ASME B16.5 standard covers Steel Pipe Flanges and Flanged Fittings from NPS 1/2 through NPS 24 Metric/Inch in pressure class 150 to class 2500. It covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Two very important flanges such as weld neck flange and blind flanges are very commonly used in piping systems. The term "B16.5" or "B16 5" is used interchangeability and refers to same standard. However, the standard ASME B16 5 (ANSI B16 5) only covers size up to 24 inches. For bigger sizes, ASME B16.47 standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60 and in ratings Classes 75, 150, 300, 400, 600, and 900.

However, 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 Weld-neck flange. Series B flange was also formerly known as API 605 flange. Term B16.47 or B 16 47 or ANSI B 16 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. Materials covered in this standard are as that in ASME B16.5 except for nickel alloys which means they share the same pressure-temperature chart for the selection of flange materials.