Fitness-for-Service of a Column Equipment Containing Dent Defects Based on API 579 Level 3 Analysis and Considering the Dynamic Loads

Fitness-for-service assessment of a pressurized component containing dents or other mechanical damage is important to ensure the operational safety and structural integrity of the damaged equipment. In the present study, the API 579 level 3 fitness-for-service analysis were performed for a column equipment containing dent defects, and the main difficulty is to determine the applied dynamic load, especially when considering wind load and earthquake load at high order mode shapes. To solve this problem, a simplified method combining the analytic calculation and finite element (FE) method were proposed in this study. At the first step, the wind load and earthquake load on different segments of the column without defect were calculated by analytic methods according to Chinese code GB4710. Then the critical load combination determined in step one were applied on a whole column FE model containing 6 dent defects with different dimensions. Based on the FE simulation, the stress linearization were performed for strength check, and buckling analysis were performed buckling collapse failure respectively. The results of strength check and critical buckling load showed that the column containing dents under static load and dynamic load conditions was acceptable for continued operation based on API 579 level 3 analysis. Thus, the methodology developed in this study provides an available fitness-for-service assessment for dents in column equipment and enables the consideration of dynamic loads.