The differences between ASME B16.5 and ...

ASME B16.5 outlines the specifications for Steel Pipe Flanges and Flanged Fittings ranging from NPS 1/2 to NPS 24 in pressure classes from 150 and above. It encompasses various details including pressure-temperature ratings, materials, dimensions, tolerances, marking, testing procedures, and methods for identifying openings in pipe flanges and flanged fittings. Two significant types of flanges, namely weld neck flanges and blind flanges, are extensively utilized in piping systems. The notation "B16.5," or variations such as "B16 5," refers to this same standard. It's noteworthy that ASME B16.5 (also known as ANSI B16.5) is limited to sizes up to 24 inches, while the larger sizes from NPS 26 to NPS 60 are governed by the ASME B16.47 standard, which also addresses pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for these larger flanges, available in ratings classes 75, 150, 300, 400, 600, and 900.

Nonetheless, the ASME B16.47 standard is further categorized into two series: ASME B16.47 Series A and ASME B16.47 Series B, catering specifically to blind flanges and weld-neck flanges. The Series B flanges were previously referred to as API 605 flanges. The terminologies B16.47, B 16 47, and ANSI B 16 47 are interchangeable and indicate the same standard.

ASME B16.47 focuses on large diameter steel pipe flanges sized from NPS 26 to NPS 60. The most recent version presents dimension and rating information in both metric and inch units. ASME B16.47 integrates two important standards: MSS SP-44, which relates to Steel Pipeline Flanges, and API 605, which pertains to Large Diameter Carbon Steel Flanges. In this framework, the MSS SP-44 flanges are categorized as ASME B16.47 Series A, while API 605 flanges fall under ASME B16.47 Series B. The materials addressed in this standard are similar to those in ASME B16.5, excluding nickel alloys. Hence, they utilize the same pressure-temperature chart for selecting flange materials.

ASME B16.47 Series A flanges offer greater thickness, weight, and strength compared to Series B flanges, enabling them to better withstand external loads. Although Series A flanges tend to be more expensive, they require fewer but larger fasteners, such as bolts and nuts, leading to a larger bolt circle diameter than their Series B equivalents. The design of Series B flanges generally results in reduced flange movement post-installation due to their smaller bolt circle diameter. Both series identify weld neck flanges and blind flanges with a raised face type; however, Series A includes the definition of ring type joint (RTJ) flanges from Class 300 to Class 900, a feature not included in Series B.

Typically, Series A flanges are favored for new pipeline construction or installations, whereas Series B flanges are often selected for refurbishment or replacement projects.

The subsequent American standards related to flanges include:

• 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 for NPS 1/2 through NPS 24 Metric/Inch Standard (Cast steel and weld-neck flanges Classes 150, 300, 400, 600, 900), covering pressure ratings, dimensions, tolerances, materials, marking, and testing.
• ASME B 16.47: Pipe flanges and flanged fittings for NPS 26 through NPS 60 Metric/Inch Standard (Classes 75, 150, 300, 400, 600, 900). This standard is further divided into ASME B16.47 Series A and B for Blinds and Weld-necks.

In addition to these standards, supplementary standards from MSS, API, and AWWA, designed to complement B16.5, include MSS SP-6 for flange facings, MSS SP-9 for spot facing for bronze, iron, and steel flanges, MSS SP-25 for marking of flanges, MSS SP-39 for bolts and nuts for flanges, API 6A for wellhead equipment, and AWWA C207 for hub flanges.

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