Weld Neck Flanges
Giriraj Impex is a manufacturer, stockist, supplier and exporter of weld neck flanges to ASME B16.5 from ½" to 24" NB and ASME B16.47 Series A and B from 26" to 60" NB, in Class 150, 300, 400, 600, 900, 1500 and 2500, and to EN 1092-1 Type 11. We manufacture weld neck flanges in stainless steel, carbon steel, alloy steel, duplex and super duplex steel and nickel alloys, with raised face, flat face and ring type joint facings, bored to match the pipe schedule, with mill test certificates.
A weld neck flange has a long tapered hub that is butt welded to the pipe. It is the preferred flange for high-pressure, high-temperature, cyclic and critical service in refineries, petrochemical plants, power stations and oil and gas facilities.
What is a weld neck flange?
The weld neck flange has a tapered hub that runs from the flange ring to a weld end matching the pipe's outside diameter and wall thickness. The pipe is joined with a full-penetration butt weld, which can be radiographed. The hub transfers stress gradually from the flange to the pipe, reducing stress concentration at the base of the hub, and the bore matches the pipe bore, so there is no step to disturb flow or trap deposits. These features make weld neck flanges suitable for high pressure, high and low temperatures, thermal cycling and vibration.
Specifications
| Item | Details |
|---|---|
| Dimensional standards | ASME B16.5, B16.47 Series A and B, B16.36 (orifice); EN 1092-1 Type 11; MSS SP-44 |
| Sizes | ½" to 24" NB (B16.5); 26" to 60" NB (B16.47) |
| Classes | 150, 300, 400, 600, 900, 1500, 2500; PN 6 to PN 100 (EN 1092-1) |
| Facings | Raised face (RF), flat face (FF), ring type joint (RTJ), tongue and groove, male and female |
| Bore | To match the pipe schedule (Sch 10S to XXS) or specified bore |
| Weld end | Bevelled to ASME B16.25 |
| Variants | Long weld neck, orifice weld neck, reducing weld neck |
| Documents | Mill test certificate (MTC); third-party inspection on request |
Weld neck flange materials
- Stainless steel flanges – ASTM A182 F304/304L, F316/316L, F321, F347.
- Carbon steel flanges – ASTM A105, A350 LF2, A694 F42–F70.
- Alloy steel flanges – ASTM A182 F5, F9, F11, F22, F91.
- Duplex steel flanges – ASTM A182 F51, F60.
- Super duplex flanges – ASTM A182 F53, F55.
- Inconel flanges – ASTM B564 alloys 600 and 625, and other nickel alloys.
All flange materials are on the flanges page.
ASME B16.5 Class 300 dimensions
| NPS | Outside diameter | Min. thickness | Bolt circle | No. of bolts | Bolt hole |
|---|---|---|---|---|---|
| ½ | 95 | 12.7 | 66.7 | 4 | 16 |
| ¾ | 115 | 14.3 | 82.6 | 4 | 19 |
| 1 | 125 | 15.9 | 88.9 | 4 | 19 |
| 1¼ | 135 | 17.5 | 98.4 | 4 | 19 |
| 1½ | 155 | 19.1 | 114.3 | 4 | 22 |
| 2 | 165 | 20.7 | 127.0 | 8 | 19 |
| 2½ | 190 | 23.9 | 149.2 | 8 | 22 |
| 3 | 210 | 27.0 | 168.3 | 8 | 22 |
| 4 | 255 | 30.2 | 200.0 | 8 | 22 |
| 5 | 280 | 33.4 | 235.0 | 8 | 22 |
| 6 | 320 | 35.0 | 269.9 | 12 | 22 |
| 8 | 380 | 39.7 | 330.2 | 12 | 25 |
| 10 | 445 | 46.1 | 387.4 | 16 | 29 |
| 12 | 520 | 49.3 | 450.8 | 16 | 32 |
| 14 | 585 | 52.4 | 514.4 | 20 | 32 |
| 16 | 650 | 55.6 | 571.5 | 20 | 35 |
| 18 | 710 | 58.8 | 628.6 | 24 | 35 |
| 20 | 775 | 62.0 | 685.8 | 24 | 35 |
| 24 | 915 | 68.3 | 812.8 | 24 | 41 |
Dimensions are from ASME B16.5 (2013 and later editions) and are given for guidance. Minimum thickness excludes the raised face for Class 400 and above. Always check the current edition of the standard and the project specification. More classes and dimensions are in the flange dimensions chart.
Weld neck flange facings
Raised face (RF) is the most common facing, with a serrated finish for spiral-wound and sheet gaskets. Ring type joint (RTJ) flanges have a machined groove for an oval or octagonal metal ring gasket and are used for high pressures and temperatures, typically from Class 900 up and in many Class 600 hydrocarbon services. Flat face (FF) flanges are used against cast iron or non-metallic equipment flanges. Tongue and groove and male and female facings are used where the gasket must be confined.
How we manufacture weld neck flanges
We manufacture weld neck flanges from forged blanks of certified material, forged close to shape so that the grain flow follows the hub, and heat treated as the material specification requires. Machining covers the bore to match the pipe schedule, the hub and weld bevel, the facing and face finish, the flange thickness and the bolt holes. Every flange is marked with material, size, class, facing, bore and heat number, and inspected for dimensions, face finish and marking before dispatch.
Long weld neck and orifice flanges
Long weld neck flanges have an extended, straight hub and are used as nozzles on vessels and columns. Orifice weld neck flanges to ASME B16.36 have pressure tappings and jack screws for flow-measuring orifice plates. Reducing weld neck flanges connect pipe of a smaller size than the flange.
Ordering weld neck flanges
Please give the material, size, class, facing and face finish, pipe schedule or bore, quantity and any testing such as ultrasonic, dye penetrant, NACE MR0175 / ISO 15156 or third-party inspection. Flanges are packed in wooden boxes with faces protected.
Frequently Asked Questions
A weld neck flange has a long tapered hub that is butt welded to the pipe. It is used for high-pressure, high-temperature and critical service.
The tapered hub spreads stress from the flange into the pipe, and the full-penetration butt weld can be radiographed, giving a strong, reliable joint.
The bore is machined to match the inside diameter of the pipe, set by the pipe schedule, so there is no step at the joint.
ASME B16.5 covers NPS ½ to 24, ASME B16.47 covers NPS 26 to 60, and EN 1092-1 Type 11 covers metric weld neck flanges.
RF flanges have a raised serrated face for flat gaskets; RTJ flanges have a groove for a metal ring gasket and are used for higher pressures and temperatures.
A long weld neck flange has an extended straight hub and is used mainly as a nozzle on vessels and columns.
Request a Quote for Weld Neck Flanges
Tell us the product, grade, size, standard, quantity and delivery location, and our sales team will reply with a quotation.
Inconel® is a trademark of Special Metals Corporation.