What is the pressure rating of a 150# flange?

The pressure rating of a 150# flange is actually 150 psi, which signifies that it is designed to handle pressures up to this value at a certain temperature. The designation "150#" can create confusion, as it refers to the flange's pressure class rather than an actual pressure rating in pounds.

The other options provided reflect various pressure classes that flanges can have. For example, a 285# rating does not correspond to the standard pressure classifications for flanges commonly in use, which include 150#, 300#, 600#, and higher. Flanges rated at 400# are also beyond the standard classification for a 150# flange. Understanding these standard ratings is essential for ensuring the proper selection and safe application of flanges in piping systems.