What is the working pressure and temperature ratings for cast iron companion flanges?

The relationship between temperature and working pressure is defined by ASME B16.1-1998, shown in Table 1 below. The normal operating pressure is 200 PSI between -20°F (-29°C) to 150°F (65°C).

They must not be used at temperatures below -20°F (-29°C). If the temperature exceeds 150°F (65°C) the allowable working pressure drops. 

* Pressure is recorded in lb/sq.in. gauge

*NPS: Nominal pipe size

Limitations

1. When Class 125 cast iron flanges and flanged fittings are used for gaseous services, the maximum pressure shall be limited to 125 psig. Tabulated pressure-temperature ratings above 125 psig for Class 125 cast iron flanges and flanged fittings are applicable for non-shock hydraulic service only.

For Class 250 (not carried by Boshart), when used for liquid service, the tabulated pressure-temperature ratings in NPS 14 and larger are applicable to Class 250 flanges only and not to Class 250 fittings.

2. 353°F (max.) to reflect the temperature of saturated steam at 125 psig.

3. 406°F (max.) to reflect the temperature of saturated steam at 250 psig.

4. Hydrostatic tests are not required unless specified by the end user.

Additional Resources

https://support.boshart.com/what-size-flange-gasket-or-bolt-kit-do-you-use-with-a-class-125-cast-iron-reducing-flange