 bar | Class 150 bar | Class 300 bar | Class 400 bar | Class 600 bar | Class 900 bar |
|---|---|---|---|---|---|---|
| min. to 38 [Note 6] | 9.8 | 19.6 | 51.0 | 68.0 | 102.0 | 153.1 |
| 50 | 9.6 | 19.1 | 49.8 | 66.4 | 99.6 | 149.3 |
| 100 | 8.8 | 17.7 | 46.7 | 62.3 | 93.4 | 140.1 |
| 150 | 7.9 | 15.8 | 45.1 | 60.1 | 90.1 | 135.2 |
| 200 | 6.9 | 13.8 | 43.8 | 58.4 | 87.6 | 131.5 |
| 250 | 6.0 | 12.1 | 42.0 | 56.0 | 83.9 | 125.9 |
| 300 | 5.1 | 10.2 | 39.9 | 53.2 | 79.6 | 119.7 |
| 325 | 4.6 | 9.3 | 38.7 | 51.6 | 77.3 | 116.0 |
| 350 | 3.1 | 8.4 | 37.6 | 50.2 | 75.3 | 112.9 |
| 375 | — | 7.4 | 36.4 | 48.5 | 72.8 | 109.2 |
| 400 | — | 6.5 | 34.6 | 46.2 | 69.3 | 103.9 |
| 425 | — | 5.5 | 28.7 | 38.3 | 57.5 | 86.2 |
| 450 | — | 4.6 | 23.0 | 30.6 | 45.9 | 68.9 |
| 475 | — | 3.7 | 17.5 | 23.3 | 35.0 | 52.5 |
| 500 | — | 2.8 | 11.5 | 15.4 | 23.0 | 34.6 |
| 538 | — | 1.4 | 5.8 | 7.7 | 11.6 | 17.4 |
- 1 Prolonged service above 427 °C can convert the carbide phase to graphite. The standard permits such service but does not recommend it.
- 2 Only killed steel may be used above 455 °C.
- 3 A537 Cl. 1 plate is limited to 371 °C.
- 4 A350 LF6 Cl. 1 is limited to 260 °C.
- 5 A350 LF3 is limited to 343 °C.
- 6 Minimum-temperature guidance is given in para. 2.5.3.
Maximum allowable working pressure in bar at the listed metal temperature. Temperatures at or below 38 °C use the 'min. to 38' row. Linear interpolation is permitted between listed temperatures; interpolation between classes is not permitted. '—' records a cell for which the standard prints no rating ('...').
Table 3C — Group 1.1 working pressure in psig (U.S. customary units)
U.S. customary table. Pressure values are psig; temperatures are degrees Fahrenheit. The same materials and temperature limits apply as in Table 3.
B16.47 · ASME B16.47-2025
| Temperature °F | Class 75 psig | Class 150 psig | Class 300 psig | Class 400 psig | Class 600 psig | Class 900 psig |
|---|---|---|---|---|---|---|
| min. to 100 [Note 6] | 140 | 285 | 740 | 985 | 1,480 | 2,220 |
| 200 | 130 | 260 | 680 | 905 | 1,360 | 2,035 |
| 300 | 115 | 230 | 655 | 870 | 1,310 | 1,965 |
| 400 | 100 | 200 | 635 | 845 | 1,265 | 1,900 |
| 500 | 85 | 170 | 605 | 805 | 1,205 | 1,810 |
| 600 | 70 | 140 | 570 | 755 | 1,135 | 1,705 |
| 650 | 60 | 125 | 550 | 730 | 1,100 | 1,650 |
| 700 | — | 110 | 530 | 710 | 1,060 | 1,590 |
| 750 | — | 95 | 505 | 675 | 1,015 | 1,520 |
| 800 | — | 80 | 410 | 550 | 825 | 1,235 |
| 850 | — | 65 | 320 | 425 | 640 | 955 |
| 900 | — | 50 | 230 | 305 | 460 | 690 |
| 950 | — | 35 | 135 | 185 | 275 | 410 |
| 1,000 | — | 20 | 85 | 115 | 170 | 255 |
- 1 Prolonged service above 800 °F can convert the carbide phase to graphite. The standard permits such service but does not recommend it.
- 2 Only killed steel may be used above 850 °F.
- 3 A537 Cl. 1 plate is limited to 700 °F.
- 4 A350 LF6 Cl. 1 is limited to 500 °F.
- 5 A350 LF3 is limited to 650 °F.
- 6 Minimum-temperature guidance is given in para. 2.5.3.
Maximum allowable working pressure in psig at the listed metal temperature. Temperatures at or below 100 °F use the 'min. to 100' row. Linear interpolation is permitted between listed temperatures; interpolation between classes is not permitted. '—' records a cell for which the standard prints no rating ('...').
ASME B16.47 pressure–temperature ratings — questions
Do Series A and Series B flanges share the same pressure ratings?
Yes. The rating depends on the pressure class and the material group, not on the flange series. A Class 300 Series A flange and a Class 300 Series B flange made from the same group 1.1 material are both rated from Table 3 or 3C. The series only changes dimensions and bolt pattern, so never use it as a proxy for pressure capability.
Why does Table 3 list a Class 75 column?
Class 75 is the surviving part of the original API 605 line, which became Series B. ASME B16.47-2025 publishes Class 75 dimensions for Series B flanges only (Tables 37 and 37C), but its pressure–temperature tables keep a Class 75 column so those flanges have a rating. The ambient value is 140 psig (9.8 bar), exactly half the Class 150 rating.
Can a Class 900 B16.47 flange be used at 500 °C?
For Group 1.1 the table still gives a rating at 500 °C — 34.6 bar (500 psig at 932 °F) — and 538 °C is the highest listed temperature. Note (1) is the constraint to respect: prolonged service above 427 °C is permitted but not recommended for these carbon steels, and no rating exists above 538 °C. Higher-temperature service needs a different material group with its own table.
What does the 'min. to 38 °C' row mean?
It is the ambient floor for the table. Paragraph 2.4 of the standard says that for any temperature below 38 °C (100 °F) the rating may not exceed the value shown at 38 °C, so design at 0 °C or 20 °C uses 19.6 bar for a Class 150 group 1.1 flange. The same convention applies to the 'min. to 100 °F' row in Table 3C.