Are B16.47 Series A Flanges available in Slip-On Style?
The standard includes only Weld Necks and Blinds. For those cases where a Slip-On Style is needed, we can supply a 1″ long hub for these applications.
In the world of large-diameter piping, precision in standards compliance is the difference between a high-integrity system and a catastrophic mechanical failure. When specifying components for diameters exceeding 24 inches, engineers frequently ask: “Can I source an ASME B16.47 Series A Slip-On flange?”
The answer is No. ASME B16.47 Series A does not include a Slip-On flange configuration. Large Diameter pipe connections above 24” are commonly specified as B16.47 series A. This specification covers only weld neck style flanges and blinds. This specification was developed for use on pressure vessel fabrications where concerns where temperature and pressure influenced design.
For piping designers seeking the installation ease of a slip-on design for large-diameter applications, there are alternative standards that maintain dimensional compatibility with Series A bolting patterns. When a customer needs a slip-on style we can offer a 1” hub height, but cannot stamp as B16.47 Series A.
Under the current ASME B16.47 specification, Series A is designed for heavy-duty, high-integrity applications. The standard explicitly excludes Slip-On (SO) flanges. If a project specification mandates a “B16.47 Series A Slip-On,” the requisition is technically non-compliant with the ASME code.
The Engineered Alternative: The 1” Hub Series A Slip-On
Sumitec provides a practical, industry-recognized solution: the Class 125/150 Slip-On flange with a 1” Hub. Industrial piping users who need larger piping and not as concerned with higher pressures and temperature have been moving toward an alternate specification for 150 psi applications and Industry Standard Class 125/150 for Slip-On applications. These flanges have the same Outside Diameter and Bolt Pattern as B16.47 Series A with a Slip-On Bore. These flanges are a better design for industrial piping application with a design pressure rating of 150 psi.
Technical Background: Why Slip-On Is Not Included
Pressure Vessel Heritage
Series A flanges are characterized by a thicker flange ring and a larger bolt circle compared to Series B. These dimensions were engineered to withstand the external loads and high internal pressures typical of pressure vessels and critical transmission pipelines.
Stress Distribution and Design Philosophy
The primary reason for the exclusion of Slip-On styles in large diameters (24”–60”+) involves stress concentration at the hub.
Weld Neck Flanges: Utilize a tapered hub to transition stress from the flange ring to the pipe, making them superior for handling bending moments and thermal expansion.
Slip-On Flanges: Rely on two fillet welds (internal and external). In large diameters, the calculated stress at these welds under high pressure often exceeds the safety margins established by ASME.
Because Series A is the “heavy-duty” standard, the committee opted to limit the scope to configurations that provide maximum structural integrity.
Sumitec Slip-On Alternative: The Solution
When high-pressure Weld Neck flanges are overkill for a specific application, the large diameter slip-on flange becomes the logical choice for cost-efficiency.
Dimensional Interchangeability
The Sumitec Slip-On alternative is engineered to match the Series A bolting pattern. This means:
Identical Bolting: You can mate a Sumitec Slip-On directly to a Series A Weld Neck valve or pump.
Bore-Over-Pipe Design: The Slip-On slides over the OD of the pipe. This simplifies alignment and allows for easier “two-holing” during installation.
1” Hub vs. Ring Flange
Standard ring flanges can sometimes lack the rigidity required for larger spans. Sumitec’s 1” hub design provides additional reinforcement at the weld point, offering a more robust profile than a flat ring while maintaining a lower profile than a standard Weld Neck.
Dimensional Comparison: Decision-Making Data
Choosing between a compliant B16.47 Series A Weld Neck and an alternative Slip-On requires a comparison of physical footprints.
| Feature | B16.47 Series A (Weld Neck) | Sumitec Alternative (Slip-On) |
| Outer Diameter (OD) | Standardized (e.g., 32″ for 24″ Class 150) | Identical to Series A |
| Bolt Circle | Standardized | Identical to Series A |
| Thickness | Heavy (Designed for high pressure) | Generally Thinner (Class 125/150) |
| Attachment | Butt-Weld (Full penetration) | Double Fillet Weld |
| Hub Design | Long Tapered Hub | 1” Short Hub or Hubless |
Key Compatibility Note: While the bolting matches, the total length through the hub is significantly shorter on a Slip-On. Piping designers must account for this difference in their 3D models and spool drawings to ensure correct pipe lengths.
Application Guide: Choosing the Right Flange
To avoid a mistake in flange selection, use the following criteria:
Specify B16.47 Series A (Weld Neck/Blind) When:
The system operates at high pressures (Class 300 and above).
The media is hazardous, flammable, or highly corrosive.
The system is subject to significant thermal cycling or vibration.
Post-Weld Heat Treatment (PWHT) is required for the entire joint.
Specify Class 150 Slip-On (Series A Pattern) When:
The operating pressure is ≤ 150 psi (or 275 psi at ambient, depending on material).
The application involves non-critical media (water, air, non-sludge waste).
Project budgets require the 30-50% cost savings associated with slip-on labor and material.
Ease of installation in tight spaces is a priority.
Sumitec Supply Capabilities
As a specialized manufacturer of large-diameter solutions, Sumitec fills the gap where standard ASME codes stop.
Stock and Fabrication Range
Size Range: 24” – 105.5” and beyond.
Materials: Carbon Steel, Stainless Steel, and specialized alloys.
Customization: We specialize in the 1” hub fabrication, ensuring the flange meets the structural requirements of your specific pressure rating while maintaining the Series A footprint.
| Flange Thickness | Length Thru Hub | Hub at Base | |||||||
| Series A | Industry Std | Series A | Industry Std | Series A | Industry Std | RF Diameter | # Holes | Hole Size | Bolt Circle |
| 2.69 | 2.00 | 3.69 | 3.38 | 26.62 | 28.50 | 29.50 | 24 | 1.375 | 31.75 |
| 2.81 | 2.06 | 3.81 | 3.44 | 28.62 | 30.75 | 31.50 | 28 | 1.375 | 34 |
| 2.94 | 2.13 | 3.94 | 3.50 | 30.75 | 32.75 | 33.75 | 28 | 1.375 | 36 |
| 3.19 | 2.25 | 4.19 | 3.63 | 32.75 | 35.00 | 36.00 | 28 | 1.625 | 38.5 |
| 3.25 | 2.31 | 4.25 | 3.68 | 34.75 | 37.00 | 38.00 | 32 | 1.625 | 40.5 |
| 3.56 | 2.38 | 4.56 | 3.75 | 36.75 | 39.25 | 40.25 | 32 | 1.625 | 42.75 |
| 3.44 | 2.38 | 4.44 | 3.75 | 39.00 | 41.75 | 42.25 | 32 | 1.625 | 45.25 |
| 3.56 | 2.50 | 4.56 | 3.88 | 41.00 | 43.75 | 44.25 | 36 | 1.625 | 47.25 |
| 3.81 | 2.63 | 4.81 | 4.00 | 43.00 | 46.00 | 47.00 | 36 | 1.625 | 49.5 |
| 4.00 | 2.63 | 5.00 | 4.00 | 45.00 | 48.00 | 49.00 | 40 | 1.625 | 51.75 |
| 4.06 | 2.68 | 5.06 | 4.06 | 47.12 | 50.00 | 51.00 | 40 | 1.625 | 53.75 |
| 4.25 | 2.75 | 5.25 | 4.13 | 49.12 | 52.25 | 53.50 | 44 | 1.625 | 56 |
| 4.38 | 2.75 | 5.38 | 4.13 | 51.25 | 54.25 | 55.50 | 44 | 1.875 | 58.25 |
| 4.56 | 2.88 | 5.56 | 4.25 | 53.25 | 56.50 | 57.50 | 44 | 1.875 | 60.5 |
| 4.75 | 3.00 | 5.75 | 4.38 | 59.50 | 58.75 | 59.75 | 44 | 1.875 | 65 |
| 5.19 | 3.13 | 6.19 | 4.50 | 61.38 | 65.25 | 66.00 | 52 | 1.875 | 69.25 |
| 3.38 | 4.88 | 71.50 | 73.00 | 52 | 1.875 | 76 | |||
| 3.50 | 5.00 | 78.50 | 79.50 | 60 | 1.875 | 82.5 | |||
| 3.88 | 5.38 | 90.50 | 92.50 | 64 | 2.125 | 95.5 | |||
| 4.25 | 5.75 | 102.75 | 105.50 | 68 | 2.375 | 105.5 | |||
The added flange thickness on the Series A was designed so there would be no deflection as a result of post weld heat treatment of the vessel after fabrication. Series A Specification stops at 60″ pipe size.
Compliance and Quality Assurance
Every flange produced by Sumitec comes with a comprehensive documentation package, including: MTRs (Material Test Reports), dimensional reports, and certifications.
Request Quote: Engineering-Focused Support
Sourcing large-diameter flanges requires a partner who understands the nuances of ASME standards and the realities of field installation.
Whether you are in the Front-End Engineering Design stage or the procurement phase of a major infrastructure project, Sumitec provides the technical data and reliable manufacturing needed to keep your project on schedule and within code.
Contact our engineering team today for Detailed CAD drawings, dimensional cross-checks, and competitive pricing.
Email RFQs and Technical Inquiries to: sales@sumitec.com