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



ASME B16.47 Large Diameter Steel Flange Standard

In November of 1980, Subcommittee C of the American Society of Mechanical Engineers (ASME) B16 began work on the B16.47 Large Diameter Steel Flange Standard to standardize dimensions, tolerances, markings, and materials for Nominal Pipe Sizes 26” to 60”. Prior to this in July of 1952, MSS-SP44 covered 12” thru 60” Nominal Pipe Sizes (NPS), in 150# to 900# pressure ratings in raised face (RF), flat faced (FF),and ring type joint (RTJ) facing. The initial draft was developed in December of 1982, and went thru several adjustments before being approved and published in 1990 as Series A (Duplicating MSS-SP44 specification) and Series B (Replacing API-605 specification). Both the Series A and Series B are a weld neck and blind specifications only. Series A and Series B are manufactured in Carbon, Stainless and other alloy materials.


What’s the difference between ASME B16.47 Series A vs Series B?

Physical attributes for Series A flanges are typically thicker in flange thickness, heavier in weight, and have large diameter bolt holes in comparison to Series B in the same size and pressure rating. Series B flanges generally have more bolt holes than are in smaller in diameter, generating the need for smaller bolting hardware.  It is important to note Series A and Series B flanges are non-compatible in bolting between each other.

Application of Series A flanges are normally used for industrial connectors such as valves, pumps and pipeline separations. Series B flanges are commonly used in pipeline application.

Price points for Series A flanges tend to be more expensive due to increased steel weight, whereas Series B consumes less steel weight therefore reducing cost.

In Conclusion: ASME B 16.47 Series A and Series B flanges are for large diameter applications for piping projects from 26” thru 60”. Both Series can be manufactured using carbon, stainless, and other alloy materials.  Series A is a carryover from MSS SP44 and Series B from API 605, thus creating a more uniform standardization for the industry thru ASME B16.47.

Please contact Coastal Flange with any questions or to receive a bid winning quote tailored to your needs.

Phone:  713-937-3333

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