A finite-element computer program, MULT-NOZZLE, was developed for the stress analysis of cylindrical pressure vessels with two or three closely spaced reinforced nozzles. MULT-NOZZLE consists of two modules which may be operated independently. The first module, FEMG, automatically prepares a finite-element mesh including the nodal point coordinates, finite-element connectivities, mesh options, and boundary value specifications for input to the finite-element solution module SAP3M. SAP3M, which is a modified and improved version of the SAP3 computer program, computes the nodal point displacements and stress tensor components, and prints and/or stores the results for later postprocessing. The accuracy of the SAP3M module is demonstrated by comparison studies of two classical theory-of-elasticity problems: a simply supported beam and a thick-walled ring under internal pressure loading. A complete discussion of MULT-NOZZLE is presented in four volumes. Volume develops the finite-element idealization for pressure vessels with two idential radially attached closely spaced nozzles for internal pressure loading. The nozzles may be unreinforced or fully reinforced according to the rules of the ASME Boiler and Pressure Vessel Code and may be located in either a longitudinal or a transverse plane of the vessel. Validation of the program for analyzing this type of structure is demonstrated bymore » the analysis of three two-nozzle pressure vessel models and comparison of results with experimental data. In general, quite satisfactory results were obtained.« less