What is difference between Series A and B flanges?

ASME B 16.47 is an American standard that refers to large-diameter steel flanges. This standard also covers the requirements about flange gaskets, flange bolting, flange joints, etc. The standard covers the design of flanges from NPS 24 to NPS 60. With rating classifications 75, 150, 300, 400, 600, and 900, the standard ASME B 16.47 offers pressure-temperature ratings, tolerances, marking, dimensions, and measurement for pipe flanges. ASME B 16.47 standard has two series such as Series A and Series B flanges. The difference between these flanges are:

Characteristics: ASME B16 47 Series A flanges are much heavier, thicker, and more robust than Series B flanges with the same pressure rating and size. Hence, series A flanges can easily withstand extra external loading than the Series B flanges.

Required Fasteners: Fastener quality requirement for ASME B16.47 Series A flanges is less than Series A. Class 150 series A flange needs 28 bolts with the sizes of 1-1/ 4 inch diameter to install. The total number of fasteners for ASME B16.47 Series B flanges are higher than series A. For class 150 Series B flange needs 44 bolts with a diameter of 3/ 4 inches diameter to install. The smaller bolt circle width affects the movement of the flange after installing.
Types: Series A and Series B standards include blind flanges as well as weld neck flanges in raised face type (RF). But Series A illustrates ring type joint (RTJ) flanges with the different classes such as from Class 300 to Class 900.
Cost: The cost of ASME B16.47 Series A flanges is more than ASME B16.47 Series B flanges.
Use: Series A flanges are perfect for many piping end users for the new pipeline or connections. Series B flanges are perfect for refurbishment or replacement work and also for non-critical piping applications. In industry, Series A flanges are suitable for all complex applications, but Series B flanges are only suitable for easy applications.
Weight of Flange: ASME B16.47 Series A flanges are heavier, and hence they can so exert more extra weight on piping supports. The weight of ASME B16.47 Series B flanges is comparatively less and therefore cannot sustain in high load.
Pressure class 75: This unique pressure class is available in ASME B16.47 Series B flanges but not available in ASME B16.47 Series A flanges.
Dimensions: The dimension of Series A flanges is larger because bolt circle diameter, flange outer diameter, bolt diameter, flange thickness, etc., are larger. But Series A flanges are compact in dimension as compared to series A flanges.
Alternative designations: In the beginning, ASME B16.47 Series A carbon steel flanges were identified as MSS SP 44 flanges, and ASME B16.47 Series B flanges were recognized as API 605 flanges.

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What is difference between Series A and B flanges?

by Piping Mart time to read: 2 min