Long Weld neck flange dimensions are covered in ASME B16.5 – which covers Pipe Flanges and Flanged Fittings for size NPS ½” to 24” for above NPS 26” to 60” it should be as per ASME B16.47.

During the dimensional inspection of a flange, you should check for

  • Outer & Inner Diameter of body
  • Bolt Circle & Bolt hole Diameter
  • The thickness of the weld end
  • Length of the Hub
  • Straightness and alignment of the bolt hole
long weld neck flange dimensions

Class 150 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC Machine Bolt Length RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 90 9.6 30 21.3 34.9 2 60.3 As Required 4 1/2 50 55 5/8 M14
3/4 20 100 11.2 38 26.7 42.9 2 69.9 As Required 4 1/2 50 65 5/8 M14
1 25 110 12.7 49 33.4 50.8 2 79.4 As Required 4 1/2 55 65 5/8 M14
1 1/4 32 115 14.3 59 42.2 63.5 2 88.9 As Required 4 1/2 55 70 5/8 M14
1 1/2 40 125 15.9 65 48.3 73 2 98.4 As Required 4 1/2 65 70 5/8 M14
2 50 150 17.5 78 60.3 92.1 2 120.7 As Required 4 5/8 70 85 3/4 M16
2 1/2 65 180 20.7 90 73 104.8 2 139.7 As Required 4 5/8 75 90 3/4 M16
3 80 190 22.3 108 88.9 127 2 152.4 As Required 4 5/8 75 90 3/4 M16
3 1/2 90 215 22.3 122 101.6 139.7 2 177.8 As Required 8 5/8 75 90 3/4 M16
4 100 230 22.3 135 114.3 157.2 2 190.5 As Required 8 5/8 75 90 3/4 M16
5 125 255 22.3 164 141.3 185.7 2 215.9 As Required 8 3/4 85 95 7/8 M20
6 150 280 23.9 192 168.3 215.9 2 241.3 As Required 8 3/4 85 100 7/8 M20
8 200 345 27 246 219.1 269.9 2 298.5 As Required 8 3/4 90 110 7/8 M20
10 250 405 28.6 305 273 323.8 2 362 As Required 12 7/8 100 115 1 M24
12 300 485 30.2 365 323.8 381 2 431.8 As Required 12 7/8 100 120 1 M24
14 350 535 33.4 400 355.6 412.8 2 476.3 As Required 12 1 115 135 1 1/8 M27
16 400 595 35 457 406.4 469.9 2 539.8 As Required 16 1 115 135 1 1/8 M27
18 450 635 38.1 505 457.2 533.4 2 577.9 As Required 16 1 1/8 125 145 1 1/4 M30
20 500 700 41.3 559 508 584.2 2 635 As Required 20 1 1/8 140 160 1 1/4 M30
24 600 815 46.1 663 610 692.2 2 749.3 As Required 20 1 1/4 150 170 1 3/8 M33

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Class 300 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC Machine Bolt Length RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 95 12.7 38 21.3 34.9 2 66.7 As Required 4 1/2 55 65 5/8 M14
3/4 20 115 14.3 48 26.7 42.9 2 82.6 As Required 4 5/8 65 75 3/4 M16
1 25 125 15.9 54 33.4 50.8 2 88.9 As Required 4 5/8 65 75 3/4 M16
1 1/4 32 135 17.5 64 42.2 63.5 2 98.4 As Required 4 5/8 70 85 3/4 M16
1 1/2 40 155 19.1 70 48.3 73 2 114.3 As Required 4 3/4 75 90 7/8 M20
2 50 165 20.7 84 60.3 92.1 2 127 As Required 8 5/8 75 90 3/4 M16
2 1/2 65 190 23.9 100 73 104.8 2 149.2 As Required 8 3/4 85 100 7/8 M20
3 80 210 27 117 88.9 127 2 168.3 As Required 8 3/4 90 110 7/8 M20
3 1/2 90 230 28.6 133 101.6 139.7 2 184.2 As Required 8 3/4 95 110 7/8 M20
4 100 255 30.2 146 114.3 157.2 2 200 As Required 8 3/4 95 115 7/8 M20
5 125 280 33.4 178 141.3 185.7 2 235 As Required 8 3/4 110 120 7/8 M20
6 150 320 35 206 168.3 215.9 2 269.9 As Required 12 3/4 110 120 7/8 M20
8 200 380 39.7 260 219.1 269.9 2 330.2 As Required 12 7/8 120 140 1 M24
10 250 445 46.1 321 273 323.8 2 387.4 As Required 16 1 140 160 1 1/8 M27
12 300 520 49.3 375 323.8 381 2 450.8 As Required 16 1 1/8 145 170 1 1/4 M30
14 350 585 52.4 425 355.6 412.8 2 514.4 As Required 20 1 1/8 160 180 1 1/4 M30
16 400 650 55.6 483 406.4 469.9 2 571.5 As Required 20 1 1/4 165 190 1 3/8 M33
18 450 710 58.8 533 457 533.4 2 628.6 As Required 24 1 1/4 170 195 1 3/8 M33
20 500 775 62 587 508 584.2 2 685.8 As Required 24 1 1/4 185 205 1 3/8 M33
24 600 915 68.3 702 610 692.2 2 812.8 As Required 24 1 1/2 205 230 1 5/8 M39

Flange and Olet Quiz – Test yourself, Take This Quiz

Class 400 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 95 14.3 38 21.3 34.9 7 66.7 As Required 4 1/2 75 5/8 M14
3/4 20 115 15.9 48 26.7 42.9 7 82.6 As Required 4 5/8 90 3/4 M16
1 25 125 17.5 54 33.4 50.8 7 88.9 As Required 4 5/8 90 3/4 M16
1 1/4 32 135 20.7 64 42.2 63.5 7 98.4 As Required 4 5/8 95 3/4 M16
1 1/2 40 155 22.3 70 48.3 73 7 114.3 As Required 4 3/4 110 7/8 M20
2 50 165 25.4 84 60.3 92.1 7 127 As Required 8 5/8 110 3/4 M16
2 1/2 65 190 28.6 100 73 104.8 7 149.2 As Required 8 3/4 120 7/8 M20
3 80 210 31.8 117 88.9 127 7 168.3 As Required 8 3/4 125 7/8 M20
3 1/2 90 230 35 133 101.6 N/A 7 184.2 As Required 8 7/8 140 1 M24
4 100 255 35 146 114.3 157.2 7 200 As Required 8 7/8 140 1 M24
5 125 280 38.1 178 141.3 185.7 7 235 As Required 8 7/8 145 1 M24
6 150 320 41.3 206 168.3 215.9 7 269.9 As Required 12 7/8 150 1 M24
8 200 380 47.7 260 219.1 269.9 7 330 As Required 12 1 170 1 1/8 M27
10 250 445 54 321 273 323.8 7 387.4 As Required 16 1 1/8 190 1 1/4 M30
12 300 520 57.2 375 323.8 381 7 450.8 As Required 16 1 1/4 205 1 3/8 M33
14 350 585 60.4 425 355.6 412.8 7 514.4 As Required 20 1 1/4 210 1 3/8 M33
16 400 650 63.5 483 406.4 469.9 7 571.5 As Required 20 1 3/8 220 1 1/2 M36
18 450 710 66.7 533 457 533.4 7 628.6 As Required 24 1 3/8 230 1 1/2 M36
20 500 775 69.9 587 508 584.2 7 685.8 As Required 24 1 1/2 240 1 3/4 M39
24 600 915 76.2 702 610 692.2 7 812.8 As Required 24 1 3/4 265 1 7/8 M45

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Class 600 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 95 14.3 38 21.3 34.9 7 66.7 As Required 4 1/2 75 5/8 M14
3/4 20 115 15.9 48 26.7 42.9 7 82.6 As Required 4 5/8 90 3/4 M16
1 25 125 17.5 54 33.4 50.8 7 88.9 As Required 4 5/8 90 3/4 M16
1 1/4 32 135 20.7 64 42.2 63.5 7 98.4 As Required 4 5/8 95 3/4 M16
1 1/2 40 155 22.3 70 48.3 73 7 114.3 As Required 4 3/4 110 7/8 M20
2 50 165 25.4 84 60.3 92.1 7 127 As Required 8 5/8 110 3/4 M16
2 1/2 65 190 28.6 100 73 104.8 7 149.2 As Required 8 3/4 120 7/8 M20
3 80 210 31.8 117 88.9 127 7 168.3 As Required 8 3/4 125 7/8 M20
3 1/2 90 230 35 133 101.6 N/A 7 184.2 As Required 8 7/8 140 1 M24
4 100 275 38.1 152 114.3 157.2 7 215.9 As Required 8 7/8 145 1 M24
5 125 330 44.5 189 141.3 185.7 7 266.7 As Required 8 1 165 1 1/8 M27
6 150 355 47.7 222 168.3 215.9 7 292.1 As Required 12 1 170 1 1/8 M27
8 200 420 55.6 273 219.1 269.9 7 349.2 As Required 12 1 1/8 190 1 1/4 M30
10 250 510 63.5 343 273 323.8 7 431.8 As Required 16 1 1/4 215 1 3/8 M33
12 300 560 66.7 400 323.8 381 7 489 As Required 20 1 1/4 220 1 3/8 M33
14 350 605 69.9 432 355.6 412.8 7 527 As Required 20 1 3/8 235 1 1/2 M36
16 400 685 76.2 495 406.4 469.9 7 603.2 As Required 20 1 1/2 255 1 5/8 M39
18 450 745 82.6 546 457 533.4 7 654 As Required 20 1 5/8 275 1 3/4 M42
20 500 815 88.9 610 508 584.2 7 723.9 As Required 24 1 5/8 285 1 3/4 M42

Class 900 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 120 22.3 38 21.3 34.9 7 82.6 As Required 4 3/4 110 7/8 M20
3/4 20 130 25.4 44 26.7 42.9 7 88.9 As Required 4 3/4 115 7/8 M20
1 25 150 28.6 52 33.4 50.8 7 101.6 As Required 4 7/8 125 1 M24
1 1/4 32 160 28.6 64 42.2 63.5 7 111.1 As Required 4 7/8 125 1 M24
1 1/2 40 180 31.8 70 48.3 73 7 123.8 As Required 4 1 140 1 1/8 M27
2 50 215 38.1 105 60.3 92.1 7 165.1 As Required 8 7/8 145 1 M24
2 1/2 65 245 41.3 124 73 104.8 7 190.5 As Required 8 1 160 1 1/8 M27
3 80 240 38.1 127 88.9 127 7 190.5 As Required 8 7/8 145 1 M24
4 100 290 44.5 159 114.3 157.2 7 235 As Required 8 1 1/8 170 1 1/4 M30
5 125 350 50.8 190 141.3 185.7 7 279.4 As Required 8 1 1/4 190 1 3/8 M33
6 150 380 55.6 235 168.3 215.9 7 317.5 As Required 12 1 1/8 190 1 1/4 M30
8 200 470 63.5 298 219.1 269.9 7 393.7 As Required 12 1 3/8 220 1 1/2 M36
10 250 545 69.9 368 273 323.8 7 469.9 As Required 16 1 3/8 235 1 1/2 M36
12 300 610 79.4 419 323.8 381 7 533.4 As Required 20 1 3/8 255 1 1/2 M36
14 350 640 85.8 451 355.6 412.8 7 558.8 As Required 20 1 1/2 275 1 5/8 M39
16 400 705 88.9 508 406.4 469.9 7 616 As Required 20 1 5/8 285 1 3/4 M42
18 450 785 101.6 565 457 533.4 7 685.8 As Required 20 1 7/8 325 2 M48
20 500 855 108 622 508 584.2 7 749.3 As Required 20 2 350 2 1/8 M52
24 600 1040 139.7 749 610 692.2 7 901.7 As Required 20 2 1/2 440 2 5/8 M64

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Class 1500 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 120 22.3 38 21.3 34.9 7 82.6 As Required 4 3/4 110 7/8 M20
3/4 20 130 25.4 44 26.7 42.9 7 88.9 As Required 4 3/4 115 7/8 M20
1 25 150 28.6 52 33.4 50.8 7 101.6 As Required 4 7/8 125 1 M24
1 1/4 32 160 28.6 64 42.2 63.5 7 111.1 As Required 4 7/8 125 1 M24
1 1/2 40 180 31.8 70 48.3 73 7 123.8 As Required 4 1 140 1 1/8 M27
2 50 215 38.1 105 60.3 92.1 7 165.1 As Required 8 7/8 145 1 M24
2 1/2 65 245 41.3 124 73 104.8 7 190.5 As Required 8 1 160 1 1/8 M27
3 80 265 47.7 133 88.9 127 7 203.2 As Required 8 1 1/8 180 1 1/4 M30
4 100 310 54 162 114.3 157.2 7 241.3 As Required 8 1 1/4 195 1 3/8 M33
5 125 375 73.1 197 141.3 185.7 7 292.1 As Required 8 1 1/2 250 1 5/8 M39
6 150 395 82.6 229 168.3 215.9 7 317.5 As Required 12 1 3/8 260 1 1/2 M36
8 200 485 92.1 292 219.1 269.9 7 393.7 As Required 12 1 5/8 290 1 3/4 M42
10 250 585 108 368 273 323.8 7 482.6 As Required 12 1 7/8 335 2 M48
12 300 675 123.9 451 323.8 381 7 571.5 As Required 16 2 375 2 1/8 M52
14 350 750 133.4 495 355.6 412.8 7 635 As Required 16 2 1/4 405 2 3/8 M56
16 400 825 146.1 552 406.4 469.9 7 704.8 As Required 16 2 1/2 445 2 5/8 M64
18 450 915 162 597 457 533.4 7 774.7 As Required 16 2 3/4 495 2 7/8 M72
20 500 985 177.8 641 508 584.2 7 831.8 As Required 16 3 540 3 1/8 M76
24 600 1170 203.2 762 610 692.2 7 990.6 As Required 16 3 1/2 615 3 5/8 M90

Class 2500 Long Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD RF Dia. RF Height PCD Hub Length No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
A B C D E F G H
1/2 15 135 30.2 43 21.3 34.9 7 88.9 As Required 4 3/4 120 7/8 M20
3/4 20 140 31.8 51 26.7 42.9 7 95.2 As Required 4 3/4 125 7/8 M20
1 25 160 35 57 33.4 50.8 7 108 As Required 4 7/8 140 1 M24
1 1/4 32 185 38.1 73 42.2 63.5 7 130.2 As Required 4 1 150 1 1/8 M27
1 1/2 40 205 44.5 79 48.3 73 7 146 As Required 4 1 1/8 170 1 1/4 M30
2 50 235 50.9 95 60.3 92.1 7 171.4 As Required 8 1 180 1 1/8 M27
2 1/2 65 265 57.2 114 73 104.8 7 196.8 As Required 8 1 1/8 195 1 1/4 M30
3 80 305 66.7 133 88.9 127 7 228.6 As Required 8 1 1/4 220 1 3/8 M33
4 100 355 76.2 165 114.3 157.2 7 273 As Required 8 1 1/2 255 1 5/8 M39
5 125 420 92.1 203 141.3 185.7 7 323.8 As Required 8 1 3/4 300 1 7/8 M45
6 150 485 108 235 168.3 215.9 7 368.3 As Required 8 2 345 2 1/8 M52
8 200 550 127 305 219.1 269.9 7 438.2 As Required 12 2 380 2 1/8 M52
10 250 675 165.1 375 273 323.8 7 539.8 As Required 12 2 1/2 490 2 5/8 M64
12 300 760 184.2 441 323.8 381 7 619.1 As Required 12 2 3/4 540 2 7/8 M72

Disclaimer –  Please check with ASME B16.5 Before using.

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About Author

Varun Patel, B.E – Mechanical, PMP®

19+ years of experience in the oil and gas sector, specializing in project management, contracts, project control, project coordination, QA/QC and inspection of large-scale Greenfield and Brownfield Projects such as Refinery, Petrochemical, Wellhead production, and Process platform. Proven track record of delivering large-scale projects while ensuring adherence to safety and quality standards. Skilled in leading and mentoring cross-functional teams and resolving technical issues to achieve successful project outcomes.