Direct factory supply from Shanxi Yuxin Casting & Forging Co., Ltd. Fully tested to ASME, EN, DIN, and JIS standard parameters.
In modern international fluid handling, petrochemical transport, and power generation infrastructure, the Slip-On Flange (SO Flange) remains one of the most widely specified piping connection components worldwide. Designed with an inner diameter slightly larger than the outer diameter of the matching pipe, a Slip-On Flange slides directly over the pipe end and is secured via double fillet welding—one performed on the outer hub shoulder and one on the inside flange face.
The global market demand for Slip-On Pipe Flanges has expanded significantly, driven by ongoing modernization in municipal water treatment, HVAC distribution headers, low-to-medium pressure hydrocarbon processing, and shipbuilding modularization. Commercial buyers, EPC contractors, and stockist distributors favor Slip-On Flanges due to their lower initial material cost compared to Weld Neck (WN) flanges, ease of alignment during field installation, and reduced requirement for high-precision pipe end preparation.
From a mechanical design perspective, choosing the optimal flange type requires balancing structural integrity, fatigue performance, installation labor costs, and thermal expansion cycles. A fundamental distinction of Slip-On Flanges lies in their dual-fillet weld attachment mechanism:
The pipe is inserted into the flange bore until the pipe end stops approximately 1.6 mm (1/16 in) short of the flange face. This gap prevents thermal stress damage to the gasket face during internal fillet welding, while the external fillet weld transfers structural bending moments.
Under internal hydrostatic pressure, a Slip-On flange connection exhibits a calculated strength approximately one-third (1/3) that of a corresponding Weld Neck flange, and its fatigue lifecycle under cyclic bending is roughly one-third that of a full-penetration butt-welded joint.
Despite lower fatigue resistance in high-vibration environments, Slip-On Flanges offer superior spatial flexibility during assembly. Beveling of pipe ends is not required, drastically cutting field fabrication costs and pipeline assembly downtime.
| Flange Type | Primary Attachment Method | Relative Calculated Strength | Fatigue Resistance | Pipe End Preparation | Ideal Application Domain |
|---|---|---|---|---|---|
| Slip-On Flange (SO) | Internal & External Fillet Welds | ~1/3 of Weld Neck | Moderate | Square cut, no bevel needed | Class 150 - 600, low/med pressure, HVAC, utility lines |
| Weld Neck Flange (WN) | Full Penetration Butt Weld | 1.0 (Baseline Standard) | High (Superior) | V-groove bevel required | Class 150 - 2500, extreme cyclic stress, high temp/pressure |
| Socket Weld Flange (SW) | Single External Fillet Weld | Equal to SO Flange | Moderate to High | Square cut + 1.6mm bottom clearance | Small bore lines (≤ NPS 2), high pressure instrument tubing |
| Lap Joint Flange (LJ) | Used with Stub End (No Direct Weld) | Varies (Similar to SO) | Low to Moderate | Square cut to Stub End | Corrosive systems requiring frequent dismantle & inspection |
China’s Shanxi Province, specifically Dingxiang County, is globally recognized as the undisputed center of precision forging. As an established industry leader operating since 1992, Shanxi Yuxin Casting & Forging Co., Ltd. exemplifies the competitive advantages of the Chinese industrial ecosystem. By integrating raw material billet sourcing, closed-die forging, automated thermal treatment, high-speed CNC machining, and non-destructive examination (NDE) under one 10,000-ton annual capacity manufacturing site, Yuxin provides global buyers with an unparalleled cost-to-quality ratio.
Direct partnerships with tier-1 steel mills enable fully traceable carbon steel (ASTM A105, Q235B), low-temperature alloy steel (ASTM A350 LF2), and stainless/duplex billets (ASTM A182 F304/F316L, F51) with verified chemical purity and fine-grain microstructures.
Multi-axis CNC turning centers ensure concentricity tolerances within ±0.1mm. Raised Face (RF) serrations are strictly controlled between 125–250 µin AARH (3.2–6.3 µm Ra) per ASME B16.5 standards to guarantee zero-leakage gasket seating.
In-house computer-controlled heat-treatment furnaces perform normalizing, tempering, and solution annealing to optimize tensile strength, yield stress, and Charpy V-notch impact toughness (down to -46°C for low-temperature service).
Shanxi Yuxin manufactures Slip-On Flanges conforming strictly to major international piping codes. Whether procuring for North American ASME projects or European EN 1092-1 plant builds, our products adhere to exacting dimensional and metallurgical boundaries.
| Standard System | Flange Designation | Pressure Class / PN Rating | Size Range | Facing Types Available |
|---|---|---|---|---|
| ASME B16.5 | Hubbed Slip-On (SO) | Class 150, 300, 600, 900, 1500 | 1/2" to 24" (DN15 - DN600) | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| ASME B16.47 Ser. A/B | Large Diameter Slip-On | Class 75, 150, 300, 600 | 26" to 60" (DN650 - DN1500) | RF, FF |
| EN 1092-1 | Type 12 (Hubbed Slip-On) / Type 01 (Plate) | PN6, PN10, PN16, PN25, PN40, PN63 | DN10 to DN2000 | Type A (Flat), Type B1/B2 (Raised), Type C/D (Tongue/Groove) |
| DIN Standards | DIN 2573, 2576, 2502, 2503 | PN6 to PN40 | DN10 to DN1000 | Form C, Form D, Form E |
| JIS B2220 | SOH (Slip-On Hubbed), SOP (Slip-On Plate) | 5K, 10K, 16K, 20K, 30K | 10A to 1500A | RF, FF |
Slip-On Flanges engineered by Shanxi Yuxin are deployed across diverse global infrastructure environments. Their adaptability makes them the preferred connection choice in numerous specialized operational settings:
In regional seawater desalination plants and refinery storage manifold networks across the GCC region, ASME B16.5 Class 150/300 ASTM A105N Slip-On Flanges handle high volumes of low-to-medium pressure brackish water and treated hydrocarbons with maximum cost efficiency.
Across EU municipal district heating systems, EN 1092-1 Type 12 PN16/PN25 P250GH forged Slip-On flanges are widely integrated into compact boiler skids where limited axial space makes socket or slip fitting faster than traditional butt welding.
US and Latin American industrial OEMs manufacturing air separation units, lube-oil skids, and HVAC pump headers rely on YUXIN's ASTM A182 F304L/F316L stainless slip-on flanges for rapid positioning and zero corrosion contamination in clean utility systems.
Procuring forged flanges for high-consequence engineering projects requires stringent verification of material microstructures and mechanical limits. Shanxi Yuxin implements a complete Quality Assurance Framework compliant with European Pressure Equipment Directive (PED 2014/68/EU) and AD 2000-Merkblatt W0 standards.
Every shipment is accompanied by an inspection certificate detailing exact heat number correlation, chemical composition analysis (Carbon, Manganese, Silicon, Phosphorus, Sulfur, Chromium, Nickel, Molybdenum), and tensile/yield stress test results. Independent 3.2 witnessing (TÜV, SGS, BV, Lloyd's) is routinely arranged.
Forged blanks undergo 100% Ultrasonic Testing (UT) per ASTM A388 to detect internal voids, shrink holes, or inclusions. Magnetic Particle Inspection (MT) and Liquid Penetrant Testing (PT) are applied to critical flange face regions to guarantee surface perfection.
To prevent transit corrosion during transoceanic shipping, flanges receive black rust-preventive paint, yellow anti-rust varnish, transparent oil coating, or hot-dip galvanizing per ASTM A123. Bores are protected with plastic caps and packaged in ISPM-15 compliant fumigation-free plywood crates.
The industrial flange manufacturing sector is undergoing rapid technological transformation. Shanxi Yuxin leads this evolution by embedding modern production methodologies across our manufacturing workflows:
Integrating AI-monitored tool wear sensors into high-speed CNC lathes allows real-time dynamic calibration of flange facing dimensions, achieving sub-micron repeatabilities and eliminating human error in serration pitch depth.
Finite Element Analysis (FEA) thermal simulation modeling optimizes heating ramp rates in our billet preheating furnaces, reducing natural gas consumption by 18% while guaranteeing uniform grain refinement throughout the forge body.
In alignment with global decarbonization goals (CBAM compliance), YUXIN prioritizes scrap-recycled electric arc furnace (EAF) steel billets, providing international EPC clients with verifiable low-carbon product lifecycles.
Direct technical answers addressing the key intent queries of piping designers and global procurement heads.
A Slip-On (SO) flange slides over the pipe and is attached using two fillet welds (one internal near the face, one external on the hub). A Weld Neck (WN) flange features a long tapered hub that is butt-welded directly to the pipe end. Weld Neck flanges offer superior fatigue resistance and are intended for high-pressure, severe cyclic loading or extreme temperature conditions, whereas Slip-On flanges are more cost-effective and easier to align in low-to-medium pressure installations.
While ASME B16.5 includes dimensional standards for Slip-On flanges up to Class 1500 in smaller sizes (NPS 1/2 to 2-1/2"), industrial piping codes (such as ASME B31.3) restrict or prohibit their use in severe cyclic conditions or high pressure classes for larger pipe sizes due to the stress concentration at the fillet welds. For Class 900 and above, Weld Neck flanges are strongly recommended.
Setting the pipe back by approximately 1.6 mm prevents the inner fillet weld from damaging or overlapping onto the critical gasket contact face. It also alleviates thermal expansion stresses during the welding process, protecting the integrity of the flange face serration finish.
All shipments include standard EN 10204 3.1 Inspection Certificates containing complete heat heat-treatment logs, chemical melt analysis, tensile strength, yield point, elongation, and impact toughness values. Third-party inspection certificates (EN 10204 3.2) witnessed by agencies such as SGS, TÜV, or Bureau Veritas are available upon request.
EN 1092-1 Type 12 refers specifically to a Hubbed Slip-On Flange for welding, featuring a forged hub shoulder that helps distribute mechanical bending stresses. EN 1092-1 Type 01 refers to a Flat Plate Flange without a hub. Type 12 provides superior structural rigidity under elevated pressure PN ratings compared to Type 01.
For standard carbon steel sizes (ASME B16.5 1/2" to 24", Class 150/300) maintained as forged blanks in stock, machining and shipment require 7 to 15 days. Custom forged-to-order non-standard flanges or special alloy grades typically require 20 to 35 days. Flexible MOQ options are provided to support trial orders and distributor replenishment.
Full range of forged steel flanges, stub ends, threaded fittings, and specialized heat exchanger tube sheets.
