Results Conclusion:The results obtained were for the 30 deg branch angle, 0.375" thk (SchSTD) branch assembly, based on nodal forces / moments per CEASER's static load case-OPE. A mesh sensitivity was also done resulting in a finer mesh size / mesh refinement being provided at the branch weld, as this was most susceptible to higher strains. The appropriate branch weld reinforcement size was increased was set during the analysis to an optimum value. To accommodate the variations of the branch angle due to site fabrication conditions, the model was also re-analyzed by changing the geometry (Branch angle) to 27 deg, this resulted in reduction in stress levels, but not significant enough to get it close to 20ksi. As a result of which it was concluded that the Stress levels revealed by FEA would not be acceptable per limits set by the piping code.

Benefits: This resulted in a better integrity and confidence in the reliability of the heat exchanger 24in piping lines connected as branches to the 30in header line at the same header cross-section.

Problem: As a result of which branch joints are closer to each other at one location along the circumference of the 30in€� header, than the other.The limitation that existed with this configuration of piping was that it is an existing piping configuration which cannot be re-routed and changed due to the existing set-up of the pressure equipment and the other plant piping to which it is connected. Also the reason for construction being replacement of the existing piping with that of an upgraded metallurgy. The existing piping configuration was designed to a relatively older version of the ANSI B31.3.

Analysis: A pipe stress/flexibility analysis was carried out using CEASER which confirms the compliance and of this piping configuration based on acceptable stress values. However, this configuration does not fulfill the branch connection spacing requirement clause of the latest revision of the design code ASME B31.3, as a result of which the need for an additional FEA was identified was this particular branch joint connection, to determine the actual stress distribution and assess is acceptance based on the above stated deviation from the ASME B31.3 piping code requirement. The FEA on the 30" (SchSTD) x 24" (SchSTD) branch connection was carried out, based on the nodal forces and moments provided by the CEASER pipe stress model reveals a stress distribution that exceeds the allowable code stress limit of 20 ksi. The same had been cross verified by applying the nodal displacements and rotations (in lieu of Forces and Moments) and have also obtained almost identical results which verify the correctness of the ANSYS simulation.