Modified solution of radial nozzle with thick reinforcement in spherical vessel head subjected to radial load

Abstract

When nozzles in the spherical vessel head are designed by area replacement method defined in the majority of pressure vessel code, the thickness of the reinforcements is so thick that the application of the thin shell theory may not be appropriate in the shell assembly problems. To obtain the solution of the thick reinforcement in the radial nozzle of the spherical vessel head subjected to radial load, the nature of the thick shell is introduced to the current solution for the thin shell: (1) use of the meridional moment at the junction in moment equilibrium equation instead of the meridional moment at middle plane of reinforcement, (2) omission of derivative of rotation in the meridional moment equation, (3) omission of double derivative of radial displacement in meridional moment equation. The current analysis based on the thin shell theory is found to be less conservative as the thickness of reinforcement increases when the middle plane of the reinforcement does not coincide with the middle plane of the main shell of pressure vessel head. The rotation modified method addressed in (2) above is applicable to the design of radial nozzle reinforced by thick shell with t/ R≥0.1 in spherical pressure vessel head subjected to radial load.