ANSI B16.47 Series B
Series B Class 150 Flanges
B16.47 Series B (API 605) Class 150 large-diameter flanges
ASME B16.47 Series B Class 150 flanges provide a cost-effective solution for large-bore, low-pressure piping where the heavier Series A pattern is not required. Derived from API 605, these flanges use fewer bolts and a thinner cross-section while maintaining the same Class 150 pressure-temperature ratings as Series A.
The reduced bolt count means faster assembly and lower hardware costs, which becomes significant when multiplied across dozens of large-diameter joints in a typical plant. For NPS 26, a Series B flange may use 24 bolts compared to 28 for Series A, with similar proportional reductions at larger sizes.
Series B Class 150 flanges are widely used in cooling water systems, large-diameter vent and flare headers, and atmospheric-pressure process vessels. The lighter weight also reduces structural support requirements for elevated piping runs and simplifies crane lifts during construction and maintenance turnarounds.
