Industrial pipe flanges
Steel flanges
Companion flanges
Table of Content
| Size range | Manufacturing technique | Flange threads |
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| Heat Treatment | Industrial flange surfaces | Dimensional standard for steel flanges |
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| Pressure Class | Connection type | Surface treatment of pipe flanges |
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| PN pressure classes | Identification Markings | Testing |
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| NPS | O | R | D | T | T J | X | Bolt Circle Dia | #/Dia of Holes a | B | B 3 | B 2 b | H | L 2 | L | L 3 c | r | Thr |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 3.50 | 1.38 | 0.38 | 0.38 | 0.44 | 1.19 | 2.38 | 4-0.62 | 0.88 | 0.90 | 0.62 | 0.84 | 1.81 | 0.56 | 0.62 | 0.12 | 0.62 |
| ¾ | 3.88 | 1.69 | 0.44 | 0.44 | 0.50 | 1.50 | 2.75 | 4-0.62 | 1.09 | 1.11 | 0.82 | 1.05 | 2.00 | 0.56 | 0.62 | 0.12 | 0.62 |
| 1 | 4.25 | 2.00 | 0.50 | 0.50 | 0.56 | 1.94 | 3.12 | 4-0.62 | 1.36 | 1.38 | 1.05 | 1.32 | 2.12 | 0.62 | 0.69 | 0.12 | 0.69 |
| 1¼ | 4.62 | 2.50 | 0.56 | 0.56 | 0.62 | 2.31 | 3.50 | 4-0.62 | 1.70 | 1.72 | 1.38 | 1.66 | 2.19 | 0.75 | 0.81 | 0.19 | 0.81 |
| 1½ | 5.00 | 2.88 | 0.62 | 0.62 | 0.69 | 2.56 | 3.88 | 4-0.62 | 1.95 | 1.97 | 1.61 | 1.90 | 2.38 | 0.81 | 0.88 | 0.25 | 0.88 |
| 2 | 6.00 | 3.62 | 0.69 | 0.69 | 0.75 | 3.06 | 4.75 | 4-0.75 | 2.44 | 2.46 | 2.07 | 2.38 | 2.44 | 0.94 | 1.00 | 0.31 | 1.00 |
| 2½ | 7.00 | 4.12 | 0.75 | 0.81 | 0.88 | 3.56 | 5.50 | 4-0.75 | 2.94 | 2.97 | 2.47 | 2.88 | 2.69 | 1.06 | 1.12 | 0.31 | 1.12 |
| 3 | 7.50 | 5.00 | 0.81 | 0.88 | 0.94 | 4.25 | 6.00 | 4-0.75 | 3.57 | 3.60 | 3.07 | 3.50 | 2.69 | 1.12 | 1.19 | 0.38 | 1.19 |
| 3½ | 8.50 | 5.50 | 0.88 | 0.88 | 0.94 | 4.81 | 7.00 | 8-0.75 | 4.07 | 4.10 | 3.55 | 4.00 | 2.75 | 1.19 | 1.25 | 0.38 | 1.25 |
| 4 | 9.00 | 6.19 | 0.94 | 0.88 | 0.94 | 5.31 | 7.50 | 8-0.75 | 4.57 | 4.60 | 4.03 | 4.50 | 2.94 | 1.25 | 1.31 | 0.44 | 1.31 |
| 5 | 10.00 | 7.31 | 0.94 | 0.88 | 0.94 | 6.44 | 8.50 | 8-0.88 | 5.66 | 5.69 | 5.05 | 5.56 | 3.44 | 1.38 | 1.44 | 0.44 | 1.44 |
| 6 | 11.00 | 8.50 | 1.06 | 0.94 | 1.00 | 7.56 | 9.50 | 8-0.88 | 6.72 | 6.75 | 6.07 | 6.63 | 3.44 | 1.50 | 1.56 | 0.50 | 1.56 |
| 8 | 13.50 | 10.62 | 1.25 | 1.06 | 1.12 | 9.69 | 11.75 | 8-0.88 | 8.72 | 8.75 | 7.98 | 8.63 | 3.94 | 1.69 | 1.75 | 0.50 | 1.75 |
| 10 | 16.00 | 12.75 | 1.31 | 1.12 | 1.19 | 12.00 | 14.25 | 12-1.00 | 10.88 | 10.92 | 10.02 | 10.75 | 3.94 | 1.88 | 1.94 | 0.50 | 1.94 |
| 12 | 19.00 | 15.00 | 1.56 | 1.19 | 1.25 | 14.38 | 17.00 | 12-1.00 | 12.88 | 12.92 | 12.00 | 12.75 | 4.44 | 2.12 | 2.19 | 0.50 | 2.19 |
| 14 | 21.00 | 16.25 | 1.63 | 1.31 | 1.38 | 15.75 | 18.75 | 12-1.12 | 14.14 | 14.18 | 13.25 | 14.00 | 4.94 | 2.19 | 3.12 | 0.50 | 2.25 |
| 16 | 23.50 | 18.50 | 1.75 | 1.38 | 1.44 | 18.00 | 21.25 | 16-1.12 | 16.16 | 16.19 | 15.25 | 16.00 | 4.94 | 2.44 | 3.44 | 0.50 | 2.50 |
| 18 | 25.00 | 21.00 | 1.94 | 1.50 | 1.56 | 19.88 | 22.75 | 16-1.25 | 18.18 | 18.20 | 17.25 | 18.00 | 5.44 | 2.62 | 3.81 | 0.50 | 2.69 |
| 20 | 27.50 | 23.00 | 2.13 | 1.62 | 1.69 | 22.00 | 25.00 | 20-1.25 | 20.20 | 20.25 | 19.25 | 20.00 | 5.62 | 2.81 | 4.06 | 0.50 | 2.88 |
| 22 | 29.50 | 25.25 | 2.38 | 1.75 | 1.81 | 24.25 | 27.25 | 20-1.38 | 22.22 | 22.25 | 21.25 | 22.00 | 5.82 | 3.07 | 4.25 | 0.50 | 3.13 |
| 24 | 32.00 | 27.25 | 2.50 | 1.81 | 1.88 | 26.12 | 29.50 | 20-1.38 | 24.25 | 24.25 | 23.25 | 24.00 | 5.94 | 3.19 | 4.38 | 0.50 | 3.25 |
| NPS | Threaded | Slip On | Lap Joint | Socket Weld | Weld Neck | Blind |
|---|---|---|---|---|---|---|
| ½ | 1 | 1 | 1 | 2 | 2 | 2 |
| ¾ | 2 | 2 | 2 | 2 | 2 | 2 |
| 1 | 2 | 2 | 2 | 2 | 3 | 2 |
| 1¼ | 3 | 3 | 3 | 3 | 3 | 3 |
| 1½ | 3 | 3 | 3 | 3 | 4 | 4 |
| 2 | 5 | 5 | 5 | 5 | 6 | 5 |
| 2½ | 8 | 8 | 8 | 8 | 10 | 7 |
| 3 | 9 | 9 | 9 | 9 | 11.5 | 9 |
| 3½ | 12 | 11 | 11 | 11 | 12 | 13 |
| 4 | 13 | 13 | 13 | 13 | 16.5 | 17 |
| 5 | 15 | 15 | 15 | 15 | 21 | 20 |
| 6 | 19 | 19 | 19 | 19 | 26 | 27 |
| 8 | 30 | 30 | 30 | 30 | 42 | 47 |
| 10 | 43 | 43 | 43 | 43 | 54 | 70 |
| 12 | 64 | 64 | 64 | 64 | 88 | 123 |
| 14 | 90 | 90 | 105 | 90 | 114 | 140 |
| 16 | 98 | 106 | 140 | 98 | 140 | 180 |
| 18 | 130 | 130 | 160 | 130 | 165 | 220 |
| 20 | 165 | 165 | 195 | 165 | 197 | 285 |
| 22 | 185 | 185 | 245 | 185 | 225 | 355 |
| 24 | 220 | 220 | 275 | 220 | 268 | 430 |
| Temperature (𐩑F) | 150# | 400# | 300# | 900# | 600# | 2500# | 1500# |
|---|---|---|---|---|---|---|---|
| -20 to 100 | 285 | 985 | 740 | 2220 | 1480 | 6170 | 3705 |
| 200 | 260 | 905 | 680 | 2035 | 1360 | 5655 | 3395 |
| 300 | 230 | 870 | 655 | 1965 | 1310 | 5450 | 3270 |
| 400 | 200 | 845 | 635 | 1900 | 1265 | 5280 | 3170 |
| 500 | 170 | 805 | 605 | 1810 | 1205 | 5025 | 3015 |
| 600 | 140 | 755 | 570 | 1705 | 1135 | 4730 | 2840 |
| 650 | 125 | 730 | 550 | 1650 | 1100 | 4575 | 2745 |
| 700 | 110 | 710 | 530 | 1590 | 1060 | 4425 | 2655 |
| 750 | 95 | 675 | 505 | 1520 | 1015 | 4230 | 2535 |
| 800 | 80 | 550 | 410 | 1235 | 825 | 3430 | 2055 |
| 850 | 65 | 425 | 320 | 955 | 640 | 2655 | 1595 |
| 900 | 50 | 305 | 230 | 690 | 460 | 1915 | 1150 |
| 950 | 35 | 185 | 135 | 410 | 275 | 1145 | 685 |
| 1000 | 20 | 115 | 85 | 255 | 170 | 715 | 430 |
| Surface Types | Maximum Roughness Value |
|---|---|
| Spiral wound gaskets. | 125 to 250 µin AARH (3.2 to 6.3 µm AARH) |
| Ring-type joint flanges (and hard gaskets) | 63 µin AARH (1.6 µm AARH) |
| Tongue and Groove, and small Male and Female | 1 25 µ.i n. or 3. 2 µ.m AARH |
| Soft gaskets. | 250 to 500 µin AARH (6.3 to 12.6 µm AARH) |
| NPS (inches) |
Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Diameter of Bolt Holes (inches) |
Bolt Circle (inches) |
|---|---|---|---|---|---|
| 1/4 | 3-3/8 | 4 | 1/2 | 0.62 | 2-1/4 |
| 1/2 | 3-1/2 | 4 | 1/2 | 0.62 | 2-3/8 |
| 3/4 | 3-7/8 | 4 | 1/2 | 0.62 | 2-3/4 |
| 1 | 4-1/4 | 4 | 1/2 | 0.62 | 3-1/8 |
| 1-1/4 | 4-5/8 | 4 | 1/2 | 0.62 | 3-1/2 |
| 1-1/2 | 5 | 4 | 1/2 | 0.62 | 3-7/8 |
| 2 | 6 | 4 | 5/8 | 0.75 | 4-3/4 |
| 2-1/2 | 7 | 4 | 5/8 | 0.75 | 5-1/2 |
| 3 | 7-1/2 | 4 | 5/8 | 0.75 | 6 |
| 3-1/2 | 8-1/2 | 8 | 5/8 | 0.75 | 7 |
| 4 | 9 | 8 | 5/8 | 0.75 | 7-1/2 |
| 5 | 10 | 8 | 3/4 | 0.88 | 8-1/2 |
| 6 | 11 | 8 | 3/4 | 0.88 | 9-1/2 |
| 8 | 13-1/2 | 8 | 3/4 | 0.88 | 11-3/4 |
| 10 | 16 | 12 | 7/8 | 1 | 14-1/4 |
| 12 | 19 | 12 | 7/8 | 1 | 17 |
| 14 | 21 | 12 | 1 | 1.12 | 18-3/4 |
| 16 | 23-1/2 | 16 | 1 | 1.12 | 21-1/4 |
| 18 | 25 | 16 | 1-1/8 | 1.25 | 22-3/4 |
| 20 | 27-1/2 | 20 | 1-1/8 | 1.25 | 25 |
| 24 | 32 | 20 | 1-1/4 | 1.38 | 29-1/2 |