When computing allowable stress values at the pipe to valve connecting nodes, AutoPIPE uses valve material properties at the “To Node”. For example if you have a valve modeled from node 5 to node 10. Allowable stresses at node 10 will be computed using valve material data. This may lead to unconservative results?
Based on the scenario above, the results will always be conservative when connecting pipe to the upstream side of a valve / flexible joint component because the general program convention is to take the material properties of the pipe / component that follows after a point when calculating the stresses. .
However, material properties defined for a valve or a flexible joint are incorrectly used to calculate the allowable stress values for pipe connected to the far end (downstream side) of that valve or flexible joint. The calculated allowable stress values on the down stream side using the material defined for the valve/flexible joint may be higher than the actual allowable stress values for the pipe, leading to un-conservative results. This error impacts all editions of ASME NB, NC and ND piping codes (logged under TFS-D407514).
Also remember that AutoPIPE does not calculate stress values for a valve. It will only calculate stress values for the pipe that is connected to the valve.
Piping connected to the upstream side of a valve / flexible joint component uses a conservative approach when calculating stress, while it was discovered that the downstream side did not. This was fixed in a future version of the program (see TFS hyperlink above for complete details).
"Code Compliance" sub-report using Results> Output Report
Bentley AutoPIPE