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WN Flange
SDFL
Welding Neck Flange | ASME B16.5 WN Flange Supplier & Manufacturer
Brief Product Introduction
ASME B16.5 Weld Neck Flange (WN Flange, WNRF Flange) is an integrally forged flange with a tapered hub. It connects to pipelines by butt welding, achieving full penetration weld. The tapered hub gradually transfers stress to the pipe, greatly lowering stress concentration at the joint. This type of flange is the preferred choice for high-pressure, high-temperature and cyclic load piping systems. It complies with ASME B16.5 standard for NPS 1/2” to 24”, covering pressure classes Class150 to Class2500LB. It is widely used in oil & gas, refinery, power generation, hydrogen, LNG, seawater desalination and chemical process pipelines.
Key Features
Integrally forged blank, free of casting porosity, sand holes and shrinkage defects for critical service
Tapered hub design, excellent fatigue resistance; butt weld joint supports RT radiographic inspection
Precision CNC machining, bore size matches pipe OD perfectly, minimize fluid turbulence
Multiple sealing face options: RF Raised Face, FF Flat Face, MFM Male & Female, TG Tongue & Groove, RTJ Ring Type Joint
Complete pressure class range: Class150, 300, 400, 600, 900, 1500, 2500LB
Strictly manufactured to ASME B16.5, interchangeable with international standard flanges
Suitable for corrosive, high temperature and high pressure working conditions
Manufacturing Process
1. Raw Material PMI Spectral Inspection
2. Closed-die Hot Forging (Hydraulic Forming Press)
3. Solution Heat Treatment (Continuous Heat Treatment Line)
4. Precision CNC Machining (5-axis Machining Center, High-precision CNC Lathe)
5. Semi-finishing Dimensional & Surface Inspection
6. Surface Finishing (Pickling & Passivation / Mechanical / Electropolishing)
7. Final Quality Control (Dimensional Test, NDT, Surface Defect Check)
8. Export Standard Packaging
9. Delivery
Flange dimensions follow ASME B16.5; parts can also be supplied to EN 1092-1, JIS B2220, GOST 12821, or customer drawings. Each batch is delivered with a material test report per EN 10204 3.1, and PMI testing can be arranged before shipment.
Item | Details |
|---|---|
FLANGE TYPE | Standard: WNRF Weld Neck Flange; other flange types available upon request |
SIZE RANGE | Standard: NPS 1/2" – NPS 24" (DN15 – DN600) to ASME B16.5; Custom sizes available per customer drawing |
PRESSURE | Class 150 – 2500, PN0.6 – PN400, 5K – 40K |
SEALING FACE | RF, FF, RTJ, Tongue & Groove, customizable |
STANDARDS | ASME B16.5, EN 1092-1, DIN, JIS B2220, GOST 12821, GB/T 9124.1-2019, custom standards |
MATCHED PIPE SCHEDULE | SCH5S – SCH160 |
MATERIAL | Standard: ASTM A182 F321 (UNS S32100 / EN 1.4541) Optional: F304/F304L, F316/F316L, F321, F347, duplex steel, nickel alloys, carbon stee |
SURFACE TREATMENT | Pickling & Passivation, As-machined, Mechanical Polishing, Electropolishing (EP) |
Applications | Petrochemical, pharmaceutical, power plants, shipbuilding, water treatment, general industrial piping |
The table below reproduces the ANSI B16.5 Class 300 flange dimensions shown in the reference table; all values are in inches.
Nom. Pipe Size | O | T | R | X | No./Dia. of Holes | Bolt Circle Dia | L2 | H | B2 | L | B | r | L3 | B3 | D | C | Thr |
1/2 | 3.75 | 0.56 | 1.38 | 1.5 | 4-0.62 | 2.62 | 2.06 | 0.84 | 0.62 | 0.88 | 0.88 | 0.12 | 0.88 | 0.90 | 0.38 | 0.93 | 0.62 |
3/4 | 4.62 | 0.62 | 1.69 | 1.88 | 4-0.75 | 3.25 | 2.25 | 1.05 | 0.82 | 1.00 | 1.09 | 0.12 | 1.00 | 1.11 | 0.44 | 1.14 | 0.62 |
1 | 4.88 | 0.69 | 2.00 | 2.12 | 4-0.75 | 3.50 | 2.44 | 1.32 | 1.05 | 1.06 | 1.36 | 0.12 | 1.06 | 1.38 | 0.50 | 1.41 | 0.69 |
1-1/4 | 5.25 | 0.75 | 2.50 | 2.50 | 4-0.75 | 3.88 | 2.56 | 1.66 | 1.38 | 1.06 | 1.70 | 0.19 | 1.06 | 1.72 | 0.56 | 1.75 | 0.81 |
1-1/2 | 6.12 | 0.81 | 2.88 | 2.75 | 4-0.88 | 4.50 | 2.69 | 1.90 | 1.61 | 1.19 | 1.95 | 0.25 | 1.19 | 1.97 | 0.62 | 1.99 | 0.88 |
2 | 6.50 | 0.88 | 3.62 | 3.31 | 8-0.75 | 5.00 | 2.75 | 2.38 | 2.07 | 1.31 | 2.44 | 0.31 | 1.31 | 2.46 | 0.69 | 2.50 | 1.12 |
2-1/2 | 7.50 | 1.00 | 4.12 | 3.94 | 8-0.88 | 5.88 | 3.00 | 2.88 | 2.47 | 1.50 | 2.94 | 0.31 | 1.50 | 2.97 | 0.75 | 3.00 | 1.25 |
3 | 8.25 | 1.12 | 5.00 | 4.62 | 8-0.88 | 6.62 | 3.12 | 3.50 | 3.07 | 1.69 | 3.57 | 0.38 | 1.69 | 3.60 | 0.81 | 3.63 | 1.25 |
3-1/2 | 9.00 | 1.19 | 5.50 | 5.25 | 8-0.88 | 7.25 | 3.19 | 4.00 | 3.55 | 1.75 | 4.07 | 0.38 | 1.75 | 4.10 | / | 4.13 | 1.44 |
4 | 10.00 | 1.25 | 6.19 | 5.75 | 8-0.88 | 7.88 | 3.38 | 4.50 | 4.03 | 1.88 | 4.57 | 0.44 | 1.88 | 4.60 | / | 4.63 | 1.44 |
5 | 11.00 | 1.38 | 7.31 | 7.00 | 8-0.88 | 9.25 | 3.88 | 5.56 | 5.05 | 2.00 | 5.66 | 0.44 | 2.00 | 5.69 | / | 5.69 | 1.69 |
6 | 12.50 | 1.44 | 8.50 | 8.12 | 12-0.88 | 10.62 | 3.88 | 6.63 | 6.07 | 2.06 | 6.72 | 0.50 | 2.06 | 6.75 | / | 6.75 | 1.81 |
8 | 15.00 | 1.62 | 10.62 | 10.25 | 12-1.00 | 13.00 | 4.38 | 8.63 | 7.98 | 2.44 | 8.72 | 0.50 | 2.44 | 8.75 | / | 8.75 | 2.00 |
10 | 17.50 | 1.88 | 12.75 | 12.62 | 16-1.12 | 15.25 | 4.62 | 10.75 | 10.02 | 2.62 | 10.88 | 0.50 | 3.75 | 10.92 | / | 10.88 | 2.19 |
12 | 20.50 | 2.00 | 15.00 | 14.75 | 16-1.25 | 17.75 | 5.12 | 12.75 | 12.00 | 2.88 | 12.88 | 0.50 | 4.00 | 12.92 | / | 12.94 | 2.38 |
14 | 23.00 | 2.12 | 16.25 | 16.75 | 20-1.25 | 20.25 | 5.62 | 14.00 | 13.25 | 3.00 | 14.14 | 0.50 | 4.38 | 14.18 | / | 14.19 | 2.50 |
16 | 25.50 | 2.25 | 18.50 | 19.00 | 20-1.38 | 22.50 | 5.75 | 16.00 | 15.25 | 3.25 | 16.16 | 0.50 | 4.75 | 16.19 | / | 16.19 | 2.69 |
18 | 28.00 | 2.38 | 21.00 | 21.00 | 24-1.38 | 24.75 | 6.25 | 18.00 | 17.25 | 3.50 | 18.18 | 0.50 | 5.12 | 18.20 | / | 18.19 | 2.75 |
20 | 30.50 | 2.50 | 23.00 | 23.12 | 24-1.38 | 27.00 | 6.38 | 20.00 | 19.25 | 3.75 | 20.20 | 0.50 | 5.50 | 20.25 | / | 20.19 | 2.88 |
22 | 33.00 | 2.63 | 25.25 | 25.25 | 24-1.63 | 29.25 | 6.50 | 22.00 | 21.25 | 4.00 | 22.22 | 0.50 | 5.75 | 22.25 | / | 22.19 | 3.13 |
24 | 36.00 | 2.75 | 27.25 | 27.62 | 24-1.62 | 32.00 | 6.62 | 24.00 | 23.25 | 4.19 | 24.25 | 0.50 | 6.00 | 24.25 | / | 24.19 | 3.25 |
Quality Control
We implement full-process quality control for every ASME B16.5 Weld Neck Flange. Raw material inspection is carried out before forging, including PMI positive material identification to verify alloy composition. After forging, heat treatment is arranged as required to adjust hardness and eliminate internal stress.
We perform dimensional inspection, visual inspection and NDT non-destructive testing (MT, PT, UT, RT) upon request. All test records are archived. MTC material test certificates, heat treatment reports and inspection reports can be supplied together with goods. Our quality system follows ISO 9001, and we support third-party inspection as required by clients.
Why Choose Us
We are a professional manufacturer and supplier of ASME B16.5 forged WN flanges. We own in-house forging, CNC machining and NDT workshops instead of outsourcing all processes. We have rich experience serving EPC contractors, pipeline distributors and end users worldwide. We can respond quickly to RFQ, provide accurate quotation and technical support for flange selection. Short lead time for standard items. We keep stable raw material supply and stable quality. All products are exported globally, and we welcome factory audit and video inspection.
 D2000 Certificate |  PED Certificate |  PED Certificate |
 TS Pressure Pipe Element Manufacturing License |  EAC Certificate |  EAC Certificate |
 ISO 9001 Quality Management System |  ISO 14001 Environmental Management System |  ISO 45001 Occupational Health & Safety System |
Available Materials
· Standard Stainless Steel: ASTM A182 F304/F304L, F316/F316L, F321, F347, 904L
· Super Austenitic & Duplex Steel: Super austenitic steel, SAF 2205, SAF 2507 super duplex steel
· Nickel & Special Alloys: Inconel 600/625/690, Incoloy 800/825/800H, Monel 400, Hastelloy series
· Custom special alloy grades available upon request
Custom Service
· Full custom production per customer drawings, samples or project requirements
· Non-standard dimensions, pressure ratings and sealing face configurations
· Special material customization: special alloys, sanitary grade materials
· Engineering Support: Working condition analysis, material selection, piping solution design
· Laser marking: logo, part number, batch number, project identification
· Custom export packaging and special protection requirements
· OEM & ODM services
Packaging & Shipping
· Packaging: Export special wooden cases; flange sealing faces protected by dedicated flange protective caps
· Marking: Custom shipping marks, batch number and material traceability marking
· Shipping: FCL/LCL sea freight, air freight, international express delivery
· Documents: Full set of export documents, MTR reports, certificates and packing lists provided
FAQ:
A1: Welding Neck Flange (WN Flange) is a flange with a tapered hub and full penetration butt weld end. The tapered hub distributes pipeline stress smoothly to the pipe, which makes it suitable for high pressure, high temperature, thermal cycling and vibration piping systems. It is widely used in critical oil, gas, chemical and power process lines.
A2: WN flange uses butt welding, full penetration weld, better stress transfer, suited for high-class high-risk service. Slip On flange is fillet welded externally only, easier for installation but weaker for high pressure and thermal shock. WN flange is the preferred choice for Class600 and above critical joints.
A3: We supply RF (Raised Face), RTJ (Ring Type Joint), M&F (Male & Female), T&G (Tongue & Groove) for WN flanges. RF is the most common general type; RTJ is standard for high-pressure high-temperature hydrocarbon and hydrogen service.
A4: Main standards: ASME B16.5, ASME B16.47 Series A/B, EN 1092-1, DIN. Pressure classes: Class150, 300, 600, 900, 1500, 2500.
A5: Carbon steel A105, A350 LF2; stainless steel 304, 304L, 316, 316L, 321, 310S; duplex 2205, 2507; alloy steel F11/F22/F91; nickel alloys Hastelloy C276, Inconel 600, Monel 400.
A6: Yes. Every batch of our Welding Neck flanges comes with 3.1 MTC. PMI positive material identification, UT, MT, PT, hardness test are available on request.
A7: Yes. Select 316L or 2205 duplex WN flanges for brackish water and seawater service to resist chloride pitting corrosion. Carbon steel and ordinary 304 are not recommended for chloride-rich media.
A8: Yes. We support custom drawing production, special hub length, special bore size, special surface treatment and marking according to your technical drawing.
A9: Oil & gas, refinery, chemical processing, power plant, LNG, offshore marine, seawater desalination, pharmaceutical and food hygienic piping.
A10: Please provide: flange standard, size, pressure class, material grade, sealing face type, quantity and special inspection requirements. We will send you quotation and technical datasheet quickly.
