ASME B16.5 Long Weld Neck Flanges (LWN) are the forged flanges designed for high-pressure, high-temperature, and critical piping systems.different from the standard weld neck flanges, LWN flanges feature an extended hub or neck, which acts as a nozzle for pressure vessels, columns, tanks, and heat exchangers.
Long Neck Welding (abbreviated LWN) flanges are basically identical to standard Welding Neck flanges, but the Neck is considerably longer. This type is often used as a nozzle for a barrel or column.
In addition, there are the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker Wall thickness.
LWN flange
Heavy Barrel
Equal Barrel ‘E’
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
Material Grades
Long weld neck flanges can be manufactured in a wide range of materials according to ASME, ASTM, and API standards:
- Carbon Steel: ASTM A105, A350 LF2, A694 F52 / F60 / F65
- Alloy Steel: ASTM A182 F11, F22, F5, F9, F91
- Stainless Steel: ASTM A182 F304 / 304L, F316 / 316L, F321, F347
- Duplex / Super Duplex: ASTM A182 F51, F53, F55
- Nickel Alloys: Inconel, Monel, Hastelloy, Alloy 20, etc.
Pressure-Temperature Ratings
- Designed as per ASME B16.5 pressure class ratings
- Operating range: Cryogenic to ~600°C (1110°F) depending on material grade
- Excellent strength for high-pressure piping, refinery, and chemical plant service
Applications of Long Weld Neck Flanges
- Pressure vessels and column nozzles
- Heat exchangers and reactors
- Offshore platforms and subsea equipment
- Petrochemical and refinery piping
- Boiler and HRSG connections
Dimensions – ASME B16.5 Long Weld Neck Flanges
Long weld neck flange dimensions generally follow ASME B16.5 (½” to 24”) standards for pressure classes:
- Class Ratings: 150, 300, 400, 600, 900, 1500, and 2500 LB
- Nominal Pipe Sizes (NPS): ½” to 24” (larger sizes available in ASME B16.47)
- Facing Types: Raised Face (RF), Ring Type Joint (RTJ), Flat Face (FF on request)
- Hub Lengths: Extended neck lengths per design or project requirement
Class 150 Long Weld Neck Flange Dimensions as per ASME B16.5
| 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 |
Class 300 Long Weld Neck Flange Dimensions as per ASME B16.5
| 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 |
Class 400 Long Weld Neck Flange Dimensions as per ASME B16.5
| 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 |
Class 600 Long Weld Neck Flange Dimensions as per ASME B16.5
| 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 as per ASME B16.5
| 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 |
Class 1500 Long Weld Neck Flange Dimensions as per ASME B16.5
| 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 as per ASME B16.5
| 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 |
We are a trusted manufacturer and exporter of Long Weld Neck (LWN) Flanges designed according to ASME B16.5 and ASME B16.47 standards. Long weld neck flanges feature an extended hub that provides extra reinforcement, making them ideal for high-pressure, high-temperature, and critical applications. Unlike standard weld neck flanges, the longer neck allows for smooth stress distribution and acts as an integral nozzle connection for pressure vessels, heat exchangers, boilers, and reactors.
Our LWN flanges are available in sizes from ½” to 24” (ASME B16.5) and larger sizes upon request per ASME B16.47, with pressure ratings Class 150 to Class 2500 LB. We supply them in Raised Face (RF), Ring Type Joint (RTJ), and Flat Face (FF) finishes depending on project requirements.
