Analisis Operabilitas Crane Vessel Saat Lowering Riser Support Structure Arch Di Splash Zone Berbasis Time Domain

Yahya, Arifta (2014) Analisis Operabilitas Crane Vessel Saat Lowering Riser Support Structure Arch Di Splash Zone Berbasis Time Domain. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Tugas Akhir ini membahas kajian kemampuan operasi (operabilitas) Crane Vessel dalam operasi menurunkan struktur bawah laut saat melewati muka air yang bergelombang (splash zone). Simulasi numerik dilakukan selama 3 jam untuk merefleksikan perilaku dinamis kapal dan obyek. Obyek yang diangkat dan diturunkan melewati muka air adalah Riser Support Structure (RSS) yang memiliki dimensi 127.3x20x11 m dan berat 1604 ton. Berdasarkan berat beban yang melebihi 1-2% displasemen kapal (displasemen kapal=78489 ton), operasi tersebut tergolong dalam heavy lift operation. Crane Vessel disebut mampu beroperasi jika memenuhi kriteria operasi. Hasil respon yang dievaluasi meliputi gerakan kapal, gerakan obyek dan tension sling. Harga tension sling harus memenuhi kriteria yang disyaratkan. Didapatkan gerakan signifikan kapal terbesar untuk gerakan heave 1.0m, roll=2.2o dan pitch 0.82o yang diakibatkan gelombang
acak Hs=3.75m dan untuk gerakan signifikan vertikal obyek tidak memenuhi kriteria yaitu 1.2m akibat gelombang acak Hs=2.75m. Untuk tension signifikan akibat Hs=3.75 terjadi kegagalan pada sling CS1 karena memiliki Safety Factor = 3.91 (SF<4) saat posisi beban di muka air. Pada saat beban tercelup air, sling A1 mengalami kekenduran dimana harga minimum signifikan tension=492kN tidak memenuhi kriteria DNV (minimum>10% berat tercelup atau min>610.3kN). Didapat batas tinggi gelombang signifikan yang menyebabkan downtime sebesar Hs=2.00 m dan harga operabilitas crane vessel dikorelasikan data sebaran gelombang Laut Natuna adalah 80.34%.
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This Final Project study on the operability of Crane Vessel when lowered subsea structure passing through the splash zone. The lowering stage is divided in two step, structure above water level and structure is submerged below water level. Numerical simulation performed to investigate the coupling effect between the load and the vessel in presence of wave. The structure which lowered through splash zone namely Riser Support Structure (RSS,) RSS has dimension of 127.3x20x11m and weight of 1604 ton. Based on the ratio between load weight and the vessel displacement is higher than 1-2%, the operation is called heavy lift operation. Crane Vessel is working safely when the responses fulfill the operational limitation criteria. These responses which evaluated are vessel motion, load motion and the hoisting wire tension. The result explain that maximum significant vessel motion in vertical mode, heave=1.0m, roll=2.2o and pitch=0.82owhilst no operational issue comply with the operational limit. Whereas the vertical motion of the load =1.2 m (due to significant wave height, Hs=2.75m) doesn’t comply the operational criteria. The tension of hoisting wire due to Hs=3.75m, fail occur at Crane Sling 1 because the Safety Factor (SF) =3.91 (SF less than 4.0) when the load is above the water level. When the load is submerged below water level, slack sling occur at sling A1 with significant minimum tension=455kN because the buoyancy already developed. DNV required minimum sling tension higher than 10% of submerged weight of the load (min significant tension > 610,3 kN) to avoid snap load due to slack. Finally, conclude that limiting significant wave height is 2.00 m and the operability of crane vessel correlate with wave scatter diagram of Natuna Sea is 80.34%.

Item Type:	Thesis (Other)
Additional Information:	RSKe 627.98 Yah a-2014
Uncontrolled Keywords:	Operabilitas, crane vessel, lowering, splash zone
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC1665 Offshore structures--Materials.
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User:	Mr. Marsudiyana -
Date Deposited:	23 Oct 2023 09:32
Last Modified:	23 Oct 2023 09:32
URI:	http://repository.its.ac.id/id/eprint/104854

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