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All Journal Zona Laut : Jurnal Inovasi Sains dan Teknologi Kelautan Indonesian Journal of Maritime Technology or abbreviated (ISMATECH)
Siregar, Hifzul Anwar
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Civil Engineering, Building, Construction & Architecture Control & Systems Engineering Energy Engineering Industrial & Manufacturing Engineering Mechanical Engineering Transportation

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ANALISIS RISIKO KEJATUHAN JANGKAR TERHADAP PIPA BAWAH LAUT DI NATUNA Adnyani, Luh Putri; Siregar, Hifzul Anwar; Putri, Destyariani Liana; Nurmawati, Nurmawati; Wirawan, Muhammad Khaisar
Zona Laut : Jurnal Inovasi Sains Dan Teknologi Kelautan Volume 6, Number 1, March 2025 Edition
Publisher : Departemen Teknik Kelautan Universitas Hasanuddin

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.62012/zl.v6i1.43394

Abstract

Energy is a fundamental element in economic and social development, with oil and natural gas remaining the primary energy sources in Indonesia. To support the distribution of hydrocarbons from production facilities to onshore locations, subsea pipelines serve as vital infrastructure in the upstream oil and gas industry. However, subsea pipelines face various external risks, including dropped ship anchors, which can cause significant damage both technically and environmentally. This study aims to analyze the risk level of dropped anchors on subsea pipelines in Natuna. The methodology involves data collection related to pipeline characteristics, vessel traffic, and anchor types. Consequence analysis is conducted by calculating pipeline dent levels due to anchor kinetic energy based on the DNV-RP-F107 guideline. The results show that the anchor impact energy on the pipeline is approximately 3,94 kJ, placing the pipeline consequence level in the <5% dent/diameter category. Risk assessment using a risk matrix indicates that the risk level remains within the ALARP (As Low As Reasonably Practicable) threshold, meaning the risk is acceptable with reasonable mitigation measures. The findings suggest that although dropped anchors can cause pipeline deformation, the resulting damage remains within safe limits. However, to further reduce potential risks, additional mitigation measures are required, such as vessel traffic monitoring, designated anchor-free zones, and enhancing pipeline resilience against external impacts.
Fatigue Life Analysis of Subsea Pipelines due to Vortex Induced Vibration (Viv) at Free Span Case: Wnts (West Natuna Transportation System) Siregar, Hifzul Anwar; Adnyani, Luh Putri; Nurcholik, Samsu Dlukha; putri, Destyariani Liana
Indonesian Journal of Maritime Technology Vol. 3 No. 2 (2025): Volume 3 Issue 2, December 2025
Publisher : Naval Architecture Department, Kalimantan Institut of Technology

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.35718/ismatech.v3i2.8481529

Abstract

Subsea pipelines in free-span conditions are highly susceptible to Vortex-Induced Vibration (VIV), which generates cyclic stresses and accelerates fatigue failure. This study investigates the fatigue life of a West Natuna Transportation System (WNTS) subsea pipeline under varying heading flow angles (30°, 45°, and 90°) using ANSYS CFD simulations and the Palmgren-Miner fatigue model, in accordance with DNV-RP-F105. Simulations considered Reynolds numbers of 100, 500, and 3.91×10⁵ to capture laminar-to-turbulent flow regimes. Results show that the 90° heading flow produces the most severe VIV, with maximum bending stresses up to 5.59×10⁸ Pa and a corresponding minimum fatigue life of less than 10⁵ cycles, while 30° heading yields significantly longer lifespans, exceeding 10¹⁶ cycles in some cases. Average fatigue life decreased by up to 99.99% when flow incidence increased from 30° to 90° under turbulent conditions. The findings highlight that pipeline orientation relative to prevailing currents strongly influences vortex dynamics, and that aligning pipelines at oblique angles (30°–45°) can substantially reduce fatigue damage risk. These insights can inform the design and operational strategies of subsea pipeline systems in regions with strong and variable currents, such as the Natuna Sea.
Co-Authors Luh Putri Adnyani Nurmawati Nurmawati Putri, Destyariani Liana Samsu Dlukha N Wirawan, Muhammad Khaisar