Large Diameter Flanges — ASME B16.47 Series A & B

What are Large Diameter Flanges?

ASME B16.47 covers weld neck and blind flanges from NPS 26 to NPS 60. Series A, derived from MSS SP-44, has heavier flanges with fewer, larger bolts and is rated Class 150, 300, 400, 600 and 900; it also includes ring joint facings. Series B, derived from API 605, is more compact, with more, smaller bolts, and adds a Class 75. In the same NPS and class, Series A and B have different OD, bolt circle and bolt count and cannot be bolted together, so the series must be stated on every order.

Key features

• Weld neck and blind flanges to ASME B16.47
• Series A (MSS SP-44 origin) and Series B (API 605 origin)
• RF on both series; RTJ on Series A
• Forged or ring-rolled, then CNC machined
• Larger sizes and slip-on rings to AWWA C207 or drawing

Specification

Applications

• Cooling water mains in power and steel plants
• Large-bore refinery and petrochemical headers
• Pipeline and terminal piping
• Desalination and water transmission
• Flare and vent headers

B16.47 Series A vs Series B

Series A flanges are thicker and heavier, with fewer and larger bolts; they suit higher external loads and are offered with RTJ facings. Series B flanges are lighter, with more and smaller bolts, and offer Class 75 for low-pressure duty. They have different bolt circles and cannot be mated. Check the series of the equipment nozzle or valve before ordering.