Analisa Keandalan Struktur Stinger Dalam Pengoperasian S-Lay Barge

Putra, Novananda Sena (2014) Analisa Keandalan Struktur Stinger Dalam Pengoperasian S-Lay Barge. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Instalasi pipa dengan metode s-lay sangat sering digunakan untuk perairan hingga kedalaman 300 m. Dalam instalasi pipa tersebut stinger adalah merupakan salah satu komponen utama yang menentukan keberhasilan operasi. Oleh karena itu analisis keandalan terhadap stinger dalam operasi dipertimbangkan penting untuk dilakukan, sebagaimana dilaporkan dalam tugas akhir ini. Studi kasus analisis keandalan telah dilakukan pada stinger dari barge peletak pipa Ombak Biru Satu, dengan kriteria operasi mampu untuk melaksanakan instalasi pipa berukuran 10 inch hingga 36 inch pada kedalaman laut maksimum 50 m saat kondisi bergelombang pada tinggi signifikan 2.62 m. Tahap pertama kajian adalah evaluasi respons gerakan barge. Untuk hal ini hasil komputasi menunjukkan gerakan signifikan terbesar dalam mode surge adalah 0.44 m pada arah gelombang 45o, mode sway adalah 0.87 m pada arah 90o, mode heave sebesar 1.38 m pada arah 90o, mode roll sebesar 4.4o pada arah 90o, mode pitch sebesar 1.6o pada arah 135o, dan yaw sebesar 3.6o pada arah 135o. Kesemua harga tersebut menunjukkan bahwa operasi akan dapat dilakukan dengan aman, jika ditinjau dari segi intensitas gerakan bargenya. Tahap kedua adalah melakukan komputasi tegangan kerja pada struktur stinger. Pada instalasi pipa 10 inch diperoleh tegangan aksial terbesar adalah 32.14 N/mm2 dan tegangan bending sebesar 90.33 N/mm2, serta unity check maksimum sebesar 0.70. Pada kasus instalasi pipa 36 inch tegangan kerja aksial paling besar adalah 44.33 N/mm2 dan tegangan bending sebesar 117.10 N/mm2, dengan unity check maksimum 0.93. Tahap ketiga adalah menganalisis keandalan stinger dengan meninjau aspek defleksi yang terjadi. Sesuai dengan kriteria dalam standar API-WSD, defleksi maksimum yang diizinkan adalah 2.6 cm. Sehubungan dengan ini hasil komputasi untuk instalasi pipa 10 inch dan 36 inch masing-masing menunjukkan defleksi maksimum sebesar 1.95 cm dan 2.44 cm, pada arah vertikal atau sumbu-z. Berdasarkan indikator moda kegagalan ini kemudian dilakukan simulasi Monte Carlo untuk memperoleh nilai keandalan struktur. Simulasi menghasilkan keandalan sebesar 0.9998 untuk instalasi pipa 10 inch, dan dapat dipertimbangkan memenuhi kriteria. Sedangkan dalam instalasi pipa 36 inch diperoleh keandalan dengan nilai 0.7029. Nilai keandalan ini belum memenuhi kriteria, sehingga harus dilakukan mitigasi dengan menambahkan member penguat dan menambahkan ketebalan pada stinger. Mitigasi ini telah meningkatkan nilai keandalan menjadi 0.9985, sehingga kriteria terpenuhi.
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Installation of pipes by way of the s-lay method is very often used for waters to a depth of 300 m. In this pipe installation stinger represents one of the primary components that determine the success of the operation. Therefore reliability analysis on the stinger in the operation is considered important to be performed, as reported in this final year project. A case study on the reliability has been performed on the stinger of a pipe lying barge Ombak Biru Satu, where the operational criteria addresses the capability of installation on the pipes sized 10 inches up to 36 inches at water depth of 50 m in the sea condition having significant wave height of 2.62 m. The first stage of evaluation is directed towards the motion responses of the barge. In this regard computational results show the highest significant motions for the surge mode is 0.44 m at the wave direction of 45o, for the sway mode is 0.87 m at the wave direction of 90o, for the heave mode is 1.38 m at the wave direction of 90o, for the roll mode is 4.4o at the wave direction of 90o, for the pitch mode is 1.6o at the wave direction of 135o, and for the yaw mode is 3.6o at the wave direction of 135o. All these intensities indicate the operation could be carried out safely, when it is viewed from the barge motion facet. The second stage is conducting the computation on the working stress for the stinger structure. In the installation of the 10-inch pipe axial stress is found to be 32.14 N/mm2 and the bending stress of 90.33 N/mm2, and further the maximum unity check of 0.70. In the case of the 36-inch pipe installation the axial stress is found to be 44.33 N/mm2 and the bending stress of 117.10 N/mm2, and further the maximum unity check of 0.93. The third stage is dedicated for the reliability analysis of the stinger by evaluating the deflection that would develop. In accordance with the criteria as contained in the API-WSD standard, the allowable maximum deflection is 2.6 cm. In this respect results of the computation for the 10-inch and 36-inch pipe installations give the maximum deflection in the order of, respectively, 1.95 cm and 2.44 cm, in the vertical or z-axis direction. On the basis of this failure mode indicator the Monte Carlo simulation was then carried out to obtain the reliability value of the structure. Simulation yields the reliability as much as 0.9998 for the 10-inch pipe, and therefore could be regarded as satisfactory to the criteria. Whereas in the installation of the 36-inch pipe the reliability is found to be 0.7029. This value of reliability does not met the criteria, and therefore a mitigation should be performed by strengthening and also increasing the thickness of the stinger. The mitigation preserves the improvement of the reliability value to 0.9985, hence the criteria is satisfied.

Item Type:	Thesis (Other)
Additional Information:	RSKe 623.829 Put a-2014
Uncontrolled Keywords:	S-lay Barge, Stinger pipelay, Keandalan, Simulasi Monte Carlo Stinger pipelay , Reliability , Monte Carlo Simulation
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:	Mr. Marsudiyana -
Date Deposited:	23 Oct 2023 10:26
Last Modified:	23 Oct 2023 10:26
URI:	http://repository.its.ac.id/id/eprint/104843

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