I hereby declare that I am responsible for the work submitted in this project, that the original work is mine except as specified in the references and acknowledgments, and that the original work contained herein was not performed or performed by anyone other than -specified sources or persons. . Last but not least, to my parents and colleagues for the support they provided during the completion of this project. There are several methods available to assess the corrosion metal loss defects to evaluate the Fitness-for-Services (FFS) of the corroded pipeline.
In this study, finite element simulations will be performed to determine the maximum allowable burst strength of a corroded pipeline with interacting defects.
CHAPTERl INTRODUCTION
Background ofstudy
Problem Statement
OBJECTIVE AND SCOPE OF STUDY
CHAPTER2
LITERATURE REVIEW
Offset Defects
In the real-life problem, corrosion does not occur rigidly at one location on the pipeline wall, instead, corrosion attacks the surface randomly, which creates a colony of defects that are distributed at the attacked location. According to the DNV code, the simplification was made for cases of multiple defects which were overlapping or compensated. The simplification made in the DNV code does not take into account the interactive fault compensation condition.
Finite Element Analysis
As for the circumferentially aligned faults, there is no significant change in the rupture pressure when the distance between the faults changes. The results of the finite element simulation were used as the database for the neutral grid system. The results of the study showed that in the case of the longitudinal direction, especially for the fault in the confined space, the relative pressure capacity of the pipe (the ratio between the burst pressure of the multiple fault and the single fault) decreased as the depth of the fault increased.
In contrast, in the case of the circumferential direction, little defect interaction was observed, which had an insignificant effect on the relative pressure performance of the pipe.
Research Methodology
Relevant parameters such as depth of defects, spacing between defects, diameter of pipeline and length of defects are determined by manipulating the correlation. 3.I.l The length of the defect is determined by the ratio between the length of the defect and the diameter of the pipeline, II D. In this study, several assumptions are made, first, the length of the two defects that are supposed to interact are equal.
After performing the analysis using DNV RP-F I 0 I code, finite element models are developed using ANSYS, a well-known engineering simulation software. The element type determines whether the element lies in two- or three-dimensional space and the degree-of-freedom quantity (which in turn implies the discipline - structural, thermal, magnetic, electrical, square, brick, etc.). The element is defined by 20 nodes that have three degrees of freedom at each node, which are translations in the nodal x, y, and z directions.
CHAPTER4
RESULTS AND DISCUSSIONS
DNV Code Results
Overall Result Summary
The graph shows that the effect of defect spacing does not differ much in the direction of burst pressure for the two techniques. In other words, the interaction effect for defects with a depth of l 00/o pipe wall thickness will not significantly affect the pipe burst pressure. Thus, the breakdown pressure has only a small increment as the fault distance increases.
The graph shows that the rupture pressure is lower when the distance between the defects is small, and when the distance between the defects increases up to .[jj;t s 4 the rupture pressure increases. The graph shows that the initial failure pressure is lower and as the distance between the defects increases, the failure pressure increases. For defects with a depth of 40% of the pipe wall thickness, the interaction effect is high when the distance between the defects is small, and the effect gradually decreases as the distance increases, resulting in increased rupture pressure.
The graph shows that the initial failure pressure is lower and as the distance between the defects increases, the failure pressure increases. The difference in terms of failure pressure is large between the distance between small defects and the distance between large defects. For defects with a depth of 60% of the pipe wall thickness, the interaction effect is greater at small defect distances, resulting in a low failure pressure.
Similar trend as from the previous case, the failure pressure increases as the distance between defects increases. However, as the distance between defects increases, the difference between the DNV code and FEA is greater. For defects with a depth of 70% of the pipe wall thickness, the interaction effect is greater for small defects, resulting in low burst pressure.
The failure pressure difference between DNV Code and FEA is small when the defect space is small. For defects with a depth of 80% of the pipe wall thickness, the interaction effect is greater at small defect spacings resulting in low rupture pressure. For the fault with the smallest depth, the failure pressure does not change significantly with increasing distance between the faults.
The failure pressure in the small defect spaces was significantly reduced and the interaction effect is critical within this region. This is due to the safety factor applied in the empirical calculation, which results in the lowest burst pressure of the corroded pipe to avoid reaching the correct burst pressure during standard operating conditions.
CHAPTERS
CONCLUSION AND RECOMMNEDATION
CONCLUSION
RECOMMENDATION,
