Explore our core catalog of heavy-duty industrial forged flanges manufactured inside Shanxi Yuxin's ISO 9001 and PED 2014/68/EU certified plant.
In high-pressure vessel construction, offshore topsides, and petrochemical refining systems, conventional weld neck flanges connected to extended pipe nipples frequently create critical structural vulnerabilities. The double-weld configuration (flange-to-pipe and pipe-to-nozzle) introduces heat-affected zone (HAZ) overlaps, high stress concentration factors (SCF), and elevated non-destructive examination (NDE) costs. A Long Neck Flange—technically designated as a Long Welding Neck (LWN) Flange or Heavy Barrel (HB) Nozzle Flange—eliminates these structural risks by integrating the flange head and the extended cylindrical neck into a monolithic forged body.
As China’s leading forged flange manufacturer based in the historic forging hub of Dingxiang, Shanxi, Shanxi Yuxin Casting & Forging Co., Ltd. (est. 1992) engineers custom and standard LWN flanges engineered to withstand severe thermal cycling, cyclic pressure shocks, and aggressive sour service environments. By transferring the circumferential butt-weld away from the high-stress region at the vessel shell wall, YUXIN Long Neck Flanges satisfy the rigorous requirements of ASME Section VIII Division 1 & Division 2, ASME B16.5, and EN 13445.
| Engineering Parameter | Standard Weld Neck (WN) + Nipple | Monolithic Long Neck Flange (LWN) | Heavy Barrel (HB) Nozzle Flange |
|---|---|---|---|
| Structural Integrity | Dual circumferential welds; high HAZ fatigue risk | Monolithic single-piece forging; zero mid-neck welds | Ultra-heavy wall single piece for extreme pressure |
| Stress Concentration (SCF) | Elevated at pipe-to-flange junction | Smooth grain-flow taper; minimized SCF at shell joint | Optimized for high thermal gradient expansion |
| NDE & Inspection Overhead | Requires 100% Radiography/UT on two weld seams | Single weld seam inspection at vessel connection | Single weld inspection; reduced overall NDT cost |
| ASME Code Compliance | ASME B16.5 Standard fitting | ASME VIII Div 1 UG-44 / ASME B16.5 extended hub | ASME VIII Div 2 tailored stress analysis |
| Typical Applications | Standard process piping manifolds | Refining reactors, heat exchangers, boiler drums | High-pressure separators, nuclear containment |
As energy transition, ultra-deepwater exploration, and green hydrogen infrastructure demand elevated pressure-temperature limits, the technological roadmap for Long Neck Flanges is shifting from standard carbon steel forgings toward advanced alloy design, digital twin modeling, and smart sensing integration.
YUXIN is pioneering the closed-die forging of Super Duplex Stainless Steels (UNS S32750/S32760), 9% Nickel steels for cryogenic LNG vessel nozzles (-196°C), and Nickel Alloys (Inconel 625/825). Advanced grain refinement techniques ensure Charpy V-notch impact energy exceeds 100 Joules at extreme low temperatures.
Utilizing Finite Element Analysis (FEA), our R&D team simulates thermo-mechanical fatigue and bolt-up gasket stress distribution. We engineer non-standard heavy barrel profiles with variable wall thickness, reducing unneeded weight by up to 15% while enhancing structural safety margins under cyclic loading.
Looking toward Industry 4.0, next-generation LWN flanges incorporate high-precision micro-piezoelectric sensors embedded in non-critical flange zones. These allow real-time telemetry monitoring of bolt preload relaxation, localized flange rotation, creep strain, and micro-crack propagation in critical offshore assets.
Long Welding Neck Flanges are vital components across heavy process industries. Shanxi Yuxin supplies custom engineered LWN solutions tailored to severe operating conditions globally:
Used as vessel nozzles on hydrocrackers, desulfurization reactors, and catalytic reformers. Engineered in ASTM A182 F11, F22, F91 steel grades with corrosion-resistant Inconel cladding to prevent high-temperature hydrogen attack (HTHA).
Forming critical nozzles on high-pressure separators and gas treatment columns subjected to wave-induced structural hull flexing. High yield strength ASTM A350 LF2 Class 2 and Duplex S31803 materials maintain tight sealing under bending moments.
For steam generator pressure boundaries and auxiliary coolant systems under ASME Section III standards. Ultra-clean vacuum degassed steel billets forged under 100% volumetric UT testing guarantee structural homogeneity without inclusions.
Specialized long neck nozzles for high-pressure electrolysis tanks and hydrogen storage spheres (up to 700 bar). Microstructure controlled to eliminate hydrogen embrittlement pathways along grain boundaries.
Located in Dingxiang County, Shanxi Province—officially designated as the “Hometown of Forging in China”—Shanxi Yuxin Casting & Forging Co., Ltd. combines regional raw material supply networks with advanced automation to offer global buyers unparalleled delivery stability and cost optimization.
Our strategic partnerships with top tier Chinese steel mills (TISCO, Baosteel, Shougang) guarantee immediate access to certified vacuum-degassed forging billets. From raw ingot receipt to final CNC finish machining, every process takes place under one roof, guaranteeing 100% material heat traceability.
Equipped with 6,000-ton hydraulic forging presses, ring rolling mills up to 3,000 mm diameter, and computerized continuous heat treatment furnaces (Normalizing, Tempering, Solution Annealing, Quenching). Our automated thermal cycles eliminate manual error and deliver uniform mechanical properties across thick-walled heavy barrels.
Through raw material hedging and large-scale manufacturing (10,000 metric tons annual output), YUXIN insulates international EPC contractors from raw material volatility while maintaining a 15–30% cost advantage over Western European forging mills without compromising quality standards.
Quality assurance is not a final inspection step at Shanxi Yuxin—it is embedded into every thermal and mechanical sequence. International buyers receive complete documentation compliant with stringent project specifications:
Certified ISO 9001:2015 by TÜV CERT, certified pressure equipment manufacturer under PED 2014/68/EU, AD 2000-Merkblatt W0 / TRD 100, and holder of the Chinese Special Equipment Manufacturing License (TS Level A).
Every shipment is accompanied by EN 10204 3.1 Mill Test Certificates reporting chemical analysis, mechanical tension, hardness, subzero impact values, and NDE test results. Independent third-party inspection (TÜV, SGS, BV, DNV, Lloyd's Register) for EN 10204 3.2 certificates is routinely supported.
For oil and gas fields containing H2S, YUXIN supplies Long Neck Flanges tested for HIC (Hydrogen-Induced Cracking) and SSCC (Sulfide Stress Corrosion Cracking), complying strictly with maximum hardness limits (e.g., ≤ 22 HRC for ASTM A105N/A350 LF2).
Procuring Long Neck Flanges for major capital expenditure (CAPEX) projects requires rigorous vendor pre-qualification and clear technical specifications. Global procurement leaders partner with Shanxi Yuxin because we satisfy all key technical checklist items:
Precision machining to match exact pipe schedule (Sch 40, 80, 160, XXS) or heavy custom vessel nozzle wall requirements, ensuring smooth hydraulic transit without turbulence.
Raised Face (RF), Ring Type Joint (RTJ), Flat Face (FF), or Tongue & Groove. Flange phonographic spiral serration strictly controlled to Ra 3.2 – 6.3 μm (125–250 μin AARH).
Thorough rust preventive oiling, plastic end cap protection on bores and flange faces, vacuum heat-sealed wrapping, and seaworthy fumigation-free plywood box enclosure.
Extensive inventory of semi-finished standard LWN forged blanks enables expedited emergency shipments within 7–15 days for shutdown maintenance orders.
Direct technical answers from Shanxi Yuxin's senior forging engineers addressing critical specification, design code, and material questions:
A standard Weld Neck (WN) flange features a short tapered hub designed to be butt-welded to a standard pipe or fitting. In contrast, a Long Neck Flange (LWN) features an extended, straight cylindrical neck (barrel) forged as a single monolithic unit with the flange head. LWN flanges are typically used as vessel nozzles on tanks, reactors, and heat exchangers. They eliminate the need for an intermediate pipe length and double weld seams, drastically reducing stress concentrations at the shell junction and lowering NDE (Radiographic/Ultrasonic testing) inspection time.
Dimensions and pressure ratings for standard Long Welding Neck flanges are defined under ASME B16.5 (sizes 1/2" through 24", Classes 150 through 2500). For custom nozzle requirements on pressure vessels, design rules are governed by ASME Section VIII Division 1 (UG-44, UG-11) and Division 2 (Part 4), as well as European standard EN 13445. Custom Heavy Barrel (HB) nozzles with non-standard lengths, variable barrel wall thicknesses, or specific weld prep chamfers are manufactured according to customer technical drawings.
We forge Long Neck Flanges across a full spectrum of materials:
• Carbon Steel: ASTM A105 / A105N, ASME SA105, Q235B, Q345D.
• Low-Temperature Carbon Steel: ASTM A350 LF2 Class 1 / Class 2, LF3.
• Alloy Steel: ASTM A182 F1, F5, F9, F11 Class 2, F22 Class 3, F91 (for high P/T steam and refining).
• Stainless Steel: ASTM A182 F304/304L, F316/316L, F321, F347.
• Duplex & Super Duplex: ASTM A182 F51 (UNS S31803), F53 (UNS S32750), F55.
• Nickel Alloys: Inconel 625, Incoloy 825, Hastelloy C276.
Every forging billet undergoes chemical analysis verification upon arrival. During production, heating temperatures are digitally monitored to ensure optimal forgeability. Post-forging heat treatment (Normalizing, Solution Annealing, or Quenching & Tempering) refines the crystalline grain structure. Finished long neck forgings undergo 100% Volumetric Ultrasonic Testing (UT) per ASTM A388 / EN 10228 to detect internal voids, laminations, or inclusions, as well as Magnetic Particle (MT) or Liquid Penetrant (PT) testing on machined surfaces.
Yes. Shanxi Yuxin specializes in OEM drawing-based forging. We manufacture Heavy Barrel (HB), Equal Barrel (EQ), and custom stepped-neck nozzles up to 3,000 mm outer diameter and overall lengths exceeding 1,200 mm. Our CNC machining shop creates complex J-bevel weld preparations, compound tapers, and internal counterbores according to your CAD/DWG specifications.
Every shipment includes a comprehensive document package:
1. Certified EN 10204 3.1 Mill Test Certificate (or EN 10204 3.2 with third-party witness endorsement).
2. Heat treatment chart and furnace log.
3. Volumetric UT / MT non-destructive examination report.
4. Dimensional inspection report recording hub length, flange thickness, bolt hole pitch, and surface roughness.
5. Certificate of Origin (CO), Commercial Invoice, Packing List, and Fumigation Statement.
For standard ASME B16.5 LWN flanges in ASTM A105 or A350 LF2, we maintain pre-forged blank stock, allowing final CNC machining and dispatch within 7 to 15 days. For non-standard custom alloy heavy barrel nozzles requiring special dies, vacuum degassed steel melting, or EN 10204 3.2 third-party inspection, typical manufacturing lead times range from 20 to 35 calendar days.
You can send your technical inquiry directly to our engineering desk via email at [email protected] or [email protected]. Please specify: nominal pipe size (NPS/DN), pressure class (Class/PN), material grade, overall neck length (L), wall thickness or bore size, facing finish (RF/RTJ), and required certification level (3.1 or 3.2). Our technical team will return an itemized quotation and forging feasibility review within 24 hours.
Browse our wider selection of ANSI, DIN, EN, and JIS standard pipe flanges and custom ring forgings manufactured to international pressure equipment standards.
