Freespan Asessment Subsea Gas Pipeline of NSO Block North Sumatera
<p align="justify">A submarine pipeline can be failed due to mechanical loadings such as local buckling and fatigue failure. Mechanical failure of a pipeline can be caused by free span growth due to scouring by wave and current until the critical length both of the static and fatigue...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/27889 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | <p align="justify">A submarine pipeline can be failed due to mechanical loadings such as local buckling and fatigue failure. Mechanical failure of a pipeline can be caused by free span growth due to scouring by wave and current until the critical length both of the static and fatigue criterion. Seabed with sand and heavy current have a greater risk of mechanical failure due to span growth and need inspection. Inspection of the free span can lead to the mitigation of free span. The aim of this final project is to determine whether the free span is safe to be operated with static, VIV screening, and fatigue life criterion according to Det Norske Veritas Offshore Standard F101 (DNV OS F101) and Det Norske Veritas Recommended Practice F105 (DNV RP F105). The maximum length of the free span is assessed with the critical length of static criteria according to Ultimate Limit State developed by DNV OS F101. The maximum length of the free span is assessed with the critical length according to VIV screening criteria developed by DNV RP F105. Freespan that failed to meet the screening criteria will be assessed with fatigue life criteria from DNV RP F105. The writer made a calculation sheet to calculate the critical length of each case. NSO-A 30” Pipeline has 100 km in length. ROV has done free span survey of the pipeline and located 1446 free span. Based on the analysis, there are 3 spans that failed to meet the static criterion. Another 372 spans failed to meet the VIV screening criterion by DNV RP F105. After doing fatigue analysis on the 372 spans that failed to meet screening criterion, 224 spans have fatigue life lower than design life, 30 years. Freespan can be rectified by numerous methods such as mass flow jetting and grout bag placement. Mass flow jetting suitable for low span gap. Grout bag placement should notice the VIV avoidance criteria according to the DNV RP F105. <p align="justify"> |
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