Flanges
Small Bore · 15mm to 80mm NB · M.S. & S.S.
Socket Weld Flanges
M.S. & S.S. Socket Weld Flange Manufacturer & Supplier — Darukhana, Mumbai · Since 1999
SWRF · SWFF · RTJ · ReducingSocket Bored to Your PipeTable D / E / F / H DrillingM.S. IS:2062 & SS 304 / 316Mumbai · PAN India · Gulf Export
A socket weld flange has a counterbored socket in its hub — the pipe end drops in and is closed with one external fillet weld, so there is no root pass and no pipe end to bevel. That is why small bore lines are built this way. On a 15mm or 25mm branch buried behind three other pipes, a fitter can make a socket weld joint with a mirror and a short lead; a butt weld in the same place cannot be made properly, let alone inspected. We machine these at Darukhana, Mumbai from mild steel IS:2062 and from stainless SS 304, 304L, 316 and 316L, in 15mm to 80mm NB, with the socket bored to the pipe schedule you are actually using and the drilling cut to the table or class on your drawing.
What You Are Ordering
Sub-TypesSWRF · SWFF · RTJ · Reducing · Screwed
Size Range15mm to 80mm NB (½" to 3")
SocketCounterbored to pipe schedule, ASME B16.11
FacingRaised Face · Flat Face · Ring Joint
DrillingTable D / E / F / H or ANSI class
MaterialM.S. IS:2062 · SS 304 / 304L / 316 / 316L
MarkingSize, table and grade stamped on the rim
SupplyMumbai · PAN India · Gulf export
15–80mmStandard NB Range
5Sub-Categories
1999Making Flanges Since
How a Socket Weld Joint Is Actually Made
The flange bore is counterbored to a socket that matches the outside diameter of your pipe, the pipe is pushed in, pulled back about 1.6mm, and a fillet weld is run around the outside. That is the whole joint. No bevel, no root gap to hold, no backing purge on carbon steel work. A fitter with a mirror can make a sound socket weld on a 15mm branch in a place where a butt weld could never be inspected, which is exactly why small bore pipework is built this way.
The trade-off is the annulus. Between the pipe outside diameter and the socket wall there is a thin ring of dead space. On clean service — instrument air, steam tracing, hydraulic oil, dosing lines — that ring is harmless. On slurry, on anything that has to be pigged, and on service where crevice corrosion is a live concern, it is not, and the line should be built with weld neck flanges and butt welds instead. We would rather tell you that before you order than after.
Socket weld or weld neck — the short answer
Up to 80mm NB on clean service, socket weld is quicker, cheaper and easier to get right; above that, or on slurry, cyclic and critical duty, use weld neck. Most plants use both: weld neck on the header, socket weld on the small branches, tappings and instrument connections coming off it. We make both in the same shop, so a mixed list is one enquiry and one delivery.
Why Buy Socket Weld Flanges From Us
Socket Bored to Your Pipe
Tell us the schedule, or just the outside diameter and wall thickness, and the socket is cut for that pipe — not for whatever a catalogue assumed you were using.
Every Flange on One Line
Weld neck on the header, socket weld on the branches, blinds for the spare nozzles, slip-ons for the utility runs. One enquiry, one lorry, one bill.
Marked So the Store Can Read It
Size, drilling table and grade stamped on the rim. Small bore flanges look alike in a bin; a stamped rim stops a Table E flange going onto a Table F joint.
Mumbai Shop, India-Wide Despatch
Machined at Darukhana and sent across Maharashtra, South India and the rest of the country, with Gulf export through Nhava Sheva. Since 1999.
Socket Weld Flange Sub-Categories We Make
Socket weld flanges are ordered by facing and by how the pipe is joined: SWRF, SWFF, RTJ, reducing, and the screwed flange that replaces a weld when welding is not allowed. The hub and the socket are the same idea in all of them; what changes is the sealing face and what the flange is bolting to. Read the row that matches your drawing, then send us the size and the drilling.
| Sub-Category | Trade Code | What Is Different | Usually Specified For |
|---|---|---|---|
| Socket Weld Raised Face | SWRF | Socket in the hub with a raised sealing face | The default on small bore process, steam and hydraulic lines |
| Socket Weld Flat Face | SWFF | Same socket, full flat sealing face | Bolting to cast iron pump, valve and strainer bodies |
| Ring Joint Socket Weld | RTJ / RJ | Ring groove cut in the face for a metal ring gasket | Small bore high pressure and high temperature, no soft gasket allowed |
| Reducing Socket Weld | SW — Reducing | Larger flange OD and drilling, socket bored for a smaller pipe | Landing a small branch on an existing larger bolt circle |
| Screwed / Threaded Flange | NPT / BSP | No weld at all — the pipe threads into the hub | Galvanised lines, hot work restrictions, temporary pipework |
SWRF — Socket Weld Raised Face
The one most people mean when they say socket weld flange. A raised sealing face puts the bolt load onto a narrow band of gasket, so it seals harder for the same torque. This is what small bore process lines, steam branches and hydraulic pipework are normally specified with. Facing, drilling and socket bore all to your drawing.
SWFF — Socket Weld Flat Face
The same flange with the face left flat, so the load spreads across the whole ring instead of a narrow band. Ask for this when the small bore connection lands on a cast iron pump casing, a cast valve body or a strainer — a raised face against cast iron is a cracked casting waiting to happen. Usually with a full face gasket.
RTJ / RJ Socket Weld
A ring groove is machined into the face and the seal is made by a metal octagonal or oval ring, not by a soft gasket. Specified on small bore high pressure and high temperature service, and on lines where a compressed fibre or spiral wound gasket will not survive. Tell us the ring number your drawing calls for.
Reducing Socket Weld Flange
Outside diameter and bolt pattern of the bigger size, socket bored for the smaller pipe. Useful when a 50mm bolt circle already exists on a vessel or a valve and you only need a 25mm line off it — one flange instead of a reducer plus a second joint. Send both numbers: the flange size and the pipe size.
Screwed / Threaded Flange (NPT or BSP)
Not a socket weld, but it does the same small bore job when a weld is out of the question — galvanised pipe you do not want to burn the coating off, a plant with a hot work permit problem, or a line that has to come apart again. Threaded to NPT or BSP as you specify. On hot or high pressure duty we will still suggest socket weld.
To Your Own Drawing
Odd socket depth, a non-standard bolt circle, an extra tapping in the hub, a thicker flange than the table gives, or a size nobody stocks. Send the drawing or a marked-up photograph of the flange you are matching and we will quote against it. This is a machining shop, not a catalogue.
Socket Weld Flange Dimensions — Table E Drilling, 15mm to 80mm NB
Below is the Table E drilling grid for the sizes socket weld flanges are normally made in — 15mm to 80mm NB. These are the figures that have to match the flange you are bolting to: outside diameter, bolt pitch circle, number and size of holes, and flange thickness. The socket itself is deliberately not in this table, because it does not belong to the drilling table — it is bored to the outside diameter of the pipe you are using and its depth follows ASME B16.11. Send the pipe schedule, or the outside diameter and wall thickness, and we will cut the socket to it.
| NB Size | Flange OD (mm) | Bolt PCD (mm) | No. of Bolts | Hole Dia (mm) | Bolt Size | Thickness (mm) |
|---|---|---|---|---|---|---|
| 15mm (½") | 95 | 65 | 4 | 14 | M12 | 12 |
| 20mm (¾") | 105 | 75 | 4 | 14 | M12 | 14 |
| 25mm (1") | 115 | 85 | 4 | 14 | M12 | 14 |
| 32mm (1¼") | 140 | 100 | 4 | 18 | M16 | 16 |
| 40mm (1½") | 150 | 110 | 4 | 18 | M16 | 16 |
| 50mm (2") | 165 | 125 | 4 | 18 | M16 | 16 |
| 65mm (2½") | 185 | 145 | 4 | 18 | M16 | 18 |
| 80mm (3") | 200 | 160 | 8 | 18 | M16 | 18 |
Other drilling tables and socket data — ask and we will send it
We hold the Table D, Table F and Table H drilling charts and the ANSI B16.5 class charts, and we will send the sheet for your size instead of you guessing from a web page. Same for socket bore and socket depth against a given pipe schedule, and for flanges above 80mm NB. Send the size and the table or class on +91 99220 47887 or sales.isengineeringco@gmail.com and you will get the figures with the rate.
Check these figures against your own drawing or the mating flange before you release an order. Where a drawing and a table disagree, we make to the drawing. If you are not sure which table you have on site, a photograph showing the outside diameter and the bolt hole spacing is usually enough for us to identify it.
Where Socket Weld Flanges Are Used
Socket weld flanges turn up wherever a line is small, the pressure is not, and there is no room to swing a torch for a butt weld. Hydraulic power packs, steam branches and tracing, instrument tappings, dosing skids, sampling points and the small utility runs that hang off every process header. Below are the duties our socket weld flanges most often go out on.
Hydraulic Power Packs
High pressure oil lines on presses, machine tools, hydraulic power packs and jacking systems are almost all small bore, and almost all socket welded. The joint is compact, it takes vibration well, and it can be made inside a crowded frame where a butt weld cannot.
Steam Branches & Tracing
Steam mains are large bore and butt welded; the branches, tracing lines and trap sets coming off them are 15mm to 40mm and socket welded. Raised face is the norm here, and the flange thickness on the table matters because these joints get hot, cool and get hot again.
Instrument Tappings & Air Headers
Pressure and flow tappings, gauge connections, instrument air headers and pneumatic control lines. Small, numerous, and usually the last thing to be routed — which is why they end up in awkward corners that only a socket weld or a screwed flange can serve.
Dosing, Sampling & Small Bore Process
Chemical dosing skids, reagent lines, sample points and analyser connections on process plant. Often in stainless SS 304 or SS 316 rather than mild steel, because the fluid is aggressive even though the flow is tiny. Tell us the grade with the size.
Pharma, Food & Clean Utility
Compressed air, purified water, CIP and clean utility branches in pharmaceutical and food plants, in SS 304L and SS 316L. Where the line has to be pigged or fully drainable, we will point you at weld neck instead — the socket annulus is not welcome on those duties.
Pipe Spool Fabrication Shops
Fabricators buy socket weld flanges by the bag because the joint is quick to fit and forgiving to weld — no bevel to grind, no root to chase, and the socket holds the flange square while the fitter tacks it. Repeat orders in Mumbai, Taloja and Bhiwandi run on this.
Where we despatch socket weld flanges
We supply from Darukhana, Mumbai to the whole of India and export to the Gulf. Local delivery across Mumbai, Navi Mumbai, Thane, Bhiwandi, Taloja, Ambernath, Pune, Nashik, Aurangabad and Nagpur. Regular despatch to South India — Chennai, Coimbatore, Madurai, Tiruchirappalli, Hosur, Bengaluru, Hyderabad, Visakhapatnam, Kochi and Mangaluru — and to Ahmedabad, Vadodara, Surat, Indore, Raipur, Jaipur, Delhi NCR, Kanpur, Kolkata, Bhubaneswar and Guwahati by the road or rail transport of your choice. Small bore flanges travel well, so mixed-size orders go out in one box. Export orders for Dubai and the wider UAE, Oman, Qatar, Kuwait and Saudi Arabia move through Nhava Sheva (JNPT) and Mumbai Port, with seaworthy packing, marking to your PO and the invoice and packing list your freight forwarder needs.
Socket Weld Flanges — Questions We Get Asked
What is a socket weld flange?
+A socket weld flange has a counterbored socket in the hub. The pipe end drops into the socket and is closed with a single external fillet weld, so there is no root pass and no bevelling of the pipe end. That makes it the practical choice for small bore lines from 15mm to 80mm NB, especially in tight spaces where a butt weld cannot be made or inspected. I.S. Engineering Co. has been machining socket weld flanges at Darukhana, Mumbai since 1999, in mild steel IS:2062 and in stainless SS 304, 304L, 316 and 316L.
What sizes of socket weld flange do you make?
+We make socket weld flanges from 15mm NB (half inch) to 80mm NB (three inch) as standard, which is the range socket weld construction is normally used in. Above 80mm most engineers move to a weld neck or a slip-on flange, but if your drawing calls for a larger socket weld flange we will make it to the drawing. Send the nominal bore, the pipe schedule or the pipe outside diameter and wall thickness, the drilling table and the facing.
Are socket weld flanges available in stainless steel?
+Yes. We supply socket weld flanges in stainless steel SS 304, SS 304L, SS 316 and SS 316L as well as in mild steel IS:2062. Stainless is asked for on chemical dosing lines, pharmaceutical and food process piping, instrument tappings on corrosive service and anywhere the line has to stay clean. Tell us the grade when you enquire, because the material decides both the rate and the delivery.
What is the difference between SWRF and SWFF?
+SWRF is a socket weld flange with a raised face and SWFF is the same flange with a flat face. The raised face concentrates the bolt load on a narrow band of gasket, which seals better and is what most process and steam lines specify. The flat face spreads the load across the whole face and is used when the flange bolts to a cast iron pump, valve or strainer body, because raised face loading can crack cast iron.
What is the difference between a socket weld flange and a weld neck flange?
+A socket weld flange is fillet-welded on the outside of a socket; a weld neck flange is butt-welded to the pipe with a full penetration weld. Socket weld is quicker, needs no pipe bevelling and suits small bore up to 80mm NB. Weld neck is the stronger joint, it can be radiographed, and it is preferred on large bore, cyclic, high temperature and critical service. On the same plant you will often see weld neck on the header and socket weld on the small branches.
Why must the pipe be pulled back 1.6mm before welding?
+Push the pipe fully home into the socket, then pull it back about 1.6mm (one sixteenth of an inch) before you tack it. That small gap gives the pipe end somewhere to expand into when the fillet weld heats it. Without the gap the trapped end can crack the socket bottom or the weld root. ASME B31.3 asks for this clearance on socket welded joints, and it costs nothing to get right at fit-up.
Which drilling table should I ask for?
+Ask the drawing, not us — the drilling has to match whatever the flange bolts to. In Indian trade practice the BS 10 lettered tables are the usual reference: Table D for light duty, Table E for general service, Table F and Table H for higher pressure. We drill to Table D, E, F or H, or to an ANSI B16.5 class pattern if your line is specified in classes. If you are not sure which one you have, send a photo of the mating flange with its outside diameter and bolt hole spacing and we will identify it.
What is a reducing socket weld flange?
+A reducing socket weld flange carries the outside diameter and bolt pattern of the larger size, but the socket is bored for the smaller pipe. It lets a small bore line land on an existing larger bolt circle without adding a separate reducer and one more joint. Give us both sizes — the flange size you have to bolt to, and the pipe size going into the socket.
Can I get a screwed flange instead of a socket weld flange?
+Yes. A screwed or threaded flange takes the pipe on an NPT or BSP thread instead of a weld, and it does the same small bore job when welding is not allowed — galvanised pipe you do not want to burn, a site with a hot work restriction, or a temporary line. Tell us the thread form and size. If the service is high pressure or high temperature, a socket weld flange is still the better joint.
Do you supply socket weld flanges outside Mumbai?
+Yes. We despatch from Darukhana, Mumbai across Maharashtra — Navi Mumbai, Thane, Bhiwandi, Taloja, Pune, Nashik, Aurangabad and Nagpur — and to the whole of India including Chennai, Coimbatore, Madurai, Tiruchirappalli, Hosur, Bengaluru, Hyderabad, Visakhapatnam, Kochi, Mangaluru, Ahmedabad, Vadodara, Surat, Indore, Raipur, Jaipur, Delhi NCR, Kanpur and Kolkata. Export orders for Dubai and the wider UAE, Oman, Qatar, Kuwait and Saudi Arabia go out through Nhava Sheva (JNPT) and Mumbai Port.
What details do you need to quote a socket weld flange?
+Six things: the nominal bore, the pipe schedule or the pipe outside diameter and wall thickness so we bore the socket correctly, the facing (RF, FF or RTJ), the drilling table or ANSI class, the material (mild steel or SS 304 / 304L / 316 / 316L) and the quantity. Send that to +91 99220 47887 on WhatsApp or to sales.isengineeringco@gmail.com and you will get a rate. A drawing or a photograph of the mating flange is enough if you do not have the numbers.
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