Local Stress Calculation In Pressure Vessels And Piping, The Finite Element Method

Calculation of local stresses is a common problem during the design of pressure vessel. Excessive local stresses need to be considered because they may cause excessive local deformation due to overloads, or fatigue failure under alternating loads, endangering the safety of equipment.Corrosion and welding defects are main factors resulting in great local stresses on piplines.The excessive local stresses will result in leakage or burst, endangering the safe operation of pipelines, which requires attentions during the periodic testing.The complete paper focused on the calculation of local stresses.Design by Stress analysis method and finite element analysis method were adopted, and the finite element calculations were carried on ANSYS Program.In the structural design of pressure vessel, the paper was specific to structurals which were commonly used for engineering but lacked for design theory,the local stresses calculation methods or were reported little (structural of horizontal and tangential nozzle jointing to elliptical head,structural of nozzle jointing to elliptical head placing a tower on it).After a detailed stress analysis, the strength assessment was carried out to each structural.Once the assessment failed,a reinforcement structural was put forward and its reinforced effect was investigated in order to obtain a ultimate safe and reliable structural design. In addition, this paper came up with a new kind of reinforcement structural(Cone transition ring) based on stresses analysis,aiming for a reference to the design of the cone-cylinder shell connection structure commonly used in chemical vessel designs.As to pressure piping, the finite element method and optimal design ideas were adopted for residual strength evaluation and life prediction of pipline containing corrosion defects,the results of which provide a theoretical basis to determine how to use the pipline(replacement, maintenance, continue to service) and to determine the testing cycle.Moreover, APDL(ANSYS Parametric Design Language)was introduced to develop special procedures used for residual strength evaluation and life prediction of pipline.Compared to burst test results,the program results were with high accuracy,which could meet project requirements.