ANSI B16.1 Cast Iron Flanges
Class 250 Flanges
Higher pressure cast iron flanges per ANSI B16.1
ANSI B16.1 Class 250 flanges are raised face cast iron flanges rated for higher pressures than the Class 125 series. The raised face provides a defined gasket seating area that concentrates bolt load on a narrower contact band, improving seal performance at elevated pressures. Class 250 flanges are available in sizes from NPS 1 through NPS 30.
The pressure-temperature ratings for Class 250 cast iron allow up to 300 psi for non-shock cold water service and 150 psi for steam and gas at temperatures up to 450 degrees F. These ratings make Class 250 flanges suitable for medium-pressure industrial steam lines, compressed air systems, and higher-pressure water distribution networks.
Class 250 flanges use heavier bolt patterns and thicker flange bodies compared to Class 125, resulting in greater clamping force and improved resistance to pressure-induced separation. Gaskets for Class 250 raised face flanges are typically confined within the raised face diameter, and spiral wound or solid metal gaskets may be used depending on the service conditions.
