Expander Flanges — ASME B16.5 Flange End

What is an Expander Flange?

An expander flange combines a reducer and a weld neck flange in one forging. The weld end matches the smaller pipe; the flange end matches a larger valve, pump or equipment nozzle, for example a 4″ pipe to a 6″ valve. It removes a reducer and a butt weld, and so shortens the spool. ASME B16.5 does not give dimensions for the expander body, so length and taper follow the manufacturer's standard or the purchaser's drawing, while the flange end follows B16.5.

Key features

• Flange end of the larger NPS to ASME B16.5
• Weld end bored and bevelled for the smaller pipe
• Typically increases size by one or two NPS
• Replaces a reducer plus weld neck flange
• RF, FF or RTJ facing

Specification

Applications

• Pump and compressor inlet and outlet connections
• Control valve stations with a larger valve body
• Equipment nozzles larger than the connected line
• Compact skids where spool length is limited

Expander flange vs reducing flange

A reducing flange has a larger flange ring bored for a smaller pipe, with a sudden step at the bore. An expander flange has a long tapered hub that increases the bore gradually from the small pipe to the larger flange, so flow transition is smoother and it behaves more like a reducer. Expanders are preferred where flow disturbance or pressure drop matters.