ASME Code Section VIII Division 2 analysis was performed using ANSYS finite element analysis on a feedwater heater for a utility.
The following assumptions were used:
• Linear elastic material behavior with small displacements
• The geometry, loading and boundary conditions consistently have one plane of symmetry down the axis of the vessel. Then analyses were completed on a half model of the heater with symmetry boundary conditions applied on the cut boundary. Nozzle N5 was treated as having half symmetry.
• The tubesheet was modeled as solid material, with appropriate adjustments in the values of Elastic Modulus and Poisson ratio to account for the effects of the holes at a representative 400°F.
• No credit was taken to increase the ligament efficiency for the effect of tubes
• The evaluation allowable values were conservatively taken at 450°F
Shown above is a closeup of the feedwater heater.