Analisis Fatigue Life dan Risiko Subsea Pipeline Akibat Scouring dan Vortex Induced Vibration

Berliantoro, Mustika (2026) Analisis Fatigue Life dan Risiko Subsea Pipeline Akibat Scouring dan Vortex Induced Vibration. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Subsea pipeline merupakan komponen vital dalam sistem transportasi fluida hidrokarbon lepas pantai, sehingga keandalan strukturalnya menjadi prasyarat utama operasi. Salah satu ancaman kritis terhadap integritas existing subsea pipeline adalah scouring, yaitu erosi sedimen dasar laut yang membentuk kondisi free span dan meningkatkan kerentanan pipa terhadap Vortex Induced Vibration (VIV), yang berpotensi memicu fatigue damage dan mempersingkat umur layan pipa. Penelitian ini menganalisis integritas struktur, fatigue life, dan risiko kegagalan pada existing subsea pipeline akibat scouring dan VIV, dengan meninjau empat skenario free span pada variasi panjang span 10–20 m dan gap 0,2–3 m. Analisis tegangan dilakukan secara analitik mengacu ASME B31.8 dan divalidasi melalui ANSYS Static Structural, sementara evaluasi fatigue life dan probabilitas kegagalan menggunakan simulasi Monte Carlo 50.000 iterasi berdasarkan DNV-RP-F105. Hasil menunjukkan seluruh skenario gap masih memenuhi allowable stress (<90% SMYS) dengan deviasi numerik 4,94% terhadap analitik, namun skenario span terpanjang (L=20 m, gap=3 m) melampaui screening statis (L/D=49,261>30) maupun screening fatigue DNV-RP-F105. Seluruh skenario menghasilkan fatigue damage melampaui kriteria Palmgren-Miner, dengan fatigue life 2,99–8,30 tahun (inline) dan 0,84–7,76 tahun (crossflow), jauh di bawah umur rencana 20 tahun. Indeks keandalan (β) seluruh skenario berada jauh di bawah ambang aman β≥3, sehingga matriks risiko menempatkan keempat skenario pada kategori unacceptable. Temuan ini menegaskan perlunya mitigasi berjenjang berupa span rectification, rockdumping, gravel bag, dan Risk Based Inspection sesuai tingkat kekritisan tiap skenario guna mencegah kegagalan struktural dini.
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Subsea pipelines are vital components of offshore hydrocarbon transportation systems, making their structural reliability a fundamental operational requirement. A critical threat to the integrity of existing subsea pipelines is scouring, the erosion of seabed sediment that creates free span conditions and increases pipeline susceptibility to Vortex Induced Vibration (VIV), which may trigger fatigue damage and shorten the pipeline's service life. This study analyzes the structural integrity, fatigue life, and failure risk of an existing subsea pipeline subjected to scouring and VIV, examining four free span scenarios with span lengths of 10–20 m and gaps of 0.2–3 m. Stress analysis was performed analytically based on ASME B31.8 and validated using ANSYS Static Structural, while fatigue life and failure probability were evaluated through a 50,000-iteration Monte Carlo simulation based on DNV-RP-F105. Results indicate that all gap scenarios remain within the allowable stress limit (<90% SMYS), with a numerical deviation of 4.94% from analytical calculations; however, the longest span scenario (L=20 m, gap=3 m) exceeded both the static screening criterion (L/D=49.261>30) and the DNV-RP-F105 fatigue screening criterion. All scenarios produced fatigue damage exceeding the Palmgren-Miner criterion, yielding fatigue lives of 2.99–8.30 years (inline) and 0.84–7.76 years (crossflow), far below the 20-year design life. The reliability index (β) for all scenarios fell well below the safe threshold of β≥3, placing all four scenarios in the unacceptable risk category according to the risk matrix. These findings underscore the need for tiered mitigation measures span rectification, rockdumping, gravel bags, and Risk Based Inspection—prioritized according to each scenario's criticality to prevent premature structural failure.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Subsea Pipeline, VIV, Fatigue Life, Risiko. Subsea Pipeline, VIV, Fatigue Life, Risk.
Subjects:	Q Science Q Science > QC Physics > QC151 Fluid dynamics T Technology > TA Engineering (General). Civil engineering (General) > TA169 Reliability (Engineering) T Technology > TA Engineering (General). Civil engineering (General) > TA169.5 Failure analysis T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method
Divisions:	Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User:	Mustika Berliantoro
Date Deposited:	20 Jul 2026 01:11
Last Modified:	20 Jul 2026 01:11
URI:	http://repository.its.ac.id/id/eprint/135666

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