ASME B16.47 covers large-diameter steel flanges from NPS 26 to NPS 60 (DN 650 to DN 1500). It is published by ASME International and applies to petroleum refinery, chemical processing, and power plant piping systems where pipe sizes exceed the NPS 24 limit of ASME B16.5.
The standard defines two flange series: Series A (based on MSS SP-44, larger outside diameter) and Series B (based on API 605, slightly smaller dimensions). Both series are dimensionally distinct — always verify which series is specified in your project documentation. Series A is more commonly specified in modern projects.
Series A vs Series B: Series A (MSS SP-44) flanges have larger outside diameters than Series B (API 605). The bolt circle diameters (W) also differ. Always confirm the applicable series from project specifications — mixing Series A and B components can cause assembly problems due to different bolt circle diameters.
Series A (MSS SP-44) — Class 150 ASME B16.47
NPS 26 – 48 (DN 650 – 1200)
NPS
(in)
DN
(mm)
O
(mm)
C
(mm)
R
(mm)
W
(mm)
dh
(mm)
n
Bolt
Size
Weight
(kg, CS)
26
650
1030
38.1
927
977
34.9
28
1¼
580
28
700
1110
41.3
984
1054
34.9
28
1¼
720
30
750
1170
41.3
1041
1114
34.9
28
1¼
810
32
800
1230
44.5
1092
1170
41.3
28
1½
960
34
850
1290
44.5
1149
1230
41.3
32
1½
1070
36
900
1350
47.7
1200
1286
41.3
32
1½
1240
38
950
1410
47.7
1262
1346
41.3
32
1½
1360
40
1000
1470
47.7
1319
1406
41.3
36
1½
1470
42
1050
1530
50.8
1372
1466
41.3
36
1½
1700
44
1100
1590
50.8
1429
1524
47.7
36
1¾
1830
46
1150
1650
53.9
1486
1584
47.7
40
1¾
2090
48
1200
1710
53.9
1543
1644
47.7
40
1¾
2250
50
1250
1770
57.2
1600
1702
47.7
44
1¾
2560
52
1300
1830
57.2
1657
1762
47.7
44
1¾
2740
54
1350
1890
57.2
1714
1822
47.7
44
1¾
2920
56
1400
1950
60.3
1772
1882
54.0
44
2
3280
58
1450
2010
60.3
1829
1942
54.0
48
2
3470
60
1500
2070
60.3
1886
2002
54.0
48
2
3690
Series B (API 605) — Class 150 ASME B16.47
Series B (API 605): Has smaller outside diameters than Series A. The bolt circle diameters are also different. Series B flanges are generally lighter than Series A at the same size. Note: API 605 has been formally withdrawn and replaced; however, Series B dimensions remain in ASME B16.47 for legacy compatibility.
NPS 26 – 48 (DN 650 – 1200) — Key Sizes
NPS
(in)
DN
(mm)
O
(mm)
C
(mm)
R
(mm)
W
(mm)
dh
(mm)
n
Bolt
Size
Weight
(kg, CS)
26
650
990
34.9
914
950
31.8
24
1⅛
490
28
700
1055
34.9
965
1016
31.8
28
1⅛
555
30
750
1110
38.1
1016
1067
34.9
28
1¼
665
32
800
1170
38.1
1067
1124
34.9
28
1¼
740
34
850
1230
38.1
1118
1181
34.9
32
1¼
820
36
900
1290
38.1
1168
1232
38.1
32
1⅜
910
38
950
1350
38.1
1219
1292
38.1
32
1⅜
990
40
1000
1410
38.1
1270
1343
38.1
36
1⅜
1080
42
1050
1470
38.1
1321
1403
38.1
36
1⅜
1175
44
1100
1530
41.3
1372
1454
41.3
40
1½
1385
46
1150
1590
41.3
1422
1510
41.3
40
1½
1490
48
1200
1650
41.3
1473
1568
41.3
40
1½
1600
Series A Class 300 / 400 / 600 — Key Dimensions ASME B16.47
Class 300+ Dimensions: Class 300, 400, and 600 dimensions for Series A (NPS 26–60) share the same basic OD as Class 150 but have progressively thicker flanges and larger bolt circles. Full tables available on request or from the ASME B16.47-2020 standard. Contact HT PIPE for specific Class 300–600 dimension datasheets.
NPS
(in)
DN
(mm)
Class 150
O / C (mm)
Class 300
O / C (mm)
Class 400
O / C (mm)
Class 600
O / C (mm)
Bolt
Circle W
(mm)
26
650
1030
38.1
1080
50.8
1110
53.9
1130
63.5
977
28
700
1110
41.3
1150
53.9
1180
57.2
1200
66.7
1054
30
750
1170
41.3
1230
57.2
1250
60.3
1280
69.9
1114
32
800
1230
44.5
1290
60.3
1320
63.5
1350
73.1
1170
34
850
1290
44.5
1350
63.5
1380
66.7
1410
76.2
1230
36
900
1350
47.7
1410
66.7
1450
69.9
1470
79.4
1286
38
950
1410
47.7
1470
69.9
1510
73.1
1540
82.6
1346
40
1000
1470
47.7
1530
73.1
1570
76.2
1600
85.8
1406
42
1050
1530
50.8
1590
76.2
1630
79.4
1660
88.9
1466
44
1100
1590
50.8
1650
79.4
1690
82.6
1720
92.1
1524
46
1150
1650
53.9
1710
82.6
1750
85.8
1790
95.3
1584
48
1200
1710
53.9
1770
85.8
1810
88.9
1850
98.5
1644
50
1250
1770
57.2
1830
88.9
1870
92.1
1910
101.6
1702
52
1300
1830
57.2
1890
92.1
1930
95.3
1970
104.8
1762
54
1350
1890
57.2
1950
95.3
1990
98.5
2030
108.0
1822
56
1400
1950
60.3
2010
98.5
2050
101.6
2090
111.2
1882
58
1450
2010
60.3
2070
101.6
2110
104.8
2150
114.3
1942
60
1500
2070
60.3
2130
104.8
2170
108.0
2210
117.5
2002
ASME B16.5 vs ASME B16.47 — Key Differences
Parameter
ASME B16.5
ASME B16.47
Size Range
NPS ½ – 24 (DN 15 – 600)
NPS 26 – 60 (DN 650 – 1500)
Standard Basis
Original ASME flange standard
B16.47 includes both Series A (MSS SP-44) and Series B (API 605)
Pressure Classes
150, 300, 400, 600, 900, 1500, 2500
150, 300, 400, 600, 900
Face Types
RF, FF, RTJ, TG
RF (Raised Face), RTJ (Ring Type Joint)
Typical Application
General industrial, chemical, oil & gas
Large refinery, petrochemical, power plants, offshore platforms
Forgings vs Plates
Mostly forged; some castings for large sizes
Often fabricated from plate for sizes ≥ NPS 26; some forged options
Weight
Lower for same Class/DN in B16.5
Heavier due to larger OD and thickness for structural reasons
When to use ASME B16.47: Use B16.47 for all piping systems with nominal pipe sizes NPS 26 and above. The standard is mandatory in API 650 storage tank nozzle design, most refinery tie-in specifications, and power plant projects per ASME Section III or Section I. Always confirm project specifications — some projects require B16.47 even for NPS 24 and below.
