Influence of holding space at pressure vessel on the stress concentration

With ANSYS finite element software, this paper analyzes the opened rim stress field with different center distances L at two adjacentholes with diameter d in a cylinder of pressure vessel, defined the parameter K as L /(2d). Analytic conclusion displays that the maximum opened rim stress value for nipple pipe free model is bigger than that of nipple pipe model, therefore, the value from the former is relatively safe. When K is more than 0.9, the minimum stress value along the center line of openings is decreased significantly with the increase of holing space. When K＝0.9~1.5, the minimum stress is gradually decreased. When K is more than 1.5, the minimum stress value is close to the stress of the cylinder's location, far away from the openings. Comprehensive analysis make clear that for the concentration factor of stress and its impact range, when K is more than 1.7, there is no interference between two openings, which can be deemed as independent openings.