ANSI B16.47 Series A
Series A Class 150 Flanges
B16.47 Series A (MSS SP-44) Class 150 large-diameter flanges
ASME B16.47 Series A Class 150 flanges are designed for large-bore, low-pressure piping systems where the pipe diameter exceeds the NPS 24 upper limit of B16.5. At Class 150, these flanges serve applications such as cooling water headers, large-diameter gas distribution mains, and atmospheric storage tank nozzles.
The Series A (MSS SP-44) pattern uses a greater number of bolts with larger diameters compared to Series B, resulting in higher gasket seating stress and improved leak resistance. For NPS 26, the outside diameter of a Series A Class 150 flange is approximately 34.25 inches, increasing to roughly 69.25 inches at NPS 60.
Material specifications typically call for ASTM A105 for carbon steel or A350 LF2 for low-temperature service. Ring-type joint and raised face configurations are both available, with raised face being the standard for Class 150. Gasket selection for these large diameters requires careful attention to bolt load distribution and flange rotation limits.
