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ASME B16.47 includes two series: Series A and Series B. Although both series belong to the same production standard, they differ in several ways.
Series A flanges are primarily used for manufacturing heavier, thicker, and stronger flanges. Series B flanges are more specifically designed for lighter, more compact designs with thinner walls. Flanges from the two series are generally not interchangeable.
The following is a comparison of these two series, focusing on dimensions, pressure ratings, materials, and types.
What is ASME B16.47?
ASME B16.47 is primarily used for manufacturing large-diameter steel pipe flanges, mostly NPS26 to NPS60 flanges.
The ASME B16.47 standard is commonly used in industrial piping systems because the production of large-diameter flanges is more stringent.
Both Series A and Series B in the ASME B16.47 standard are quite common. This standard flange includes welding flanges, blind flanges, and slip-on flanges.
What is ASME B16.47 Series A?
ASME B16.47 Series A flanges are heavier than ASME B16.47 Series B flanges. The Series A flange standard is related to MSS SP-44.
Compared to other standard flanges of the same size, Series A flanges have a larger outer diameter and relatively larger bolt holes. Therefore, they are more often used in the production of large-diameter flanges.
Of course, in engineering, the choice of flange should focus more on the standard, size, pressure rating, and compatibility with the pipeline.
What is ASME B16.47 Series B?
Compared to Series A flanges, ASME B16.47 Series B flanges have a smaller outer diameter and are more compact. They are also lighter. Series B is related to the API 605 series.
Series B flanges are also quite common in industrial applications. They can be used in applications where weight is not a major concern. This series of flanges is lighter, making them easier to transport and install. Of course, Series B flanges cannot completely replace Series A flanges.
What is the Main Flange Series A and B Difference?
While Series A and B have the same nominal pipe size and pressure rating, their specific dimensional standards differ. For example, the outer diameter of Series B flanges of the same specification is smaller than that of Series A flanges.
Below is a comparison of Series A and B:
| Comparison Point | Series A Flange | Series B Flange |
|---|---|---|
| General design | Heavier and more robust | More compact and lighter |
| Outside diameter | Usually larger | Usually smaller |
| Bolt circle | Usually larger | Usually smaller |
| Bolt size | Usually larger | Usually smaller |
| Number of bolts | Often fewer than Series B | Often more than Series A |
| Weight | Higher | Lower |
| Installation space | Requires more space | More compact |
| Interchangeability | Not normally interchangeable with Series B | Not normally interchangeable with Series A |
The differences between these two series can be compared in several aspects, including outer diameter, bolt hole diameter, number of bolt holes, and flange thickness.
Are Series A and Series B Flanges Interchangeable?
In most cases, flanges from the two series are not interchangeable.
Although both series have the same NPS size and pressure rating, their outer diameter and bolt hole diameter differ. Therefore, the compatible pipe fitting diameters will also differ. If flanges from two different series are connected, the number of bolt holes will be inconsistent.
Therefore, to better understand the differences between the two series, please refer to the following table:
| Item to Confirm | Why It Matters |
|---|---|
| NPS size | Confirms nominal pipe size |
| Pressure class | Confirms pressure-temperature rating category |
| Series A or Series B | Confirms dimensional series |
| Bolt circle diameter | Prevents bolt mismatch |
| Bolt hole quantity and diameter | Ensures installation compatibility |
| Flange facing | Matches gasket and sealing design |
| Mating flange standard | Prevents site rework |
The buyer should specifically determine which series under the ASME B16.47 standard they require.
Which Flange Is Stronger: Series A or Series B?
Series A flanges are heavier and thicker than Series B flanges, and therefore generally considered more robust.
This is because the outer diameter and wall thickness of Series A flanges are thicker than those of the same model in other series.
Which Flange Is More Cost-Effective?
Cost-effectiveness involves more than just the purchase price; maintenance costs must also be considered.
From a cost-effectiveness perspective alone: Series A flanges are lighter and more compact, thus lower in price. Series B flanges have larger outer diameters and thicker walls, resulting in higher costs for materials, transportation, etc.
However, the actual application must be considered when choosing a flange series that best suits the project, rather than solely focusing on price.
Carbon Steel vs Stainless Steel ASME B16.47 Flanges
Carbon steel and stainless steel are both common raw materials in industrial systems.
Carbon steel is more widely used due to its lower price, but its strength and mechanical properties are quite good. Therefore, carbon steel is generally more commonly used in projects.
A more significant characteristic of stainless steel is its corrosion resistance. Therefore, stainless steel is often used in projects requiring corrosion and rust resistance, such as in the pharmaceutical, chemical, and some underwater projects.
How Do Series A and Series B Affect Bolts, Gaskets, and Installation?
The bolts and gaskets required differ between series.
Series A flanges use larger diameter bolts and correspondingly larger gaskets. Therefore, different series standards correspond to different gasket standards.
Series A vs Series B for Distributors and Construction Buyers
Distributors may prioritize commonly used sizes and specifications. They also value both quality and price.
Construction buyers, on the other hand, may focus more on quality and require manufacturers to offer customized or less commonly used large-diameter flanges.
In short, besides quality and price, both groups also pay close attention to inspection reports, test reports, and shipping details.
How to Choose Between ASME B16.47 Series A and Series B Flanges
Below is a list of key points to consider when choosing between Series A and Series B:
| Selection Factor | What Buyers Should Check |
|---|---|
| Project specification | Does it require Series A or Series B? |
| Existing pipeline | What standard is the mating flange? |
| Size and class | Confirm NPS and pressure class |
| Flange type | Weld neck, blind, or other required type |
| Material | Carbon steel or stainless steel |
| Dimensions | OD, thickness, bolt circle, bolt holes |
| Facing | Raised face, flat face, or RTJ if required |
| Gasket | Confirm matching gasket dimensions |
| Bolts | Confirm bolt size, quantity, and material |
| Documents | Drawing, MTC, inspection report |
| Packing | Suitable for export and site handling |
Summary
The differences and similarities between Series A and Series B in ASME B16.47 have been described above. The main differences are in outer diameter, wall thickness, number of bolt holes, etc. Customers need to select the most suitable flange based on the requirements of their project.
