Attention: Please see the following AutoPIPE help section: Help > Contents> Contents Tab> Modeling Approaches> Modeling Approaches>This help has been provided in order to give users ideas for modeling typical piping arrangements. The steps shown in each example should not be taken as the only method available to create models. In addition, the intent of the examples is to present ways to create adequate models of specific piping components for analytical purposes. Anchors Bends Cuts Flexible Joints Frames Hangers Nozzles Pipes Reducers Rotating Equipment Supports Tees Valves Vessels
In AutoPIPE, Flanges are a 1 point element with no length i.e. considers only the flange weight and type of weld connection to pipe for SIF calculation. Yes, assuming flange stiffness is same as the pipe is technically incorrect because a flange is more rigid than pipe, but no, it doesn't affect analysis results to any significant extent in most cases. Cases you may wish to model the rigid length of the flange would be in a short stiff piping arrangement or close to equipment like pumps. If you want to input flange length, insert a pipe run and insert flanges at the mating point then select this short length and use Insert > Rigid options over Range, change settings as needed and press OK to continue. AutoPIPE has an option to do ANSI flange loading check.
Model Different Types of PIPING Components