ASME 코드의 피로해석을 통한 맥동감쇠기의 구조안전성에 관한 연구

Abstract

The objective of structural analysis is to verify the fatigue life of pulsation dampener using the thermo-mechanical analysis due to the operating pressure and thermal gradients at the event of start up and shot down, operating and load change.

This study provides the sizing and stress calculation for the pulsation dampener using the applicable rules and calculation methods specified in ASME Section VIII Division 2.

The pulsation dampener consists of shell, head, nozzle, saddle and pad plate. There are cylindrical shell type, horizontally supported by a pair frames. Finite Element Analysis models are constrcted for each analysis and consisted of nodes and elements. Three-dimensional isoparametric solid elements are used.

Material properties are listed in ASME Section II Part D. The boundary conditions applied to the finite element model are that the node on the symmetrical section are fixed in the direction normal to the section surface and one saddle is fixed and the other is sliding to axis direction of vessel.

The first step of analysis is to determine the internal temperature distribution as a function of time for all operating mode and the internal stresses were calculated for the critical temperature distributions with operating pressure.

The second step is to calculate stress levels and code requirement and satisfy material allowable stress.

The third step is calculate fatigue life. The pulsation dampener is verified the integrity, become evaluated fatigue usage factors are not exceed 1.0. The critical fatigue regions of pulsation dampener are the junction of the shell, nozzle and pad plate of support. The accumulated factor are 0.039 for unwelded region and 0.012 and 'infinite' for welded region. The usage factors are the sum of the individual usage factors, and shall not exceed 1.0 and safety ASME Section VIII Division 2.