Long Weld Neck Flanges Manufacturer & Exporter — India
ASME B16.5 | Class 150 – 2500 |
LWNRF · LWNFF · LWNRTJ |
Heavy Barrel LWN | ISO 9001:2015
✓ ASME B16.5
✓ Class 150 – 2500
✓ LWNRF / LWNFF / LWNRTJ
✓ Heavy Barrel LWN
✓ ½″ – 56″ NB
✓ Nozzle / Vessel Flanges
✓ NACE MR0175
✓ EN 10204 3.1/3.2 MTC
✓ ISO 9001:2015
Long Weld Neck (LWN) flanges are a specialty flange type featuring an extended, tapered hub that acts as an integral, self-reinforcing nozzle. Unlike a standard Weld Neck flange designed for pipe-to-pipe connections, the LWN's elongated neck is engineered specifically for butt-welding to pressure vessel nozzles, heat exchanger channel heads, and column connections — applications where the hub must satisfy both the flange standard (ASME B16.5) and the vessel design code (ASME Section VIII). Tesco Steel & Engineering, ISO 9001:2015 certified, manufactures and exports LWN flanges from ½″ NB to 56″ NB in all ASME B16.5 pressure classes (150 through 2500), including standard and heavy barrel configurations.
We supply LWNRF, LWNFF, and LWNRTJ flanges in carbon steel, stainless steel, alloy steel, duplex/super-duplex, Inconel, Hastelloy, Titanium, Monel, and Copper Nickel — with full EN 10204 3.1/3.2 MTCs, heat treatment certificates, and NDE reports. The LWN's butt-weld joint with matching inside diameters makes it the preferred choice for cyclic, fatigue, and vibration-prone service per ASME B31.3 (joint efficiency E = 1.0).
Long Weld Neck Flange — ASTM A182 F316 RFLWN, DN65 Class 300 Sch 40 (marked & traceable)
At a glance: a long weld neck flange = a flange and a length of heavy-wall nozzle neck in one forging — butt-welded straight into a vessel shell, exchanger head or column, replacing the pipe-nipple-plus-flange assembly and its extra weld. Specify it by six things: size, pressure class, facing (RF/FF/RTJ), neck length, bore (schedule or heavy barrel) and material grade.
Why Long Weld Neck Flanges Are Specified for Critical Equipment
▶ Self-Reinforcing Nozzle Hub
The long neck acts as an integral reinforcement pad, eliminating the need for a separate reinforcement pad on vessel nozzles per ASME Section VIII Div.1 UG-37, reducing fabrication cost and weld inspection scope.
▶ Full Bore Butt Weld
Matching inside diameters between neck and pipe produce a smooth, turbulence-free bore — critical in high-velocity flow, slurry, and erosive service where a mismatched bore would cause localized erosion.
▶ NDE-Friendly Weld Joint
The long neck geometry allows full radiographic (RT) and ultrasonic (UT) examination of the butt weld per ASME B31.3 and ASME VIII. Joint efficiency E = 1.0, the highest value achievable for pressure calculations.
▶ Cyclic & Fatigue Resistance
The smooth bore transition eliminates stress concentrations present in socket weld and slip-on flanges. Preferred by ASME for cyclic and fatigue-prone services per ASME VIII Div.2 fatigue design rules.
▶ High Pressure & Temperature Range
Available in Class 600 through 2500 with materials rated from -196°C (cryogenic LTCS and 304L/316L) to +816°C (Inconel 625), covering the widest range of process conditions.
▶ Heavy Barrel Configuration
Heavy barrel LWN flanges provide a thicker neck bored to a custom ID for any pipe schedule — the most versatile option for engineering-critical equipment nozzles requiring custom bore per ASME PCC-1 or Section VIII calculations.
How Our Long Weld Neck Flanges Are Manufactured
1
Forging — a single billet of certified heat is hot-forged into the integral flange-plus-neck blank, giving continuous grain flow from face to weld end — the structural advantage a welded nipple assembly cannot match.
2
Heat treatment — normalizing for carbon steel, solution annealing for stainless and nickel grades, with the thermal record retained per heat.
3
Machining — face, bolt holes and the full neck length to drawing; the bore machined to the stated pipe schedule (or left heavy-barrel), and the weld end bevelled for the vessel butt weld.
4
Facing & finish — raised face serrations (stock finish per ASME B16.5), flat face, or RTJ groove as ordered.
5
Testing & marking — mechanical and chemical verification against the heat, UT of the barrel where specified, PMI, then permanent marking of grade, size, class, schedule and heat number — exactly as visible on the photo on this page.
6
Certification & packing — EN 10204 3.1 MTC (3.2 witnessed on request), face and weld bevel protected, export-packed.
Long Weld Neck Flange Specifications
| Parameter | Details |
|---|
| Size Range | ½″ NB to 56″ NB |
| Pressure Classes | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# |
| Pressure Ratings | PN 1 – PN 400 |
| Standard | ASME B16.5 (NPS ½–24); custom to B16.47 on request |
| Facing Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Configuration | Standard LWN, Heavy Barrel LWN, Nozzle LWN |
| Carbon Steel | ASTM A105 |
| LTCS | ASTM A350 LF2 |
| Alloy Steel | ASTM A182 F5, F9, F11, F21, F22, F91 |
| Stainless Steel | ASTM A182 F304/304H/304L, F316/316H/316L/316Ti, F309, F310, F317L, F321, F347, F904L |
| Duplex / Super Duplex | ASTM A182 F51 (2205), F53 (2507), F55 (Zeron 100) |
| Nickel Alloys | UNS N02200, UNS N02201 |
| Monel | UNS N04400, UNS N05500, Alloy 20 |
| Inconel / Incoloy | UNS N06600, N06601, N06625, N08800, N08810, N08825 |
| Hastelloy | UNS N10276, N06022, N10665, N06455 |
| Titanium | Gr.1, Gr.2, Gr.3, DTH 3.7035, DTH 3.7055 |
| Copper Nickel | C70600 (90/10), C71500 (70/30), C71640 |
| Surface Treatments | Hot Dip Galvanizing, Sand Blasting, Shot Peening, Epoxy Coating, FBE Coating |
| Test Certificates | EN 10204 3.1/3.2 MTC, PMI, Hydro Test, RT/UT/PT/MT, NACE MR0175 |
Long Weld Neck Flange Dimensions — ANSI / ASME B16.5
ANSI / ASME B16.5 Long Weld Neck Flange Dimensions
LWNRF vs LWNFF vs LWNRTJ — Facing Comparison
| Factor |
LWNRF (Raised Face) |
LWNFF (Flat Face) |
LWNRTJ (Ring Type Joint) |
| Seating Surface |
1/16″ raised ring, concentric serrations |
Full flat face across bore |
Machined oval/octagonal groove |
| Gasket Type |
Spiral wound, ring, sheet gasket |
Full-face soft or sheet gasket |
Metallic ring gasket (R, RX, BX) |
| Pressure Classes |
150 – 2500 |
150 – 600 (most common) |
300 – 2500 |
| Primary Use |
Standard process vessel & equipment nozzles |
Connection to cast iron / brittle equipment |
High-pressure, high-temp, critical service |
| ASME B16.5? |
Yes — standard |
Yes |
Yes (RTJ groove per B16.5) |
| Industries |
Refineries, petrochemical, power |
Chemical, water treatment |
Offshore, subsea, HPHT wellheads |
Industries & Applications
| Industry | Typical Application | Common Grade |
|---|
| Oil & Gas Refineries | Reactor nozzles, column nozzles, drum connections | A182 F22, F91 |
| Petrochemical Plants | Heat exchanger channel heads, vessel nozzles | A182 F316L, F904L |
| Power & Nuclear | Boiler drum nozzles, steam header connections | A182 F91, F304H |
| Offshore & Subsea | Wellhead nozzle flanges, riser connections | A182 F51 (Duplex) |
| Chemical Processing | Corrosive media vessel nozzles | Inconel 625, Hastelloy C276 |
| Cryogenic / LNG | LNG storage vessel nozzles, cold box connections | A350 LF2, A182 F304L |
Long Weld Neck Flanges by Type & Material Grade
How to Specify & Order a Long Weld Neck Flange
A complete LWN specification has six elements — one more than a standard weld neck, because the neck length is yours to define:
1
Size & standard — nominal bore and dimensional basis, e.g. DN65 / 2½″ NB to ASME B16.5 flange dimensions.
2
Pressure class — Class 150/300/600/900/1500/2500.
3
Facing — RF (LWNRF, default), FF (LWNFF) or RTJ (LWNRTJ, state ring number).
4
Neck length — overall length from face to weld end; 6″, 9″ and 12″ are the common stock lengths, any length to drawing.
5
Bore — matched to a pipe schedule (Sch 40/80/160), or specify heavy barrel (HB) where the neck OD stays cylindrical for maximum reinforcement.
6
Material grade & certification — e.g. ASTM A105N, A182 F316, A350 LF2 — plus EN 10204 3.1 or 3.2, NACE, UT or vessel-code requirements, then quantity, sent to
sales@tescosteel.com or the
inquiry form.
Example of a complete line item: “Long Weld Neck Flange, DN65 (2½″ NB), ASME B16.5 Class 300, RF, 9″ long, Sch 40 bore, ASTM A182 F316, EN 10204 3.1 — 6 pcs.”
Frequently Asked Questions — Long Weld Neck Flanges
What is a Long Weld Neck (LWN) flange?▼
A Long Weld Neck (LWN) flange is a flange with an extended tapered hub — essentially a long, thick-walled neck — that is butt-welded directly to a pipe or pressure vessel nozzle. The elongated hub acts as a self-reinforcing integral nozzle, distributing stress away from the weld and providing exceptional strength under high pressure, high temperature, and cyclic loading. LWN flanges are governed by ASME B16.5 and available in Class 150 through Class 2500.
How does a Long Weld Neck flange differ from a standard Weld Neck flange?▼
The key difference is
neck length and application. A standard
Weld Neck flange has a short, gradually tapering hub for pipe-to-pipe connections. A Long Weld Neck (LWN) flange has a significantly longer neck — matching the bore and wall thickness of the mating pipe or vessel nozzle — making it ideal for
nozzle connections on pressure vessels, heat exchangers, and columns. The longer neck also enables full UT/RT examination of the weld per ASME B31.3.
What ASME standard governs Long Weld Neck flanges?▼
LWN flanges are dimensionally covered by ASME B16.5 (NPS ½–24, Classes 150–2500). For equipment nozzle connections, the governing design code is ASME Section VIII Division 1 (UG-37 reinforcement) or Division 2 (fatigue analysis). The flange dimensions and pressure-temperature ratings follow ASME B16.5; the neck bore and length are typically specified by the vessel designer to match the nozzle schedule or meet reinforcement area calculations.
What is a heavy barrel Long Weld Neck flange?▼
A heavy barrel Long Weld Neck flange (also called extra-heavy or XH LWN) features a thicker, heavier neck barrel compared to standard LWN flanges. The increased wall thickness allows the neck to be custom-bored to a specific inside diameter for any pipe schedule. Heavy barrel LWN flanges are commonly used in Class 600, 900, 1500, and 2500 applications where custom bore sizing is required for ASME PCC-1 or ASME Section VIII compliance.
What is the difference between LWNRF, LWNFF, and LWNRTJ?▼
LWNRF (Long Weld Neck Raised Face) has a 1/16″ raised seating area with concentric serrations — the standard facing for most process vessel and equipment nozzle connections. LWNFF (Long Weld Neck Flat Face) has a flat seating surface across the full flange bore, used when connecting to cast iron or brittle equipment. LWNRTJ (Long Weld Neck Ring Type Joint) features a machined groove that accepts a metallic ring gasket for very high pressure or high temperature service, typically Class 900 and above in refineries, offshore platforms, and HPHT wellhead applications.
Which industries use Long Weld Neck flanges?▼
LWN flanges are predominantly used where high-integrity nozzle connections are required: Oil & Gas Refineries (reactor nozzles, column and drum connections); Petrochemical Plants (heat exchanger channel heads); Power & Nuclear Plants (boiler drum nozzles, steam headers); Offshore Platforms (subsea wellhead and riser nozzles); Chemical Processing (pressure vessel nozzles in corrosive media); and Cryogenic / LNG Service (LTCS and stainless steel LWN flanges on cold boxes and storage vessels).
What materials are used for LWN flanges in high-temperature service?▼
For high-temperature service: ASTM A182 F5 / F9 (Cr-Mo alloy steel up to 650°C), F11/F22/F91 (up to 700°C+), 316H and 321 SS for creep resistance, Inconel 625 (UNS N06625) beyond 816°C, and Incoloy 800HT (UNS N08811) for furnace and reformer service. For cryogenic service, ASTM A350 LF2 and A182 F304L/F316L are specified. All supplied with EN 10204 3.1/3.2 MTCs and heat treatment certificates.
Are Long Weld Neck flanges suitable for cyclic or fatigue service?▼
Yes — LWN flanges are the preferred choice for cyclic, fatigue, and high-vibration service. The butt-weld joint between the neck and pipe produces matching inside diameters and a smooth bore transition, eliminating stress concentrations present in socket weld or slip-on flanges. ASME B31.3 and ASME Section VIII Division 2 recognise the LWN butt-weld configuration with a joint efficiency factor of E = 1.0. The long neck is also fully radiographable (RT) and ultrasonically testable (UT) for weld quality verification in safety-critical applications.
What neck lengths are available for long weld neck flanges?▼
Common stock lengths are 6", 9" and 12" overall (face to weld end), and any length can be forged and machined to drawing — vessel nozzle projections are routinely non-standard. State the overall length and whether it is measured from the raised face or the back face, and we machine to it. Neck length is the one dimension no standard fixes for you: ASME B16.5 governs the flange end, but the neck is defined by your vessel drawing.
What is the difference between a long weld neck flange and a nozzle neck with a weld neck flange?▼
Function is the same — a flanged nozzle — but construction differs. A fabricated nozzle uses a pipe nipple butt-welded to a standard weld neck flange: two components, one extra circumferential weld to make, examine and maintain. A long weld neck is the flange and neck in one forging: no intermediate weld, continuous grain flow, thicker self-reinforcing walls, and one less examination point on the vessel. That is why pressure-vessel and exchanger specifications default to LWNs for critical nozzles despite the higher forging cost.
How much does a long weld neck flange weigh?▼
Noticeably more than a standard weld neck of the same size and class — the extended heavy-wall neck adds metal roughly in proportion to its length, and a heavy-barrel version adds more still. Because the neck length and bore are customer-defined, there is no standard weight table; as a guide, a DN65 Class 300 LWN at 9" long weighs about twice the standard weld neck flange. Every Tesco quotation states the exact calculated unit weight for your length and bore.
Can long weld neck flanges be machined from bar instead of forged?▼
For small sizes some suppliers machine LWNs from rolled bar, but forged construction is the engineering default: hot forging aligns the grain flow along the neck and flange profile, giving better toughness and fatigue performance than the transverse grain of bar stock, and ASTM A105/A182 forgings are what vessel codes expect. Tesco supplies hot-forged LWNs with the forging route documented on the certificate; bar-machined construction is offered only where the customer's specification explicitly permits it.
What details are needed to get an accurate long weld neck flange quotation?▼
Six specification elements plus commercial terms: (1) size — e.g. DN65 / 2-1/2" NB; (2) pressure class — 150 to 2500; (3) facing — RF, FF or RTJ with ring number; (4) neck length overall; (5) bore — pipe schedule or heavy barrel; (6) material grade and certification — e.g. ASTM A105N, A182 F316, with EN 10204 3.1 or 3.2, NACE MR0175, UT or vessel-code requirements stated. Add the quantity and destination and we return price, weight and delivery — normally within 24 hours.
Who manufactures long weld neck flanges in India?▼
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, forging long weld neck flanges — LWNRF, LWNFF, LWNRTJ and heavy barrel — in carbon steel A105, LTCS A350 LF2, stainless and duplex A182 grades, and nickel alloys, Hastelloy and titanium. Flanges are supplied to ASME B16.5 Class 150-2500 with customer-defined neck lengths, EN 10204 3.1/3.2 certification and full heat traceability, and exported to more than 50 countries.
GET A QUOTE FOR LONG WELD NECK FLANGES
ISO-certified manufacturer & exporter. ASME B16.5 Class 150–2500. LWNRF, LWNFF, LWNRTJ, Heavy Barrel. All materials. Fast delivery worldwide from Mumbai, India.
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