Weld Neck Flange Manufacturer, Supplier & Exporter
A weld neck flange (WNF) is a forged pipe flange with a long, tapered hub that is butt-welded to the pipe. Raaj Fittings manufactures and exports weld neck flanges in stainless steel, duplex and super duplex, nickel alloys, carbon steel and alloy steel, to ASME B16.5, ASME B16.47, EN 1092-1 and other international standards, for process plants, pipelines and pressure equipment worldwide.
The hub tapers gradually from the thickness of the flange ring down to the wall thickness of the pipe. This carries bending and thermal stresses away from the flange and into the pipe, which is why the weld neck is the flange most piping specifications call for on high-pressure, high-temperature and cyclic-service lines.
Each flange is bored to suit the schedule of the mating pipe, so the bore runs smoothly through the joint. Flanges are supplied with EN 10204 3.1 mill test certificates as standard, with 3.2 certification and third-party inspection available on request.
We export weld neck flanges to EPC contractors, refineries and stockists across the Middle East and GCC, Europe and the Americas, made to the ASME, EN or DIN standard your project specifies, with PED-compliant supply for European projects on request.
Weld Neck Flange Specifications
½" NPS to 24" NPS to ASME B16.5; 26" NPS to 60" NPS to ASME B16.47 Series A and Series B
Bored to match the specified pipe schedule or wall thickness
Bevelled for butt welding to ASME B16.25
Forged, heat treated as required by the material specification, and CNC machined
EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request
Materials & Grades
We supply weld neck flanges in the following materials and grades. All grades are supplied with EN 10204 3.1 / 3.2 Mill Test Certificates.
Stainless Steel Weld Neck Flanges
Stainless steel flanges offer excellent corrosion resistance and are essential in chemical, pharmaceutical, food processing, and marine environments.
(ASTM A182 F304 / F304L) General corrosion resistance
(ASTM A182 F316 / F316L) Superior resistance to chlorides, acids; marine & pharmaceutical service
(ASTM A182 F316H) High-temperature elevated creep strength
(ASTM A182 F321) Titanium-stabilized; suitable for sustained elevated temperatures
(ASTM A182 F347) Columbium-stabilized; used in heat exchangers and high-temperature piping
High alloy; exceptional resistance to strong acids
Duplex & Super Duplex Stainless Steel Weld Neck Flanges
Duplex and super duplex grades offer approximately twice the yield strength of standard austenitic stainless steel, combined with excellent resistance to stress corrosion cracking and pitting — making them ideal for offshore, subsea, and chemical processing.
(UNS S31803 / S32205) Used in offshore platforms and chemical processing plants
(UNS S32750) Ideal for seawater handling and desalination systems
(UNS S32760) Designed for high-chloride offshore service applications
Nickel Alloy Weld Neck Flanges
For the most aggressive corrosive environments — including concentrated acids, caustic solutions, sour gas service, and extreme temperatures — we offer flanges in a full range of nickel alloys.
(UNS N06600) High-temperature oxidation resistance
(UNS N06625) Outstanding corrosion resistance for offshore and subsea service
(UNS N08825) Excellent resistance to phosphoric and sulfuric acids
(UNS N10276) Broad-spectrum corrosion resistance in acids and chlorides
(UNS N06022) Superior resistance to oxidizing acids
(UNS N04400) Suitable for seawater, hydrofluoric acid, and marine environments
(UNS N08020) Engineered for sulfuric acid service
Exceptional corrosion resistance with low weight
(C70600 / C71500) Preferred for marine and seawater piping systems
Carbon Steel Weld Neck Flanges
Carbon steel is the standard choice for general-purpose, non-corrosive, and elevated-temperature services. The primary grade for forged carbon steel flanges is ASTM A105, and for low-temperature service, ASTM A350 LF2.
Primary grade for forged carbon steel fittings and flanges — covers ambient and elevated-temperature service in pressurised piping systems.
Low-temperature carbon steel, impact-tested for service down to -46°C (-50°F) — LNG, cold climate, and cryogenic piping applications.
Alloy Steel Weld Neck Flanges
Alloy steel flanges are specified for high-temperature, high-pressure service in power generation, petrochemical, and refinery applications.
(5% Cr, ½% Mo) Designed for elevated temperature refinery service
(9% Cr, 1% Mo) Suitable for high-temperature steam and hydrogen service
(1¼% Cr, ½% Mo) Widely used in thermal power plant piping systems
(2¼% Cr, 1% Mo) Used in high-temperature pressure vessels and reactors
(9% Cr, 1% Mo, V, Nb) Engineered for ultra-high-temperature power plant steam lines
Why Specify a Weld Neck Flange?
The weld neck differs from a slip on flange or a socket weld flange in one important way: the pipe is joined to it with a full-penetration butt weld rather than a fillet weld. A butt weld can be fully examined by radiography or ultrasonic testing, and the tapered hub spreads stress over a longer length of metal. The result is a joint with far better resistance to fatigue, vibration and repeated temperature cycles.
- Tapered hub — reinforces the flange ring and reduces the stress concentration where the ring meets the pipe.
- Matched bore — the bore equals the inside diameter of the pipe, so there is no step in the line to cause turbulence, erosion or a crevice for corrosion.
- Full-penetration butt weld — inspectable by RT or UT, and suitable for hazardous, toxic and flammable fluid service.
- Bevelled weld end — machined to ASME B16.25 so the flange can be welded directly to the pipe.
Facing Options
Raised Face (RF) is the most widely used facing and suits spiral wound and flat gaskets. Ring Type Joint (RTJ) flanges have a machined groove for an oval or octagonal metal ring gasket and are common in Class 900 and above and in oil and gas production. Flat Face (FF) is used when mating with cast iron or non-metallic equipment flanges. Male & Female and Tongue & Groove facings are machined to order for confined-gasket designs.
Weld Neck or Long Weld Neck?
A standard weld neck flange has a hub length fixed by the dimensional standard. Where a nozzle must project from a vessel, column or heat exchanger shell, a long weld neck flange with an extended straight neck is used instead. To close the end of a line or a spare nozzle, the weld neck is bolted to a blind flange.
Applications & Industries
Weld neck flanges are used wherever the integrity of a bolted joint matters most:
- Oil and gas production, refining and petrochemical process piping
- High-pressure steam, feedwater and boiler piping in power plants (alloy steel F11, F22 and F91)
- Offshore platforms and seawater systems in duplex, super duplex and nickel alloys
- Chemical, fertiliser and pharmaceutical plants
- LNG and low-temperature lines in ASTM A350 LF2 and austenitic stainless steel
See every flange type we manufacture, or our buttweld fittings for the same pipelines.
Testing, Inspection, Marking & Packing
Every weld neck flange passes through our documented quality assurance process:
- Incoming material verification with PMI testing — no unverified material enters production
- Chemical and mechanical testing to the applicable ASTM material specification
- Controlled heat treatment where the grade requires it, with pickling and passivation for stainless steels
- Dimensional inspection of outside diameter, bolt circle, hub, bore and facing against the ordered standard
- Hydrostatic testing where specified by the purchase order or the applicable standard
- Marking with grade, size, pressure class and heat number for full traceability
Flanges are supplied with EN 10204 3.1 mill test certificates. EN 10204 3.2 certificates, witnessed by inspection bodies such as SGS, Bureau Veritas, TÜV or Lloyd's Register, are available on request, as is NACE MR0175 / ISO 15156 compliant material for sour service.
Flanges are packed for export with gasket faces protected by covers, rust-preventive coating on carbon and alloy steel, and seaworthy wooden cases; marking, tagging and packing to your specification are available on request.
Why Choose Raaj Fittings for Weld Neck Flanges?
Raaj Sagar Steels has supplied piping components since 2003 and today manufactures flanges at two plants in India for buyers in the Middle East, Europe and the Americas.
- Manufactured in-house — Weld neck flanges are made in our own plants, so material, dimensions and delivery stay under our control.
- Ready stock, short lead times — common sizes and grades are held in stock for prompt dispatch; other sizes, grades and specials are manufactured to order.
- Certified quality — ISO 9001:2015, ISO 14001:2015 and ISO 45001:2018 certified; PED 2014/68/EU and IBR supply available, and NACE MR0175 / ISO 15156 material on request.
- 100% material verification — PMI testing on incoming material and EN 10204 3.1 mill test certificates with every order; 3.2 certificates on request.
- Third-party inspection ready — we regularly work with SGS, Bureau Veritas, TÜV and DNV.
- Export documentation — MTCs, certificates of origin, packing lists and inspection reports to suit projects in the GCC, Europe and the Americas.
- Export packing — seaworthy packing with end and face protection, and packing to your specification on request.
- Fast response — our team replies to enquiries within one business day.
Weld Neck Flanges — FAQs
Weld neck flanges are used on high-pressure, high-temperature and cyclic-service piping, where the joint must resist fatigue and be fully inspectable. Typical uses are refinery and petrochemical process lines, steam and boiler piping, offshore systems, pipelines and nozzles on pressure vessels.
A weld neck flange is butt-welded to the pipe through its tapered hub, giving a full-penetration weld that can be radiographed and a joint with high fatigue strength. A slip on flange slides over the pipe and is fillet-welded inside and outside; it is cheaper and easier to align but is generally limited to lower-pressure, non-critical service.
Give the pipe schedule or wall thickness the flange will be welded to, such as SCH 40, SCH 80, XS or SCH 160. The bore and the weld bevel are then machined to that schedule so the inside surfaces of flange and pipe match after welding.
Raised face suits most process piping and is used with spiral wound or flat gaskets. Ring type joint flanges use a metal ring gasket in a machined groove and are generally chosen for Class 900 and higher, and for oil and gas production service. Follow the facing given in your piping specification.
Weld neck flanges are supplied from ½" to 24" NPS to ASME B16.5 in Class 150 to 2500, and from 26" to 60" NPS to ASME B16.47 Series A and B. EN 1092-1, DIN, BS, JIS and IS standard flanges, and flanges made to customer drawings, are also available.
Yes. We supply weld neck flanges for projects under the European Pressure Equipment Directive (PED 2014/68/EU), and with IBR certification for Indian boiler applications. NACE MR0175 / ISO 15156 compliant material is also available on request for sour service in the Middle East and the Americas.
