LWNFF Flanges — Long Weld Neck Flat Face (FFLWN) Flange Manufacturer
Tesco Steel & Engineering manufactures LWNFF flanges — Long Weld Neck Flat Face, written FFLWN in facing-first piping classes — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The construction is the LWN's: the flange and the nozzle in one forging, a long heavy-walled barrel replacing the pipe nipple and its butt weld, with one closing weld made out at the shell. The facing is the flat face's: the gasket surface machined dead flush, sealing through a full-face gasket per B16.21 — the pattern demanded by the equipment a raised face would crack: cast iron, bronze, glass-lined and FRP mates, which is exactly the company lined vessels and water-treatment plants keep. The rule is absolute and explained below: the flange face follows the weaker mate — never bolt a raised ring against flat cast iron. Standard, heavy-barrel and equal-barrel patterns, barrel lengths 150/230/300 mm from stock, bores to schedule. Full range from A105 and A350 LF2 through stainless, duplex and the nickel bench. Raised-face sibling? LWNRF. Ring joint? LWNRTJ. Every lot with EN 10204 3.1/3.2 MTC. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
Long Weld Neck × Flat FaceThe One-Forging Nozzle, Machined FlushFull-Face Gasket per B16.21For Cast Iron · Glass-Lined · FRP MatesB16.5 Flange Ends · Class 150–2500Barrel: Length & Bore to OrderA105 · LF2 · SS · Duplex · Ni-AlloysEN 10204 3.1 / 3.2 · ISO 9001:2015
Long Weld Neck Flanges — Machined Barrels, Faced to Order (RF / FF / RTJ)
What is a LWNFF Flange?
The one-forging nozzle, machined flush. LWNFF — also written FFLWN — = Long Weld Neck Flat Face: the LWN's long, heavy-walled barrel replaces the pipe nipple and its butt weld — one certificate, one closing weld at the shell — while the gasket face is machined dead flush with no raised ring, sealing through a full-face gasket (B16.21) that spreads bolt load across the whole surface. Specified wherever the mate is cast iron, bronze, glass-lined or FRP — equipment a raised ring would crack. Flange ends per ASME B16.5, Classes 150–2500; barrel length and bore stated by you. EN 10204 3.1 on every lot.
Also searched as: long welding neck flat face flange, LWN FF flange, FFLWN flange, flat face nozzle flange, full-face LWN — all the same product. Related pages: LWNRF (raised face) / LWNRTJ (ring joint) siblings, the long weld neck hub, the SWFF flat-face cousin on small bore, flat flanges generally, and flange-o-lets for the couplet alternative.
LWNFF Flange Specifications
LWNFF (Long Weld Neck Flat Face) Flanges are available in the following specifications:
Type / Facing
Long weld neck flange with flat face — gasket surface machined flush, no raised ring; serrated or smooth finish per gasket system
Construction
Integral heavy-walled straight barrel, bevelled weld end (37.5° standard) — one closing butt weld at the shell, no pipe nipple
Flange End
OD, drilling and P-T ratings per ASME B16.5; EN 1092-1 drilling to order
Size
1/2"NB to 24"NB per B16.5; larger to order per B16.47 or drawing
Full-face per ASME B16.21 — CNAF, elastomer, PTFE, graphite composite — soft grades for glass-lined and FRP mates
Modifications
Special bores (level bridles, standpipes), non-standard bevels, tapped holes, galvanizing / epoxy on carbon steel
Testing
Chemistry & mechanicals per heat; barrel bore and length gauged piece by piece; face flatness checked; PMI on alloy grades
Certification
EN 10204 3.1 (standard) / 3.2 witnessed; NACE MR0175 where specified
Why the Flat Face on a Nozzle Forging
The Face Follows the Weaker Mate
Cast iron pumps, bronze valves, glass-lined reactors and FRP tanks cannot survive a raised ring's bending lever — the flat face spreads bolt load across the full width and the hazard disappears.
Three Parts Still Become One
The LWN argument is unchanged: weld neck + nipple + one whole butt weld collapse into a single certified forging, with the closing weld out at the shell and one weld to examine instead of two.
Full-Face Gasket, Gentle Numbers
B16.21 full-face gaskets in soft grades seal at the modest seating stresses lined and brittle equipment allow — star-pattern bolt-up at the gasket card's torque, not habit's.
Lined-Vessel Country Is Alloy Country
Glass-lined and FRP equipment exists because the fluid is aggressive — so LWNFF nozzles are routinely F316L and better, forged individually with no pattern penalty on exotic grades.
Specification Notes — Getting Flat-Face Nozzles Right
Three honest notes.Never bolt a raised face against flat cast iron: the ring props the centre while the bolts pull the rim — the casting cracks through its bolt holes; specify the flat face from the start or machine the ring off, and the FAQ below explains the mechanics. A ring gasket defeats a flat face: full-face per B16.21, holes for every bolt — a ring inside the bolt circle reintroduces the very bending the face was chosen to avoid. And “long” is still not a dimension: barrel length (face to weld end) and bore (schedule or millimetres) belong on the enquiry — the flange end is B16.5's business, the barrel is yours.
How Our LWNFF Flanges Are Manufactured
1
Forging — each piece individually forged from the certified heat with the barrel integral — no welded build-ups — in every grade from A105 to the nickel alloys.
2
Heat treatment — normalised, quenched-and-tempered or solution annealed per the material specification; furnace records retained.
3
Machining — flange end to ASME B16.5; barrel turned to pattern (standard / HB / equal) and bored to the ordered schedule or drawing, length gauged face-to-weld-end.
4
Facing & bevelling — gasket face machined dead flush with flatness checked — serrated or smooth per the gasket system; weld end bevelled 37.5° (or per drawing).
5
Testing & marking — chemistry and mechanicals per heat, PMI on alloy grades; laser-marked with grade, size, class, schedule and heat number.
6
Certification & packing — EN 10204 3.1 MTC (3.2 witnessed on request); faces and bevels protected, packed sea-worthy.
Where LWNFF Flanges Are Used
Wherever a nozzle meets equipment that demands a flat face: glass-lined reactor and receiver nozzles, FRP and rubber-lined tank connections, water- and effluent-treatment vessels mating cast iron pumps and valves, utility and low-pressure process drums, bronze-trimmed marine systems, and instrument or level connections on any of them. Production below:
Long Weld Neck Flanges — Barrels Machined, Faced to OrderLong Weld Neck Flanges — Straight-Barrel BatchHeavy-Barrel LWN — Palletised for Export
LWNFF Flange Dimensions
Flange-end dimensions are class-governed per ASME B16.5; barrel length and bore per order. Full class-by-class charts:
Six elements — name the mating equipment, and the facing choice explains itself. Write LWNFF or FFLWN as your piping class prefers:
1
Size & standard — e.g. DN80 / 3″ NB ASME B16.5.
2
Pressure class — 150#–2500#; flat-face duty is usually 150# or 300#.
3
Barrel length — overall, face to weld end: 150 / 230 / 300 mm stock or any stated length.
4
Barrel bore & pattern — pipe schedule to match or finished bore in mm; standard, heavy barrel or equal barrel; weld-end prep if non-standard.
5
Material, mate & certification — e.g. ASTM A105 or A182 F316L; the mating equipment named (cast iron / glass-lined / FRP) so facing and gasket guidance follow; coating for carbon steel; EN 10204 3.1 (our standard) / 3.2, PMI, NACE MR0175 as applicable.
Example: “FFLWN Flange, DN80, ASME B16.5 Class 150, barrel 230 mm, Sch 40 bore, ASTM A182 F316L, mates to glass-lined receiver — full-face gasket, EN 10204 3.1 — 4 pcs.” Quotations normally within 24 hours with price, unit weight and delivery.
LWNFF Flanges — Frequently Asked Questions
What is a LWNFF flange?
LWNFF stands for Long Weld Neck Flat Face — a long weld neck flange whose gasket surface is machined dead flush, with no raised ring. The construction is the LWN's: instead of tapering to meet a pipe, the neck continues as a long, heavy-walled straight barrel that is itself the nozzle, bevelled at its far end for one closing butt weld made out at the vessel shell or header. The facing is the flat face's: the full width of the flange seals against a full-face gasket that spans the bolt circle, spreading bolt load gently across the entire surface — the pattern specified wherever the mating equipment is cast iron, bronze, glass-lined or FRP and a raised face would concentrate force it cannot survive. Flange-end dimensions and ratings follow ASME B16.5.
How does a long weld neck differ from a standard weld neck flange?
Geometry and mission. A standard weld neck's hub tapers quickly down to the pipe's outside diameter and wall, ending in a weld bevel a few centimetres from the flange face — it is designed to butt-weld to pipe and continue as a piping run. A long weld neck keeps a full-section straight barrel for its entire length: no taper to pipe dimensions, wall far heavier than the matching schedule, length made to order. The mission follows the shape — the LWN is not a fitting on a pipe run but a nozzle in its own right, projecting through insulation, vessel walls or exchanger channels, with the butt weld relocated to the shell side where the fabricator wants it. In one certified forging it replaces the weld neck flange, the pipe nipple and one whole circumferential weld.
Why choose a flat face instead of a raised face on a LWN nozzle?
To protect the other flange. A raised face concentrates bolt load onto a narrow ring — exactly right against another steel flange, exactly wrong against brittle or low-modulus equipment: bolt up a raised ring against a flat cast iron pump flange and the bending moment cracks the casting; against glass-lined or FRP it crushes and spalls the lining. The flat face removes the concentration: full metal contact across the whole width, a full-face gasket spreading load evenly, no bending lever anywhere. Vessels and tanks in water treatment, FRP and rubber-lined chemical service, glass-lined reactors and cast-iron auxiliaries are precisely where flat-faced nozzles are demanded — and an LWN nozzle serving such equipment is machined flat to match. The rule is absolute: the flange face follows the weaker mate.
Why must a raised face never be bolted against flat-faced cast iron?
Because the geometry builds a lever. With a raised ring bearing at the centre and bolts pulling at the rim, the joint becomes a bending machine: as the bolts tighten, the outer edge of the weaker flange is pulled toward the steel one while the raised ring props the middle apart, and cast iron — strong in compression, poor in tension — cracks through the bolt holes. Codes and every equipment manufacturer's manual say the same thing: against flat-faced cast iron, bronze or FRP, use a flat-faced steel flange with a full-face gasket, torqued evenly. Where an RF steel flange is unavoidable, the raised face is machined off first. Specifying the LWNFF from the start costs nothing and removes the hazard — which is exactly why this page exists beside the LWNRF.
What gasket is used with a LWNFF flange?
A full-face gasket per ASME B16.21 — soft sheet material (CNAF, elastomer, PTFE or graphite composite) cut to the flange's full outside diameter, with holes for every bolt, so the entire face is supported and the bolt load spreads evenly. The soft grades matter: against glass linings and FRP the gasket is deliberately the most compliant member, sealing at the modest seating stresses those materials allow. Ring gaskets sitting inside the bolt circle belong to raised-face practice and defeat the flat face's purpose — unsupported rim, bending reintroduced. One practical note for nozzles: full-face gaskets on large flanges want even, staged bolt-up in a star pattern at moderate torque; the gasket maker's card, not habit, sets the numbers.
How are the barrel length and bore of a LWN specified?
Two numbers that belong on every enquiry. Length: measured overall from the flange face to the weld end — 150 mm (6"), 230 mm (9") and 300 mm (12") are the common stock lengths, and any length machines to order; state it explicitly, because 'long' is not a dimension. Bore: the barrel is drilled and bored to order — most commonly to match the inside diameter of the connecting pipe schedule, sometimes cylindrical special bores for level bridles, instrument standpipes or restriction work; state the schedule or the finished bore in millimetres. Add the weld-end preparation (standard 37.5° bevel unless told otherwise) and the nozzle is fully defined.
What are standard, heavy-barrel and equal-barrel LWN flanges?
Three barrel weights for three duties. The standard LWN carries a barrel a little heavier than the matching pipe — the general-purpose vessel nozzle. The heavy-barrel (HB) pattern thickens the wall substantially — often approaching the hub section for its full length — for high-pressure nozzles, heavy nozzle loads and reinforcement-limited openings, where the extra metal does the area-replacement work the code asks of a vessel opening. The equal-barrel pattern keeps the barrel outside diameter equal to the hub for a clean cylindrical profile — favoured on manway and instrument connections. All three share B16.5 flange ends and all three machine flat-faced identically; the barrel section is the variable, and the design calculation or the equipment drawing normally decides which is wanted.
Is the LWNFF flange covered by ASME B16.5?
Half of it, honestly — the same split as every long weld neck. The flange end — outside diameter, bolt circle and drilling, thickness, and the pressure-temperature ratings — follows ASME B16.5 for its class and material group; the flat face itself is a recognised B16.5 facing, normally supplied at the full RF-inclusive thickness so drilling and stand-off interchange cleanly. The barrel — length, wall and bore — is not a B16.5 dimension: it is defined by the purchaser's drawing or by stock patterns. The practical consequence is unchanged: an LWNFF enquiry needs the barrel numbers stated rather than implied, and our class-by-class LWN dimension charts cover the standardised flange ends from Class 150 to 2500.
Is LWNFF the same as FFLWN?
Yes — LWNFF, FFLWN, LWN FF and 'long weld neck flat face' all name the same flange, abbreviated type-first or facing-first exactly as the raised-face sibling is written LWNRF or RFLWN. Piping classes, vessel data sheets and marking practices differ between companies and regions, and the marking follows the paper: write whichever form your specification uses and that is what the laser marking and the certificate will say. The product, the price and the delivery are identical.
What materials are LWNFF flanges available in?
The complete industrial range, with a bias the duty explains: carbon steel ASTM A105 dominates, because flat-faced nozzles overwhelmingly serve water treatment, utility and lined-equipment plants where the vessel is steel but the mates are cast iron or FRP; LTCS A350 LF2 covers low temperature; stainless ASTM A182 F304/L, F316/L and the higher grades serve chemical duty against glass-lined and FRP equipment — a classic pairing, since the lined vessel exists precisely because the fluid is aggressive; and duplex, chrome-moly and the nickel bench — Monel, Inconel, Incoloy, Hastelloy, titanium — forge to order. Each piece is forged individually, so odd sizes and exotic grades carry no pattern penalty. All grades ship with EN 10204 3.1 or 3.2 and PMI where specified.
When is a long weld neck the wrong choice?
Three honest cases, unchanged from the raised-face page. On a piping run: if the flange simply joins pipe to pipe, a standard weld neck plus the pipe you already own is lighter and cheaper — the LWN's value begins only where a nozzle or standpipe is being built. On very long projections: barrels beyond roughly 300-400 mm cost forging weight that a welded pipe nipple provides cheaply, so extreme lengths deserve a cost comparison in both constructions. And on weight-critical small connections where a forged couplet — a flange-o-let welded to the shell — does the same job with less metal. Inside its envelope — vessel, tank and exchanger nozzles at ordinary lengths, flat-faced for the equipment that demands it — the one-forging argument usually wins, and our quotation will show both routes when it is close.
What sizes and pressure classes do LWNFF flanges come in?
Flange ends follow ASME B16.5 from ½" to 24" NB in Classes 150 through 2500, though flat-face service concentrates heavily in Classes 150 and 300 — cast iron, FRP and lined equipment live at modest pressures, which is precisely why their flanges can afford full-face gaskets. Larger diameters forge to order against B16.47 or drawing dimensions, and EN 1092-1 drilling is machined on the same barrels for European equipment. Small-bore LWNFFs serve instrument and level connections on lined vessels; the middle sizes are tank and process nozzles. State size, class, barrel length and bore together — the four numbers define the forging — and our quotation returns price, unit weight and delivery per class.
What details are needed to get an accurate LWNFF flange quotation?
Six elements plus commercial terms: (1) size and dimensional standard — e.g. DN80 / 3" NB ASME B16.5; (2) pressure class — 150 to 2500, with flat-face duty usually 150 or 300; (3) barrel length overall, face to weld end — 150/230/300 mm stock or any stated length; (4) barrel bore — pipe schedule to be matched or finished bore in millimetres, with weld-end preparation if non-standard; (5) material grade and pattern — e.g. ASTM A105 or A182 F316L, standard or heavy barrel — with coating stated for carbon steel, and the mating equipment named (cast iron, glass-lined, FRP) so the facing and gasket guidance follow; (6) certification — EN 10204 3.1 (our standard) or 3.2, PMI, NACE MR0175 where applicable. Add quantity and destination; quotations normally within 24 hours.
Who manufactures LWNFF flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing long weld neck flat face flanges with B16.5 flange ends from ½" to 24" NB (larger to order) in Classes 150-2500, in standard, heavy-barrel and equal-barrel patterns — each forged individually from certified heats, heat treated per the material specification, machined with the gasket face dead flush and the barrel bored to the ordered schedule or drawing, bevelled for the closing weld, and laser-marked with grade, size, class, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification alongside the LWNRF and LWNRTJ facing siblings and the complete weld neck range. Exported to more than 50 countries.
