ANSI Flanges allowable load

ANSI Standards like B16.5 and B16.42 do not offer methods to handle external loads (ie pipe bending loads), but they are there and should be evaluate using good engineering practice. The Pressure Vessel Research Council (PVRC) has conducted some studies, but I do not believe that they have published a method for calculation - see WRC Bulletins 450, 461 and 473 for research reports. They can be found on the website: http://www.forengineers.org/pvrc/index.html .

The issue with bending moments on flanges is that they introduce a non-symmetrical load on the flange. The root issues to analyze are:

1. does the tension side of the bending pipe increase the load so as to overcome the bolt preload and let the gasket decompress and thus cause a leak?

2. does the compression side of the bending pipe increase the gasket compression such that the gasket extrudes and thus cause a leak?

3. does the flange distort and thus cause a leak?

These are not straight forward matters, but do need to be considered.