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In modern process piping design—spanning petrochemical refineries, offshore oil platforms, LNG terminal networks, power plants, and industrial water treatment facilities—the selection of flanged connections impacts structural safety, installation velocity, and operational lifecycle cost. Among all standardized piping components defined under ASME B16.5, ASME B16.47, and EN 1092-1 (Type 12), the Raised Face Slip-On (SO-RF) Flange holds a decisive position in global procurement schedules.
A Slip-On flange slides directly over the outer diameter of the process pipe. Unlike a Weld Neck (WN) flange which features a long tapered hub butt-welded to the pipe end, a Slip-On flange is attached via two fillet welds: one internal weld at the pipe end face and one external weld around the flange hub. The integration of a Raised Face (RF)—a raised platform elevated by 1.6 mm (1/16 in) for Class 150/300 or 6.4 mm (1/4 in) for Class 600 and higher—focuses clamping load onto a confined gasket surface area during bolt torqueing. This concentrated surface pressure yields superior sealing integrity compared to Flat Face (FF) alternatives when joining low-to-medium pressure pipelines.
As a leading China Raised Face Slip-On Flange Manufacturer situated in Dingxiang County, Shanxi—the recognized home of heavy forging in China—Shanxi Yuxin Casting & Forging Co., Ltd. combines raw material vertical integration, closed-die ring forging, precision CNC machining, and rigorous testing protocols to manufacture high-durability SO-RF flanges engineered for demanding piping environments worldwide.
Understanding mechanical stress distribution, dual fillet weld geometry, and flange face surface finishes for optimal leak prevention.
Slip-On flanges require both internal and external fillet welds to establish mechanical connection strength. The external fillet weld seals the outer hub connection to the pipe wall, while the internal fillet weld seals the inner bore connection, preventing fluid penetration between the flange bore ID and the pipe OD.
The raised face is machined with concentric or phonographic (spiral) serrations at a roughness of 125–250 µin AARH (Ra 3.2–6.3 µm). When bolted, these micro-grooves bite into soft gaskets (graphite, PTFE, sheet rubber) or compress metal spiral wound gaskets, creating a high-impermeability fluid barrier.
While Weld Neck flanges are mandatory for extreme fatigue loading, SO-RF flanges offer superior ease of alignment on-site. Because the pipe slides inside the flange hub prior to welding, field piping crews can quickly adjust bolt hole concentricity, significantly reducing piping fit-up time.
Why sourcing Raised Face Slip-On Flanges from Dingxiang, Shanxi provides unmatched cost performance, scale flexibility, and rapid order execution.
Dingxiang County in Shanxi Province produces over one-third of China's exported forged flanges. Shanxi Yuxin operates within this mature industrial ecosystem. Raw carbon steel (ASTM A105, Q235B), alloy steel (ASTM A182 F11/F22, A350 LF2), and stainless steel (A182 F304/F316L) billets are procured directly from tier-1 steel mills like Baosteel and Taiyuan Iron & Steel (TISCO). This localized supply chain reduces raw material transit lead time to under 48 hours.
Shanxi Yuxin operates 5,000-ton hydraulic forging presses, high-precision radial-axial ring rolling machines, and computerized gas heat treatment furnaces. By executing forging, normalizing (890°C–920°C), tempering, high-speed CNC turning, and bolt-hole gang drilling inside our single 10,000 t/year plant, we eliminate subcontracting delays and guarantee complete quality control across all manufacturing stages.
Where Raised Face Slip-On Flanges are specified across key global energy, marine, utility, and civil engineering infrastructure.
Class 150 & 300 ASTM A105 SO-RF flanges specified in hydrocarbon transfer lines, flare headers, and storage tank manifold assemblies where operating pressure remains within moderate limits.
EN 1092-1 PN10/PN16 Type 12 hubbed slip-on flanges utilized extensively in municipal chilled water distribution, district heating loops, and seawater desalination plants.
Stainless steel (A182 F316L) and Duplex (UNS S31803) slip-on flanges for firewater lines, bilge pumping, and non-critical utility gas headers exposed to marine salt spray.
Preferred by equipment packagers building air compressors, industrial boiler skids, and chemical dosing units due to fast field positioning and zero requirement for beveling pipe ends.
How Shanxi Yuxin is transforming traditional drop forging into automated, digitally traceable, and eco-efficient green manufacturing.
Integrating automated robotic billet transfer arms and real-time infrared thermal cameras to monitor billet temperature dynamically (1150°C to 950°C). This eliminates micro-cracks, guarantees uniform plastic deformation, and refines metal grain structure.
Deploying 2D matrix laser marking on every flange neck. Scanning the QR code instantly reveals the chemical heat number, mechanical yield/tensile test data, heat-treatment furnace log, and Ultrasonic Testing (UT) wave spectrum via cloud database.
Upgrading forging reheat furnaces to clean natural gas and electric induction loops, reducing carbon footprint per ton of forged steel by 35% to meet European Union CBAM (Carbon Border Adjustment Mechanism) environmental compliance.
Full compliance with ASME B16.5, EN 1092-1, DIN 2527, and NACE MR0175 sour service requirements.
| Material Grade | Standard Specs | Pressure Ratings | Service Conditions | Traceability Cert |
|---|---|---|---|---|
| ASTM A105 Carbon Steel | ASME B16.5 / B16.47 | Class 150, 300, 600, 1500 | Ambient & High-Temp Oil/Gas/Steam | EN 10204 3.1 Mill Test Cert |
| ASTM A350 LF2 (Class 1) | ASME B16.5 / BS 1560 | Class 150 to Class 2500 | Low-Temperature Impact Service (-46°C) | EN 10204 3.1 / 3.2 Third Party |
| ASTM A182 F304 / F304L | ASME B16.5 / EN 1092-1 | Class 150–600 / PN6–PN40 | Corrosive Chemical & Food Processing | EN 10204 3.1 PMI Verified |
| ASTM A182 F316 / F316L | ASME B16.5 / EN 1092-1 | Class 150–1500 / PN10–PN100 | Offshore Marine & Sour Service (NACE) | EN 10204 3.1 NACE MR0175 |
| EN 1092-1 C22.8 / P250GH | EN 1092-1 Type 12 Hubbed | PN6, PN10, PN16, PN25, PN40 | European Pressure Vessels & Boilers | PED 2014/68/EU & AD 2000 W0 |
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