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ITS » Undergraduate Theses » Teknik Kelautan
Posted by eny at 25/08/2009 14:57:13  •  4187 Views


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Salah satu bagian penting dalam desain sebuah sistem pipa bawah laut adalah mempertimbangkan terjadinya freespan pada pipa bawah laut. Freespan harus mendapat perhatian khusus dalam proses desain pipa bawah laut karena kondisi ini dapat menyebabkan vibrasi atau biasa dikenal sebagai fenomena Vortex Induce Vibration VIV. Tugas akhir ini adalah melakukan analisa pengaruh VIV pada freespan pipa bawah laut Data yang digunakan merupakan data pipa Hess Indonesia-Pangkah Limited di perairan Ujung Pangkah. Analisis dilakukan dengan menggunakan perhitungan manual MATLAB berdasarkan code yang mengacu pada ASME B31.8 untuk analisa statis dan DnV RP F105 untuk analisa dinamis sedangakan untuk memodelkan VIV menggunakan software ORCA. Dari hasil analisa maka diperoleh panjang span yang diijinkan adalah panjang span yang terpendek dari perhitungan yaitu untuk KP Shore I II III IV V VI pada kondisi operasi adalah 17.28 m 20.41 m 20.34 m 14.04 m 16.41 m 13.65 m 13.17 m . Sedangkan Dari hasil analisa VIV diketahui bahwa frekuensi natural span pada pipa lebih besar dari frekuensi vortex. Aliran vortex yang terjadi pada disekitar pipa kurang teratur karena harga Reynold number antara 3.46.106 1.78.107. Harga reduced velocity Vr berdasarkan hasil analisis maka response yang terjadi adalah in-line response dan cross-flow response. In-line response terjadi pada harga 1.0 dengan syarat 1.2 UR 4.5 sedangkan cross-flow response terjadi pada harga 3.9 dengan syarat 5 UR 9 . Hasil ini menunjukkan pipa akan aman dioperasikan


One of the most essential parts on designing an offshore pipeline system is to consider the occurrence of freespan which will likely to take place on the pipes. Freespan must acquire special attention during the process of designing the offshore pipeline since such condition could cause vibration which is also well-known as the Vortex Induce Vibration VIV phenomenon. This thesis is intended to analyze the effect of VIV on the freespan offshore pipeline. Data being used is the Hess Indonesia-Pangkah Limited pipe data on the waters of Ujung Pangkah. Analysis was completed using manual calculation MATLAB based on the code which refers to ASME B31.8 for static analysis and DnV RP F105 for dynamic analysis whereas ORCA software is used to model VIV. The analysis conclusion shows that the length of the span permitted is the shortest length from the calculation on which case for KP Shore I II III IV V VI on operational condition is 17.28 m 20.41 m 20.34 m 14.04 m 16.41 m 13.65 m 13.17 m while it is acknowledged from the VIV analysis that natural span frequency on the pipe is bigger than vortex frequency. Vortex flow which occurs around the pipe is not steady due to the Reynold number value which is between 3.46.106 1.78.107. The value of reduced velocity Vr based on the analysis result will lead to in-line response dan cross-flow response. In-line response occurs on 1.0 value with 1.2 UR 4.5 condition while cross-flow response occurs on 3.9 value with 5 UR 9 condition. This result indicates the pipe will be safe to operate.

KeywordsFreespan ; Vortex induced vibration ; In-line response ; Cross-flow response
Subject:  Pipelines ; Underwater pipelines
  1. Prof. Ir. SOEGIONO
    Ir. JOSWAN J. S., M.Sc.
Date Create: 25/08/2009
Type: Text
Format: pdf
Language: Indonesian
Identifier: ITS-Undergraduate-3100009035259
Collection ID: 3100009035259
Call Number: RSKe 621.867 2 Lek a

Undergraduate Theses, Ocean Engineering, RSKe 621.867 2 Lek a, 2009

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