What are the pressure ratings for Class 150 and Class 300 malleable fittings?

MAXIMUM WORKING PRESSURE GUIDE ALLOWABLE (PSI / kPa) @ TEMPERATURE (°F / °C) - ASME B16.3 MALLEABLE IRON THREADED FITTINGS, CLASSES 150 & 300

The Malleable Pipe Fittings "Classes" state the maximum working presure at the maximum temperature. You will notice that Class 150 fittings are rated for presures up to 300 PSI at 150° F (65.5°C) 

FOR REFERENCE ONLY !

This information is a reference guide only. Specifying the correct pipe schedule and pressure class of fitting depends on many factors. It is the ultimate responsibility of the end user's piping engineer to specify the correct pipe schedule and pressure class of fitting which will meet the maximum operating pressures / temperatures of the system for safe operation in the intended application.

IMPORTANT NOTES:

1) Ratings are independent of the contained fluid and are maximum Non-Shock pressures at the tabulated temperatures. Intermediate ratings maybe obtained by linear interpolation between temperatures shown.

2) The temperature shown for the corresponding pressure rating shall be the material temperature of the pressure retaining structure. It may be assumed that the material temperatures is the same as the fluid temperature. Use of a pressure rating at a material temperatures other than that of the contained fluid is the responsibility of the user and subject to the requirements of any applicable code.

3) Piping loads, stresses and moments are not taken into account.

4) Class 300 Street Elbows are not recommended for gauge pressures above 600 PSI (4136 kPa).