Difference between ASME B 16.47 Series A and Series B Flanges

ASME B 16.47 is an American standard for large diameter steel flanges. This standard covers the design of flanges from NPS 26 to NPS 60. For lower sizes i.e, up to NPS 24, ASME B 16.5 has to be referred. ASME B 16.47 provides pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges with rating class designations 75, 150, 300, 400, 600, and 900. The Standard also includes the requirements and recommendations regarding flange bolting, flange gaskets, and flange joints.

What is ASME B 16.47 Flange Series?

The ASME B 16.47 standard provides the use of two types of flange series.

  • Series A flanges and
  • Series B flanges.

Series A specifies flange dimensions for general use flanges whereas Series B specifies flange dimensions for compact flanges. Series A flanges have larger bolt circle diameters than Series B flanges.

This is to be noted that Series A and Series B flanges are not interchangeable. So, the user must take care of the compatibility issues that may arise by mistake. In most of the cases, flanged valves, equipment bolted between flanges, and flanged equipment are compatible with only one series of these flanges.

Difference between ASME B 16.47 Series A and Series B Flanges

The following table provides the major differences between ASME B 16.47 Series A and Series B flanges.

Sr. NoParameterASME B 16.47 Series A FlangesASME B 16.47 Series B Flanges
1OriginEarlier Series A flanges were known as MSS SP 44 flanges.This flanges were known as API 605 flanges.
2DimensionFlange Outer diameter, Bolt Circle Diameter, Flange Thickness, Bolt Diameter, etc. are larger for Series A Flanges for same pressure rating class.This flanges are compact as compared to series A flanges.
3StrengthStronger. Hence, can handle more external loading before leakage.Load bearing for the same pressure class is relatively less.
4Fastener RequirementQuality requirement is less but bigger size. For example as seen from Fig. 1, 30 inch class 150 series A flange needs 28 bolts of 1-1/4 inch diameter.Quantity of fasteners is more. For example, 30 inch class 150 Series B flange requires 44 bolts with diameter 3/4 inch.
5Ring type joint TypesAvailable from Class 300 through Class 900Does not exist.
6Pressure Class 75Not available for series A flangesAvailable for Series B flanges
7Flange WeightMore flange weight so exerts more load on piping supports.Weight is comparatively less
8CostMore expensive.cheaper.
9Industry UseMore frequently used. Used for critical applications.Less frequently used. Normally used for non-critical applications.
ASME B 16.47 Series A vs Series B

Dimensional Comparison for ASME B 16.47 Series A and Series B Flanges

Refer to Fig. 1 which shows the comparative dimensions for a 30″ (150 class) Series A and Series B ASME B 16.47 flanges.

ASME B 16.47 Series A vs Series B Flange Dimensions
Fig. 1: ASME B 16.47 Series A vs Series B Flange Dimensions

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Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

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