What’s the Difference Between ASME B16.47 Series A and Series B Flanges?

ASME B16.47 is a US standard that defines large-diameter, steel flanges ranging from NPS 26-60 in size. They are commonly used for making pipeline, valve, and pump connections in heavy-duty applications in the oil and gas, chemical and petrochemical processing, nuclear and other power, water treatment, and pulp and paper industries.

The ASME B16.47 flanges are further divided into two series: Series A and Series B. They are generally not interchangeable and have several differences in dimensions, bolt size and quantity for fastening, pressure-temperature ratings, and other characteristics. Series B is a carryover from API 605 and Series A from MSS SP44, thus creating a more uniform industry standard through ASME B16.47.

It’s important to note there are multiple types and sizes of ASME-certified flanges, including ASME B16.5, which covers flanges up to size NPS 24. Here, we’ll look at the types of ASME B16.47 Series A and B flanges and how they differ from each other.

Breaking Down the Differences Between ASME B16.47 Series A Flanges and Series B Flanges

These flanges are available in three basic configurations:

Raised face: Raised protrusion inside the bolt ring, which concentrates pressure in that area to create a tight seal

Flat or blind face: Flat, smooth ring used with soft or semi-metallic gaskets

Ring-type joint (RTJ): Flat ring that includes a groove on the surface used with a hard metallic gasket to make a tight seal

Both Series A and B flanges come in these three configurations; however, ASME only defines RTJ dimensions for flanges in sizes NPS 26 through NPS 36 for pressure-temperature classes 300, 400, 600, and 900.

Series A and B flanges are not interchangeable; therefore, it’s important to understand how they differ, as this impacts where and how they can be used.

Physical Attributes

These flanges are available in a range of sizes that are compatible with a range of standard pipe sizes from NPS 26-60 (depending on pressure-temperature class rating). Series A flanges are heavier and thicker than Series B flanges. They also have a larger bolt circle and use larger bolts. Series B flanges are lighter and thinner with a smaller bolt circle, using smaller bolts.

Pressure-Temperature Ratings

ANSI and ASME standards define maximum pressure classes for flanges. These classes define the maximum pressure the flange can withstand at a given temperature, and they vary depending on the dimensions, NPS, and other characteristics of the flange. Various ASME B16.47 Series A and B flanges are specified for classes 150, 300, 400, 600, and 900. In addition, Series B flanges are available for class 75 as well.

Strength and Load Handling

The increased material weight and thickness of Series A flanges make them stronger and able to bear higher loads than Series B flanges. As for Series B flanges, because they are smaller and made of thinner steel than Series A flanges, these have lower load strength.

Fasteners

Series A flanges use fewer bolts because they are larger than those used for Series B flanges. Accordingly, Series B flanges utilize more bolts because they are smaller than those used for Series A flanges.

Cost

Series A flanges are typically more expensive due to their higher steel content and weight (i.e., higher transportation expenses). Because they are smaller and lighter, Series B flanges typically cost less to manufacture and transport.

Uses and Compatibility

Series A and B flanges are commonly used in pipeline systems and to make secure connections with valves and pipes in oil and gas pumping, chemical processing, power generation, water treatment, and other industrial applications.

Series A flanges are not interchangeable with Series B flanges. Equipment that requires Series A flanges is not compatible with Series B flanges, and vice versa. This is due to differences in dimensions, bolt size and patterns, and pressure-temperature ratings.

ASME Series A and B Flanges from Coastal Flange

For over 100 years, Coastal Flange has been a trusted manufacturer and distributor of pipe flanges in sizes from 12 in. through 200 in. OD. We are located in Jersey Village, with convenient, easy access to rail, truck, air, and water transportation for quick, reliable delivery.