I have in the past set up my own load combinations for the Hydrotest case - GR T3 P3 (Functional) and use the Hoop stress values for my reports. This gives me 118.54 MPa. For a change, I thought that I would give the default Hydrotest load case a try and but it gives me a different value of 148.17 MPa. Now when I just do a pure Hoop stress calculation (Pd/2t), it gives me another different result of 134.19 MPa. I am trying to understand why these 3 values are different
Please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> ASME B31.8 Chapter VIII - 2010> for calculations used in AutoPIPE. pay special attention to the hoop stress calculation.
In this case, the Hoop stress hand calculation use Dmean (PDmean/2t) and with the correct values for pressure factor in the Hydrotest load case so all stress values match now.