The differences between ASME B16.5 and ...

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 . 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.

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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.

ASME B16 47 Series A flanges are thicker, heavier and stronger than their Series B counterparts. They also can often handle more external loading than Series B. Series A flanges tend to be more costly than Series B flanges. ASME B16.47 Series B flanges need more but smaller fasteners, such as bolts & nuts. They also usually have a smaller bolt circle diameter than Series A flanges. Generally, there is less flange movement after installation due to the smaller bolt circle diameter. Both Series A and B define weld neck flanges and blind flanges in raised face type. However, Series A defines ring type joint (RTJ) flanges from Class 300 through Class 900 within this standard while Series B does not.

Series A flanges are popular for new pipeline projects or equipment. Meanwhile, many choose Series B flanges for refurbishment or replacement jobs.

American standards for flanges

• ASME B 16.1: Gray iron pipe flanges and flanged fittings (cast iron flanges, Classes 25, 125 and 250),
• ASME B 16.5: Pipe flanges and flanged fittings: NPS 1/2 through NPS 24 Metric/Inch Standard; (Cast steel and weld-neck flanges Classes 150, 300, 400, 600, 900, and ), this includes pressure ratings, dimensions, tolerances, materials, marking, and testing.
• ASME B 16.47: Pipe flanges and flanged fittings: NPS 26 through NPS 60 Metric/Inch Standard; (Classes 75, 150, 300, 400, 600, and 900). Then, ASME B16.47 is further divided into ASME B16.47 Series A and ASME B16.47 Series B flanges for Blinds and Weld-necks.

The following MSS, API and AWWA standards are written to supplement B16.5:

MSS SP-6: Flange facings

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MSS SP-9: Spot facing for bronze, iron and steel flanges

MSS SP-25: Marking of flanges

MSS SP-39: Bolts and nuts for flanges

API6A: Wellhead equipment

AWWA C207: Hub flanges

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