Lap Joint Flanges & Stub Ends Supplier in India

A two-piece joint: a stub end welded to the pipe and a loose flange that rotates to line up bolt holes. Lets you use a low-cost backing flange on stainless lines and dismantle quickly for cleaning.

Loose / backing flangeSS 304 / 316L stub endsCS, MS or SS backing flangeASME B16.5 Class 150 / 300MSS SP-43 / ASME B16.9 stub ends½" to 24"
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Lap joint flange drawing with loose backing flange and stub end welded to pipe
Only the stub end touches the fluid; the loose flange just clamps it.

How a lap joint flange works

A lap joint connection has two parts. A stub end, a short pipe piece with a flared lip, is butt-welded to the pipe. A loose lap joint flange slides over the pipe and stub end before welding and then bears on the back of the lip. When the flanges are bolted, the lips of the two stub ends are clamped together with the gasket between them.

Because the flange never touches the fluid, it can be a cheaper material than the pipe, for example a carbon steel or galvanized flange on a 316L stainless line. The loose flange also rotates freely, so bolt holes line up easily even if the stub ends were welded slightly out of position.

How a lap joint flange works: specification summary
Backing flange materialsCarbon steel ASTM A105, MS IS 2062 (black or galvanized), stainless ASTM A182 F304 / F316
Stub end materialsStainless 304 / 304L / 316 / 316L; carbon steel on request
Stub end standardsLong pattern to ASME B16.9; short pattern to MSS SP-43
Flange standardASME B16.5 Class 150 and 300; other drilling on request
Sizes½" to 24"
Gasket faceFormed by the stub end lip

When to choose a lap joint

  • Expensive pipe material: only the stub end needs to be stainless or alloy, so the flange cost drops sharply on large sizes.
  • Frequent dismantling: food, dairy, pharma and chemical lines that are opened for cleaning or inspection.
  • Alignment: connecting to pumps or equipment where bolt holes are hard to line up.
  • Moderate pressure: lap joints have lower fatigue resistance than weld neck flanges, so they suit Class 150 and 300 service without heavy cycling.

Long or short stub ends?

Long-pattern stub ends (ASME B16.9) have a longer barrel, giving room for the butt weld away from the flange. Short-pattern stub ends (MSS SP-43) are more compact and common on thin-wall stainless lines. The radius at the stub end's lip must suit the backing flange's bore corner, so tell us which flange you will use, or let us supply both as a set.

Lap joint vs slip-on

Lap joint + stub endSlip-on
PartsLoose flange plus stub endSingle flange
Flange touches fluidNoYes
Bolt-hole alignmentFlange rotates freelyFixed once welded
Cost on SS linesLower in larger sizes (CS backing flange)Full SS flange needed
Fatigue resistanceLowerModerate

Compare with slip-on flanges and weld neck flanges.

Where lap joint flanges are used

  • Stainless process lines in food, dairy and beverage plants
  • Pharma utilities and CIP lines
  • Water treatment, RO and chemical dosing
  • Lines connected to pumps, filters and skids that are removed often

Pipes and fittings to go with lap joint flanges

Pipe or fittingUse it with these flanges when…
SS seamless pipes (Sch 10S / 40S)the stub ends are welded to stainless schedule pipe
SS round pipesthe line uses welded stainless pipe
Stainless steel flangesyou prefer SS backing flanges
SS elbows, tees and reducersyou need butt-weld fittings for the same line
Pricing a stainless line?Send sizes and schedule. We will compare full SS flanges with lap joint sets.
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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 lap joint flange is a loose flange used with a stub end. The stub end is welded to the pipe and the flange slides over it, clamping the stub end's lip against the mating joint when bolted.

Yes. The lap joint flange itself is not welded to anything; it needs a stub end (or a pipe with a formed lap) to bear against.

Some stub ends are designed to work with slip-on flanges as backing flanges, but the bore corner must suit the stub end's radius. Tell us what you plan to use and we will match the stub end.

With a lap joint, only the stub end touches the fluid. A carbon steel or galvanized backing flange is much cheaper than a stainless flange and does not affect the line's corrosion resistance.

Long-pattern stub ends to ASME B16.9 have a longer barrel; short-pattern stub ends to MSS SP-43 are compact and common on thin-wall stainless pipe.

They are commonly used in Class 150 and 300 service. Their fatigue resistance is lower than weld neck flanges, so avoid them in severe cyclic service.

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
WhatsApp Us Call +91 98678 43347

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