Determination of stresses at shell intersections due to pressure or external loadings is a complicated process that has been the subject of numerous research and testing projects. Design formulas and design curves have been developed by various investigators. Guidance for estimating stresses due to external loads, for nozzle diameter to vessel diameter ratios, d/D, less than about one-half, is given in WRC 107 and WRC 297. WRC 107 is based on Bijlaard’s theory for a distributed load over a rectangular area of the surface of a vessel: there is no opening in the vessel and there is no nozzle. WRC 297 is based on Prof. Steele’s shell theory for a nozzle, with diameter d and thickness t, in a vessel, with diameter D and thickness T. The elastic solution is based on dimensionless parameters d/D, D/T and t/T. Guidance for estimating stresses due to internal pressure, for d/D less than about one-half, is given in WRC 383. This guidance is also based on Prof. Steele’s Shell theory. With the advent of finite element analysis, an intersection may be modeled and stresses calculated with a reasonable degree of accuracy. However, the number of openings in pressure vessels may be numerous, making the routine application of finite element analysis uneconomical or impractical. Therefore, easily applied design tools are desired. The second and third parts of this WRC Bulletin provide the results of finite element analyses to extend the range of coverage up to d/D of 100. Design guidance is provided in the form of correlation equations rather than the numerous graphs used in WRC Bulletins 107 and 297. It is the intent of Part 1 of this bulletin to address local stresses at isolated nozzle intersections, where the stresses are not significantly affected by adjacent discontinuities. The computation of stresses is, of course, only part of the design process. Appropriate limits to those stresses must also be specified to complete the design process. This report covers guidance for vessels constructed in accordance with ASME B and PV Code, Section VIII Division 1 and Division 2. In this report, guidance for appropriate limits to stresses is based on the concepts contained in Part 5 of Section VIII, Division 2. The allowable stress limits in this bulletin do not address design in the creep range. This bulletin is based on elastically computed stresses using shell elements and not directly applicable to fatigue calculations. The correlation equations are for primarily static loading with a small number of cycles such that fatigue does not govern. The guidance of this bulletin is not intended to supersede code requirements and in cases of conflict between this report and code requirements, the code requirements govern. For example, the maximum allowable pressure computed with the equations in this bulletin may exceed or be less than the maximum pressure rating determined by Code requirements. It is the intent of this bulletin that the Code requirements establish the pressure rating of the vessel and the procedure contained in this bulletin be used to evaluate the total combined stresses due to pressure and combined loads.