Analisis Keandalan pada Offshore Pipeline Akibat Vortex Induced Vibration (VIV) di Perairan Madura

Raisya, Nadira Ifti (2019) Analisis Keandalan pada Offshore Pipeline Akibat Vortex Induced Vibration (VIV) di Perairan Madura. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Eksplorasi minyak dan gas lepas pantai membutuhkan pipa bawah laut sebagai salah satu alat transportasi minyak dan gas. Salah satu permasalahan yang sering terjadi pada pipa bawah laut adalah free span. Free span di akibatkan oleh kontur permukaan dasar laut yang tidak teratur dan menyebabkan pipa terbentang bebas di antara dua tumpuan (support). Sehingga, analisa panjang allowable free span dan analisa VIV (Vortex Induced Vibration) yang menyebabkan osilasi pada pipa merupakan aspek yang penting dalam perancangan offshore pipeline. Analisis free span dilakukan memacu pada kode standar DNV RP F105 (Free Spanning Pipelines). Setiap span memiliki panjang span kritis, terdapat 4 titik span yang mengalami kondisi kritis atau melebihi allowable span length pada kondisi inline yaitu span 33.9 m dengan panjang kritis 31.6 m, span 34.8 m dengan panjang kritis 31.2 m, span 42.9 m dengan panjang kritis 25.4 m, dan span 49.9 m dengan panjang kritis 21.9 m. VIV akan menyebabkan terjadinya tegangan dinamis pada pipa, tegangan paling besar terjadi pada span 49.9 m dengan arah crossflow 9,59 x 10^7 Pa dan arah inline 2,61 x 10^8 Pa. Sedangkan, tegangan dinamis yang terjadi paling kecil dengan kondisi crossflow pada span 14,73 m 1,03 x 10^7 Pa dan untuk arah inline pada span 11,06 m yaitu 1,16 x 10^7 Pa. Kemudian dilakukan simulasi vortex menggunakan ANSYS Fluent. Untuk mengetahui apakah pipa andal terhadap VIV digunakan simulasi Monte Carlo dengan moda kegagalan persamaan screening kriteria VIV, dan dihasilkan 5 titik span terpanjang 31.8 m, 33.9 m, 34.8 m, 42.9 m, 49.9 m memiliki peluang keandalan 0.001 dan tidak andal terhadap VIV. ================================================================================================ Oil and gas exploration on offshore generally uses subsea pipelines as one of the oil and gas transportation method. The problems that often occurs in subsea pipelines is free span. Free span is caused by irregular contours of the seabed and causes the pipe to hang up between two supports. Thus, the analysis of allowable free span length and VIV (Vortex Induced Vibration) analysis that causes oscillations in the pipeline is an important aspect in the design of the offshore pipeline. This study based on the standard code DNV RP F105 (Free Spanning Pipelines). Each span has an allowable span length, there are 4 span points that experience a critical condition or exceed the allowable span length in an inline condition which is span 33.9 m with a critical length 31.6 m, span 34.8 m with a critical length 31.2 m, span 42.9 m with a critical length 25.4 m, and span 49.9 m with a critical length 21.9 m. VIV will cause a dynamic stress on the pipe, the biggest stress occurs at span 49.9 m on crossflow direction 9,59 x 10^7 and inline direction 8,89 x 10^8 Pa. Whereas, the smallest dynamic stress occurs at span 14,73 m crossflow direction 1,03 x 10^7 Pa and inline direction occurs at span 11,06 m 1,16 x 10^7Pa. To find out whether reliable pipes against VIV, Monte Carlo simulations are used by using VIV criteria screening equation as the failure modes, and has an outcome that the 5 longest span 31.8 m, 33.9 m, 34.8 m, 42.9 m, 49.9 m having probability of reliability 0.001 and means by that the critical pipelines not reliable against VIV.

Item Type: Thesis (Undergraduate)
Additional Information: RSKe 620.004 52 Rai a-1 2019
Uncontrolled Keywords: Free Span, VIV, Monte Carlo, Keandalan, ANSYS Fluent
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA169 Reliability (Engineering)
T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures
T Technology > TJ Mechanical engineering and machinery > TJ930 Pipelines (General). Underwater pipelines.
Divisions: Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis
Depositing User: Nadira Ifti Raisya
Date Deposited: 17 Sep 2021 15:23
Last Modified: 22 Sep 2021 03:41
URI: https://repository.its.ac.id/id/eprint/60370

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