Engineering-grade long welding neck flanges designed for high-pressure and high-temperature piping systems. Get factory-direct pricing with full material traceability, third-party inspection, and global delivery in as fast as 15 days.
β ASME B16.5 Compliant | Factory-Direct
Engineering-grade long welding neck flanges designed for high-pressure and high-temperature piping systems. Get factory-direct pricing with full material traceability, third-party inspection, and global delivery in as fast as 15 days.
Every day, we speak to engineers and purchasing managers who are struggling with the same flange procurement issues.
Trading companies add 20β45% markup on flange prices. A WN flange that costs $85 ex-works can easily become $130+ by the time it reaches your warehouse. Overpaying by 35% on average is common when buying through multi-tier distribution chains.
A 2024 industry audit found that 12% of imported flanges fail chemical composition tests. Non-certified material in a long welding neck flange creates catastrophic risk, especially in ASME B16.5 Class 900+ applications where a single failure can cost millions in downtime and safety fines.
Flange shipments from smaller suppliers often arrive in multiple partial shipments, with freight costs 30% higher than necessary. In 2025, shipping delays averaged 22 days longer for non-integrated suppliers β affecting project timelines and causing site idle-crew costs of up to $2,500/day on large pipeline projects.
Incomplete EN 10204 3.1/3.2 certificates, missing heat numbers, and improper PMI reports cause 27% of imported WN flanges to face customs holds or rejection during client audits in the EU and USA. Engineering firms are increasingly blacklisting suppliers unable to produce full traceability packs.
Off-the-shelf ASME B16.5 WN flanges from US warehouses carry lead times of 6β10 weeks for common materials like A105 or F316. For special materials or face finishes, 12β16 weeks is routine. This alone can delay a plant turnaround by a full quarter.
A βcheapβ flange that fails early leads to unplanned shutdowns. Research from Cureus Journal of Engineering (2025) on material selection in rigid flange coupling systems confirms that over-specification waste and in-service failures are directly tied to inadequate material traceability and non-optimized material choice β costing operators 2β3Γ the original component price in lifecycle maintenance.
Recognize these pain points? We'll show you how a direct manufacturing partnership eliminates each one.
See the Solution βWe are a manufacturer-direct source β not a trading company. Forging, heat treatment, machining, and testing all happen under one roof in our 12,000mΒ² facility in Cangzhou, Hebei Province. This vertical integration gives us uncompromised quality control and enables pricing that is typically 25β40% below Western distributor levels.
Every long welding neck flange we ship is manufactured and tested in accordance with ASME B16.5, with dimensional inspection reports available upon request. We also meet ASME B31.1 and ASME B31.3 piping code requirements for the end-user systems where our flanges are installed.
Each flange carries a permanently stamped heat number with an accompanying EN 10204 3.1 material certificate. Options for 3.2 certification with third-party inspection (SGS, BV, TΓV, Lloyds) are available for project-critical requirements.
Standard WN flanges (A105 / F304 / F316) in sizes 1/2"β12" ship in 15β20 days. Larger diameters and exotic alloys typically require 25β35 days. Air freight options are available for emergency requirements.
We accept custom drawings for non-standard hubs, longer weld necks, special bore sizes, and unique face finishes. Our engineering team works with your specs to deliver OEM-compliant flanges for legacy installations, including direct replacements for major brand flanges.
Exporting to 20+ countries including the USA, Canada, Russia, Kazakhstan, Algeria, and across Europe and the Middle East. We understand export packing, INCOTERMS, and documentation requirements for every region we serve.
The following tables provide critical engineering data for specifying WN flanges, covering dimensions, pressure-temperature ratings, and material classes.
| NPS | OD (mm) | Bolt Circle (mm) | Bolt Holes | Hub OD (mm) | Length thru Hub (mm) | Bore (mm) |
|---|---|---|---|---|---|---|
| 1/2" | 89 | 60.3 | 4 | 38 | 51 | 16 |
| 1" | 108 | 79.4 | 4 | 49 | 64 | 26 |
| 2" | 152 | 120.7 | 4 | 73 | 84 | 52 |
| 4" | 229 | 190.5 | 8 | 117 | 114 | 102 |
| 6" | 279 | 241.3 | 8 | 171 | 140 | 152 |
| 10" | 406 | 362.0 | 12 | 267 | 184 | 254 |
| 16" | 597 | 542.9 | 16 | 406 | 235 | 406 |
| 24" | 813 | 749.3 | 20 | 584 | 298 | 610 |
* For complete dimensional tables covering all classes and sizes up to 24", download our full brochure. Custom hub dimensions available for OEM requests.
| Temp (Β°C) | Class 150 (bar) | Class 300 (bar) | Class 600 (bar) | Class 900 (bar) | Class 1500 (bar) | Class 2500 (bar) |
|---|---|---|---|---|---|---|
| 38 | 19.6 | 51.1 | 102.1 | 153.2 | 255.3 | 425.5 |
| 100 | 17.9 | 46.6 | 93.2 | 139.8 | 233.0 | 388.3 |
| 200 | 15.0 | 42.1 | 84.2 | 126.3 | 210.5 | 350.8 |
| 300 | 12.5 | 38.5 | 77.0 | 115.5 | 192.5 | 320.8 |
| 400 | 9.0 | 28.5 | 57.0 | 85.5 | 142.5 | 237.5 |
| 450 | 7.1 | 23.2 | 46.4 | 69.6 | 116.0 | 193.3 |
| 500 | 4.8 | 16.7 | 33.4 | 50.1 | 83.5 | 139.2 |
* Ratings per ASME B16.5 Table 2-1.1 for Group 1.1 materials (ASTM A105). For other materials, refer to the applicable material group tables.
Provides maximum stress distribution at the hub-to-pipe junction. Ideal for high-pressure, high-temperature, and cyclic loading applications. The tapered hub creates a smooth transition that minimizes stress concentration under bending and thermal loads β a critical advantage in ASME B31.3 process piping.
Lower cost and easier alignment, but only provides approximately 2/3 the fatigue strength of a WN flange. Not recommended for severe service conditions such as vibration, thermal cycling, or high-pressure gas service.
Suitable only for low-pressure, non-critical applications with small diameters. Threaded connections are prone to leakage in harsh services and are not recommended above 300 psi or 250Β°C.
Raised Face (RF): Most common, features a raised surface 1.6mm to 6.4mm above the flange face, used with sheet or spiral-wound gaskets.
Full Face (FF): Flat surface across the entire flange face β ideal for low-pressure applications with full-face gaskets.
Ring Type Joint (RTJ): Precision-machined grooves that accept metal ring gaskets (R, RX, BX styles). Designed for high-pressure and high-temperature services, typically Class 600 and above.
Tongue & Groove (T&G): Matched male/female faces that improve gasket seating and alignment for premium sealing.
π‘ Engineering note: For offshore pipeline applications, the sealing structure's contact pressure and equivalent stress distribution determine joint reliability. Our flange face finishes are machined to a 125β250 Β΅inch Ra serrated finish per ASME B16.5 Table 4, optimizing gasket grip while minimizing galling risk.
Choosing the right material is the single most critical decision in flange selection. The 2025 Cureus Journal of Engineering material selection framework emphasizes evaluating mechanical properties, corrosion resistance, thermal stability, and cost-effectiveness in tandem. We present the data below to support your decision.
The workhorse standard for general-purpose flanges in non-corrosive and mildly corrosive service.
Yield Strength: 250 MPa min
Temp Range: -29Β°C to 538Β°C
Common Uses: Water, oil, gas, steam, general process lines
Cost Index: Baseline (1.0Γ)
Austenitic stainless steels for corrosive media, food processing, pharmaceutical, and high-purity systems.
F304: 18Cr-8Ni, excellent general corrosion resistance
F316: 16Cr-12Ni-2Mo, superior pitting/crevice resistance
Temp Range: -254Β°C to 815Β°C
Cost Index: 2.2β2.8Γ
Chrome-moly steels engineered for high-temperature and hydrogen service, common in refining and petrochemical plants.
F11 (1.25Cr-0.5Mo): Elevated temp strength up to 650Β°C
F22 (2.25Cr-1Mo): Hydrogen attack resistance per API 941
Temp Range: -29Β°C to 650Β°C
Cost Index: 1.8β2.4Γ
Higher strength + superior chloride stress-corrosion cracking resistance. Ideal for offshore and chemical environments.
Yield Strength: 450 MPa min
Temp Range: -50Β°C to 315Β°C
PREN β₯ 35 for enhanced pitting resistance
Cost Index: 4.0β5.5Γ
π οΈ Manufacturing processes included in every WN flange:
Forging: Open-die or closed-die forging ensures a continuous grain structure, eliminating porosity and producing superior mechanical properties vs. cast flanges.
Heat Treatment: Normalizing, annealing, or quenching-and-tempering as required by material spec, verified with hardness testing.
NDE: Ultrasonic testing (UT) per ASTM A388, magnetic particle (MT) per ASTM E709, or liquid penetrant (PT) per ASTM E165 available on request.
Hydrostatic Test: Each flange can be certified to hold the rated pressure with no visible leakage when tested per ASME B16.5.
WN flanges are the industry standard for API 6A wellhead equipment, manifolds, and high-pressure gas lines. Class 900β2500 flanges in F22 or F51 duplex are commonly used in HPHT wells and refinery hydroprocessing units.
Relevant standard: ASME B31.3 Process Piping requires WN flanges for severe cyclic conditions.
In thermal and nuclear power plants, WN flanges handle high-pressure steam lines at temperatures up to 600Β°C. Alloy steel F22 and F91 grades are often specified to achieve the required creep-rupture strength. Flange dynamics in steam piping are analyzed using nonlinear bolted-flange models to predict vibration response.
Corrosive acid and caustic services demand materials like F316 stainless steel or high-nickel alloys. The WN flange's smooth bore-to-pipe transition reduces dead zones and minimizes corrosion-erosion at welded joints β a key factor in increasing mean time between failures (MTBF).
For large-diameter water pipelines and desalination plants, WN flanges in Super Duplex F53 provide exceptional chloride resistance. Our 24" Class 300 WN flanges are widely used in Middle East seawater intake systems.
A Texas-based EPC contractor engaged us for 2,400 ASME B16.5 long welding neck flanges across Classes 150β900, in materials A105 and F22. By sourcing directly from our factory, the client achieved a 37% cost reduction compared to their previous distributor pricing while compressing delivery from 14 weeks to 6 weeks total. Every flange came with EN 10204 3.1 certification and was inspected by an independent third-party agency before shipment.
π± Real-time client communication β live quotes, spec confirmations, and order updates
ISO 9001:2015
CE Compliant
UL Recognized
GS Safety
ANSI/ASME
Serving industrial leaders across 20+ countries
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About the Author
Senior Piping Systems Engineer with 16 years of experience in industrial flange and fitting design, ASME B31 code applications, and global supply chain management. Daniel has overseen more than 200 piping projects across upstream oil & gas, refining, and chemical processing. He currently serves as the Technical Director of International Business Development at Cangzhou Weihuan Pipeline Equipment Co., Ltd.
A standard welding neck (WN) flange has a tapered hub of a defined length per ASME B16.5. A long welding neck (LWN) flange has an extended hub beyond the standard ASME B16.5 length, providing additional reinforcement and stress distribution at the weld joint. LWN flanges are often used in high-pressure nozzles on pressure vessels, heat exchangers, and columns where the extra hub length helps anchor the nozzle and minimize thermal/mechanical stress. In some OEM applications, the "LWN" refers to a flanged stub-end or nozzle neck that replaces a full pipe length and welded standard flange assembly.
ASME B16.5 is the American standard explicitly covering flanges and flanged fittings for nominal pipe sizes from 1/2" to 24". It specifies dimensions, tolerances, pressure-temperature ratings, materials, bolt sizes, face finishes, and test methods. For sizes larger than 24", ASME B16.47 applies. It covers flange classes 150, 300, 400, 600, 900, 1500, and 2500. All our WN flanges are manufactured and dimensionally inspected per the latest ASME B16.5 edition.
For standard materials (A105, F304, F316) and sizes 1/2"β12" in Classes 150β600, production takes 15β20 days from order confirmation. For larger sizes (14"β24") or higher classes (900β2500), lead times extend to 25β35 days. When third-party inspection or special coatings are required, add 3β5 days. Express production is available for urgent requirements β contact our sales team to evaluate your schedule.
Yes. Our engineering team regularly designs and manufactures customized LWN flanges with non-standard hub lengths, reduced bores, special face finishes, and unusual materials. We accept customer drawings (PDF, DWG, or STEP) and can provide a free design review. For legacy installations, we can reverse-engineer flanges to match existing equipment dimensions.
Every order ships with a complete documentation pack including: EN 10204 3.1 material certificate, dimensional inspection report, heat treatment chart, and pressure test certificate (if applicable). We can also provide defect detection reports (UT/MT/PT), PMI reports, and original mill test certificates on request. For export, we provide commercial invoice, packing list, bill of lading, and country-of-origin certificate (Form A, C/O, EUR.1 as required).
There is no minimum order quantity for standard sizes β we serve both large-scale projects and urgent single-flange replacements. Small orders are welcome, and we offer competitive pricing tiers that improve with quantity. For custom OEM flanges, the MOQ depends on forging die availability, but is typically 5β10 pieces.
We ship worldwide via sea freight (FOB/CIF/CFR/DAP), air freight, or express courier (DHL, FedEx, UPS) depending on your urgency and budget. Our export team ensures proper seaworthy export packing (wooden cases or steel pallets with rust-proof coating). For USA and EU orders, we can assist with customs clearance documentation, FDA certifications, and ASTM import compliance to ensure smooth arrival.
Yes, we provide free samples for standard WN flange sizes up to 4". Samples are offered on a basis where shipping costs are covered by the customer, or in coordination with larger orders. This allows you to verify the quality, machining accuracy, and documentation quality before committing to full-scale procurement.
"We switched to Weihuan after previously overpaying for A105 WN flanges sourced through a Texas distributor. Their first order β 1,200 flanges across Classes 150 and 300 β arrived 2 weeks ahead of schedule, with spotless documentation. We saved roughly 31% on total procurement cost and they've since become our preferred supplier."
π Houston, TX β Refining & Petrochemical
"Their F316 LWN flanges for our chemical plant project met every dimensional and surface-finish requirement from our QA team. The serrated finish was consistent across the 340 flanges. Outstanding traceability- every heat number and test report was verifiable. A truly professional supplier."
π Rotterdam, Netherlands β Chemical Processing
"For our offshore water injection project, we required 600 Class 900 WN flanges in F51 duplex with RTJ faces. Weihuan delivered on time and all passed third-party inspection β including a 100% UT check. Their price was 22% below the next international bidder. Impressive manufacturing capability."
π Abu Dhabi, UAE β Offshore Oil & Gas
"High-temperature F22 flanges for a biomass power plant. What impressed me most was their communication β daily updates with actual production photos, honest delivery forecasts, and proactive notification of a bolt hole tolerance improvement they implemented. This is what a supplier partner looks like."
π Stockholm, Sweden β Power Generation
"We ordered 24" Class 150 WN flanges in A105 for a major water pipeline upgrade. The oversized order was handled flawlessly - flanges went through 100% inspection at a SGS lab. All certificates were fully validated. Delivery took only 18 days from PO to SΓ£o Paulo via air + road. Impressive."
π SΓ£o Paulo, Brazil β Infrastructure
"I've inspected flange shipments from 9 different factories in China and India over the last 4 years. Weihuan's quality control stands in the top 5% β consistently correct bolt-hole alignment, proper Garlock surface finish, and documentation that matches the physical product perfectly. They're now my recommended supplier for critical projects."
π Manchester, UK β Quality Assurance
Get a factory-direct quote for your project specification within 24 hours.
π What you'll receive in your quote:
Itemized pricing per flange size/class/material
Available certifications & inspection options
Production lead time & shipping cost estimate
Payment terms (T/T, L/C, Western Union, trade assurance)
Or contact us at whxs@weihuantube.com | +86 18531701777 | π Middle Section of National Highway 338, Mengcun Hui Autonomous County, Cangzhou, Hebei, China
π Your inquiry is confidential. We respect your privacy and will never share your information with third parties.
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