Stainless Steel Socket Weld Flanges
High-quality stainless steel socket weld flanges are a specialty of Sunhy, a leading manufacturer and supplier. Our products are engineered for small-diameter piping systems (typically DN50/NPS 2 and below) operating under high pressure, high temperature, and stringent corrosion resistance requirements.
We specialize in SS316/L and SS304/L grades, manufactured in strict accordance with ASME B16.5 standards. The socket weld design (fillet weld) provides greater structural strength and superior leak-proof performance compared to slip-on flanges. This makes them the ideal choice for chemical, pharmaceutical, food processing, and marine engineering applications.
Types of Socket Weld Flanges We Supply
Stainless Steel Flanges
By Design Type
By Standard & Class
Advanced Materials
304/316 Stainless Steel ISO Socket weld flange
High Quality Socket Weld Flange
- Materials: All flanges are forged from premium SS316/L (for maximum corrosion resistance) and SS304/L (for excellent general-purpose use).
- Standards: We manufacture in strict accordance with ASME B16.5 for dimensions and ASTM A182 for material specifications.
- Quality Assurance: We provide full Material Test Reports (MTRs) and conduct Positive Material Identification (PMI) and 100% dimensional inspections to guarantee chemical composition and tolerance.
| Specification | Details |
|---|---|
| Material Grades | Stainless Steel (SS316/L, SS304/L, F321, F347) |
| Size Range | NPS 1/2″ to NPS 4″ (DN15 to DN100) (Most common: 1/2″ to 2″) |
| Pressure Class | Class 150, 300, 600, 900, 1500 (Note: Class 2500 available by request) |
| Face Type | Raised Face (RF), Flat Face (FF), Ring-Type Joint (RTJ) |
| Applicable Standards | ASME B16.5, ASTM A182, ASME B16.34 |
Your Factory-Direct Wholesale Program
Maximize your project budget by sourcing directly from the factory. Our wholesale program is designed for B2B clients who demand quality and value. We maintain a comprehensive inventory of standard stainless steel socket weld flanges, enabling us to provide fast, reliable global shipping to meet your project timelines.
Not sure which bore schedule matches your piping? Avoid common sizing errors by reviewing our [Engineer’s Guide: How to Order Socket Weld Flanges] before you request a quote.
What is a Socket Weld Flange ？
A Socket Weld Flange (SWF) is a high-pressure pipe flange designed with a “socket” or recessed shoulder. A pipe is inserted into this socket and then secured with an external fillet weld. This design offers superior structural strength and leak integrity over Slip-On flanges, making it ideal for small-bore piping systems (NPS 2″ and smaller).
Socket Weld Flanges (SWF) Specifications
Standard Compliance
The dimensions listed below are based on ASME B16.5 requirements for socket weld flanges. These specifications support dimensional interchangeability in ASME-based piping systems when used with the correct piping class, facing type, and material requirements.
Material & Scope
These dimensions apply to our forged stainless steel socket weld flanges, commonly supplied in SS304/304L and SS316/316L (typical forging material specification: ASTM A182, subject to purchase order and project requirements).
- Design: Socket Weld (SW) flange configuration for small-bore welded piping systems.
- Pressure Classes: Commonly supplied in ASME Class 150 through Class 600 (other classes subject to project requirements and availability).
- Service Fit: Frequently used in small-bore systems where compact joints and repeatable fit-up are important.
Dimensional Reference
Refer to the cross-section diagram to identify key dimensions:
- OD: Outside Diameter
- BC: Bolt Circle Diameter
- ID: Inner Diameter / Bore reference (as specified)
Note: Always confirm that the flange bore and socket dimensions match the specified pipe size and schedule before installation to prevent fit-up issues, flow restriction, or improper weld geometry.
Socket Weld Flange (SW) Dimensions
Unit: Millimeters (mm)ASME B16.5 Class 150 SW (Small Bore)
| NPS (Size) |
Outside Dia (O) (mm) |
Hub Dia (X) (Base of Hub) |
Bolt Circle (BC) (mm) |
Holes (Qty) |
Bolt Size (Inch) |
|---|---|---|---|---|---|
| 1/2" | 88.9 | 30.2 | 60.5 | 4 | 1/2" |
| 3/4" | 98.6 | 38.1 | 69.9 | 4 | 1/2" |
| 1" | 108.0 | 49.3 | 79.2 | 4 | 1/2" |
| 1-1/4" | 117.3 | 58.7 | 88.9 | 4 | 1/2" |
| 1-1/2" | 127.0 | 65.0 | 98.6 | 4 | 1/2" |
| 2" | 152.4 | 77.7 | 120.7 | 4 | 5/8" |
| 2-1/2" | 177.8 | 90.4 | 139.7 | 4 | 5/8" |
| 3" | 190.5 | 108.0 | 152.4 | 4 | 5/8" |
ASME B16.5 Class 300 SW
| NPS (Size) |
Outside Dia (O) (mm) |
Hub Dia (X) (Base of Hub) |
Bolt Circle (BC) (mm) |
Holes (Qty) |
Bolt Size (Inch) |
|---|---|---|---|---|---|
| 1/2" | 95.3 | 38.1 | 66.5 | 4 | 1/2" |
| 3/4" | 117.3 | 47.8 | 82.6 | 4 | 5/8" |
| 1" | 124.0 | 53.8 | 88.9 | 4 | 5/8" |
| 1-1/4" | 133.4 | 63.5 | 98.6 | 4 | 5/8" |
| 1-1/2" | 155.4 | 69.9 | 114.3 | 4 | 3/4" |
| 2" | 165.1 | 84.1 | 127.0 | 8 | 5/8" |
| 2-1/2" | 190.5 | 100.1 | 149.4 | 8 | 3/4" |
| 3" | 209.6 | 117.3 | 168.1 | 8 | 3/4" |
ASME B16.5 Class 600 SW
| NPS (Size) |
Outside Dia (O) (mm) |
Hub Dia (X) (Base of Hub) |
Bolt Circle (BC) (mm) |
Holes (Qty) |
Bolt Size (Inch) |
|---|---|---|---|---|---|
| 1/2" | 95.3 | 38.1 | 66.5 | 4 | 1/2" |
| 3/4" | 117.3 | 47.8 | 82.6 | 4 | 5/8" |
| 1" | 124.0 | 53.8 | 88.9 | 4 | 5/8" |
| 1-1/2" | 155.4 | 69.9 | 114.3 | 4 | 3/4" |
| 2" | 165.1 | 84.1 | 127.0 | 8 | 5/8" |
| 3" | 209.6 | 117.3 | 168.1 | 8 | 3/4" |
High Pressure Socket Weld Use
In practical engineering, socket weld flanges are generally limited to Class 600 and sizes up to NPS 3 (DN80). For Class 900 / 1500 / 2500 service, Weld Neck flanges are typically used due to better performance under cyclic loads and thermal stress.
Looking for Sizes > 3 Inch?
Socket Weld flanges are typically limited to NPS 3 (DN80) and smaller
due to stress concentration at the socket weld in larger pipe sizes.
For larger diameters (4" - 24"), we recommend using
Slip On (SO) or Weld Neck (WN) flanges.
Applications for Stainless Steel Socket Weld Flanges
Socket weld (SW) flanges are commonly specified for small-bore piping systems where compact welded joints and repeatable fit-up are required. In stainless grades such as SS304L and SS316L, they are often used where corrosion resistance is also required—subject to piping class rules, service chemistry, and fabrication controls.
- Chemical Processing & Petrochemical: Small-diameter service lines where compact welded joints are required and corrosion resistance is important. Material grade selection (e.g., SS316L) should match the actual chemical environment and chloride/sulfur exposure.
- Pharmaceutical & Food Processing Utilities: High-pressure utility lines (for example, project-approved clean utility services) where stainless corrosion resistance and compact small-bore welded joints are needed. Final suitability depends on hygiene/service requirements and owner specifications.
- Offshore & Marine (Oil & Gas): Instrumentation and hydraulic control lines may use SS316L socket weld flanges where corrosion resistance is required; vibration/fatigue control and support design remain critical.
- Power Generation: Auxiliary steam and high-pressure water service lines where project specifications allow socket weld flanges and require durable small-bore welded joints.
Technical Limitation: Crevice / Corrosion Considerations
Engineers should note that socket weld joints include a stand-off region that can create a crevice condition. In aggressive wet services, deposit-forming services, or some high-purity applications, this area may trap fluid and increase corrosion risk. For these services, the piping class may favor alternative joint types (for example, a butt-welded design such as a weld neck flange) depending on the service and specification.
Welding Best Practices for Stainless Steel SW Flanges
Welding stainless steel socket weld flanges requires controlled procedures to preserve corrosion resistance and joint reliability. Improper heat input, poor cleaning, or incorrect fit-up can reduce fatigue life and increase corrosion risk.
- External fillet weld is the standard welded joint: In typical socket weld flange construction, the required weld is the external fillet weld between the pipe OD and flange socket/hub region. Additional internal seal welding is not typical unless explicitly required by the project specification.
- Stand-off (installation gap) must follow code/spec/WPS: Many project procedures and code-based practices require a small stand-off (commonly 1.6 mm / 1/16 in.) after full insertion to accommodate welding shrinkage and thermal expansion effects. Always follow the applicable piping code, project specification, and qualified WPS.
- Use compatible filler metal: Filler metal should match or exceed the base material and service requirements (for example, ER316L for many SS316L applications and ER308L for many SS304L applications), subject to WPS and engineering approval.
- Control heat input (GTAW/TIG commonly used): Stainless steel is sensitive to excessive heat input. Use a qualified welding procedure with controlled heat input and appropriate interpass temperature control to reduce sensitization risk and preserve corrosion resistance.
- Cleaning is critical: Thoroughly clean and degrease the flange socket and pipe end before welding. Use suitable cleaning materials and avoid contamination that can damage the passive layer or create corrosion initiation points.
- Post-weld verification: Perform visual inspection after welding. For critical services, leak/hydrostatic testing and additional inspection methods should follow the project procedure and code requirements.
Need a comparison before selecting SW vs SO? Read our Socket Weld Flange vs Slip On Flange comparison guide for installation differences, vibration/fatigue considerations, and common leakage causes.
FAQ
What is a Stainless Steel Socket Weld Flange?
A Stainless Steel Socket Weld Flange combines the high-strength socket weld design with the advanced corrosion resistance of grades like SS316L or SS304L. This makes it the ideal choice for small-bore, high-pressure piping systems used in corrosive environments, such as chemical processing, pharmaceutical, and marine applications where both strength and integrity are critical.
do socket weld flanges have a schedule
No, socket weld flanges do not have a “Schedule.” Flanges are rated by Pressure Class (e.g., Class 150, 600, 1500).
However, the bore of the flange is manufactured to match a specific pipe schedule (e.g., SCH 40, SCH 80, SCH 160) to ensure a correct, tight fit for welding. You must specify the pipe schedule when ordering.
how to order socket weld flanges
To order the correct stainless steel socket weld flanges, please provide your supplier with these 6 key specifications for an accurate, factory-direct quote:
Nominal Pipe Size (NPS): e.g., 1.5″ or DN40
Pressure Class: e.g., Class 600, 900, or 1500
Pipe Schedule (for Bore): The schedule of the matching pipe (e.g., SCH 80)
Material Grade: e.g., SS316L or SS304L
Flange Face Type: e.g., Raised Face (RF)
Required Standards: e.g., ASME B16.5