Socket Weld Flanges Supplier & Stockist in India

Flanges for small-bore, high-pressure lines: the pipe sits in a socket and is joined with one outside fillet weld. Supplied in carbon steel A105 and stainless steel to ASME B16.5.

SWRF / SW RTJASME B16.5Class 150 to 1500A105, LF2, F304L, F316L½" to 3"Bore to pipe schedule
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Socket weld flange drawing: pipe inserted into socket with expansion gap and fillet weld
The pipe stops short of the socket shoulder, leaving an expansion gap before welding.

How a socket weld flange works

A socket weld flange has a counterbore (the socket) that the pipe end slides into, and a smaller bore beyond it that matches the pipe's inside diameter. One fillet weld on the outside, at the hub, makes the joint. The flow sees a smooth bore with no weld bead inside.

Socket weld flanges are used on small-bore lines, typically up to 2" and sometimes 3", where they are quicker to fit than weld neck flanges and stronger than slip-ons. They pair naturally with ASME B16.11 socket weld fittings.

How a socket weld flange works: specification summary
MaterialsCarbon steel ASTM A105 / A105N, A350 LF2; stainless ASTM A182 F304 / F304L / F316 / F316L
StandardASME B16.5
Pressure classes150, 300, 600, 900, 1500 (size range narrows in the higher classes)
Sizes½" to 3", most commonly ½" to 2"
BoreSocket sized to the pipe OD; through-bore matched to the pipe schedule
FacingRaised face; RTJ on request
WeldingOne external fillet weld at the hub

Leave the expansion gap

Before welding, the pipe is pushed into the socket until it bottoms out and is then pulled back, leaving a gap of about 1.6 mm (1/16") between the pipe end and the socket shoulder. The gap stops the weld from cracking when the joint heats up and the pipe expands. Piping codes such as ASME B31.1 and B31.3 describe this practice; follow your welding procedure for the exact figure.

Socket weld, threaded or slip-on for small bore?

Socket weldThreadedSlip-on
JointOne external fillet weldScrewed, no weldingTwo fillet welds
PressureHighLow to moderateModerate
Leak riskLowHigher under vibration or heatLow
BoreSmooth, matched to scheduleSmoothStep at the pipe end
Best forHydraulic, steam drains, process small-boreGI water, air, no-hot-work areasUtility lines

See also threaded flanges and slip-on flanges.

Where to avoid socket welds

The gap at the bottom of the socket leaves a small crevice. In corrosive service, liquids trapped in that crevice can cause crevice corrosion, and some specifications restrict socket welds in severe cyclic service. In those cases, a small-bore weld neck flange is the usual alternative.

Where socket weld flanges are used

  • Hydraulic and lube oil lines
  • Steam trap, drain and vent connections
  • Instrument and sampling connections
  • Chemical dosing and injection lines
  • Compressed air and gas manifolds on skids

Pipes and fittings to go with socket weld flanges

Pipe or fittingUse it with these flanges when…
Hydraulic pipesthe flanges are on hydraulic or lube oil lines
MS seamless pipesyou need Sch 80 or Sch 160 small-bore pipe
SS seamless pipesthe line is stainless
Socket weld couplings and fittingsyou need ASME B16.11 fittings for the same line
Small-bore package to quote?Send sizes, class, schedule and grade for flanges and SW fittings together.
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Flange types we supply

Each page covers materials, standards, sizes and where that flange fits. All flanges can be quoted with matching pipes and fittings.

MS Flanges drawingMS FlangesIS 2062 mild steel, Table E / IS 6392 / ASA 150 Stainless Steel Flanges drawingStainless Steel FlangesSS 304, 304L, 316, 316L to ASME B16.5 Carbon Steel Flanges drawingCarbon Steel FlangesForged ASTM A105, A350 LF2, Class 150 to 1500 Slip-On Flanges (SORF) drawingSlip-On Flanges (SORF)Pipe slides in, two fillet welds Weld Neck Flanges (WNRF) drawingWeld Neck Flanges (WNRF)Butt-welded, bored to pipe schedule Blind Flanges drawingBlind FlangesClose pipe ends, nozzles and test points Socket Weld Flanges drawingSocket Weld FlangesSmall-bore, high-pressure lines Threaded Flanges drawingThreaded FlangesNPT / BSP, no welding, GI lines Lap Joint Flanges drawingLap Joint FlangesLoose flange with stub end Plate Flanges drawingPlate FlangesFlat flanges, Table D/E/F/H, custom Flange Size & Class Chart drawingFlange Size & Class ChartASME B16.5 OD, PCD, bolts and ratings
FAQ

Frequently Asked Questions

A socket weld flange has a socket that the pipe end fits into, plus a smaller bore that matches the pipe ID. It is joined with one fillet weld on the outside and is used on small-bore, high-pressure lines.

A gap of about 1.6 mm (1/16") between the pipe end and the socket shoulder lets the pipe expand when heated, so the fillet weld does not crack.

ASME B16.5 covers socket weld flanges in small sizes only, up to about 3" in the lower classes. Most are used from ½" to 2".

Yes. The bore beyond the socket is matched to the pipe inside diameter, so give the schedule, for example Sch 80 or Sch 160.

Socket weld flanges are quicker to fit and suit most small-bore high-pressure lines. Choose weld neck where the specification bans crevices, for corrosive or severe cyclic service.

Yes, socket weld couplings, elbows and tees to ASME B16.11 can be quoted with the flanges.

Buyer Guides & Tools

Flange Size Chart & Pressure ClassesASME B16.5 OD, PCD, bolts, Class 150 to 2500ERW vs Seamless PipeWhich pipe to use with your flangesPipe & Tube Weight CalculatorMS / SS / GI round, square & rectangularSteel Pipe Buying Guide for IndiaChecklist before you request a quoteSS 304 vs SS 316Choosing the stainless grade
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Get a Flange Quote

Tell us the flange type, size, class or table, material and quantity. We reply on call, WhatsApp or email.

  • MS, carbon steel and stainless steel flanges on one quotation
  • Matching pipes, elbows, tees and reducers from the same order
  • Dispatch from Thane / Panvel to sites across India
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