Standard piping analysis programs, used to determine the deflections and stresses in piping systems, are often employed under conditions that are not within the scope of assumptions in the formulation of the programs. Such a case is the analysis of closely interconnected heat exchangers, pressure vessels and other such equipment. The major problem when using a piping analysis program is that the nozzle connections are modeled infinitely rigid rather than as an element with a finite flexibility. The results generated by such misapplication of the programs is usually (but not always) very conservative. This paper will demonstrate a hybrid method which employs conventional piping analysis software, WRC-107, WRC-297 and Finite Element (FE) software to attempt to obtain a better estimate of the deflections, forces, moments, and stresses. The results of the hybrid analysis are then compared to a complete FE analysis and a standard piping analysis of a sulfur recovery system. The indicated nozzle flexibilities and stresses varied considerably depending upon the analysis methodology used.
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