Related
WNRF · LWN · RTJ · Reducing · Table & ANSI Drilling
M.S. & S.S. Weld Neck Flanges
Weld Neck Flange Manufacturer & Supplier – Darukhana, Mumbai · Machining flanges since 1999
Mild Steel & Stainless5 Weld Neck Sub-TypesBore Cut to Your ScheduleMachined at DarukhanaIndia · Gulf Export
A weld neck flange is a flange with a long tapered hub that is butt-welded to the end of the pipe, so the bolt load feeds gradually into the pipe wall instead of stopping dead at a fillet weld. That one difference is why it gets specified wherever a line sees real pressure, heat cycling or vibration. We machine five sub-types at our Darukhana works — weld neck raised face (WNRF), long weld neck (LWN), ring type joint (RTJ / RJ), weld neck flat face (WNFF) and reducing weld neck — in mild steel to IS:2062 and stainless steel in SS 304, 304L, 316 and 316L. Sizes run 15mm to 600mm NB, drilled to Table D, E, F or H or to an ANSI pressure class, with the bore cut to match your pipe schedule. Send us a bore, a table letter and a facing and you get a rate back the same working day.
Quick Specifications
Sub-Types MadeWNRF · LWN ·
RTJ · WNFF · Reducing
Size Range15 to 350mm NB
regular · 400–600mm to order
DrillingTable D / E / F / H
· ANSI Class 150–2500 on request
BoreMachined to your pipe
schedule
FacingRF · FF · RTJ (ring
type joint)
MaterialM.S. IS:2062 · S.S.
304 / 304L / 316 / 316L
Lead Time3–10 working days
regular · 10–20 days S.S. / RTJ / large bore
Dispatch FromDarukhana,
Mumbai · PAN India & Gulf export
1999Machining Since
5Weld Neck Sub-Types
600mmLargest NB Cut
How a Weld Neck Flange Differs From the Rest
The hub is the whole point. On a slip-on or socket weld flange the pipe sits inside the flange and is held by fillet welds, so the load changes direction abruptly at the weld toe. A weld neck flange instead tapers from full flange thickness down to the pipe wall thickness and is joined end-to-end with a butt weld, giving one continuous metal path from the bolt circle into the pipe.
Two practical consequences follow. The bore is machined to your pipe’s inside diameter, so there is no internal step for the flow to trip over — which matters on high-velocity, abrasive and slurry lines. And the butt weld is a full-penetration joint that can be radiographed or ultrasonically tested, which is usually what a third-party inspector wants to see.
Because the joint is end-to-end, the pipe wall thickness matters as much as the bore. Give us the schedule, or the actual wall in millimetres, and we cut the bore and the taper to suit it. Get that detail wrong at the ordering stage and your fitter ends up grinding a mismatch on site.
Order a weld neck flange with four numbers
- Nominal bore — 15mm to 600mm NB
- Drilling — Table D, E, F or H, or an ANSI class
- Facing — RF, FF or RTJ
- Pipe wall or schedule — so the bore and taper match
Why Buyers Come to Darukhana for Weld Necks
Flange Work Only, Since 1999
Twenty-five years cutting flanges at one address in Darukhana. Weld necks are day-to-day work here, not a sideline.
Priced From the Bar
You are buying from the shop that cuts the flange, so the rate reflects material and machining rather than a reseller’s margin.
Checked Before It Leaves
Every weld neck is measured for outside diameter, pitch circle, bore and hub taper against your order before it is packed.
Mumbai, South India, Gulf
Regular dispatch to Chennai, Coimbatore, Bengaluru, Hyderabad, Kochi and Visakhapatnam, plus export to the UAE, Oman, Qatar, Kuwait and Saudi Arabia.
Weld Neck Flange Sub-Categories We Machine
Five weld neck sub-types are in regular production here: WNRF, LWN, RTJ (also written RJ), WNFF and reducing weld neck. All five share the same tapered hub and the same butt-weld end. What changes is the sealing face, the length of the barrel, or which pipe size the bore is cut for. Naming the sub-type in your enquiry saves a round of questions.
| Sub-Category | Trade Code | What Is Different | Usually Specified For |
|---|---|---|---|
| Weld Neck Raised Face | WNRF | Standard tapered hub, raised sealing face | The default for process and utility piping |
| Long Weld Neck | LWN | Extended straight barrel in place of a short hub | Vessel and header nozzles, heavy-wall lines |
| Ring Type Joint | RTJ / RJ | Machined groove for a solid metal ring gasket | High pressure and high temperature duty |
| Weld Neck Flat Face | WNFF | No raised ring — the whole face is flat | Bolting to cast iron pumps, valves and bodies |
| Reducing Weld Neck | RWN | Large flange drilling, bore cut for a smaller pipe | Stepping a line down at the flange joint |
Weld Neck Raised Face – WNRF
The one most people mean when they say weld neck. Tapered hub, butt-weld end, and a small raised ring that concentrates the bolt load onto the gasket. Order it by nominal bore, drilling table and pipe schedule.
Long Weld Neck – LWN
Instead of a short hub it has a long straight barrel, so the flange becomes the nozzle. Welded straight into a vessel shell, header or column rather than onto a run of pipe. Give us the barrel length as well as the bore.
Ring Type Joint – RTJ / RJ
The face carries a machined groove that seats a solid metal octagonal or oval ring in place of a compressed gasket. Specified where pressure and temperature would chew through a soft gasket. State the ring number if your drawing gives one.
Weld Neck Flat Face – WNFF
Same hub, no raised ring: the sealing surface is flat across the whole face. Used when the mating half is cast iron, where a raised face can concentrate enough load in one band to crack the casting. Common on pump and valve connections.
Reducing Weld Neck – RWN
Keeps the outside diameter and bolt pattern of the bigger line while the hub and bore are cut for the smaller pipe, so you change size at the joint without adding a reducer. Always send both sizes — flange NB and pipe NB.
To Your Own Drawing
Odd bolt counts, a non-standard pitch circle, a deeper hub, spot-facing on the back, or a bore between two schedules — send the drawing or even a marked-up sketch on WhatsApp and we will cut to it.
Weld Neck Flange Dimension Tables
Weld neck flanges are drilled here to Table D, E, F and H and to ANSI classes, and the complete Table E drilling grid from 15mm to 600mm NB is published below. The bore is not listed because a weld neck bore is not fixed by the table — it is machined to the schedule of the pipe it will be butt-welded to, so tell us the pipe wall or schedule along with the size. Table D, F and H grids and the full ANSI B16.5 hub, length-through-hub and raised-face dimensions are sent on request; ring the works and we will WhatsApp the sheet the same day.
Table E Drilling — Weld Neck Flanges, 15mm to 600mm NB
| NB Size | Flange OD | PCD | No. of Bolts | Bolt Hole Dia | Bolt Size | Flange Thickness |
|---|---|---|---|---|---|---|
| 15mm (½") | 95mm | 65mm | 4 | 14mm | M12 | 12mm |
| 20mm (¾") | 105mm | 75mm | 4 | 14mm | M12 | 14mm |
| 25mm (1") | 115mm | 85mm | 4 | 14mm | M12 | 14mm |
| 32mm (1¼") | 140mm | 100mm | 4 | 18mm | M16 | 16mm |
| 40mm (1½") | 150mm | 110mm | 4 | 18mm | M16 | 16mm |
| 50mm (2") | 165mm | 125mm | 4 | 18mm | M16 | 16mm |
| 65mm (2½") | 185mm | 145mm | 4 | 18mm | M16 | 18mm |
| 80mm (3") | 200mm | 160mm | 8 | 18mm | M16 | 18mm |
| 100mm (4") | 220mm | 180mm | 8 | 18mm | M16 | 18mm |
| 125mm (5") | 250mm | 210mm | 8 | 18mm | M16 | 20mm |
| 150mm (6") | 285mm | 240mm | 8 | 22mm | M20 | 20mm |
| 200mm (8") | 340mm | 295mm | 8 | 22mm | M20 | 22mm |
| 250mm (10") | 395mm | 350mm | 12 | 22mm | M20 | 24mm |
| 300mm (12") | 445mm | 400mm | 12 | 22mm | M20 | 24mm |
| 350mm (14") | 505mm | 460mm | 12 | 22mm | M20 | 26mm |
| 400mm (16") | 565mm | 515mm | 16 | 26mm | M24 | 26mm |
| 450mm (18") | 615mm | 565mm | 16 | 26mm | M24 | 28mm |
| 500mm (20") | 670mm | 620mm | 20 | 26mm | M24 | 28mm |
| 600mm (24") | 780mm | 725mm | 20 | 30mm | M27 | 30mm |
Sizes up to 350mm NB are regular running stock work; 400mm to 600mm NB is cut to order. Reducing weld necks take the drilling row of the larger size with the hub and bore cut for the smaller pipe — send both nominal bores. For long weld necks, add the barrel length you need.
Working to a drawing with Table D, F or H drilling, an ANSI class, or a bolt pattern that is not in any table? Send it across — the machines are set up from the drawing, not from a catalogue.
ANSI Pressure Classes We Drill To
Alongside the lettered tables we drill weld neck flanges to ANSI B16.5 Class 150 through Class 2500. Which class you need is set by the design pressure and temperature of the line, not by the pipe size, so quote the class from your piping specification if you have one.
| Class | Pressure (bar @ 38°C) | Temperature Range | Typical Application |
|---|---|---|---|
| Class 150 | 19.6 bar (285 PSI) | -29°C to +538°C | General process, utilities |
| Class 300 | 51.1 bar (740 PSI) | -29°C to +538°C | Higher pressure process |
| Class 600 | 102.1 bar (1480 PSI) | -29°C to +538°C | Oil & gas transmission |
| Class 900 | 153.2 bar (2220 PSI) | -29°C to +538°C | High-pressure gas systems |
| Class 1500 | 255.3 bar (3705 PSI) | -29°C to +538°C | Wellhead, HP process |
| Class 2500 | 425.5 bar (6170 PSI) | -29°C to +538°C | Ultra-high pressure critical |
Please check every dimension against your own drawing before release. Ratings above are the published ANSI class values at 38°C and derate as temperature rises — material grade, not the flange, decides the ceiling. For Table D, F and H grids, ANSI hub and length-through-hub dimensions, tolerances or a written specification sheet, call +91 99220 47887 or +91 91373 32945.
Where Weld Neck Flanges Are Used — and Where We Send Them
Weld necks are specified wherever the joint has to survive pressure, heat or repeated cycling — refineries, petrochemical units, boiler and steam lines, chemical plants, LPG and cryogenic storage, and marine repair work. Anything that gets bolted up, run hot, shut down and bolted up again is weld neck territory, because the tapered hub carries the load into the pipe wall instead of dumping it at a fillet weld.
Refineries & Tank Farms
Crude, product and gas lines, pump and exchanger connections, manifold headers. RTJ weld necks where the duty is hot and high pressure; WNRF for the balance of the plant. Bore cut to the schedule on your line list.
Petrochemical & Fertiliser
Reactor and column nozzles, reboiler and condenser piping, catalyst transfer lines. Long weld necks are the usual pick for vessel nozzles because the barrel welds straight into the shell.
Boiler & Steam Lines
Main steam, feedwater, blowdown and turbine connections in thermal and captive power plants. Thermal cycling is exactly the fatigue case a weld neck is built for, which is why steam specs rarely allow slip-ons.
Chemical, Pharma & Dyes
Corrosive and solvent duty where the joint has to stay tight and the bore has to stay clean. This is where S.S. 304, 304L, 316 and 316L weld necks go instead of mild steel.
LPG, LNG & Storage
Bullet and sphere connections, loading arms, tanker filling lines and bottling plant headers. Class and material are chosen for the service temperature; tell us the design temperature and we will confirm what we can cut.
Shipyards & Marine Repair
Darukhana is a ship-repair belt, so a fair share of our weld necks walk out of the gate to yards a few lanes away — ballast, bilge, fuel transfer and deck service lines, often against a hand-marked sketch rather than a drawing.
Delivery: Mumbai, PAN India and Gulf export
Weld neck flanges leave our Darukhana works for buyers across India and for export to the Gulf. Local delivery covers Mumbai, Navi Mumbai, Thane, Taloja, Ambernath, Pune, Nashik and Nagpur. Transport goes out regularly to South India — Chennai, Coimbatore, Tiruchirappalli, Madurai, Bengaluru, Hosur, Hyderabad, Visakhapatnam, Kochi and Mangaluru — and to Ahmedabad, Vadodara, Surat, Rajkot, Indore, Raipur, Kolkata and Delhi NCR. Export consignments are packed and documented for Dubai and the wider UAE, Oman, Qatar, Kuwait and Saudi Arabia, cleared through Nhava Sheva (JNPT) and Mumbai Port. Ask for a delivered price and we will quote freight to your city or port with the flanges.
Weld Neck Flange Questions We Get Asked
Straight answers to what buyers actually ring up and ask. If yours is not here, WhatsApp the question with your size and drilling to +91 99220 47887 and you will get a reply from the works, not a call centre.
What is a weld neck flange?
+A weld neck flange has a long tapered hub that is butt-welded to the pipe end instead of being slipped over it. The taper carries the bolt load gradually into the pipe wall, so the joint copes with pressure, temperature swings and vibration better than any other flange type. I.S. Engineering Co. machines them in mild steel and stainless steel at Darukhana, Mumbai.
Which weld neck flange sub-types do you make?
+Five. Weld neck raised face (WNRF) is the everyday version. Long weld neck (LWN) has an extended barrel and is used on vessel nozzles and heavy-wall lines. Ring type joint (RTJ, also written RJ) is grooved for a solid metal ring gasket on high-pressure service. Weld neck flat face (WNFF) is for bolting to cast iron equipment. Reducing weld neck carries the bolt pattern of the larger line with the bore machined for a smaller pipe.
What is the difference between RF, FF and RTJ facing?
+RF (raised face) has a small raised ring that the gasket sits on and is the default for most piping. FF (flat face) has no raised ring and is used when the mating part is cast iron, which can crack under the concentrated load of a raised face. RTJ (ring type joint) has a machined groove that takes a solid metal octagonal or oval ring instead of a soft gasket, and is specified where pressure and temperature are too high for a compressed gasket.
What is the difference between a weld neck and a long weld neck flange?
+A standard weld neck flange has a short tapered hub that butt-welds to a pipe of the same nominal bore. A long weld neck has a much longer straight barrel that acts as the nozzle itself, so it is welded directly into a vessel shell or header rather than onto a pipe. LWN is ordered by barrel length and bore, not by schedule alone.
What is a reducing weld neck flange?
+A reducing weld neck flange keeps the bolt pattern of the larger line size while the hub and bore are machined for the smaller pipe. It lets you step a line down at the flange joint without a separate reducer. Give us both sizes, the flange NB and the pipe NB, along with the drilling table or pressure class.
What materials and grades are available for weld neck flanges?
+Mild steel to IS:2062 covers the bulk of our work, and stainless steel is available in SS 304, 304L, 316 and 316L. Tell us the service fluid and temperature and we will confirm the grade against your enquiry. Mill test certificates for the parent material are passed on with the consignment on request.
What sizes and drilling can you supply?
+15mm to 300mm and 350mm NB are our regular running sizes, and 400, 450, 500 and 600mm NB are made to order. Drilling can follow Table D, E, F or H, or an ANSI pressure class. The drilling table fixes the outside diameter, pitch circle, bolt count and bolt hole size; the tapered hub is what makes it a weld neck rather than a slip-on.
Do you supply weld neck flanges to South India?
+Yes. We dispatch from Darukhana, Mumbai to Chennai, Coimbatore, Bengaluru, Hyderabad, Visakhapatnam, Kochi and Madurai as regularly as we do to Pune, Nashik and Ahmedabad. Send the delivery city and we will quote ex-works and delivered separately so you can see the freight.
Do you export weld neck flanges outside India?
+Yes. We handle export consignments to Dubai and the wider UAE, Oman, Qatar, Kuwait and Saudi Arabia. Give us the discharge port and whether you need FOB Nhava Sheva or CIF, and we will quote with packing suited to sea freight.
What do you need from me to quote a weld neck flange?
+Four things: nominal bore, drilling table or pressure class, facing (RF, FF or RTJ) and quantity. For weld neck also give the pipe wall thickness or schedule so the bore is machined to match, and for a long weld neck give the barrel length. Send it on WhatsApp to +91 99220 47887 and you will get a rate back.
What is the lead time for weld neck flanges?
+Regular sizes in mild steel usually move in three to ten working days from our Darukhana works. Stainless steel, bores above 350mm NB, RTJ facing and anything to your own drawing generally need ten to twenty working days. Call +91 99220 47887 for the current position before you plan a shutdown around a delivery date.
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