Stresses in reinforced nozzle-cylinder attachments under external moment loadings analyzed by the finite-element method: a parameter study

A parameter study was conducted on stresses in reinforced nozzle-to-cylinder attachments under external moment loadings as analyzed by the finite-element method. Twenty-five models with nozzle-to-cylinder diameter ratios 0.08 less than or equal to d/D less than or equal to 0.50 and cylinder diameter-to-thickness ratios 10 less than or equal to D/T less than or equal to 100 were investigated. A three-dimensional finite-element program, CORTES-SA, developed specifically for analyzing tee-joint configurations, was used in the study. Each of the 25 models was analyzed for 6 individually applied external moment loadings, with 3 mutually orthogonal moment loadings on the nozzle end and 3 on the cylinder. Two of the recommended nozzle reinforcement designs given in Subsection NB-3338.2, Section III, of the ASME Boiler and Pressure Vessel Code were examined: nozzle thickening or standard reinforcement (S1 models) and 300 triangular pad reinforcement (P30 models). Essentially unreinforced models (U models) were also included for comparison. Although these design configurations have been recommended by the Code for many years, very little specific stress analysis information exists by which the adequacy or relative safety margins of the Code design rules can be judged. Results from the parameter studies reported here provide some of the needed information.It was concluded from the study that both of the reinforcement designs investigated significantly reduce maximum stresses relative to configurations having little or no reinforcement. Out-of-plane bending moment loading on the nozzle gave high maximum stress values for both unreinforced and reinforced configurations having relatively large, thin (d/D = 0.50, D/T greater than or equal to 20) nozzle attachments