Rated Flange - Why can't I put an opening in a blind rated flange?
The rated flange pressure temperature ratings come from ASME B16.5 and ASME B16.47. These ratings were determined from failure tests with full intact geometries as provided in the mentioned standards. Altering this geometry, by putting a hole in the blind for instance, is not supported in the test data. In addition, there is not a tr basis in the flange ratings, which is required for area of reinforcement calculations for openings that are not exempt.