ASME B16.47 Series A

Covers — large diameter steel flanges:

• Sizes from NPS 26 through NPS 60.
• Pressure classes: 150, 300, 400, 600, 900 (Class 75 is also included for low pressure).
• Series A geometry (thicker flanges, fewer but larger bolts).

Does NOT cover (exclusions) — the following are governed elsewhere:

• Flanges NPS 24 and smaller → ASME B16.5.
• Series B large flanges (compact design) → ASME B16.47 Series B.

B16.47 Series A extends the principles of B16.5 to large bores:

• P-T Ratings — uses the exact same material groups and Pressure-Temperature ratings as ASME B16.5.
• Design Basis — Series A prioritizes robustness, accommodating severe external loads from cross-country pipelines and massive equipment nozzles.

For large-bore piping, engineers must explicitly choose between Series A and Series B because they are physically incompatible.

Series A Characteristics

Series A flanges are thicker, have a larger bolt circle diameter, and use fewer, but significantly larger, diameter bolts than Series B. This makes them heavier and more expensive, but highly resistant to bending moments and external forces. They are the preferred choice for new pipeline construction and heavy equipment connections.