Adityawan, Ferdy (2010) Analisis Umur Kelelahan Akibat Vortex Induced VIbration pada Pipa Bawah Laut Berlokasi di Terang Sirasun Batur Field. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Freespan merupakan suatu kondisi yang dialami oleh subsea pipeline dimana terdapat
bentangan karena ketiadaan support dari tanah. Freespan terjadi akibat adanya perubahan
topografi dasar laut dan penggerusan akibat arus yang berada pada dasar laut. Arus yang
mengenai pipa akan mengakibatkan adanya aliran vortex pada belakang sisi pipa. Vortex
Induced Vibration (VIV) merupakan fenomena yang terjadi pada komponen yang berbentuk
silindris yang disebabkan arus laut, menyebabkan terjadinya getaran oleh pergerakan fluida
yang mengenai pipa sehingga menimbulkan getaran pada pipa. Oleh karena itu, pada penelitian
ini penulis melakukan analisa umur kelelahan akibat VIV. Tahap pertama yang dilakukan dalam
Tugas Akhir ini adalah screening kriteria statis sesuai DNV GL-RP-F105. Dari screening
tersebut dihasilkan panjang free span maksimal yang diizinkan. Panjang tersebut selanjutnya
dilakukan screening tahap dua dengan kriteria FLS untuk fatigue criteria sesuai DNV-GL RP
F105. Tegangan ekuivalen (Von Mises) yang diperoleh pada setiap span yang ditinjau untuk 24
bentangan bebas dipatatkan range tegangan sebesar 161,14 MPa – 189,41 MPa. Berdasarkan
hasil perhitungan frekuensi natural, didapatkan bahwa hubungan antara panjang bentangan pipa
dengan frekuensi natural pipa dalam kondisi in-line maupun cross-flow, hasil menunjukkan
bahwa pada panjang span terkecil memiliki frekuensi natural pipa yang besar, dan sebaliknya.
Umur Kelelahan pada 24 bentangan pipa mengalami kegagalan kondisi in-line dan crossflow
dan diharuskan ditambah support.
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Freespan is a condition experienced by the subsea pipeline where there is a stretch due to the lack
of support from the ground. Freespan occurs due to changes in the seabed topography and scouring
due to currents that are on the seabed. The current that hits the pipe will cause vortex flow on the
back side of the pipe. Vortex Induced Vibration (VIV) is a phenomenon that occurs in cylindrical
components caused by ocean currents, causing vibrations by the movement of fluids that hit the
pipe, causing vibrations in the pipe. Therefore, in this study the authors analyzed the age of fatigue
due to VIV. The first step carried out in this Final Project is screening static criteria according to
DNV GL-RP-F105. The screening results in the maximum free span length allowed. The length is
then carried out stage two screening with FLS criteria for fatigue criteria according to DNV-GL
RP F105. The equivalent voltage (Von Mises) obtained at each span reviewed for 24 free stretches
is recorded with a voltage range of 161.14 MPa - 189.41 MPa. Based on the results of natural
frequency calculation, it is found that the relationship between the length of the pipe stretch with
the natural frequency of the pipe in both in-line and cross-flow conditions, the results show that
the smallest span length has a large natural frequency of the pipe, and vice versa. Fatigue life in
24 stretches of pipe has failed in-line and crossflow conditions and support must be added.
| Item Type: | Thesis (Other) |
|---|---|
| Uncontrolled Keywords: | Freespan, Fatigue, Vortex Induced Vibration, in-line, crossflow |
| Subjects: | T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures |
| Divisions: | Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis |
| Depositing User: | Ferdy Adityawan |
| Date Deposited: | 21 Aug 2020 03:02 |
| Last Modified: | 12 Oct 2023 09:39 |
| URI: | http://repository.its.ac.id/id/eprint/79794 |
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