Chusaini, Dwi Fakhri (2018) Studi Eksperimen Scouring Pada Dua Pipa Kondisi In-Trench Dan Meletak Akibat Gelombang Reguler Dengan Variasi Jarak (Gap) Antar Pipa. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Pipa bawah laut menjadi salah satu perkembangan teknologi yang banyak digunakan dalam moda transportasi hasil produksi fluida berupa minyak atau gas dari offshore ke onshore maupun antar platform untuk proses olah dan produksi. Dengan jarak yang panjang dan kondisi dasar laut yang ekstrim, scouring menjadi salah satu permasalahan yang sering terjadi. Scouring terjadi akibat arus dan gelombang yang mengenai struktur pipa kemudian membuat aliran vortex yang akan menggerus tanah sekitar pipa dengan arah yang sejajar. Apabila fenomena ini dibiarkan terus menerus maka menimbulkan freespan dan mengalami kegagalan pada struktur. Pada kasus penggunaan dua pipa (two pipelines) sebagai distribusi hasil migas juga akan mengalami scouring. Karena scouring dapat mengganggu kinerja operasi pipa bawah laut maka dalam Tugas Akhir ini akan dibahas tentang eksperimen scouring pada dua pipa dengan memvariasikan jarak antar pipa (gap) akibat gelombang regular untuk mengetahui besar maksimum kedalaman, lebar dan laju propagarsi scouring. Eksperimen dilakukan di Laboratorium Energi dan Lingkungan Laut Jurusan Teknik Kelautan FTK ITS. Skala yang digunakan dalam eksperimen adalah 1:10, dengan model pipa PVC diameter 1,5 inch. Dengan total 12 eksperimen, memvariasikan 3 jarak antar pipa, 2 peletakan (e/D) dan 2 tinggi gelombang (H). Hasil pengujian tanah diperoleh data butiran tanah dengan SG = 2.658 dan d50 = 0.56 mm. Eksperimen yang dilakukan dengan 12 variasi mendapatkan beberapa profil scouring dari dua pipa dari variasi gap (40 cm 60 cm 80 cm), tinggi gelombang (H = 11 cm, H = 13 cm) dan posisi peletakan (e/D = 0, e/D = -0.1). Waktu saat scouring mengalami scouring maksimum adalah 25 menit. Profil scouring 2D tersebut diskala dan digambar dalam Autocad untuk diperoleh kedalaman dan lebar scouring per masing-masing variasi. Hasil kedalaman dan lebar scouring dibandingkan dengan perhitungan empiris dengan menggunakan Ms Excel. Kondisi kedalaman dan lebar eksperimen scouring yang terbesar terjadi pada kondisi H = 11 cm. e/D = -0.1, dan gap 40 cm yaitu 0.23 cm dan 3.36 cm. Hubungan hasil scouring dengan parameter-parameter tak berdimensi yaitu Keulegan Carpenter (KC), Shield Parameter (Ѳ), tinggi gelombang relatif (H/gT^2), dan Burial Depth Diameter Ratio (e/D). Berdasarkan perbandingan hubungan tersebut, semakin besar nilai KC, shield parameter, dan tinggi gelombang relative maka akan semakin besar pula nilai kedalaman dan lebar scouring yang terjadi. Pada kondisi peletakan pipa (e/D) semakin terbenam, maka pipa mengalami kedalaman scouring semakin kecil namun lebar semakin membesar.
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Pipelines is one of technology that used to transport the oil and gas products from offshore platform to onshore platform or between each platform to continue the process of production. Since long distance and extreme condition of seabed, scouring is be the one problem that always happened on pipelines. Scouring is caused by wave and current that contact the structure, then formed the flow’s vortex and made the erosion of pipe’s ground in one direction. If this phenomenon occurs many more, freespan will formed and get failure in structure. In the case using of two pipelines to distribute the oils and gas product, will get the scouring. Because the scouring can damage the operation of pipelines, so in this final research the scour will be studied specifically. The topic is about experimental study of scouring below two pipelines with in-trench and laid condition due to regular waves and variate spacing between pipes (gap). The object of research is to know the maximum depth and width scour, propagation of scour, and the relation between scour and non-dimensioanal parameter. The experiment was tested in Energy and Enviromental of Ocean Laboratory, Department Ocean Engineering FTK ITS. The scale of experiment using is 1:10, with 1.5 inch diameter PVC’s pipe for the model. Total of experiments were twelve, variated three spacing between pipes (gap), two position of pipes (e/D), and two waves height (H). The result of soil testing was known a grain soil’s data with SG = 2.658 and d50 = 0.56 mm. The result of twelve experiments got some data profile of scouring below to pipelines with gap variation (40 cm 60 cm 80 cm), wave height (H = 11 cm, H = 13 cm) and position of pipes (e/D = 0, e/D = -0.1). Time spended on a maximum depth and width of scouring is 25 minutes. The 2D profil of scouring is scaled and sketched in Autocad to know the depth and width every one variation. That scouring’s result is compared by equation of empirical law using Ms. Excel. The largest depth and width of scouring occurs in condition H = 11 cm, e/D = -0.1, and gap 40 cm, are 0.23 cm and 3.36 cm. The relation between scouring and non-dimensional parameter are Keulegan Carpenter (KC), Shield Parameter (Ѳ), wave stepness (H/gT^2), dan Burial Depth Diameter Ratio (e/D). According to the relation of them, increasingly the value of non-dimensional parameter, so the depth and width of scouring value are higher. In pipe position (e/D) is more trenchingly, so the scouring depth of the pipelines is smaller but the width is the larger.
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Additional Information: | RSKe 621.867 2 Chu s-1 2018 |
| Uncontrolled Keywords: | pipa bawah laut, scouring dua pipa, eksperimen, gelombang regular, jarak antar pipa (gap) |
| 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: | Dwi fakhri Chusaini |
| Date Deposited: | 24 Jun 2021 02:20 |
| Last Modified: | 24 Jun 2021 02:20 |
| URI: | http://repository.its.ac.id/id/eprint/54793 |
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