A design method is presented that allows a designer to predict the maximum allowable working pressure of an opening reinforcement using an allowable stress basis. Primary application of the method is directed toward large openings as defined by ASME Section VIII, Division 1, paragraph UA-7. Recent hydrotests conducted on several production pressure vessels have demonstrated that existing paragraph UA-7 area replacement rules are inadequate in certain d/D and D/T ranges. The inadequate designs were initially indicated by leakage at a flange located close to the nozzle shell intersection. Later, another vessel hydrotest was terminated because of distortion and high readings from strain gages located at the nozzle-to-shell intersection. The proposed empirical design method produces nozzle reinforcements that should remain in the elastic stress range for internal pressure up to the Code-required hydrotest.

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