Orifice flange dimensions are covered in ASME B16.36. Orifice flanges are available from Class #300 to Class #2500. Class #300 flanges are available in threaded, slip-on, and weld neck end types. Class #600 and above flanges are available only in weld neck type end connection.

During an inspection of the orifice 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
  • Tap holes dimensions
orifice flange dimensions

Class 300 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD Welding Neck Length RF Dia. RF Height PCD Orifice Hole dia No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
A B C D E F G H I
1 25 125 36.6 54 33.4 81 50.8 2 88.9 6.4 4 5/8 125 3/4 M16 4.5
1 1/2 40 155 36.6 70 48.3 84 73 2 114.3 6.4 4 3/4 135 7/8 M20 6.5
2 50 165 36.6 84 60.3 84 92.1 2 127 6.4 8 5/8 125 3/4 M16 7
2 1/2 65 190 36.6 100 73 87 104.8 2 149.2 6.4 8 3/4 135 7/8 M20 7.5
3 80 210 36.6 117 88.9 87 127 2 168.3 9.5 8 3/4 135 7/8 M20 9.4
4 100 255 36.6 146 114.3 90 157.2 2 200 12.7 8 3/4 135 7/8 M20 13.2
6 150 320 36.6 206 168.3 98 215.9 2 269.9 12.7 12 3/4 135 7/8 M20 14.6
8 200 380 39.7 260 219.1 110 269.9 2 330.2 12.7 12 7/8 145 1 M24 30
10 250 445 46.1 321 273 116 323.8 2 387.3 12.7 16 1 165 1 1/8 M27 41
12 300 520 49.3 375 323.8 129 381 2 450.8 12.7 16 1 1/8 180 1 1/4 M30 62
14 350 585 52.4 425 355.6 141 412.8 2 514.4 12.7 20 1 1/8 185 1 1/4 M30 84
16 400 650 55.6 483 406.4 144 469.9 2 571.5 12.7 20 1 1/4 195 1 3/8 M33 111
18 450 710 58.8 533 457 157 533.4 2 628.6 12.7 24 1 1/4 205 1 3/8 M33 138
20 500 775 62 587 508 160 584.2 2 685.8 12.7 24 1 1/4 215 1 3/8 M33 171
24 600 915 68.3 702 610 167 692.2 2 812.8 12.7 24 1 1/2 240 1 5/8 M39 247

Class 600 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD Welding Neck Length RF Dia. RF Height PCD Orifice Hole dia No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
A B C D E F G H I
1 25 125 36.6 54 33.5 81 50.8 7 88.9 6.4 4 5/8 125 3/4 M16 5.5
1 1/2 40 155 36.6 70 48.3 84 73 7 114.3 6.4 4 3/4 135 7/8 M20 7.8
2 50 165 36.6 84 60.3 84 92.1 7 127 6.4 8 5/8 125 3/4 M16 8.3
2 1/2 65 190 36.6 100 73 87 104.8 7 149.2 6.4 8 3/4 135 7/8 M20 10.8
3 80 210 36.6 117 88.9 87 127 7 168.3 9.5 8 3/4 135 7/8 M20 12.6
4 100 275 38.1 152 114.3 102 157.2 7 215.9 12.7 8 7/8 150 1 M24 19
6 150 355 47.7 222 168.3 117 215.9 7 292.1 12.7 12 1 180 1 1/8 M27 37
8 200 420 55.6 273 219.1 133 269.9 7 349.2 12.7 12 1 1/8 195 1 1/4 M30 53
10 250 510 63.5 343 273 152 323.8 7 431.8 12.7 16 1 1/4 220 1 3/8 M33 86
12 300 560 66.7 400 323.8 156 381 7 489 12.7 20 1 1/4 230 1 3/8 M33 102
14 350 605 69.9 432 355.6 165 412.8 7 527 12.7 20 1 3/8 240 1 1/2 M36 150
16 400 685 76.2 495 406.4 178 469.9 7 603.2 12.7 20 1 1/2 260 1 5/8 M39 190
18 450 745 82.6 546 457.2 184 533.4 7 654 12.7 20 1 5/8 280 1 3/4 M42 240
20 500 815 88.9 610 508 190 584.2 7 723.9 12.7 24 1 5/8 300 1 3/4 M42 295
24 600 940 101.6 718 609.6 203 692.2 7 838.2 12.7 24 1 7/8 335 2 M48 365

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Class 900 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD Welding Neck Length RF Dia. RF Height PCD Orifice Hole dia No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
A B C D E F G H I
1 25 150 38.1 52 33.5 83 50.8 7 101.6 6.4 4 7/8 150 1 M24 5.4
1 1/2 40 180 38.1 70 48.3 89 73 7 123.8 6.4 4 1 160 1 1/8 M27 7.8
2 50 215 38.1 105 60.3 102 92.1 7 165.1 6.4 8 7/8 150 1 M30 11.5
2 1/2 65 245 41.3 124 73 105 104.8 7 190.5 6.4 8 1 165 1 1/8 M27 15.8
3 80 240 38.1 127 88.9 102 127 7 190.5 9.5 8 7/8 150 1 M24 22
4 100 290 44.5 159 114.3 114 157.2 7 235 12.7 8 1 1/8 180 1 1/4 M30 22
6 150 380 55.6 235 168.3 140 215.9 7 317.5 12.7 12 1 1/8 195 1 1/4 M30 70
8 200 470 63.5 298 219.1 162 269.9 7 393.7 12.7 12 1 3/8 230 1 1/2 M36 119
10 250 545 69.9 368 273 184 323.8 7 469.9 12.7 16 1 3/8 240 1 1/2 M36 204
12 300 610 79.4 419 323.8 200 381 7 533.4 12.7 20 1 3/8 260 1 1/2 M36 303
14 350 640 85.8 451 355.6 213 412.8 7 558.8 12.7 20 1 1/2 280 1 5/8 M39 400
16 400 705 88.9 508 406.4 216 469.9 7 616 12.7 20 1 5/8 290 1 3/4 M42 510
18 450 785 101.9 565 457.2 229 533.4 7 685.8 12.7 20 1 7/8 330 2 M48 738
20 500 855 108 622 508 248 584.2 7 749.3 12.7 20 2 355 2 1/8 M52 932
24 600 1040 139.7 749 609.6 292 692.2 7 901.7 12.7 20 2 1/2 445 2 5/8 M64 1511

Class 1500 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD Welding Neck Length RF Dia. RF Height PCD Orifice Hole dia No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
A B C D E F G H I
1 25 150 38.1 52 33.5 83 50.8 7 101.6 6.4 4 7/8 150 1 M24 5.4
1 1/2 40 180 38.1 70 48.3 89 73 7 123.8 6.4 4 1 160 1 1/8 M27 7.8
2 50 215 38.1 105 60.3 102 92.1 7 165.1 6.4 8 7/8 150 1 M24 11.5
2 1/2 65 245 41.3 124 73 105 104.8 7 190.5 6.4 8 1 165 1 1/8 M27 15.8
3 80 265 47.7 133 88.9 117 127 7 203.2 9.5 8 1 1/8 185 1 1/4 M30 22
4 100 310 54 162 114.3 124 157.2 7 241.3 12.7 8 1 1/4 205 1 3/8 M33 22
6 150 395 82.6 229 168.3 171 215.9 7 317.5 12.7 12 1 3/8 265 1 1/2 M36 70
8 200 485 92.1 292 219.1 213 269.9 7 393.7 12.7 12 1 5/8 300 1 3/4 M42 119
10 250 585 108 368 273 254 323.8 7 482.6 12.7 12 1 7/8 345 1 M48 204
12 300 675 123.9 451 323.8 283 381 7 571.5 12.7 16 2 380 2 1/8 M52 303
14 350 750 133.4 495 355.6 298 412.8 7 635 12.7 16 2 1/4 415 2 3/8 M56 400
16 400 825 146.1 552 406.4 311 469.9 7 704.8 12.7 16 2 1/2 450 2 5/8 M64 510
18 450 915 162 597 457.2 327 533.4 7 774.7 12.7 16 2 3/4 500 2 7/8 M72 738
20 500 985 177.8 641 508 356 584.2 7 831.8 12.7 16 3 545 3 1/8 M76 932
24 600 1170 203.2 762 609.6 406 692.2 7 990.6 12.7 16 3 1/2 620 3 5/8 M90 1511

Class 2500 Orifice Flange Dimensions (Weld Neck Raised Face)

Size in Inch Size in mm Outer Dia. Flange Thick. Hub OD Weld Neck OD Welding Neck Length RF Dia. RF Height PCD Orifice Hole dia No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
A B C D E F G H I
1 25 160 38.1 57 33.5 92 50.8 7 108 6.4 4 7/8 150 1 M24 6.5
1 1/2 40 205 44.5 79 48.3 111 73 7 146 6.4 4 1 1/8 180 1 1/4 M30 13
2 50 235 50.8 95 60.3 127 92.1 7 171.4 6.4 8 1 185 1 1/8 M27 19
2 1/2 65 265 57.2 114 73 143 104.8 7 196.8 6.4 8 1 1/8 205 1 1/4 M30 24
3 80 305 66.7 133 88.9 168 127 7 228.6 9.5 8 1 1/4 230 1 3/8 M33 43
4 100 355 76.2 165 114.3 190 157.2 7 273 12.7 8 1 1/2 260 1 5/8 M39 66
6 150 485 108 235 168.3 273 215.9 7 368.3 12.7 8 2 350 2 1/8 M52 172
8 200 550 127 305 219.1 318 269.9 7 438.2 12.7 12 2 385 2 1/8 M52 261
10 250 675 165.1 375 273 419 323.8 7 539.8 12.7 12 2 1/2 490 2 5/8 M64 485
12 300 760 184.2 441 323.8 464 381 7 619.1 12.7 12 2 3/4 540 2 7/8 M72 730

Disclaimer –  Please check with ASME B16.36 Before using.

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Varun Patel - HardHat Engineer

About Author: Varun Patel is a Mechanical Engineer and an Oil & Gas Professional. He is a Certified Project Management Professional – PMP® from PMI® USA. With over nineteen years of experience, he has worked with Fortune 500 Oil & Gas Companies. Know more.