Explore our premium grade ASME, DIN, and EN forged flange solutions engineered for critical industrial applications worldwide.
A comprehensive examination of structural mechanics, joint integrity, and precision forging standards for modern fluid infrastructure.
Slip-On (SO) flanges, designated under ASME B16.5 and EN 1092-1 Type 12 standards, are engineered to slide over the outer diameter of the connecting pipe. Unlike Weld Neck (WN) flanges that feature a long tapered hub butt-welded to the pipe wall, an SO flange is secured via two fillet welds: one inside the flange bore and one on the outer hub shoulder.
This dual-fillet weld arrangement distributes mechanical loading across the flange body while providing dynamic shear resistance against axial pressure thrusts. Lower initial procurement costs, ease of alignment during field installation, and reduced pipe cutting precision requirements make SO flanges the preferred connection choice for low-to-medium pressure utility and process lines (Class 150 to Class 1500).
At Shanxi Yuxin Casting & Forging Co., Ltd., every SO flange is forged from killed steel billets using closed-die hot forging presses. This manufacturing process forces the grain flow of the steel to follow the radial contour of the flange ring and hub, eliminating directional weakness inherent in flame-cut plate rings.
Information Gain Insight: Under cyclic thermal fatigue tests, closed-die forged SO flanges display up to 40% higher fatigue resistance and superior toughness at sub-zero temperatures compared to flame-cut plate flanges (ASME B16.5 vs. AWWA plate standards).
Key drivers influencing global industrial piping procurement, sustainability standards, and digital supply chain integration.
Global decarbonization initiatives require piping components capable of handling hydrogen-blended natural gas and cryogenic fluids. Modern SO flanges must comply with stringent fugitive emission requirements (ISO 15848-1) and ultra-low helium leak thresholds.
Global EPC contractors no longer accept generic mill test reports. End-users require digital EN 10204 3.1 and 3.2 certification linked to heat numbers laser-etched directly onto the flange rim, providing instant verification of chemical heat analysis and mechanical impact test data.
Procurement teams are optimizing total cost of ownership by utilizing SO flanges with matching stub ends or duplex/alloy clad designs. This strategy allows the use of carbon steel backer flanges in aggressive chemical environments, significantly reducing material costs without compromising structural safety.
Located in Dingxiang County, Shanxi — China's world-famous forging epicenter — Shanxi Yuxin Casting & Forging Co., Ltd. integrates modern digital manufacturing with 33+ years of metallurgical expertise.
Our facility houses over 40 high-speed multi-axis CNC vertical lathes and automated drilling machines. Bolt hole concentricity, bolt circle diameter (BCD), and flange face roughness (AARH 125-250 serrated finish) are continuously monitored by laser CMM sensors to ensure zero assembly misalignment on site.
Full heat-treatment capability in-house including Normalizing, Annealing, Quenching, and Tempering. Computerized multi-zone temperature monitoring guarantees uniform grain refinement, preventing localized stress fractures in high-pressure oil & gas applications.
By maintaining a strategic standing stock of certified steel billets (ASTM A105, A350 LF2, A182 F304/316L), YUXIN mitigates raw material price volatility and guarantees rapid lead times—shipping standard SO flange orders within 7 to 15 days.
Compare mechanical parameters, pressure ratings, and structural advantages across standard forged flange configurations.
| Flange Type | Welding Connection | Pressure Class Range | Stress Concentration | Field Installation Complexity | Primary Industrial Application |
|---|---|---|---|---|---|
| Slip-On (SO) Flange | Double Fillet Weld (Internal & External) | Class 150 to Class 1500 / PN6 to PN100 | Moderate (1.5x pipe stress) | Low (Easy alignment, simple pipe cutting) | Chemical processing, water utilities, low-pressure steam, HVAC networks |
| Weld Neck (WN) Flange | Full Penetration Butt Weld | Class 150 to Class 2500 / PN6 to PN400 | Low (Smooth stress transition hub) | High (Requires precise beveling & alignment) | High-pressure oil & gas pipelines, critical chemical reactors, severe cyclic load |
| Blind (BL) Flange | Bolted Closure (No Weld) | Class 150 to Class 2500 / PN6 to PN400 | High at center disk under pressure | Moderate (Requires proper bolt torque sequence) | Pipeline end caps, pressure vessel inspection ports, maintenance isolation points |
| Socket Weld (SW) Flange | Single External Fillet Weld | Class 150 to Class 1500 (Small Bores) | Moderate-High (Thermal clearance gap needed) | Moderate (For small diameter pipes <= 2") | High-pressure hydraulic lines, instrumentation, small-bore chemical tubing |
| Lap Joint (LJ) Flange | Loose Flange over Stub End | Class 150 to Class 600 / PN6 to PN40 | Moderate | Very Low (Rotatable bolt holes for easy mating) | Corrosive fluid lines requiring exotic alloy stub ends with low-cost steel flanges |
| Material Specification | Material Classification | Tensile Strength (MPa) | Yield Strength (MPa) | Operating Temp Range | Key Service Capability |
|---|---|---|---|---|---|
| ASTM A105 | Forged Carbon Steel | ≥ 485 MPa | ≥ 250 MPa | -29°C to 425°C | General ambient and medium temperature industrial liquid/gas service |
| ASTM A350 LF2 (Cl. 1) | Low-Temp Carbon Steel | 485 - 655 MPa | ≥ 250 MPa | -46°C to 345°C | Cryogenic and low-temperature oilfield pipelines in arctic or gas chillers |
| ASTM A182 F304 / F304L | Austenitic Stainless Steel | ≥ 485 MPa (F304) / ≥ 415 (F304L) | ≥ 205 MPa / ≥ 170 MPa | :-196°C to 815°CFood processing, general nitric chemical pipelines, clean utility lines | |
| ASTM A182 F316 / F316L | Molybdenum Stainless Steel | ≥ 515 MPa (F316) / ≥ 485 (F316L) | ≥ 205 MPa / ≥ 170 MPa | -196°C to 870°C | Offshore marine environment, sulfuric acid handling, chlorides & sour gas |
| Duplex 2205 (F51 / UNS S31803) | Austenitic-Ferritic Duplex | ≥ 625 MPa | ≥ 450 MPa | -50°C to 300°C | High strength combined with extreme resistance to pitting & stress corrosion cracking |
Demonstrated performance across heavy industry, energy infrastructure, marine transport, and municipal processing facilities.
SO flanges are used extensively across storage tank farms, loading headers, and low-pressure hydrocarbon transport lines. Dual-fillet welding prevents joint vibration leakage while facilitating fast component maintenance during scheduled turnaround operations.
For chemical synthesis plants utilizing aggressive media, YUXIN supplies stainless steel (F316L) and Duplex SO flanges certified to NACE MR0175 / ISO 15156, providing long-term immunity against sulfide stress cracking (SSC) and chloride pitting.
Used in ballast water systems, fire main piping, and cooling water circuits on commercial vessels and offshore platforms. Available with hot-dip galvanizing or heavy epoxy coatings to resist marine salt spray corrosion.
Every flange leaving the YUXIN facility undergoes thorough quality verification to guarantee structural compliance with global engineering codes.
Executed per ASTM A388 to detect internal voids, forging bursts, or inclusions within the flange ring and hub wall prior to final machining.
Optical Emission Spectrometry (OES) verifies exact percentage ratios of C, Mn, Si, P, S, Cr, Ni, Mo to ensure chemistry matches raw material certificates.
Destructive tensile, yield, elongation, and Brinell hardness testing (HBW) performed per batch to confirm strength parameters.
Laser coordinate measuring machines verify flange bore tolerance (+1.5mm / -0mm), bolt circle diameters, face finish, and parallelism.
Expert guidance from YUXIN senior engineering directors on ordering, compliance, and installation best practices.
The core distinction lies in how the flange attaches to the pipe and how mechanical stress is distributed. A Weld Neck flange features a long tapered hub that is butt-welded to the pipe wall, providing a smooth transition of stress ideal for extreme pressures (Class 900 to 2500) and severe cyclic thermal loads. A Slip-On flange slides over the pipe diameter and is attached using two fillet welds (one internal, one external). While an SO flange has approximately 2/3 the calculated strength of a WN flange under internal pressure, it offers lower initial purchase costs, simplified pipe alignment, and lower installation labor cost in low-to-medium pressure applications (Class 150 to Class 600).
Shanxi Yuxin Casting & Forging Co., Ltd. manufactures Slip-On flanges conforming to ASME B16.5 (sizes 1/2" to 24", Class 150 to Class 1500), ASME B16.47 Series A & B (sizes 26" to 60"), EN 1092-1 Type 12 (PN6 to PN100), DIN 2527 / 2566, JIS B2220, and GOST 12820-80. We also produce custom non-standard SO flanges up to 3000 mm (120 inches) outer diameter according to client engineering drawings.
Standard engineering codes (including ASME B31.3 Process Piping Code) specify that Slip-On flanges must be welded both on the outside of the hub and on the inside of the flange face. Welding the inside prevents corrosive line fluids from leaking into the crevice between the pipe OD and the flange bore, which could otherwise lead to accelerated crevice corrosion or catastrophic thread-like joint failure under pressure surges.
Every shipment is accompanied by a full EN 10204 3.1 Mill Test Certificate (MTC) detailing steel heat numbers, chemical composition analysis, heat-treatment temperature logs, mechanical yield/tensile/impact results, and 100% NDT inspection records. Third-party inspection (EN 10204 3.2) by independent authorities such as TÜV, SGS, Lloyd's Register, or Bureau Veritas is available upon customer request.
All finished flanges undergo automated surface cleaning followed by the application of buyer-specified protective coatings: yellow/black anti-rust paint, clear rust-preventive varnish, hot-dip galvanizing, or specialized anti-corrosion oils. Sealing faces are protected with plastic caps, and items are packed securely inside ocean-worthy, fumigation-free ISPM-15 compliant plywood cases or steel-framed crates.
For standard carbon steel (ASTM A105) and stainless steel (F304/F316L) SO flanges in common sizes (1/2" to 12"), our typical factory lead time is 7 to 15 days due to our standing raw material stock. Custom forging sizes or specialized alloy grades take 20 to 35 days. We maintain a flexible MOQ policy, accommodating small trial orders and consolidated full-container stock shipments for global distributors.
Browse our complete catalog of industrial pipe joint solutions, specialized stub ends, and engineered custom forgings.
Direct factory pricing, comprehensive EN 10204 3.1 certification, and expert engineering assistance for your high-pressure piping projects.
