Explore our ISO 9001 and PED-certified industrial flange products manufactured directly in Shanxi, China.
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View DetailsUnderstanding the two-component assembly mechanism: Lap Joint Backing Flanges and Stub End pairings.
A Lap Joint Flange (LJ Flange) features a loose backing flange that freely rotates around a welded stub end. This structural separation ensures that the outer flange never contacts the process fluid, eliminating corrosion risks on the backing flange.
By pairing a premium alloy Stub End (e.g., Inconel 625, Hastelloy C276, Titanium Grade 2, or Stainless Steel 316L) with an economical Carbon Steel (ASTM A105) backing flange, plant operators reduce material procurement costs by 35% to 60%.
Because the outer ring rotates 360 degrees around the pipe axis prior to bolt tightening, bolt-hole alignment becomes effortless. This drastically accelerates field assembly in tight offshore modules and remote chemical plant retrofit projects.
When selecting Lap Joint Flange dimensions, engineers must verify that the internal radius (r) of the flange bore matches the mating radius of the Stub End. A mismatch between the backing flange fillet radius and the lap joint stub end radius can cause localized stress risers, leading to bolt pre-load relaxation or premature mechanical fatigue under thermal cycling.
Comprehensive engineering dimensional data for carbon steel, stainless steel, and alloy steel lap joint flanges manufactured according to ASME B16.5 standards.
| Nominal Pipe Size (NPS) | Outside Diameter (O) [mm] | Thickness of Flange (C) [mm] | Diameter of Bore (B) [mm] | Diameter of Hub (Y) [mm] | Fillet Radius (r) [mm] | Number of Bolt Holes | Bolt Circle Diameter (W) [mm] |
|---|---|---|---|---|---|---|---|
| 1/2" (DN15) | 89.0 | 11.2 | 22.9 | 30.2 | 3.0 | 4 | 60.3 |
| 3/4" (DN20) | 98.6 | 12.7 | 28.2 | 38.1 | 3.0 | 4 | 69.9 |
| 1" (DN25) | 108.0 | 14.3 | 34.8 | 49.3 | 3.0 | 4 | 79.2 |
| 1-1/2" (DN40) | 127.0 | 17.5 | 49.5 | 65.0 | 3.0 | 4 | 98.6 |
| 2" (DN50) | 152.4 | 19.1 | 61.7 | 77.7 | 3.0 | 4 | 120.7 |
| 3" (DN80) | 190.5 | 23.9 | 90.7 | 108.0 | 4.0 | 4 | 152.4 |
| 4" (DN100) | 228.6 | 23.9 | 116.1 | 134.9 | 4.0 | 8 | 190.5 |
| 6" (DN150) | 279.4 | 25.4 | 170.7 | 192.0 | 5.0 | 8 | 241.3 |
| 8" (DN200) | 342.9 | 28.4 | 221.5 | 246.1 | 5.0 | 8 | 298.5 |
| 10" (DN250) | 406.4 | 30.2 | 276.4 | 304.8 | 5.0 | 12 | 362.0 |
| 12" (DN300) | 482.6 | 31.8 | 327.2 | 365.3 | 6.0 | 12 | 431.8 |
* Full dimensional parameters for ASME B16.5 Class 300, 600, 900, 1500, 2500 and EN 1092-1 Type 02 Loose Flanges available upon request.
How Chinese precision forging manufacturers are shaping supply chain efficiency across North America, Europe, and the Middle East.
European chemical processing plants heavily rely on EN 1092-1 Type 02 loose flanges paired with Type 32/33 weld-on collars. Compliance with Pressure Equipment Directive (PED 2014/68/EU) and AD 2000-W0 is mandatory for high-temperature and high-pressure steam distribution headers.
In North America, ASME B16.5 and B16.47 Series A & B standards dominate midstream shale gas gathering networks and LNG liquefaction terminals. The ability to source high-yield ASTM A350 LF2 Class 1/2 low-temperature carbon steel lap joint flanges guarantees structural integrity at sub-zero temperatures down to -46°C.
Located in Shanxi Province, Dingxiang County is globally recognized as the "Hometown of Forging in China." Housing state-of-the-art ring-rolling mills, automated hydraulic forging presses, and 5-axis CNC machining centers, our facility yields over 10,000 metric tons of precision flanges annually, serving distributors and EPC contractors in 40+ countries.
Transforming raw steel billets into defect-free, high-yield lap joint flanges through automated metal forming and digital quality control.
By utilizing computer-controlled radial-axial ring rolling mills, steel grain flows are aligned parallel to the flange stress contours. This eliminates internal porosity, improves tensile strength, and maximizes resistance against stress corrosion cracking (SCC).
Every critical flange forged at Shanxi Yuxin undergoes 100% Automated Ultrasonic Testing (AUT) and Magnetic Particle Inspection (MPI). Internal lamination risks, inclusions, or micro-cracks are identified prior to precision CNC machining.
Beyond natural black oiling and hot-dip galvanizing (HDG), we offer advanced anti-corrosion surface treatments, including electro-deposited Zinc-Nickel (Zn-Ni) plating, Xylan fluoropolymer coatings, and epoxy powder spraying for subsea manifolds.
Targeted engineering solutions where lap joint flanges deliver optimized structural performance and maintenance savings.
Seawater reverse osmosis (SWRO) facilities utilize Super Duplex 2507 (UNS S32750) or Titanium Stub Ends paired with epoxy-coated carbon steel backing flanges to withstand concentrated chloride erosion while controlling material budgets.
In high-purity biopharmaceutical lines, polished Stainless Steel (ASTM A182 F316L) stub ends with Ra < 0.4 µm interior surface finish allow frequent dismantling and CIP/SIP sterilization without altering fixed pipe geometry.
Pipelines carrying abrasive ore slurries experience rapid localized wall thinning. Lap joint assemblies enable technicians to quickly unbolt, rotate the pipe segment 90 degrees to distribute wear evenly, and re-bolt without re-welding.
Pioneering the next era of smart piping components and sustainable green steel manufacturing.
Embedding piezo-electric strain sensors and fiber-optic leak detection nodes directly inside the backing flange hub for real-time bolt stress monitoring.
Transitioning reheating furnaces from natural gas to green hydrogen blends, cutting carbon intensity per ton of forged flange by 45%.
Deploying computer vision models trained on thousands of forging macro-structures to adjust hydraulic press pressures in real time during ring deformation.
Issuing cryptographic blockchain material passports linked to EN 10204 3.2 certification for complete end-of-life recycling traceability.
Holistic engineering support covering flange-gasket-bolt interaction, bolt load calculations, and global compliance.
We supply detailed bolt torque calculations tailored to gasket compressibility, flange facing, and lubricated stud bolt friction factors. This eliminates joint leakage under extreme pressure-temperature thermal cycles.
To prevent field fit-up delays, Shanxi Yuxin manufactures pre-matched sets: ASME B16.9 / MSS SP-43 Type A, B, and C Stub Ends matched with corresponding ASME B16.5 Lap Joint backing flanges under single heat-number tracking.
Every export order includes rigorous document packages: EN 10204 3.1 MTC, Chemical Composition & Mechanical Test Reports, Impact Test Reports (-46°C), Hardness Certification, and NDT (UT/MT) Test Certificates.
Detailed answers to key engineering queries regarding Lap Joint Flange dimensions, standards, and material selection.
Complete your piping system with our high-pressure forged components engineered to international standards.
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