Long Weld Neck Flange Manufacturer in India | LWN / LWNF / Long Hub / Nozzle Flange | ASME B16.5 | Remax Forge
Key Features
Extended neck — acts as a pressure vessel nozzle
Unlike a standard WN flange, the LWN neck is long enough to serve as the nozzle itself — eliminating the need for a separate pipe nipple.
Fewer welds = safer vessel (ASME Sec. VIII)
LWN satisfies ASME Section VIII minimum nozzle projection requirements in a single forged piece — one weld replaces two.
Always made to order — specify neck length + bore schedule
Neck length and bore schedule are custom per project. Must specify: NPS + Class + Material + Neck Length + Bore Schedule + Face Type.
Important: Long Weld Neck Flanges are Made-to-Order
LWN Flanges are not standard stock items. Every LWN flange is manufactured to your specific neck length, bore schedule, and face type. To request a quote, we need:
What is a Long Weld Neck Flange?
A Long Weld Neck Flange (LWN Flange) is essentially a Weld Neck Flange with an extended neck (hub) that is long enough to serve as a nozzle neck on a pressure vessel, column, drum, or heat exchanger. Instead of welding a short WN flange to a separate pipe nipple, the LWN eliminates the nipple entirely — the long neck IS the nozzle.
Industry Abbreviations & Variants
Key Distinction — LWN vs Standard Weld Neck Flange:
Standard WN Flange
Short tapered hub → connects to a pipe in a pipeline system. Hub length is fixed by ASME B16.5.
Long WN (LWN) Flange
Extended neck → connects directly as a nozzle on a pressure vessel. Neck length specified by buyer.
🔗 For pipeline connections, see our standard Weld Neck Flange. For permanent vessel nozzle closures, see our Blind Flange.
Standard Specifications
Complete specifications for Long Weld Neck Flanges — all made to order:
| Property | Detail |
|---|---|
| Product Names | Long Weld Neck Flange, LWN Flange, Long Hub Flange, Nozzle Flange, LWNCF (Companion Flange variant) |
| Size Range | 2" (50 NB) to 24" (600 NB) standard; larger per ASME B16.47 on request |
| Pressure Classes | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# |
| Face Types | RF (LWNRF), FF (LWNFF), RTJ (LWNRTJ) — specify when ordering |
| Standards | ASME B16.5 (flange face/bolt); ASME Sec. VIII Div.1 (vessel nozzle); ASME B31.3 |
| Neck Length | Made to order — buyer must specify required neck length (in mm or inches) |
| Bore Schedule | Any schedule (SCH 40/80/120/160/XXS) — machined to match connecting pipe |
| Custom Options | Special neck lengths, taper bore, counterbore, hub taper angle; NACE/low-temp/impact tested |
| MANDATORY INFO | NPS + Pressure Class + Material + Neck Length + Bore Schedule + Face Type |
| MTC | EN 10204 3.1 standard; 3.2 available for pressure vessel applications |
| Lead Time | 3–6 weeks (all LWN flanges are made to order) |
Long Weld Neck Flange Material Grades
We forge LWN Flanges in all standard and exotic materials for pressure vessel service — including NACE MR0175/MR0103 compliant and low-temperature impact tested grades:
| Material Category | Grades / Specifications |
|---|---|
| Stainless Steel Long 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 Long Weld Neck Flanges | UNS S31803/S32205 — ASTM A182 Gr F51, F52, F53, F54, F55, F57, F59, F60, F61 |
| Super Duplex Long Weld Neck Flanges | UNS S32750/S32760 — ASTM A182 Gr F53, F55; Zeron 100 |
| Carbon Steel Long 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 Long Weld Neck Flanges | ASTM A182/ASME SA182: F5, F9, F11, F12, F22, F91 (all P-grades for high temp service) |
| Nickel Alloy Long Weld Neck Flanges | Inconel 600, 601, 625, 718, 690, X750 (ASTM B564/ASME SB564); Incoloy 800, 800H, 800HT, 825, 925 |
| Hastelloy Long Weld Neck Flanges | C276 (UNS N10276), C22 (UNS N06022), C4, C2000, B2, B3, X (ASTM B564) |
| Monel Long Weld Neck Flanges | Monel 400 (UNS N04400), Monel K500 (UNS N05500) — ASTM B564 |
| Pure Nickel Long Weld Neck Flanges | Nickel 200, 201, 205, 205LC — ASTM B564/ASME SB564 |
| Copper Nickel Long Weld Neck Flanges | CuNi 90/10 (C70600), CuNi 70/30 (C71500), UNS C71640 — ASTM/ASME SB 61/62/151/152 |
| Titanium Long 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 Long Weld Neck Flanges | 5052, 6061, 6063, 2017, 7075 |
| Brass Long Weld Neck Flanges | 3602, 2604, H59, H62 |
| Special Alloy Long 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 stockLong Weld Neck Flange Standards & Specifications
LWN flange faces per ASME B16.5; nozzle design per ASME Section VIII Div.1; piping per ASME B31.3:
| 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 |
LWN Flange Dimensions & Ordering Guide
LWN Flanges are made-to-order. The face OD, bolt circle, and bolt holes follow ASME B16.5 for the selected NPS and class — same as a standard WN Flange. What changes is the neck length, which you specify:
Typical Minimum Neck Lengths (Reference Only)
| NPS | Typical Min. Neck Length | Purpose |
|---|---|---|
| 2" | 150 mm | Clear vessel wall + insulation |
| 4" | 200 mm | Clear vessel wall + insulation |
| 6" | 250 mm | Clear vessel wall + insulation |
| 8" | 300 mm | Clear vessel wall + insulation |
| 10" | 350 mm | Clear vessel wall + insulation |
| 12" | 400 mm | Clear vessel wall + insulation |
Actual neck length is specified by the vessel designer per ASME Section VIII nozzle projection requirements. Contact us for engineering assistance.
📋 To Order an LWN Flange — Send Us These 7 Parameters
Flange Face Types
LWN Flanges are available as LWNRF (Raised Face — most common), LWNFF (Flat Face), and LWNRTJ (Ring Type Joint — for high-pressure critical vessel connections).
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.
Why Specify Long Weld Neck on Pressure Vessels?
Eliminates Nipple Weld
One less weld at the most stress-concentrated point (vessel shell-to-nozzle junction) → fewer leak points → safer vessel.
Code Compliant
Meets ASME Section VIII minimum nozzle projection requirements directly — no need for a separate nipple.
Radiographable
The long neck allows full radiographic examination of the vessel shell weld without obstruction from the flange face.
Thermal Stress Buffer
Extended neck reduces thermal gradient between a hot vessel and the cooler flanged piping connection.
Custom Bored
Neck bore exactly matches the connecting pipe schedule — zero flow restriction, zero turbulence at the nozzle entry.
Simplifies Installation
One forged piece replaces a short WN flange + separate pipe nipple + two additional welds.
Industries & Applications
✓ Primary Applications — Pressure Vessel Nozzles
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
For pressure vessel service, LWN flanges undergo additional testing including charpy impact testing (for low-temperature), NACE hardness testing, and 100% UT on critical bore areas.
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
EN 10204 3.1 MTC standard; 3.2 available for pressure vessel ASME Section VIII applications. Full traceability from raw billet to finished nozzle flange.
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.
LWN Flange vs Standard WN Flange vs Slip On
Understanding the key differences helps you select the right flange for your application:
| Feature | Long Weld Neck | Weld Neck | Slip On |
|---|---|---|---|
| What it replaces | WN flange + separate pipe nipple | Connects pipe to pipe | Connects pipe to pipe |
| Primary Use | Pressure vessel nozzle | Pipeline connections | General pipeline |
| Neck Length | Extended (custom — to order) | Short tapered hub | No hub |
| Weld Count at Vessel | 1 weld (neck to vessel shell) | 2 welds (WN to nipple + nipple to vessel) | Not used on vessels |
| Code Requirement | Satisfies ASME VIII nozzle projection directly | Requires additional nipple | N/A |
| Radiography | Yes — full access for shell weld RT | Limited by short hub | No |
| Lead Time | 3–6 weeks (made to order) | 7–14 days (standard stock) | 7–14 days (standard stock) |
| Best For | Vessel nozzles, code compliance | Critical piping | General process piping |
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 Long Weld Neck Flange Catalogue (PDF)
Technical catalogue including typical neck lengths, material grades, ordering guide, face types, and ASME B16.5 flange face dimensions.
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
Common questions about Long Weld Neck Flanges — LWN vs standard WN, how to specify neck length, ASME Sec. VIII compliance, and special materials.
Related Products
Compare our complete range of industrial flanges for your piping and vessel project.
Slip On Flange
Slides over pipe. Cost-effective and simple.
Weld Neck Flange
Tapered neck for high pressure and temperature service.
Blind Flange
Bolts onto line to isolate sections securely.
Socket Weld Flange
Shoulder socket. Great for high-pressure small lines.
Drop your details below
Let our experts take over from here!