Weld Neck Flange Manufacturer in India | WN / WNRF / WNFF / WNRTJ | ASME B16.5 | Remax Forge
Key Features
Single full-penetration butt weld
The strongest connection method — one V-groove butt weld with zero flow restriction and full RT capability.
Long tapered hub — stress transfer
Gradually transfers stress from flange body to pipe wall, eliminating stress concentration at the junction.
Bore matched exactly to pipe schedule
Hub bore = pipe bore — no step, no turbulence, no erosion. Must specify NPS + pipe schedule when ordering.
What is a Weld Neck Flange?
A Weld Neck Flange (WN Flange) is the most structurally superior flange type, featuring a long tapered hub that is welded to the pipe via a single full-penetration butt weld (V-groove). The tapered hub gradually transfers stress from the flange to the pipe wall, eliminating stress concentration at the flange-pipe junction — the primary failure point in other flange types.
Industry Abbreviations
Why It Is the Strongest Flange Type:
- Single full-penetration butt weld — the strongest weld joint possible
- Tapered hub distributes mechanical stress smoothly — no abrupt stress transitions
- Internal bore matches exactly to pipe bore — NO flow restriction, NO turbulence
- Radiographic examination (X-ray) of the weld is possible — defects are detectable
- Required by code (ASME B31.3) for: lethal service, cyclic service, Class 900# and above in critical systems
- The ONLY flange type recommended for: high pressure, high temp, cryogenic, fatigue-loading, and corrosive media
🔗 For lower-pressure applications, our Slip On Flange is more economical. For pipe end closures, see our Blind Flange. Compare our complete flange range.
Standard Specifications
Remax Forge & Fittings manufactures forged Weld Neck Flanges to the most stringent international standards. The table below answers the most common buyer questions in one place:
| Property | Detail |
|---|---|
| Product Names | Weld Neck Flange, WN Flange, WNRF, WNFF, WNRTJ, Welding Neck Flange |
| Size Range | ½" (15 NB) to 60" (1500 NB); custom sizes available |
| Pressure Classes | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# (ASME B16.5); PN6 to PN400 (DIN/EN) |
| Pipe Schedule | SCH 10S, 20, 40, 80, 120, 160, XXS — bore machined to match exact pipe schedule |
| Face Types | RF (Raised Face), FF (Flat Face), RTJ (Ring Type Joint), T&G, M&F |
| Standards | ANSI/ASME B16.5, B16.47 Series A & B, EN 1092-1, DIN 2633/2635, JIS B2220, BS 4504, MSS SP-44, API 6A, API 605, GOST, AWWA |
| Weld Type | Single full-penetration V-groove butt weld (1 weld only) |
| MTC | EN 10204 3.1 standard; 3.2 on request; NACE MR0175/MR0103 available |
| Radiography | 100% RT available; mandatory for lethal/critical service per ASME B31.3 |
| Lead Time | 7–14 days (standard); 3–6 weeks (special alloy/custom) |
Weld Neck Flange Material Grades
We forge industrial Weld Neck Flanges in a wide variety of metallic materials to handle diverse chemical and corrosion requirements. Our range includes Stainless Steel, Duplex, Super Duplex, LTCS Carbon Steel, Alloy Steel, and corrosion-resistant Nickel Alloys (Inconel, Hastelloy, Monel):
| Material Category | Grades / Specifications |
|---|---|
| Stainless Steel Weld Neck Flanges | ASTM/ASME A/SA182: F304, F304L, F316, F316L, F316H, F316Ti, F321, F347; Cast: CF3, CF3M, CF8, CF8M; DIN: 1.4301, 1.4306, 1.4401, 1.4404, 1.4408, 1.4409 |
| Duplex Steel Weld Neck Flanges | UNS S31803/S32205 — ASTM A182 Gr F51, F52, F53, F54, F55, F57, F59, F60, F61 |
| Super Duplex Weld Neck Flanges | UNS S32750/S32760 — ASTM A182 Gr F53, F55; Zeron 100 |
| Carbon Steel Weld Neck Flanges | ASTM/ASME A/SA105, A105N, A216-WCB; A350 LF2 (low temp); A694 F52/F56/F60/F65/F70/F80 (high yield); DIN 1.0460, 1.0402, 1.0619 |
| Alloy Steel Weld Neck Flanges | ASTM A182/ASME SA182: F5, F9, F11, F12, F22, F91 (all P-grades for high temp service) |
| Nickel Alloy Weld Neck Flanges | Inconel 600, 601, 625, 718, 690, X750 (ASTM B564/ASME SB564); Incoloy 800, 800H, 800HT, 825, 925 |
| Hastelloy Weld Neck Flanges | C276 (UNS N10276), C22 (UNS N06022), C4, C2000, B2, B3, X (ASTM B564) |
| Monel Weld Neck Flanges | Monel 400 (UNS N04400), Monel K500 (UNS N05500) — ASTM B564 |
| Pure Nickel Weld Neck Flanges | Nickel 200, 201, 205, 205LC — ASTM B564/ASME SB564 |
| Copper Nickel Weld Neck Flanges | CuNi 90/10 (C70600), CuNi 70/30 (C71500), UNS C71640 — ASTM/ASME SB 61/62/151/152 |
| Titanium Weld Neck Flanges | Gr.1, Gr.2, Gr.4, Gr.5, Gr.7 — ASTM B381/ASME SB381; R50250/R50400/R50550/R50700/R52400/R53400/R56400 |
| Aluminium Weld Neck Flanges | 5052, 6061, 6063, 2017, 7075 |
| Brass Weld Neck Flanges | 3602, 2604, H59, H62 |
| Special Alloy Weld Neck Flanges | Alloy 20 (ASTM B462 SB462 — Carpenter 20Cb-3); SMO 254/6Mo (UNS S31254, DIN 1.4547); Al6XN; AISI 4130; AISI 4140; Nimonic 75/80A/90; Gunmetal; Cast Iron |
Forged Raw Billets stockWeld Neck Flange Standards & Specifications
Our forged Weld Neck Flanges are engineered according to ASME, ANSI, DIN, EN, JIS, API, and BS standards. We also offer customization to client-specific drawings:
| Standard / Spec | Scope / Application Details |
|---|---|
| 🇺🇸ANSI/ASME B16.5 | NPS ½" to 24" — the primary standard for most flanges |
| 🇺🇸ASME B16.47 Series A (MSS SP-44) | NPS 26" to 60" — large diameter |
| 🇺🇸ASME B16.47 Series B (API 605) | NPS 26" to 60" — large diameter (lighter) |
| 🇺🇸ASME B16.36 | Orifice flanges |
| 🇺🇸ASME B16.48 | Line blinds & spectacle blinds |
| 🇪🇺DIN 2501 / EN 1092-1 | European metric standard — PN ratings |
| 🇯🇵JIS B2220 | Japanese Industrial Standard |
| 🇬🇧BS 4504 / BS 10 Table D/E/F/H | British Standard |
| 🇺🇸MSS SP-44 | Large diameter steel pipeline flanges |
| 🇺🇸API 6A | Wellhead and Christmas tree equipment |
| 🇺🇸API 605 | Large diameter carbon steel flanges |
| 🇺🇸AWWA C207 | Water works flanges |
| 🇷🇺GOST 12820 / 12821 | Russian/CIS standard |
| 🇦🇺AS 2129 / AS 4087 / AS/NZS 4331.1 | Australian standard |
| 🇰🇷KS B1503 | Korean standard |
| 🌐ISO 7005-1 / ISO 9624 | International standard |
| 🇺🇸SAE J518 | Hydraulic flanged tube fittings |
| 🇨🇳GB Standard | Chinese national standard |
ASME B16.5 Weld Neck Flange Dimensions Table
Detailed dimensional chart for Class 150# forged Weld Neck Flanges. Dimensions per ASME B16.5. Weights are approximate for Carbon Steel A105. Click column headers to sort:
Contact us for exact drawings, Class 300#/600#/900# dimensions, or downloadable PDF catalogue.
NPS (inch)↕ | DN (mm)↕ | Pipe OD (mm)↕ | Flange OD (mm)↕ | Bolt Circle (mm)↕ | No. Bolts↕ | Bolt Ø (mm)↕ | Flange Thickness T (mm)↕ | Hub OD @ base (mm)↕ | Hub Length (mm)↕ | Approx. Wt CS (kg)↕ |
|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 15 | 21.3 | 89 | 60 | 4 | 16 | 11.2 | 35 | 30 | 0.5 |
| ¾ | 20 | 26.7 | 98 | 70 | 4 | 16 | 12.7 | 43 | 32 | 0.7 |
| 1 | 25 | 33.4 | 108 | 79 | 4 | 16 | 14.3 | 51 | 38 | 0.9 |
| 1½ | 40 | 48.3 | 127 | 98 | 4 | 16 | 17.5 | 73 | 44 | 1.4 |
| 2 | 50 | 60.3 | 152 | 121 | 4 | 19 | 19.1 | 92 | 51 | 2.0 |
| 3 | 80 | 88.9 | 190 | 152 | 4 | 19 | 23.9 | 127 | 57 | 3.5 |
| 4 | 100 | 114.3 | 229 | 190 | 8 | 19 | 23.9 | 157 | 64 | 5.5 |
| 6 | 150 | 168.3 | 279 | 241 | 8 | 22 | 25.4 | 216 | 76 | 9.0 |
| 8 | 200 | 219.1 | 343 | 298 | 8 | 22 | 28.6 | 270 | 86 | 14.0 |
| 10 | 250 | 273.1 | 406 | 362 | 12 | 25 | 30.2 | 324 | 102 | 21.0 |
| 12 | 300 | 323.9 | 483 | 432 | 12 | 25 | 31.8 | 381 | 114 | 31.0 |
| 14 | 350 | 355.6 | 533 | 476 | 12 | 29 | 35.1 | 413 | 127 | 40.0 |
| 16 | 400 | 406.4 | 597 | 540 | 16 | 29 | 36.6 | 470 | 140 | 53.0 |
| 18 | 450 | 457.2 | 635 | 578 | 16 | 32 | 39.7 | 533 | 152 | 68.0 |
| 20 | 500 | 508.0 | 699 | 635 | 20 | 32 | 42.9 | 584 | 165 | 86.0 |
| 24 | 600 | 609.6 | 813 | 749 | 20 | 35 | 47.8 | 692 | 178 | 122.0 |
* Dimensions per ASME B16.5. Weights are approximate for Carbon Steel A105. Contact us for Class 300#, 600#, and 900# dimension tables.
Flange Face Types
Weld Neck Flanges are available in all face configurations — RF (Raised Face, standard for oil & gas), FF (Flat Face, for cast iron mating), and RTJ (Ring Type Joint, for high-pressure critical service). WNRTJ is the most specified face type for Class 900# and above.
Raised Face (RF)
Most common. A raised circular ring that concentrates pressure on a smaller area to compress the gasket. Height: 1/16" for Class 150/300; 1/4" for Class 400 and above.
Flat Face (FF)
No raised portion; entire flange face is in the same plane. Used when mating against cast iron or non-metallic flanges to avoid cracking on bolt tightening.
Ring Type Joint (RTJ)
Oval or octagonal groove machined into the face; a metal ring gasket seats in the groove. Used in high-pressure, high-temperature critical service (refineries, oil fields).
Tongue & Groove (T&G)
One flange has a raised ring (tongue); the other a matching groove. Provides excellent alignment and a confined gasket. Used in pumps and valve bonnets.
Male & Female (M&F)
Similar to T&G but the female face is flat and the male face raised. Used in heat exchangers, pressure vessels, and high-integrity process joints.
Large Male & Female
Same operating principle as the standard Male & Female flange, scaled up with larger step contact surfaces for specialized heavy industrial equipment.
Advantages & Limitations of Weld Neck Flange
✅ Advantages
Strongest Flange
Single full-penetration butt weld — the strongest weld joint possible; code-required for critical service.
Radiographic Inspection Possible
Full-penetration butt weld can be X-rayed (100% RT) to detect internal defects — ensuring zero-leak joints.
Perfect Bore Match
Hub bore machined to exact pipe bore — zero turbulence, zero pressure drop, zero erosion at the joint.
Best for Extremes
For high temp (up to 700°C alloy steel), high pressure (2500#), cryogenic (-196°C LNG), and cyclic fatigue.
Maximum Fatigue Life
Tapered hub distributes stress smoothly into pipe wall — outlasts Slip-On by 3× under fatigue loading.
Code-Mandated
Required by ASME B31.3 for lethal, high-temp, cyclic, and Class 900# and above critical service.
One Weld Only
Just one weld joint to inspect and maintain (vs. two fillet welds for Slip-On flanges).
Limitations — Transparent Disclosure
Weld Neck is the strongest flange — but it comes with trade-offs that buyers should understand before specifying:
Industries & Applications
✓Primary Applications
💡 For low-to-medium pressure general service, the more economical Slip On Flange may be a better fit. Weld Neck is specified where safety and code compliance demand the highest integrity connection.
Oil & Gas
Upstream extraction, midstream pipelines, downstream refineries.
Petrochemical
Chemical reactors, process lines, heat exchangers.
Power Generation
Boilers, steam turbines, nuclear plants, thermal power.
Pharmaceuticals
Hygienic piping, clean steam, pure water systems.
Food & Beverage
Sanitary flanges, sugar mills, beverage processing.
Paper & Pulp
Chemical recovery, bleaching lines.
Water Treatment
Municipal water, desalination, irrigation.
Shipbuilding
Offshore platforms, FPSOs, marine piping.
Chemical Plants
Acid service, caustic lines, solvent handling.
Construction
HVAC, fire suppression, utility headers.
Testing & Inspection
We implement a rigorous, zero-defect quality control protocol on all flange fabrications. Every production batch undergoes visual inspection and dimensional checking. Advanced NDT including ultrasonic testing, PMI spectrometer analysis, hydrostatic pressure testing, and 100% radiography available on request.
Hydrostatic / Hydro Pressure Test
Each flange pressure tested at 1.5x working pressure per ASME code requirements.
Ultrasonic Testing (UT)
Non-destructive testing to detect internal sub-surface cracks, inclusions and forging defects.
Radiographic Testing (RT / X-Ray)
100% radiography available; mandatory for critical Class 900+ high pressure services.
Positive Material Identification (PMI)
Spectrometer validation to verify alloy chemistry precisely matches the Mill Test Certificate.
Dye Penetrant Test (DPT / LPT)
Detects micro surface cracking and porosity on critical machined seating surfaces.
Magnetic Particle Inspection (MPI)
For ferromagnetic alloys; flags surface and near-surface structural discontinuities.
Hardness Test (Brinell/Rockwell)
Verifies correct heat treatment structure and ensures mechanical properties are hit.
Direct-Reading Spectrograph
In-house lab chemical checks of billets before forging process begins.
Impact / Charpy Test
Crucial for low-temperature applications to verify ductility (e.g. A350 LF2, LTCS).
NACE Compliance Testing
Verifies sour-gas / H2S environment service capability (NACE MR0175 / MR0103).
Documents & Certificates
We supply a comprehensive documentation package with every shipment — Mill Test Certificates (EN 10204 3.1), NACE compliance documentation, heat treatment records, hydrostatic test charts, and third-party inspection clearances from SGS, Lloyd's, and DNV.
Mill Test Certificate (MTC)
Provided as per EN 10204 3.1 detailing chemical & mechanical analysis.
EN 10204 3.2 Certificate
Independent third-party inspection validation (available upon request).
NACE MR0175 / MR0103 Compliance
Certified suitability for sour gas/H2S environments.
Raw Materials Certificate
Provides 100% trace origin tracking from steel billet to finished flange.
Dimensional Inspection Report
All critical tolerances checked and certified against CAD designs.
Heat Treatment Certificate
HTR and PWHT thermal chart records included where requested.
Hydrostatic Test Certificate
Pressure log documentation verifying weld integrity.
Third Party Inspection (TPI)
Bureau Veritas, SGS, Lloyds, DNV, TUV inspection options.
Packing List & Weight Certificate
Proper documentation for simple custom clearance and cargo log.
Country of Origin Certificate
Enables import tariff relief and compliance logging.
Weld Neck Flange vs Other Flange Types
Use this quick comparison to decide whether Weld Neck is the right choice for your application:
| Feature | Weld Neck Flange | Slip On Flange | Socket Weld Flange |
|---|---|---|---|
| Weld Joints Required | 1 butt weld (full penetration) | 2 fillet welds | 1 fillet weld (external) |
| Pressure Rating | Highest (all classes 150–2500#) | Medium (up to 600# preferred) | High (small bore ½"–3") |
| Fatigue Life | Highest (3× Slip-On) | ~1/3 of Weld Neck | ~2/3 of Weld Neck |
| Radiography (RT) | Yes — 100% RT capable | Not feasible (fillet weld) | Not feasible |
| Bore Match to Pipe | Exact — zero turbulence | Slides over pipe OD | Socket bore ≈ pipe OD |
| Installation Speed | Slower (precise cut & butt weld) | Faster (slide & fillet weld) | Moderate |
| Cost (Relative) | Highest | Lowest | Moderate |
| Code-Mandated For | Lethal, cyclic, Class 900+ | General/low-medium pressure | Small-bore high pressure |
Surface Finish & Coating Options
Anti-rust Paint
Standard protection coat applied on carbon steel flanges.
Oil Black Paint
High-grade finish offering superior long-term storage corrosion block.
Yellow Transparent Lacquer
Allows technical inspectors to visually inspect metal surface during receiving.
Zinc Plated
Electro-galvanized bright zinc barrier layer for light industrial environments.
Hot Dip Galvanized (HDG)
Thick zinc alloy barrier layer for maximum outdoor marine rust protection.
Epoxy Coating
FBE or liquid epoxy coating for heavy buried pipelines and sewage lines.
Bare/Pickled & Passivated
Chemical acid cleaning to restore corrosion resistance for stainless steel.
Custom Coating
Special finishes customized exactly to customer painting specifications.
Export Markets
Global Export Network
Why Choose Remax Forge?
Remax Forge & Fittings stands out as a leading flange manufacturer due to our complete in-house forging, heat treatment, and precision CNC machining capabilities based in Mumbai. We provide certified compliance, factory-direct wholesale pricing, and custom forging schedules tailored to your engineering blueprints. With over 20 years of manufacturing experience, zero-defect quality management, and short lead times, we are a trusted supply partner for critical industrial piping projects.
ISO 9001:2015 Certified
Fully audited quality management workflows.
In-House Forging
Forging, heat-treat, machining in Mumbai.
Testing Laboratory
PMI, Spectro, UT, Hydro labs on-site.
Mill Certificates
EN 10204 3.1 standard; 3.2 available.
20+ Years Experience
Serving critical gas/oil clients globally.
45+ Export Countries
Proven global logistics and documentation.
Custom Forging
Special shapes, alloys and schedules.
Factory-Direct Price
Competitive pricing with no agent markup.
Technical Support
Engineers ready to assist spec selection.
Short Lead Times
Fast turnaround of custom and stock orders.
📥 Download Weld Neck Flange Catalogue (PDF)
Get the complete technical catalogue including product description, full ASME B16.5 Class 150#, 300#, 600# & 900# dimension tables, material grades, standards, and weight charts — ready to attach to your RFQ.
How to Order
Ordering high-quality forged flanges from Remax is straightforward. To ensure our engineering team provides you with a precise and competitive quote, please specify the exact flange type, nominal pipe size (NPS), pressure class rating, material grade, and facing configuration. Let us know your total quantity requirements and if you require any specialized testing or custom coatings. Contact us via email or phone for a quick, same-day response.
Direct Inquiries
Estimated Lead Times
Frequently Asked Questions
Find answers to the most common questions about Weld Neck Flanges — including WNRF vs WNFF, pipe schedule matching, API 6A, large bore B16.47, and temperature limits. Contact our metallurgical engineers for project-specific guidance.
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