ASME B16.5 | Class 150 – 2500 | LWNRF · LWNFF · LWNRTJ | Heavy Barrel LWN | 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).
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.
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.
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.
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.
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 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.
| 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 |
| 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 |
| 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 |
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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