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IJOCE (International Journal of Offshore and Coastal Engineering)

ijoce
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Published by Institut Teknologi Sepuluh Nopember Surabaya

ISSN : - EISSN : 25800914 DOI : -

Core Subject : Engineering,

Engineering

IJOCE, International Journal of Offshore and Coastal Engineering, is an academic journal on the issues related to offshore, coastal and ship science, engineering and technology. Published quarterly in February, May, August, and November.

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Articles 8 Documents

Search results for , issue "Vol 1, No 2 (2017)" : 8 Documents clear

Prelimenary Modeling for Assessing Tidal Stream Energy Potential at the Alas Strait, Indonesia Mukhtasor Mukhtasor; Luli Bangkit Sugito; Sujantoko Sujantoko
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

This study is on ocean current prelimenary modelling in Alas Strait, Indonesia, to be compared with the field observation data. The model maps coordinate for ocean current so that the potential energy resource can be identified. The model simulation is established with two different scenarios; the first scenario is using windspeed factor and the second without using that factor. Complementary variables such as bathymetry, water elevation, bottom friction, and eddy viscosity have the same value for both scenarios. This ocean current modelling use finite element method with flexible mesh. This method use two dimension numerical solution from the average incompressible Reynolds Navier – Stokes equation with the assumption from Boussinesq dan hydrostatic pressure. This model consists of continuity equation and momentum which closed by turbulen scheme. This study concludes the first scenario is a success and valid with the water surface elevation mean error is 4.2% and water current speed mean error is 10.7%. The second scenario is unseccesful as indicated by the water surface elevation mean error of 13.4% and the water current speed mean error of 11,7%, and also the phase and the trend of current speed is verging the field observation data.

Analysis of Configuration of Stinger Angle with Depth Variation During Installation On Pipe Diamater 20" in Banyu Urip, Bojonegoro Imam Rochani; Juniavi Dini Kumala Putri; Handayanu Handayanu
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

The selection of subsea pipeline construction methods used depends on the environmental conditions and behavior of the pipe installation system which acquires a variety of loads during installation and may the result in failure. In this case the required angle stinger configuration is in accordance with the criteria to avoid overstress and local buckling on the pipe during installation, the variation of the depth of 15 meters, 18 meters, 20.65 meters, 21.25 meters and 22.25 meters can help analysis the stress on the pipe in each case. The pipeline is 23.4 km north of Bojonegoro. From the results of the analysis, it is known that the configuration of stinger angles used during installation for each water depth is 15 m with stinger angle 8.88 degree, 18.65 m stinger angle 8.88 degree, 20.65 m stinger angle 8.88 degree, 21.25 m stinger angle 8.88 degree and 22.25 m stinger angle 8.88 degree. The result of pipe stress on the overbend area has a value of 85.13% SMYS or 352.42 Mpa when the direction of wave comes 90 degrees, while the sagbend area of the pipe has a maximum stress of 51.01% SMYS or 211.2 Mpa when the direction of wave comes 180 degrees. Local buckling check results in all conditions show safe results during the installation process.

Risk Analysis on Leakage Failures of Pipelines Using Hybrid Risk Analysis Method Daniel Mohammad Rosyid; Bassam Muhammad Drehem; Agro Wisudawan
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

In this final project has been conducted a study on risk analysis on subsea pipeline leakage by using hybrid risk analysis method. The study begins by determining the scope of the analysis using fault tree analysis which can be determined the main event of the leakage failure of subsea pipeline until the basic event. After determining the scope of the analysis then proceeded to calculate the frequency of each event using the quantitative method. In this calculation is known the frequency of basic event through data from scientific paper programming and scientific research and then calculated the frequency result of top event using Boolean Equation until we get the frequency of failure due to leakage pipelines for 0.0141213. After knowing how big the probability of failure, followed by determining how much impact or consequence of the failure. The consequences of failure are determined based on their impact on safety, environment, and business. In the determination of the impact with the qualitative method using questionnaires interviews to some respondents. After obtaining the result of questionnaire interview then calculated the mean of the questionnaire result to determine how big impact of the failure is based on safety, environment, and business. After knowing how big the probability and consequences of the failure, then determine the position of the risk zone on the risk matrix that refers to DNV RP-G101. After knowing the position of the risk zone, it can be determined how to control risk based on cause-effect.

Analysis of the Effect of Welding Sequence Variations on Residual Stresses and Distortions for Welding Pressure Vessels Structures at PT. Petrokimia Gresik using the Finite Element Method Nur Syahroni; Bayu Iman Fatkurokhim; Handayanu Handayanu
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

The development of oil and gas industry technology has been very advanced, one of the implementation is to connect material materials to support oil and gas industry facilities. Residual stress may occur due to high temperature differences due to welding and also uneven heat distribution. This causes the material to become hard but brittle so that it may cause structural failure in the connection area. In this final project will be simulated welding pressure vessels to determine the structure of residual stresses that occur as well as the influence of Post Weld Heat Treatment on residual stress itself. The material used is aluminum and WPS data coming from the fabrication company. The simulation is divided into 2 steps: thermal and structural analysis. The value of the residual voltage of 1 to pathline pathline 3 is 189 MPa, 124.8 MPa, 100.76 MPa with distortion value of 40.43 mm. Then analyzed Post Weld Heat Treatment referring to AWS D1.1: 2000 to reduce residual stresses that occur. From the results of the Post Weld Heat Treatment value of the residual stress can be reduced significantly. After being treated Post Weld Heat Treatment with variations of temperatures of 200 C, 300 C The maximum residual voltage reduction occurs in pathline 1 to pathline 3 at 125 MPa, 93 MPa, 100 MPa.

Analitical Study of Vertical and Lateral Buckling on Pipeline Using Hobbs Method Yoyok Setyo Hadiwidodo; Muhammad Makki Romadhoni; Herman Pratikno
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

During its operation, the pipeline will receive loads of internal pressure and thermal loads of fluid flowed until the pipes have both vertical and lateral buckling. Numerical analysis of vertical and lateral buckling Hobbs this method on a high friction coefficient and the coefficient of friction (0.3 ≤ φ ≤ 0.7) as well as the length of buckling as many as 20 variants were then performed comparisons, as well as axial tension comparison with DnV RP L110. So we get the relationship of temperature increase with the length and amplitude buckling. The data which is used is the gas pipeline Labuhan Maringgai-Muara Bekasi PT. Perusahaan Gas Negara (Persero) Tbk., Including the outer diameter of the pipe = 0.8128 m, plate thickness = 0.015875 m, thermal linear expansion coefficient = 11 x 10-6 m / oC, etc. So the higher coefficient of friction, temperature rise of 13.4%, 13.4% reduced buckling length, and axial tension increased to 12.95%. For the comparisons, the coefficient of friction does not affect the length of buckling on the vertical buckling. Comparison with DnV RP F110, increased coefficient of friction will increase the voltage axial (Seff) of 0.00024% and up 13.4% axial stress (P0) Hobbs.

The Study of Tandem Offloading Performance and Operability on The Cylindrical Hull FPSO Sevan Stabilized Platform with Variation in Mooring System Configuration Eko Budi Djatmiko; Jousie Rebecca; Murdjito Murdjito
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

This study has been carried out to evaluate the dynamic behavior of the Cylindrical FPSO Sevan Stabilized Platform (SSP) and the LNG Carrier (LNGC) during the process of tandem offloading. The study includes hydrodynamics modellings, computations, and simulations of both cases SSP and LNGC operated individually and in combination for offloading operations. The SSP is moored with two variations of mooring, namely taut and catenary. Environmental loads are waves with the incorporated winds and currents propagating 90o, 210o, and 330o relative to the SSP headings. Excitation of random waves up to Hs = 4.50 m instigates the relatively low SSP motions in standalone condition. In offloading condition, when LNGC is connected, the SSP motion could magnify as much as 2.0 up to 5.0 times higher than that in standalone condition, but still considered in an acceptable level. The motion quality of LNGC in offloading operation is comparable with the SSP. For various random wave headings with Hs = 4.50 m during offloading operation may generate maximum tensions between 1,600 kN up to 2,600 kN in the casse of catenary mooring, and between 4,700 kN up to 7,000 kN in the case of taut mooring. Even then, this largest tension preserves a safety factor of 2.05 which is well above the limit of 1.67 as required by the governing standards. Finally, the study conclude an operability of as much as 90% could be achieved on SSP and LNGC offloading operation in the Masela Block of the Abadi Gas Field.

Impact of Reclamation Development on Sedimentation and Current Pattern in East Coast Surabaya (Pamurbaya) Suntoyo Suntoyo; Mohammad Iqbal Hidayah; Hasan Ikhwani
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

Reclamation is an effort to establish a new land area either in coastal areas or in the middle of the ocean. In Pamurbaya area a number of property projects both housing and apartments is still continuing. Environmental impacts of the coastal reclamation project is in the potential increase of flooding. The changes include the extent of the cluster, the composition of river sediments, the tidal pattern, the pattern of ocean currents along the coast and damaging the water system. This study examines changes in current patterns, morphology, and sedimentation rate due to the reclamation modeled using Delft3D software. The pattern of current flow after the reclamation has changed. Basic surface changes that occur before and after reclamation in each crossection is by difference, crossection 1 = +0.22 m, crossection 2 = -0.19 m, and crossection 3 = +0.11 m. The sign (+) shows the occurrence of sedimentation, while (-) is erosion. The condition after the reclamation in crossection 1 is sedimentation, crossection 2 is erosion, and crossection 3 is sedimentation. The difference in intensity is very small, therefore the erosion and sedimentation which took place after reclamation is not too significant.

The Influence of Slopes to the Stability of Stones in front of Seawall Haryo Dwito Armono; Danny Indra Setyawan; Muhammad Zikra
International Journal of Offshore and Coastal Engineering (IJOCE) Vol 1, No 2 (2017)
Publisher : DRPM (Direktorat Riset dan Pengabdian kepada Masyarakat) ITS

Seawall is a coastal protection structure to prevent coastal erosion from wave forces. In this research, rubble-mound of stones are used as armor due to the availability of the material in coastal areas and ease of construction. A series of physical model tests with a scale of 1:25 with a variation of four wave heights (H), two wave periods (T), and three different slopes of rubble-mound in front of seawall were performed. Parameters used in the research are stability coefficient (KD),wave steepness (H/gT2), and percentage of damages (Do). The slope variations of rubble-mound were 1:1.15, 1:1.5, and 1:2. The experiments also displayed that the stone stability coefficient (KD) directly proportional with wave steepness (H/gT2). The value of KD for the seawall model with the slope angle of cot = 1.15 is 4.4, cot = 1.5 is 4.28 and cot = 2 is 3.02. From all three variations of slope, the most stable is on the slope 1:2 with the least damage impact on the model. The gentlest slope is the most stable structure.

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