




Forged Flanges
M.S. & S.S. Forged Flange Manufacturer & Supplier – Darukhana, Mumbai · Since 1999
A forged flange is one whose blank was hammered or pressed into shape while the steel was hot, rather than cut out of rolled plate — so the grain follows the shape of the flange instead of running straight through it, and whatever porosity was in the original stock has been closed up. That is the whole reason pressure piping specifications ask for a forging: not because it looks different, but because the metal behaves better where the hub meets the plate, which is exactly where a flange is worked hardest. We buy forged blanks and do the turning, facing and drilling ourselves at Darukhana, Mumbai, in forged weld neck, blind, slip-on, socket weld and threaded patterns, 15mm to 600mm NB in M.S. IS:2062 or SS 304 / 304L / 316 / 316L. Where your specification calls for ASTM A105, say so on the enquiry and we work from A105 material with the mill certificate against it.
What Forging Changes, And What It Does Not
Forging changes the metal, not the dimensions. A forged 100mm NB Table E flange and a plate-cut 100mm NB Table E flange share the same outside diameter, the same pitch circle and the same holes — they bolt to the same mating flange and take the same gasket. What differs is what is going on inside the steel. In a forging the blank was squeezed into shape while hot, so the grain bends around the hub instead of being sliced straight through it, and porosity or segregation in the original stock is closed up and broken apart.
That matters most at the one place a flange is worked hardest — the fillet where the hub meets the back of the plate. That is where a flange under repeated pressure and temperature swings eventually cracks, and unbroken grain across that fillet is what buys the extra life. On a static, low-pressure water or air line it buys very little, which is why we will say so plainly when a plate-cut flange is the sensible thing to order.
What you are actually paying for in a forging:
- Grain that follows the shape — unbroken metal flow around the hub and the fillet radius
- A sounder blank — hot working closes porosity and disperses segregation in the stock
- Better behaviour under cycling — pressure and temperature swings are what kill flanges, and this is where a forging earns its price
- Toughness in the cold — relevant on refrigerated, cryogenic and exposed outdoor service
- A grade the consultant will accept — most pressure specifications name a forging, and a plate-cut flange is simply rejected at inspection
When your specification insists on a forging
If the drawing or the specification page says ASTM A105, names a forging, or writes the line to ASME B31.1 or B31.3, then a forged flange is what the inspector will look for and there is nothing to negotiate. The same usually holds from Class 300 upwards. If the specification says nothing at all and the line is water, air, slurry or low-pressure service drilled to a BS 10 table, a plate-cut flange is ordinary Indian practice. Send us the specification page if you are unsure — it takes a minute to read and it can save you paying for a forging you did not need.
Why Buy Your Forgings From Us
The Machining Is Ours
The blank is forged; the facing, the drilling and the bore are cut here in Darukhana. A change of table or an odd PCD is a setup change on our lathe, not a new order upstream.
We Read The Specification
Send the specification page and we will tell you whether it is asking for a forging, which class it wants and which grade — before you commit to a price.
Certificates That Match The Steel
A material test certificate traceable to the mill certificate of the actual stock, when you ask for it at order stage. Third-party inspection built into the schedule if you name the agency.
Mild Steel And Stainless
M.S. IS:2062 and SS 304 / 304L / 316 / 316L in the same five sub-types, with stainless kept clear of mild steel swarf. Despatch across India and by sea to the Gulf.
The Sub-Categories of Forged Flange
Forged is a description of how the blank was made, not a flange type — so a forged flange still has to be one of the five familiar patterns: weld neck, blind, slip-on, socket weld or threaded. All five are available as forgings from our Darukhana works, in mild steel and in stainless, and all five are machined here to the facing and the drilling you nominate. Pick the pattern by how the flange joins the pipe, then tell us it has to be a forging.
| Sub-Category | Trade Code | What Is Different | Usually Specified For |
|---|---|---|---|
| Forged Weld Neck | WNRF / WNFF | Tapered hub bored to the pipe schedule, butt welded to the line | Pressure and cyclic service; the default choice in ASME B31.1 and B31.3 work |
| Forged Blind | BLRF / BLFF | Solid disc with no bore at all | Closing a vessel opening, a header end, or a line left for future extension |
| Forged Slip-On | SORF / SOFF | Ring bored slightly over the pipe outside diameter, welded inside and out | Lower-class lines where fit-up speed matters more than fatigue life |
| Forged Socket Weld | SWRF | Socket counterbore and shoulder, fillet welded on the outside only | Small-bore instrument and utility tappings, 15mm to 80mm NB |
| Forged Threaded | NPT / BSP | Tapped bore — the pipe screws in, nothing is welded | Galvanised lines, and sites where a hot work permit is not available |
Forged Weld Neck (WNRF)
The pattern most pressure specifications name. The forged hub tapers down to the pipe wall thickness and is butt welded, so the joint is a full-penetration weld with no crevice and the stress spreads gradually out of the pipe into the flange. We bore it to the schedule of the pipe you are actually using — tell us Sch 40, Sch 80 or a wall thickness in millimetres.
Forged Blind (BLRF)
A solid forged disc, faced and drilled to match whatever it is bolting to, with no bore through it. Used to blank a vessel nozzle, close the end of a header, or cap a line that has been left for a future tie-in. Where you want a gauge, a drain or a vent through it, we tap the hole at the same setting.
Forged Slip-On (SORF)
A forged ring bored a little over the pipe outside diameter, so it slides on and is then welded on both the inside and the outside. Easier and quicker to line up on site than a weld neck, and perfectly adequate where the class allows it. Not the right answer on a line that cycles hard, because the two fillet welds carry everything.
Forged Socket Weld (SWRF)
For small bore. The pipe drops into a counterbore, seats on a shoulder, and is fillet welded on the outside only — there is nothing to weld on the inside, which is why it suits 15mm to 80mm NB instrument, sampling and utility tappings. Give us the pipe outside diameter and schedule so the socket is cut to fit that pipe.
Forged Threaded (NPT or BSP)
Tapped so the pipe screws straight in and no welding is needed anywhere. That is the point of it: on galvanised pipe a weld destroys the coating, and on a running plant a hot work permit may simply not be available. State NPT or BSP and the size, because the two thread forms are not interchangeable.
To Your Own Drawing
Odd outside diameter, a pitch circle that matches nothing in the tables, a thicker plate than the table calls for, a raised face of a particular height, or a ring joint groove — send the sketch. We work from the drawing, confirm every figure back to you in writing, and only then start cutting.
Forged Flange Dimension Tables
The grid below is BS 10 Table E drilling for 15mm to 600mm NB — the flange outside diameter, the bolt pitch circle, the number and size of holes and the plate thickness. It applies to all five sub-types, because how the flange joins the pipe does not change how it bolts to the flange facing it. What is deliberately not tabulated is the bore and the hub: on a weld neck the bore is cut to the schedule of your pipe, on a slip-on it is cut a little over the pipe outside diameter, and on a socket weld the counterbore is cut to seat that pipe — so those figures come off your pipe size, not off a chart. Give us the pipe and we will confirm them in writing before machining.
| NB Size | Flange OD (mm) | Bolt PCD (mm) | No. of Bolts | Hole Dia (mm) | Bolt Size | Thickness (mm) |
|---|---|---|---|---|---|---|
| 15mm | 95 | 65 | 4 | 14 | M12 | 12 |
| 20mm | 105 | 75 | 4 | 14 | M12 | 14 |
| 25mm | 115 | 85 | 4 | 14 | M12 | 14 |
| 32mm | 140 | 100 | 4 | 18 | M16 | 16 |
| 40mm | 150 | 110 | 4 | 18 | M16 | 16 |
| 50mm | 165 | 125 | 4 | 18 | M16 | 16 |
| 65mm | 185 | 145 | 4 | 18 | M16 | 18 |
| 80mm | 200 | 160 | 8 | 18 | M16 | 18 |
| 100mm | 220 | 180 | 8 | 18 | M16 | 18 |
| 125mm | 250 | 210 | 8 | 18 | M16 | 20 |
| 150mm | 285 | 240 | 8 | 22 | M20 | 20 |
| 200mm | 340 | 295 | 8 | 22 | M20 | 22 |
| 250mm | 395 | 350 | 12 | 22 | M20 | 24 |
| 300mm | 445 | 400 | 12 | 22 | M20 | 24 |
| 350mm | 505 | 460 | 12 | 22 | M20 | 26 |
| 400mm | 565 | 515 | 16 | 26 | M24 | 26 |
| 450mm | 615 | 565 | 16 | 26 | M24 | 28 |
| 500mm | 670 | 620 | 20 | 26 | M24 | 28 |
| 600mm | 780 | 725 | 20 | 30 | M27 | 30 |
Forged Against Plate-Cut, Side By Side
| Property | Plate-Cut Flange | Forged Flange |
|---|---|---|
| How the blank is made | Profile cut from rolled plate | Hot worked into shape, then machined |
| Grain direction | Runs straight through the section | Follows the hub and the fillet |
| Soundness of the blank | Depends on the plate | Hot working closes porosity |
| Under pressure cycling | Shorter life at the hub fillet | Where a forging earns its price |
| Bolting dimensions | Same table, same PCD, same holes | Same table, same PCD, same holes |
| Typical use here | Water, air, slurry, low-pressure lines | Steam, gas, hydrocarbon, coded piping |
| What the inspector wants | Accepted where nothing is specified | Named in most pressure specifications |
| Cost | Lower | Higher, and for a reason |
Sent on request, not published here
We only publish figures we can stand behind on every order, so ask us for: Table D, Table F and Table H drilling; ASME B16.5 Class 150, 300 and 600 charts with hub and bore dimensions; bore sizes worked to your pipe schedule; ring joint groove details; and anything above 600mm NB or outside the standard tables, which we quote against your drawing. WhatsApp or email us the size list and you will get the sheet that matches your job rather than a general chart. Dimensions are always confirmed in writing before we start machining.
Where Forged Flanges Are Used
Forged flanges go on the lines where a failure is expensive — steam, gas, hydrocarbon, and anything written to a piping code. Below is the work our forged flanges actually leave Darukhana for.
Refinery & Petrochemical Lines
Process piping carrying hydrocarbon at temperature, where the specification names a forging and the inspector checks for it. Weld neck is the usual pattern; blinds go on the nozzles and the spare tie-in points.
Boiler & Steam Distribution
Steam headers, boiler connections and turbine-side piping. Steam lines heat up, cool down and do it again every start-up, and it is that cycling — not the peak pressure — that decides how long a flange lasts.
Gas Transmission & City Gas
Valve stations, meter skids, pig launchers and distribution headers. Gas work is inspected closely and the paperwork matters as much as the metal, so the test certificate goes out with the consignment.
Chemical & Pharmaceutical Plant
This is where the stainless goes — SS 304 / 304L for general duty, 316 / 316L where chlorides or acids are in the line. Socket weld and threaded forgings for the small-bore instrument tappings around the vessels.
Marine, Dockyard & Ship Repair
We are in Darukhana, so marine work walks in. Engine room and ballast line flanges, replacements taken off a worn part or measured on the ship, and one-off pieces wanted the same week rather than the next month.
Coded Fabrication & EPC Work
Fabricators and EPC contractors working to ASME B31.1 or B31.3, where the material grade, the marking and the certificate all have to line up with the purchase order before the spool is released.
Where we despatch forged 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. Machined faces are protected and stainless items are packed clear of mild steel. 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.
Forged Flanges — Questions We Are Asked
What is a forged flange?
+A forged flange starts life as a blank that was hammered or pressed into shape while the steel was hot, instead of being cut out of rolled plate. The forging is then turned, faced and drilled to size. Because the metal is worked hot, the grain follows the shape of the flange rather than running straight through it, and any porosity in the original stock is closed up — which is why pressure piping specifications usually call for a forged flange rather than a plate-cut one. I.S. Engineering Co. supplies forged flanges from Darukhana, Mumbai in mild steel IS:2062 and stainless SS 304 / 304L / 316 / 316L, 15mm to 600mm NB.
Which flange types do you supply as forgings?
+Five — forged weld neck, forged blind, forged slip-on, forged socket weld and forged threaded. Each one starts as a forged blank and is then machined at our Mumbai works to the facing, the drilling and, on a weld neck, the bore you nominate. Anything outside those five, or any drilling that is not to a standard table, is made to your drawing.
Should I order forged or plate-cut flanges?
+Order forged when the specification, the piping code or the pressure class asks for it, and plate-cut when it does not. On a low-pressure water, air or slurry line drilled to Table D or Table E, a plate-cut flange is ordinary Indian practice and there is nothing to gain by paying for a forging. Where the line carries steam, gas or hydrocarbon, or where the job is written to ASME B31.1 or B31.3, the specification will name a forging and that settles it. If you are not sure which side of that line your job falls on, send us the specification page and we will tell you what it is asking for.
Is IS:2062 the same as ASTM A105?
+No. They are different specifications and they are not interchangeable. IS:2062 is an Indian structural steel and it is the grade our standard M.S. flanges are made from. ASTM A105 is an American specification written specifically for forged carbon steel piping components, with its own chemistry limits and its own testing. If your specification says A105, say so on the enquiry and we will work from A105 material and hand over the mill test certificate against it. Nobody should substitute one grade for the other on a pressure line without the consultant’s written approval.
Which pressure classes do you make forged flanges in?
+Class 150, Class 300 and Class 600 are the classes we make as routine work, alongside the BS 10 lettered tables D, E, F and H. Class 900 and above we quote case by case against your drawing, the material specification and the certification you need, because the blank, the machining and the testing all have to be arranged for that particular order. We would rather quote those honestly than list them and let you down on delivery.
What sizes are forged flanges made in?
+15mm NB to 600mm NB is the standard range we work in. Above 600mm NB, and for any non-standard outside diameter, thickness or drilling, we work to your drawing — send a sketch with the OD, the PCD, the number and size of holes, the thickness and the facing, and we will confirm it back in writing before anything is cut.
What drilling and thickness will I get?
+Whatever table or class you nominate. The grid published on this page is BS 10 Table E for 15mm to 600mm NB, giving the flange outside diameter, the bolt pitch circle, the number of holes, the hole diameter, the bolt size and the thickness. Table D, Table F, Table H and the ASME B16.5 class charts are sent on request rather than published here, so that you are quoting from the sheet that matches your job.
Do you supply forged flanges in stainless steel?
+Yes — SS 304, 304L, 316 and 316L, in the same five sub-categories as the mild steel range. Stainless work is kept away from mild steel swarf so the machined faces are not contaminated, and stainless flanges are marked and packed separately from M.S. items in the same consignment. Tell us the grade at enquiry stage, because 316 stock costs appreciably more than 304 and the rate moves with it.
Will I get a material test certificate?
+Yes, if you ask for it at order stage. We issue a material test certificate traceable to the mill certificate of the stock the flange was made from. If your client requires third-party inspection, name the agency on the purchase order so the inspection can be built into the machining schedule instead of holding up despatch at the end.
Where do you supply forged flanges?
+From Darukhana, Mumbai to the whole of India, and by sea 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. Export orders for Dubai and the wider UAE, Oman, Qatar, Kuwait and Saudi Arabia move through Nhava Sheva (JNPT) and Mumbai Port.
How do I get a price for forged flanges?
+Send the size in NB, the class or table for the drilling, which of the five types you want, the facing, the grade, the certification you need and the quantity. WhatsApp +91 99220 47887 or email sales.isengineeringco@gmail.com. A specification page or a drawing is enough. We are at Gala No 10, Plot No 255, Mehta Lane, Kolsa Bunder, Darukhana, Rey Road, Mumbai 400010, open Monday to Saturday, 9:00 to 18:30.



