ENGINEERING CRITICAL ASSESSMENT SUBMARINE PIPE INSTALLATION WITH S-LAY METHOD
Submarine pipe joints (girth welds) are an area that is likely to experience defects. The defect has the potential to cause stress concentrations, so that the initial crack will occur. These cracks will spread out due to the cyclic loads that the structure receives. This study was conducted to evalu...
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| Format: | Theses |
| Language: | Indonesia |
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| Online Access: | https://digilib.itb.ac.id/gdl/view/61722 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Submarine pipe joints (girth welds) are an area that is likely to experience defects. The defect has the potential to cause stress concentrations, so that the initial crack will occur. These cracks will spread out due to the cyclic loads that the structure receives. This study was conducted to evaluate the mechanical integrity and thickness of welds that had weld defects using Engineering Critical Analysis (ECA) with the Failure Analysis (FAD) method. ECA is a fairly good method for evaluating the integrity of a pipe structure that is defective in the weld. FAD divides two areas, namely the safe area and the unsafe area which is created by two axes, namely the x-axis is stress ratio (Lr) and the y-axis is the stress intensity ratio (Kr). Stress ratio (Lr) is ratio between reference stress (?ref) and material stress (?ys), while stress intensity ratio (Kr) is ratio between stress intensity factor (KI) and material toughness (KIC). ECA is carried out in two conditions, firstly during installation with bending loading due to S-Lay notation and secondly during hydrotest. Based on analysis at installation conditions, it is found that crack dimensions with a: 4 mm, c: 100 mm are declared unsafe, whereas defect dimensions below 4 mm at the time of installation it is declared safe. Whereas in the hydrotest condition, the crack dimensions with dimensions greater than a: 3 mm, c: 12.5 mm were declared unsafe, while under these dimensions it was declared safe. In installation conditions, welded joint number 20 with depth defect 4 mm, width of 200 mm is unacceptable or unsafe. In hydrotest conditions, welded joints numbered 13 to 20, with a depth of defect (a) strating from 3 mm to 4 mm, are unacceptable or unsafe. Based on the analysis, the depth of the defect (a) are more influential to material toughness. |
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