ANSI B16.1 Cast Iron Flanges
Class 125 Weld Neck Flanges
Weld neck variant for Class 125 cast iron service
Class 125 Weld Neck flanges under the B16.1 standard provide a tapered hub design that transitions smoothly from the pipe wall thickness to the flange face. This gradual transition reduces stress concentrations at the base of the flange, making weld neck flanges the preferred choice when thermal cycling, vibration, or bending loads are present in the system.
In cast iron service, weld neck flanges offer superior structural integrity compared to slip-on or threaded alternatives. The butt-weld connection between the pipe and flange hub creates a continuous grain structure that resists fatigue cracking and ensures full penetration welds can be radiographically examined for critical installations.
These flanges are commonly specified for Class 125 piping systems in water treatment plants, industrial cooling loops, and condensate return lines where the combination of moderate pressures and cyclic thermal loads demands a robust connection method.
