ASME-B16.47 Flanges

The standard ASME B16.47 is further divided into ASME B16.47 series A and ASME B16.47 series B flange for Blind flange and Weldneck flange. Series B flange was also formerly known as API 605 flange. Term B16.47 or B16.47 or ANSI B16.47 are all used interchangeabily and refers to the same standard.

ASME B16.47(Large Diameter Steel Flanges) is a standard for large diameter steel pipe flanges sized from NPS 26 through NPS 60. The latest version provides dimensions and ratings in both metric and inch units. The ASME B16.47 incorporate MSS SP-44: Steel Pipeline Flanges and API 605: Large Diameter Carbon Steel Flanges. Therefore, the MSS SP-44 flanges are designated as ASME B16.47 Series A flanges, while API 605 flanges are designated as ASME B16.47 Series B flanges within this standard. 

So what is the difference between ASME B16.47 Series A and Series B (API605) flanges?

Generally speaking, ASME B16.47 Series A flanges are much thicker, heavier and stronger than Series B flanges in the same size and pressure rating thus can withstand more external loading than Series B type. ASME B16.47 Series B flanges need more but smaller fasteners (bolts & nuts) than Series A flanges and have a smaller bolt circle diameter than that of Series A flanges. The smaller bolt circle diameter results in less flange movement after installation. Both Series A and Series B standards define weld neck flanges and blind flanges in raised face type (RF) but only Series A defines ring type joint (RTJ) flanges from Class 300 through Class 900 within this standard. From a commercial point of view, ASME B16.47 Series A flanges are more expensive than ASME B16.47 Series B flanges.