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View Product SpecsA comprehensive analysis of stress distribution, rotational flexibility, and metallurgical compatibility in loose-flange piping assemblies.
The Vanstone Flange system—historically known as the Lap Joint Flange—consists of two distinct structural components: a forged stub end (lap) butt-welded to the process pipe, and a loose backing flange that slides over the pipe. This allows 360-degree rotational alignment during field installation, eliminating bolt hole alignment stress.
By decoupling the fluid-wetted section (the Stub End) from the pressure-retaining structural ring (the Backing Flange), engineers can specify expensive corrosion-resistant alloys (such as Hastelloy, Titanium, or 316L Stainless) strictly for the stub end, while using an economical Carbon Steel (ASTM A105) backing flange.
The inner bore radius of the backing flange is specifically machined to clear the outer radius of the stub end. Precise compliance with ASME B16.5 and MSS SP-43 dimensional tolerances prevents stress concentration at the fillet junction, guaranteeing hydrostatic seal integrity under high-cycle thermal expansion.
In high-pressure industrial piping systems, joint failure is predominantly driven by bending moments, bolt fatigue, and thermal cycling. Standard rigid flanges—such as Weld Neck or Slip-On types—transfer piping misalignment torque directly into the gasket face, leading to non-uniform gasket compression and localized leakage. The Vanstone design neutralizes torsional stresses. Because the backing flange rotates freely until final bolt torque is applied, fit-up technicians can achieve perfect parallel alignment of gasket faces regardless of minor angular misalignments in fixed pipe runs.
Furthermore, when internal fluid temperatures fluctuate rapidly, the thermal expansion coefficient of the pipe material may differ from that of the external structural flange. Shanxi Yuxin’s precision CNC machining ensures that the internal bore radius ($r$) and the stub end shoulder fillet fit together with micrometer accuracy. This exact tolerance matching guarantees that clamping force is uniformly distributed across the gasket surface area ($G$), maintaining seal retention even during pressure surges up to 250 bar.
Critical dimensional data for engineering procurement, pipe layout drafting, and quality control validation.
The table below outlines standard industrial dimensions for ASME B16.5 Class 150 Lap Joint / Vanstone flanges manufactured by Shanxi Yuxin Casting & Forging Co., Ltd. All dimensions are specified in millimeters (mm) unless noted otherwise.
| Nominal Size (NPS) | Pipe O.D. (mm) | Flange O.D. - D (mm) | Thickness - C (mm) | Bore - B (mm) | Diameter of Lap - G (mm) | Bolt Circle - K (mm) | No. & Dia. of Bolt Holes | Approx Weight (kg) |
|---|---|---|---|---|---|---|---|---|
| 1/2" (DN15) | 21.3 | 90 | 11.1 | 22.9 | 35.1 | 60.3 | 4 x 15.9 mm | 0.5 |
| 3/4" (DN20) | 26.7 | 100 | 12.7 | 28.2 | 42.9 | 69.9 | 4 x 15.9 mm | 0.7 |
| 1" (DN25) | 33.4 | 110 | 14.3 | 34.8 | 50.8 | 79.2 | 4 x 15.9 mm | 0.9 |
| 1-1/2" (DN40) | 48.3 | 127 | 17.5 | 49.8 | 73.0 | 98.4 | 4 x 15.9 mm | 1.4 |
| 2" (DN50) | 60.3 | 152 | 19.1 | 61.7 | 92.1 | 120.7 | 4 x 19.0 mm | 2.3 |
| 3" (DN80) | 88.9 | 190 | 23.8 | 90.7 | 127.0 | 152.4 | 4 x 19.0 mm | 4.1 |
| 4" (DN100) | 114.3 | 230 | 23.8 | 116.1 | 157.2 | 190.5 | 8 x 19.0 mm | 5.9 |
| 6" (DN150) | 168.3 | 280 | 25.4 | 170.7 | 215.9 | 241.3 | 8 x 22.2 mm | 8.6 |
| 8" (DN200) | 219.1 | 343 | 28.6 | 221.5 | 269.9 | 298.5 | 8 x 22.2 mm | 13.6 |
| 10" (DN250) | 273.0 | 406 | 30.2 | 276.4 | 323.8 | 362.0 | 12 x 25.4 mm | 18.5 |
| 12" (DN300) | 323.8 | 483 | 31.8 | 327.2 | 381.0 | 431.8 | 12 x 25.4 mm | 29.0 |
Analyzing shifting procurement trends across North America, Europe, Middle East, and Asia-Pacific energy infrastructure.
The global industrial pipe fitting market has seen a rapid acceleration in the adoption of Vanstone (Lap Joint) flange systems. Drive factors include the global expansion of Liquefied Natural Gas (LNG) liquefaction skids, seawater reverse osmosis (SWRO) desalination facilities, and specialized chemical processing plants. In these capital-intensive projects, fluid pipelines are constructed using high-grade alloys such as Duplex Stainless Steel (UNS S31803 / S32750), Titanium Grade 2, Nickel Alloy C276, or 90/10 Copper-Nickel.
Utilizing full-body forged weld neck flanges in solid high-grade alloys incurs massive capital expenditure. By deploying ASME B16.5 Vanstone systems, engineering contractors achieve up to a 40% reduction in total raw material cost without compromising pressure ratings or structural integrity. The stub end provides 100% chemical resistance against aggressive process fluids, while the backing flange—typically forged from ASTM A105 carbon steel or low-alloy steel—handles the external mechanical bolt loads.
Procurement directors across the EU and North America are prioritizing supply chain resilience, total cost of ownership (TCO), and absolute material traceability. In Western Europe, strict adherence to the Pressure Equipment Directive (PED 2014/68/EU) and AD 2000-Merkblatt W0 mandates that manufacturers provide EN 10204 3.1 or 3.2 certified inspection reports tied directly to heat numbers.
Meanwhile, EPC contractors in the Middle East energy sector require specialized external surface treatments—such as zinc phosphating, hot-dip galvanizing, or yellow chromate coating—to withstand extreme ambient marine humidity and salt spray exposure. Shanxi Yuxin's dedicated export infrastructure fulfills these exact compliance demands with seamless global logistics shipping directly to major ports worldwide.
How Shanxi Yuxin Casting & Forging Co., Ltd. combines regional industrial clustering with advanced automation to deliver unmatched cost and quality efficiency.
Located in the Zhuangli Enclave Industrial Zone of Dingxiang County, Shanxi Province, Shanxi Yuxin operates at the geographic epicenter of China’s steel forging industry. This cluster provides instant access to raw billet stocks, specialized heat-treatment plants, and specialized testing laboratories.
Spanning over 33 years of production expertise, YUXIN maintains 100% in-house manufacturing control. From closed-die precision forging and ring-rolling to CNC face-machining and automatic bolt-hole drilling, every step is executed within our owned facilities.
Audited by TÜV Rheinland, YUXIN holds ISO 9001:2015, PED 2014/68/EU, AD 2000-W0, and Chinese Special Equipment Manufacturing Licenses. We guarantee full microstructural soundness via 100% Ultrasonic Testing (UT) on critical forgings.
By eliminating third-party intermediaries and utilizing high-efficiency CNC production lines, we reduce lead times for custom Vanstone dimensions to 20–30 days while reducing unit costs by 25–35% compared to Western European forging mills.
Real-world deployment analysis across high-demand industrial sectors.
Scenario: Concentrated sulfuric acid transfer lines requiring frequent disassembly for cleaning and inspection.
Solution: PTFE/Lined Stainless Steel Stub Ends combined with Shanxi Yuxin Epoxy-Coated Carbon Steel Lap Joint Backing Flanges. The rotatable backing flange allows rapid bolt removal without stressing rigid lined pipes, drastically reducing maintenance downtime.
Scenario: Seawater cooling systems on offshore platforms exposed to high ambient salt air and vibration.
Solution: Copper-Nickel 90/10 Stub Ends paired with Hot-Dip Galvanized ASME B16.5 Lap Joint Flanges. The setup withstands galvanic corrosion while absorbing mechanical vibrations caused by engine vibration.
Scenario: Large-diameter (DN600-DN1800) underground water distribution headers installed in tight trenches.
Solution: Large-diameter forged Vanstone flanges manufactured per EN 1092-1 Type 02. The loose design allows site installation teams to align bolt holes perfectly without force-fitting misaligned underground pipe spools.
How we ensure complete compliance, chemical integrity, and zero-defect shipments for critical infrastructure projects.
To satisfy global EPC inspection regimes (including BV, SGS, Lloyd's Register, and TÜV), every forging lot undergoes strict Quality Assurance protocols:
Every order exported by Shanxi Yuxin is backed by a full documentation dossier to streamline port customs clearance and project site handovers:
Innovation directions shaping the next decade of industrial piping components.
Integration of fully automated robotic drop-forging lines and multi-axis CNC machining cells ensures dimensional tolerances within $\pm 0.1\text{ mm}$, driving down scrap rates and energy consumption per ton produced.
Transition from standard black varnish to advanced fluoropolymer (Xylan), 3-layer Polyethylene (3LPE), and fusion-bonded epoxy (FBE) coatings designed for subsea energy lines with 30+ year maintenance-free lifespans.
Implementation of 2D Data Matrix laser etching directly on the outer flange rim, enabling site engineers to scan a flange with a mobile device and instantly access its MTC, heat treatment chart, and CAD model.
Clear, definitive technical responses from Shanxi Yuxin's engineering department.
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View Product SpecsNeed urgent pricing for ASME B16.5, EN 1092-1, or custom drawing-based Vanstone flanges? Speak directly with our Shanxi plant export engineers today.
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