What is the maximum allowable pressure for threaded fittings for a 3" diameter?

The maximum allowable pressure for threaded fittings, specifically for a 3-inch diameter, is indeed 400 psi. This value is determined based on factors including the material properties of the fitting, the manufacturing standards it adheres to, and the application in which it is used.

Threaded fittings are often subject to certain limitations concerning pressure due to the stress concentrations created at the threads. The design factors applied during manufacturing ensure that these fittings can handle pressures typically encountered in various systems without risking failure, leaks, or breaks.

Maintaining proper pressure ratings is critical because exceeding them can lead to catastrophic failures, potentially causing injury or property damage. It is vital for anyone working with high-pressure piping systems to understand the ratings associated with different fittings to ensure safe and effective operation.