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Journal : Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)

Failure Assessment Diagram Constraint Used for Integrity Analysis of Cylindrical Shell with Crack Akbar, Musthafa; Setiawan, Rachman
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 27 No 1 (2016): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v27i1.427

Abstract

During itsoperation time, cylindrical pressure vessel could experience cracks. If this happens, the question is raised whether the pressure vessel could still be used or not, moreoever whether further treatment is required. In process and petroleum industry, an integrity analysis using Fitness For Service methodology is common, for instance referring to API 579/ASME FFS-1 2007 Code. Level 3 assessment within the Code requires a finite element simulation in order to generate both the evaluation point and the Failure Assessment Diagram (FAD) that serves as an acceptance criteria. Here, a parametric study based on the methodology given by the Code has been carried out to generate such result for the cases of internal longitudinal crack defect in a cylindrical shells for a number of common cases, in terms of thickness-to-radius ratio, crack size ratio, and crack aspect ratio. The evaluation of Stress Intensity Factor is determined through J-integral parameter found using a finite element analysis with a specially-meshed strategy incorporating the crack. The result of the model is first verified with that of the Code for a number of cases, before being used for parametric study. The model yields a relatively close comparison with that of the Code. A number of regressed equation was derived for several cases, and proposed to be used in integrity assessment of cylindrical shell. A procedure of using the parametric study result from this investigation is also outlined here.
Integrity Assessment of Cracked Pressure Vessel with Considering Effect of Residual Stress Based on Failure Assessment Diagram Criteria Akbar, Musthafa; Setiawan, Rachman
Journal of Ocean, Mechanical and Aerospace -science and engineering- Vol 28 No 1 (2016): Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse)
Publisher : International Society of Ocean, Mechanical and Aerospace -scientists and engineers- (ISOMAse)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36842/jomase.v28i1.422

Abstract

During the period of its operation, a pressure vessel may experience excessive loading which can cause crack defects. Integrity analysis needs to be carried out to evaluate the feasibility operation of that cylindrical pressure vessel with defects. In this paper, integrity assessment of cracked pressure vessel under internal pressure and tensile residual stress was conducted based on failure assessment diagram criteria. This criteria applied widely and adopted in API 579-1/ASME FFS-1 2007 Code. There are three assessment levels provided in code. Level 1 and 2 assessment performed using analytical calculation while Level 3 assessment is conducted using finite element method. On a case study, failure criteria for the integrity analysis is based on the Failure Assessment Diagram (FAD), that distinguish safe and unsafe region based on two failure criteria, namely brittle fracture and ductile fracture. This diagram is built using finite element method with the assumptions of both Linear Elastic Fracture Mechanics (LEFM) and Elastic Plastic Fracture Mechanics (EPFM). Based on Level 1 assessment, the pressure vessel under study is not recommended to be operated, whilst based on Level 2 and 3 assessments the pressure vessel is considered acceptable. This study concludes that Level 1 and 2 analysis provide more conservative results when compared with level 3 analysis. Failure Assessment Diagram for Level 3 analysis relatively more conservative at elastic-plastic region (0.4<Lr<1), but less conservative at plastic collapse region. Parametric studies performed with increasing operating pressure and size of defects. Based on analysis, failures of the pressure vessel occur at pressure of 403 psi and an aspect ratio of 0.18 for analysis with including the effect of tensile residual stresses. Meanwhile, if the analysis is done by ignoring the effect of residual stress, pressure vessel failed at pressure of 589 psi and leak when aspect ratio reaching 0.42.