ASME B16.5 Class 900 Weld Neck Flange Dimensions
Weld Neck flange dimensions to ASME B16.5 Class 900 in millimetres: outside diameter, thickness, raised face, hub, length through hub, bolt circle and drilling, NPS ½" to 24". A weld neck flange has a long tapered hub butt-welded to the pipe. The taper transfers stress smoothly into the pipe, so weld necks are the first choice for high pressure, high or low temperature and cyclic service.
Key to dimensions
- O
- Outside diameter of flange
- tf
- Minimum flange thickness
- R
- Diameter of raised face
- X
- Diameter of hub at base
- A
- Hub diameter at the welding end (pipe outside diameter)
- Y
- Length through hub (weld neck)
- W
- Bolt circle diameter
ASME B16.5 Class 900 weld neck flange dimensions (mm)
| NPSin | DN | OOutside dia | tfMin thickness | RRaised face dia | XHub dia | AHub at weld | YWeld neck | WBolt circle | HolesNo. | Hole diamm | Boltin |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ½" | 15 | 120 | 22.3 | 34.9 | 38 | 21.3 | 60 | 82.6 | 4 | 22.2 | ¾" |
| ¾" | 20 | 130 | 25.4 | 42.9 | 44 | 26.7 | 70 | 88.9 | 4 | 22.2 | ¾" |
| 1" | 25 | 150 | 28.6 | 50.8 | 52 | 33.4 | 73 | 101.6 | 4 | 25.4 | ⅞" |
| 1¼" | 32 | 160 | 28.6 | 63.5 | 64 | 42.2 | 73 | 111.1 | 4 | 25.4 | ⅞" |
| 1½" | 40 | 180 | 31.8 | 73.0 | 70 | 48.3 | 83 | 123.8 | 4 | 28.6 | 1" |
| 2" | 50 | 215 | 38.1 | 92.1 | 105 | 60.3 | 102 | 165.1 | 8 | 25.4 | ⅞" |
| 2½" | 65 | 245 | 41.3 | 104.8 | 124 | 73.0 | 105 | 190.5 | 8 | 28.6 | 1" |
| 3" | 80 | 240 | 38.1 | 127.0 | 127 | 88.9 | 102 | 190.5 | 8 | 25.4 | ⅞" |
| 4" | 100 | 290 | 44.5 | 157.2 | 159 | 114.3 | 114 | 235.0 | 8 | 31.8 | 1⅛" |
| 5" | 125 | 350 | 50.8 | 185.7 | 190 | 141.3 | 127 | 279.4 | 8 | 34.9 | 1¼" |
| 6" | 150 | 380 | 55.6 | 215.9 | 235 | 168.3 | 140 | 317.5 | 12 | 31.8 | 1⅛" |
| 8" | 200 | 470 | 63.5 | 269.9 | 298 | 219.1 | 162 | 393.7 | 12 | 38.1 | 1⅜" |
| 10" | 250 | 545 | 69.9 | 323.8 | 368 | 273.0 | 184 | 469.9 | 16 | 38.1 | 1⅜" |
| 12" | 300 | 610 | 79.4 | 381.0 | 419 | 323.8 | 200 | 533.4 | 20 | 38.1 | 1⅜" |
| 14" | 350 | 640 | 85.8 | 412.8 | 451 | 355.6 | 213 | 558.8 | 20 | 41.3 | 1½" |
| 16" | 400 | 705 | 88.9 | 469.9 | 508 | 406.4 | 216 | 616.0 | 20 | 44.5 | 1⅝" |
| 18" | 450 | 785 | 101.6 | 533.4 | 565 | 457.0 | 229 | 685.8 | 20 | 50.8 | 1⅞" |
| 20" | 500 | 855 | 108.0 | 584.2 | 622 | 508.0 | 248 | 749.3 | 20 | 54.0 | 2" |
| 24" | 600 | 1040 | 139.7 | 692.2 | 749 | 610.0 | 292 | 901.7 | 20 | 66.7 | 2½" |
Class 900 weld neck flange bolting and approximate weight
| NPSin | StudsNo. | Stud diain | Stud lengthRF, mm | Weightkg, approx. |
|---|---|---|---|---|
| ½" | 4 | ¾" | 110 | — |
| ¾" | 4 | ¾" | 115 | — |
| 1" | 4 | ⅞" | 125 | 4.1 |
| 1¼" | 4 | ⅞" | 125 | 4.5 |
| 1½" | 4 | 1" | 140 | 6.4 |
| 2" | 8 | ⅞" | 145 | 11.3 |
| 2½" | 8 | 1" | 160 | 16.3 |
| 3" | 8 | ⅞" | 145 | 13.6 |
| 4" | 8 | 1⅛" | 170 | 24.0 |
| 5" | 8 | 1¼" | 190 | 39.0 |
| 6" | 12 | 1⅛" | 190 | 50.0 |
| 8" | 12 | 1⅜" | 220 | 84.0 |
| 10" | 16 | 1⅜" | 235 | 121 |
| 12" | 20 | 1⅜" | 255 | — |
| 14" | 20 | 1½" | 275 | — |
| 16" | 20 | 1⅝" | 285 | — |
| 18" | 20 | 1⅞" | 325 | — |
| 20" | 20 | 2" | 350 | — |
| 24" | 20 | 2½" | 440 | — |
Notes
- Dimensions are in millimetres unless stated otherwise.
- Flange thickness tf and length through hub Y do not include the 7 mm raised face.
- Blind flanges have the same outside diameter, thickness tf and drilling as the other flange types of the same size and class.
- In ASME B16.5, Class 900 flanges NPS ½" to 2½" use Class 1500 dimensions.
- The bore of a weld neck or socket weld flange is machined to match the inside diameter of the pipe schedule stated in the order.
- Bolt holes are tabulated in inches in ASME B16.5; the millimetre values shown are direct conversions (bolt diameter plus ⅛").
- Stud bolt lengths do not include the height of the points. Weights are approximate catalogue values and vary with bore and manufacturer.
Reference information compiled from the published standard for convenience. It does not replace the current edition of the governing standard, which takes precedence. Verify critical dimensions and properties before design, purchase or fabrication. Teshi Engineers & Sales Promoters (P) Ltd accepts no liability for errors or omissions.
Other Class 900 flange types
Weld Neck flange dimensions in other classes
FAQ
Class 900 weld neck flange: common questions
What is the outside diameter of a 4" Class 900 weld neck flange?
290 mm, with a minimum thickness tf of 44.5 mm, bolt circle 235.0 mm and 8 bolt holes of 31.8 mm.
Which sizes are covered?
This chart covers NPS ½" to 24" (DN 15 to 600).
Are dimensions the same for all flange types of one class?
Outside diameter, thickness and drilling are the same for every flange type of the same size and class; the hub length Y, hub and bore differ by type.
Does Teshi Group manufacture Class 900 weld neck flanges?
Yes. Teshi Group is an OEM manufacturer of ASME B16.5 flanges in India, in carbon, low-temperature, chrome-moly, stainless, duplex, super duplex and nickel alloys, with EN 10204 3.1 certificates and IBR certification on request.
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