Here's a detailed breakdown of the differences between Series A and Series B flanges, covering characteristics, required fasteners, cost, use, weight, dimensions, and alternative designations:
| Sr. No | Parameter | ASME B16.47 Series A Flanges | ASME B16.47 Series B Flanges |
| 1 | Origin | Earlier Series A flanges were known as MSS SP 44 flanges. | These flanges were known as API 605 flanges. |
| 2 | Dimension | Flange Outer diameter, Bolt Circle Diameter, Flange Thickness, Bolt Diameter, etc. are larger for Series A Flanges for the same pressure rating class. | B16.47 Series B flanges are compact as compared to series A flanges. |
| 3 | Strength | ASME B16.47 Series A flanges are comparatively stronger. Hence, can handle more external loading before leakage. | Load bearing for the same pressure class is relatively less. |
| 4 | Fastener Requirement | The quality requirement is less but bigger size. For example, as seen in Fig. 1, a 30-inch class 150 series A flange needs 28 bolts of 1-1/4 inch diameter. | The quantity of fasteners is more. For example, a 30-inch class 150 Series B flange requires 44 bolts with a diameter of 3/4 inch. |
| 5 | Ring type joint Types | Available from Class 300 through Class 900 | Does not exist. |
| 6 | Pressure Class 75 | Not available for series A flanges | Available for Series B flanges |
| 7 | Flange Weight | The weight of ASME B16.47, series A flanges are more. So, they exert more load on piping supports. | Weight is comparatively less |
| 8 | Cost | More expensive. | cheaper. |
| 9 | Industry Use | More frequently used. Used for critical applications. | Less frequently used. Normally used for non-critical applications. |
Series A Flanges:
1. Characteristics:
- Pressure Rating: Higher pressure ratings compared to Series B.
- Dimensions: Larger overall dimensions, including outside diameters and bolt circle diameters.
- Face Types: Available with both raised face (RF) and ring-type joint (RTJ) face types.
2. Required Fasteners:
- Generally requires larger and stronger fasteners due to higher pressure ratings.
3. Cost:
- Typically higher cost due to larger size, higher pressure ratings, and availability of multiple face types.
4. Use:
- Suited for high-pressure applications such as oil and gas transmission pipelines, chemical processing, and power generation.
5. Weight:
- Heavier than Series B flanges due to larger dimensions and higher pressure ratings.
6. Dimensions:
- Larger overall dimensions to accommodate higher pressure requirements.
7. Alternative Designations:
- Common alternative designations include ANSI/ASME B16.47 Series A or ASME B16.5.
Series B Flanges:
1. Characteristics:
- Pressure Rating: Lower pressure ratings compared to Series A.
- Dimensions: Smaller overall dimensions, suitable for lower-pressure applications.
- Face Types: Typically available with ring-type joint (RTJ) face type.
2. Required Fasteners:
- Generally requires smaller and less robust fasteners compared to Series A.
3. Cost:
- Generally lower cost due to smaller size, lower pressure ratings, and simplified face type.
4. Use:
- Suited for lower-pressure applications where the lower cost is a consideration, such as water treatment plants, HVAC systems, and general industrial piping.
5. Weight:
- Lighter than Series A flanges due to smaller dimensions and lower pressure ratings.
6. Dimensions:
- Smaller overall dimensions, making them suitable for applications with space constraints.
7. Alternative Designations:
- Common alternative designations include ANSI/ASME B16.47 Series B or ASME B16.5.
In summary, Series A flanges are designed for higher-pressure applications, have larger dimensions, and come with multiple face types. They are suitable for critical applications where pressure integrity is crucial. On the other hand, Series B flanges are used in lower-pressure applications, are more cost-effective, and have smaller dimensions, making them suitable for less critical or space-constrained scenarios. The choice between Series A and Series B depends on the specific requirements of the piping system and the application's pressure and dimensional considerations.
let's consider an example of the difference between Series A and Series B flanges in the context of piping systems for oil and gas transmission:
Scenario: Oil and Gas Transmission Pipeline
Series A Flanges:
- Application: The pipeline is part of a high-pressure oil and gas transmission system, carrying crude oil or natural gas at high pressures.
- Pressure Rating: Series A flanges are chosen due to their higher pressure ratings, which are necessary to withstand the elevated pressures typical in oil and gas transmission pipelines. For example, Series A flanges may have a pressure rating of ANSI/ASME B16.47 Class 900 or higher.
- Dimensions: Series A flanges have larger dimensions to accommodate the higher pressure ratings. They typically have larger outside diameters, bolt circle diameters, and overall dimensions compared to Series B flanges.
- Face Types: Both raised face (RF) and ring-type joint (RTJ) face types are available for Series A flanges. The choice of face type depends on factors such as sealing requirements and system design.
- Example: In this scenario, Series A flanges with RTJ face types are selected for their superior sealing performance and ability to handle high pressures. These flanges are installed at critical points along the transmission pipeline, such as pump stations, compressor stations, and interconnection points with other pipelines.
Series B Flanges:
- Application: The pipeline is part of a lower-pressure section of the oil and gas transmission network, such as distribution lines or gathering lines.
- Pressure Rating: Series B flanges are suitable for applications where lower pressure ratings are acceptable. For example, Series B flanges may have a pressure rating of ANSI/ASME B16.47 Class 300 or lower.
- Dimensions: Series B flanges have smaller dimensions compared to Series A flanges, making them suitable for lower pressure applications where space constraints may be a consideration.
- Face Types: Series B flanges typically come with ring-type joint (RTJ) face types only. This face type provides a reliable seal for moderate pressure applications.
- Example: In this scenario, Series B flanges are selected for use in less critical sections of the transmission pipeline, such as distribution lines within a refinery or gathering lines in remote oil fields. These flanges help maintain the integrity of the pipeline while accommodating lower operating pressures and space constraints.
By considering the specific pressure requirements, dimensions, and application scenarios, engineers can select the appropriate Series A or Series B flanges to ensure the safe and efficient operation of oil and gas transmission pipelines.
