ASME B16.5 | Class 150 – 2500 | LJ Flange + Stub End System | 360° Rotating Ring | ISO 9001:2015
A lapped joint flange (LJF), also called a loose flange or backing flange, is a two-piece flanging system consisting of a loose rotating flange ring and a lap joint stub end. The stub end is butt-welded to the pipe; the flange ring slides freely over the pipe and backs up against the stub end's lapped face. Because the ring can rotate freely through 360°, bolt holes align with the mating flange without rotating the pipe — a critical advantage when connecting to fixed equipment or in tight spaces.
Tesco Steel & Engineering, ISO 9001:2015 certified, manufactures and exports lapped joint flanges from ½″ NB to 56″ NB in all ASME B16.5 pressure classes (150 through 2500) across the full range of materials. A key economic benefit of the LJF system: only the stub end contacts the process fluid, so the stub end can be made from the required corrosion-resistant alloy (e.g., SS 316L, Hastelloy C276, Titanium) while the flange ring is supplied in low-cost carbon steel — reducing assembly cost by up to 60% versus an all-alloy weld neck flange of the same size.
The loose flange ring rotates freely around the stub end, enabling bolt holes to be aligned with the mating flange without rotating or stressing the pipe — essential when connecting to fixed nozzles, pumps, or tanks.
The flange ring is not welded to the pipe. The joint can be broken and re-made repeatedly without disturbing pipe welds — ideal for systems requiring frequent inspection, cleaning, or maintenance access.
Only the stub end contacts the fluid. Use an alloy stub end (SS 316L, Hastelloy, Titanium) with a low-cost ASTM A105 carbon steel flange ring — reducing flanging cost by 40–60% versus all-alloy weld necks on corrosive services.
The stub end face can accommodate PTFE liners, rubber linings, or glass linings that extend over the sealing face — making LJFs the standard choice for non-metallic lined piping systems where a raised face weld neck is not compatible.
LTCS and SS 304L/316L stub ends with carbon steel flange rings are widely used in LNG, cryogenic storage, and cold process service — where alloy material continuity at the sealing face is required but the flange backing ring does not need to be alloy-grade.
ASME B16.5 Class 150–2500, ½″–56″ NB, in carbon steel, SS 304/316/316L, duplex 2205/2507, Inconel 625, Hastelloy C276, Titanium Gr.2, Monel, and Copper Nickel — all with full EN 10204 3.1/3.2 MTC documentation.
| Parameter | Details |
|---|---|
| Size Range | ½″ NB to 56″ NB |
| Pressure Classes | 150#, 300#, 400#, 600#, 900#, 1500#, 2500# |
| Pressure Ratings | PN 1 – PN 400 |
| Standard | ASME B16.5; Stub End to ASME B16.9 |
| Facing Type | Flat Face (flange ring); Stub End lapped face |
| Carbon Steel | ASTM A105 (flange ring); A234 WPB (stub end) |
| LTCS | ASTM A350 LF2 |
| Alloy Steel | ASTM A182 F5, F9, F11, F21, F22, F91 |
| Stainless Steel | ASTM A182 F304/304H/304L, F316/316H/316L/316Ti, F309, F310, F317L, F321, F347, F904L |
| Duplex / Super Duplex | ASTM A182 F51 (2205), F53 (2507), F55 (Zeron 100) |
| Nickel Alloys | UNS N02200, UNS N02201 |
| Monel | UNS N04400, UNS N05500, Alloy 20 |
| Inconel / Incoloy | UNS N06600, N06601, N06625, N08800, N08810, N08825 |
| Hastelloy | UNS N10276, N06022, N10665, N06455 |
| Titanium | Gr.1, Gr.2, Gr.3, DTH 3.7035, DTH 3.7055 |
| Copper Nickel | C70600 (90/10), C71500 (70/30), C71640 |
| Surface Treatments | Hot Dip Galvanizing, Sand Blasting, Shot Peening, Epoxy Coating, FBE Coating |
| Test Certificates | EN 10204 3.1/3.2 MTC, PMI, Hydro Test, RT/UT/PT/MT |
| Factor | Lapped Joint | Weld Neck | Slip-On |
|---|---|---|---|
| Bolt Hole Alignment | 360° rotation — easiest alignment | Fixed — pipe must be rotated | Fixed — pipe must be rotated |
| Dismantling for Maintenance | Excellent — ring is loose | Standard — requires full flange break | Standard — requires full flange break |
| Mixed Material Option | Yes — ring and stub end can differ | No — single piece material | No — single piece material |
| Fatigue Life | ~1/10th of WN (lower) | Highest (butt weld, E=1.0) | Lower than WN |
| Lined Pipe Compatibility | Excellent (PTFE, rubber, glass) | Limited | Limited |
| Typical Use | Frequent maintenance, corrosive, lined | High-pressure, cyclic, critical service | Low/moderate pressure, utilities |
| Industry | Typical Application | Stub End Material |
|---|---|---|
| Chemical & Petrochemical | Corrosive fluid lines, frequent inspection break-ins | A182 F316L, Hastelloy C276 |
| Food, Beverage & Pharma | Hygienic lines requiring frequent dismantling | A182 F316L (Ra <0.8µm) |
| Cryogenic / LNG | Cold process lines, PTFE-lined cryogenic pipe | A350 LF2, A182 F304L |
| Water Treatment | Large-bore flanging to fixed infrastructure | A105 / A182 F316 |
| Lined Piping Systems | PTFE-lined, rubber-lined, glass-lined pipe | PTFE-faced or alloy stub end |
| Offshore & Marine | Seawater systems, ballast, fire water lines | Duplex 2205, Cu-Ni 90/10 |
ISO-certified manufacturer & exporter. ASME B16.5 Class 150–2500. All materials — carbon steel, SS, alloy, Inconel, Hastelloy, Titanium. Fast delivery worldwide from Mumbai, India.
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