Reference tables are transcribed from ASME B16.47-2025; table numbers, printed page numbers and cell values keep the standard's original wording.
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.
StandardASME B16.47-2025
Tables3 (bar) and 3C (psig)
Material group1.1
Classes75, 150, 300, 400, 600, 900
Ambient rating9.8 bar (Class 75) to 153.1 bar (Class 900)
Top temperature538 °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.
Table 3/3C header — Group 1.1 materials (p. 14-15)
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.
Table 3 (p. 14) — pressure–temperature ratings for Group 1.1 materials, SI units
Temperature°C
Class 75bar
Class 150bar
Class 300bar
Class 400bar
Class 600bar
Class 900bar
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
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 ('...').
1Prolonged service above 427 °C can convert the carbide phase to graphite. The standard permits such service but does not recommend it.
2Only killed steel may be used above 455 °C.
3A537 Cl. 1 plate is limited to 371 °C.
4A350 LF6 Cl. 1 is limited to 260 °C.
5A350 LF3 is limited to 343 °C.
6Minimum-temperature guidance is given in para. 2.5.3.
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.
Table 3C (p. 15) — pressure–temperature ratings for Group 1.1 materials, U.S. customary units
Temperature°F
Class 75psig
Class 150psig
Class 300psig
Class 400psig
Class 600psig
Class 900psig
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
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 ('...').
1Prolonged service above 800 °F can convert the carbide phase to graphite. The standard permits such service but does not recommend it.
2Only killed steel may be used above 850 °F.
3A537 Cl. 1 plate is limited to 700 °F.
4A350 LF6 Cl. 1 is limited to 500 °F.
5A350 LF3 is limited to 650 °F.
6Minimum-temperature guidance is given in para. 2.5.3.
FAQ
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.
Sources
ASME B16.47-2025, Table 3, Pressure-Temperature Ratings for Group 1.1 Materials — SI Units, p. 14 (PDF p. 29)
ASME B16.47-2025, Table 3C, Pressure-Temperature Ratings for Group 1.1 Materials — U.S. Customary Units, p. 15 (PDF p. 30)
ASME B16.47-2025, paras. 2.1 and 2.4 (interpolation and ambient floor), p. 2 (PDF p. 17)
ASME B16.47-2025, Table 1, List of Material Specifications, pp. 11-12 (PDF pp. 26-27)