Arief, Iqbal Rusdan (2019) Analisis Fatigue Free Span Pipa Bawah Laut Akibat Pengaruh Vortex Induced Vibration (VIV) dengan Simulasi Computational Fluid Dynamics (CFD) ; Studi Kasus : Eastern Java Gas Pipeline (EJGP). Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Salah satu masalah utama yang sering terjadi pada sistem perpipaan bawah laut yaitu Free Span. Free span tersebut rentan mengalami kegagalan struktur, seperti kelelahan, yang disebabkan oleh vibrasi yang terjadi oleh vortex shedding atau biasa disebut fenomena vortex induced vibration (VIV). Fenomena disebabkan oleh beban lingkungan terutama gelombang dan arus laut, hingga rasio gap seabed (e/D) dan kekasaran dari pipa (k/D). Pada tugas akhir ini, analisis free span yang dilakukan terdiri analisis dinamis free span dan analisis kelelahan. Untuk perhitungan dari analisis dinamis, keluaran yang dihasilkan berupa panjang efektif untuk arah cross-flow dan arah in-line, kemudian akan didapatkan panjang span yang diijinkan dari pipa bawah laut. Adapun acuan yang digunakan dalam analisis dinamik dan kelelahan dari free span adalah DNV-RP-F105 mengenai Free Spanning Pipelines dan juga dilakukan permodelan dinamik free span, vortex induced vibration, dan stress pada pipa dengan metode Computational Fluid Dynamic. Sedangkan untuk analisis kelelahan, perhitungan hanya dilakukan dengan kriteria dari DNV-RP-C203 untuk mendapatkan fatigue life (Tlife). Setelah dilakukan analisis, 1. Panjang span yang dizinkan pada pipa EJGP yang diizinkan ialah antara 24.1578 m – 53.639 m pada kondisi inline, sementara pada kondisi cross flow panjang span yang diizinkan yaitu antara 54.5101 m – 66.54 m. Berdasarkan hasil screening geometri yang dilakukan pada pipa EJGP KP 3 – KP 380 dari 181 titik free span, sebanyak 29 titik free span perlu dilakukan analisis fatigue dan 5 titik free span sangat krusial karena melebihi panjang span yang diizinkan pada kondisi inline maupun crossflow yaitu pada KP 102.650, KP102.840, KP105.176, KP129.961, KP131.914. 2. Akibat Vortex Induced Vibration yang terjadi pada pipa didapatkan damage fatigue ratio pada 29 titik pipa pada kondisi inline yaitu antara 11.20 – 42.91 dan 5 titik juga terjadi pada kondisi crossflow antara 61.78 – 69.37 kemudian sisa umur kelelahan pipa pada 29 titik pada kondisi inline yaitu antara 2.52 – 9.65 tahun dengan 5 titik pada kondisi crossflow antara 1.56 - 1.75 tahun. Berdasarkan hasil tersebut perlu ditambahkan suppression device dan koreksi panjang free span untuk mengurangi dampak dari vortex induced vibration pada pipa untuk memperpanjang umur pipa.
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One of the main problems that often occurs in subsea piping systems is the Free Span. The free span is susceptible to structural failure, such as fatigue, which is caused by vibrations that occur by vortex shedding or commonly called the vortex induced vibration (VIV) phenomenon. The phenomenon is caused by environmental loads, especially ocean waves and currents, to the gap seabed ratio (e / D) and roughness of the pipe (k / D). In this final project, the free span analysis consists of dynamic free span analysis and fatigue analysis. For calculations from dynamic analysis, the resulting output is the effective length for the cross-flow direction and in-line direction, then the allowable span length from the subsea pipeline will be obtained. The reference used in the dynamic and fatigue analysis of free span is DNV-RP-F105 regarding Free Spanning Pipelines and also dynamic modeling of free span, vortex induced vibration, and stress on pipes using the Computational Fluid Dynamic method. Whereas for fatigue analysis, the calculation is only done with criteria from DNV-RP-C203 to obtain fatigue life (Tlife). After analysis, it was found that the allowable span length in the EJGP pipe allowed was between 24.1578 m - 53,639 m in inline conditions, while the cross flow conditions for the permitted span were between 54.5101 m - 66.54 m. Based on the results of geometry screening carried out on EJGP KP 3 - KP 380 pipes from 181 free span points, 29 free span points need to be analyzed for fatigue and 5 free span points are crucial because they exceed the allowable span length in inline and crossflow conditions, namely at KP 102,650, KP102,840, KP105,176, KP129,961, KP131,914. As a result of Vortex Induced Vibration that occurs in the pipeline, the damage fatigue ratio at 29 pipelines in inline conditions is between 11.20 - 42.91 and 5 points also occur in crossflow conditions between 61.78 - 69.37 then the remaining pipe fatigue life at 29 points in inline conditions is between 2.52 - 9.65 years with 5 points in crossflow conditions between 1.56 - 1.75 years. Based on these results, it is necessary to add a suppression device and correct the length of free span to reduce the impact of vortex induced vibration on the pipe to extend the life of the pipe.
| Item Type: | Thesis (Other) |
|---|---|
| Uncontrolled Keywords: | Fatigue Life, Vortex Induced Vibration, Free Span, Damage Ratio, Allowable Span, CFD. |
| Subjects: | T Technology > TC Hydraulic engineering. Ocean engineering > TC1665 Offshore structures--Materials. T Technology > TJ Mechanical engineering and machinery > TJ935 Pipe--Fluid dynamics. Tubes--Fluid dynamics V Naval Science > VM Naval architecture. Shipbuilding. Marine engineering |
| Divisions: | Faculty of Marine Technology (MARTECH) > Marine Engineering > 36202-(S1) Undergraduate Thesis |
| Depositing User: | Iqbal Rusdan Arief |
| Date Deposited: | 03 Jul 2024 04:21 |
| Last Modified: | 03 Jul 2024 04:21 |
| URI: | http://repository.its.ac.id/id/eprint/68808 |
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