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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.

Line Clashing Probability Analysis of Catenary Anchored Leg Mooring with Quadraple Marine Hose Configuration Gumilang Alhafiz; Murdjito; Eko Budi Djatmiko; Fajar Rachmadiarto
International Journal of Offshore and Coastal Engineering Vol. 10 No. 1 (2026)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25800914.v10i1.9920

Global efforts to reduce carbon emissions have encouraged the adoption of lighter and more flexible offshore structures in support of Sustainable Development Goal (SDG) 13 and the International Maritime Organization (IMO) climate initiatives. This study investigates the technical performance of a Catenary Anchored Leg Mooring (CALM) terminal system connected to a Floating Storage and Offloading (FSO) facility using four subsea hose configurations of the Chinese lantern and lazy S types. Due to their flexibility, subsea hoses are susceptible to clashing under extreme environmental conditions, potentially causing damage and reducing operational reliability. Dynamic simulations were conducted to evaluate tensile forces, minimum bending radius, bending moments, shear forces, torsion moments, and the probability of hose clashing. Prior to the analysis, buoy stability was assessed following modifications to the hose configuration. The results indicate that the additional hose arrangement increased the buoy draft by 14.9% to 2.73 m. Under Accidental Limit State (ALS) conditions caused by anchor chain failure, structural loads on the hoses increased significantly, while the minimum bending radius decreased by 6%. Furthermore, the probability of hose clashing was substantially higher in ALS conditions than in Ultimate Limit State (ULS) conditions, demonstrating that anchor chain failure significantly increases the risk of subsea hose interaction and potential damage.

Operability Analysis During Topside Platform Removal with Dynamic Method Due to Wave Load Muhammad Zakaria Al Amin; Murdjito; Eko Budi Djatmiko; Fajar Rachmadiarto
International Journal of Offshore and Coastal Engineering Vol. 9 No. 2 (2025)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j225800914.v9i2.8929

Topside removal is one of the main activities in the offshore platform decommissioning process, with one of the methods in this process being reverse installation-single lift. Corrosion, one of the common problem factors in steel structures, is used as a parameter to reduce the strength of topside structures. In the structural strength analysis with a thickness reduction of 1.5mm, the maximum unity check values for members and joints are 0.854 and 0.602, respectively. Meanwhile, the dynamic analysis results show that the hoisting line and sling tension increase with increasing wave height and period. The response to increasing tension due to wave loads increases exponentially. The beam seas loading direction produces the highest tension response due to the roll motion response to the crane barge. The shortest hoisting line influences tension due to the higher stiffness value, which results in velocity and acceleration in the topside movement as a pendulum, thereby increasing the snap force. This pattern also applies to the dynamic amplification factor (DAF) and factor of safety (FOS) sling values. The distribution fitting results on the DAF value, 3-Parameter Lognormal, is the correct distribution model with a correlation value 0.999. So, the operational operability in the range of conditions for this research model is 89.4%.

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; Murdjito Murdjito; Jousie Rebecca
International Journal of Offshore and Coastal Engineering Vol. 1 No. 2 (2017)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j2580-0914.v1i2.7054

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.

The Study of Mooring Buoy Operability to Support Offloading Operation of Shuttle Tankers with Various Capacities Eko Budi Djatmiko; Murdjito Murdjito; Mochammad Afif Zahiru Fajar
International Journal of Offshore and Coastal Engineering Vol. 4 No. 1 (2020)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j2580-0914.v4i1.8704

This study was conducted to analyse of the operability of mooring buoy initially designed for offloading operation of 35,000 DWT shuttle tankers enhanced to serve the offloading operations of shuttle tankers with 50,000 DWT, 75,000 DWT, and 111,000 DWT capacities. Operability is reviewed in term of mooring line tensions induced by each new variation of tanker capacity under environmental conditions of 1-year, 10-year, and 100-year recurrence. The governing criteria is that the safety factor should meet the appropriate limit as stated in the API RP2SK. Tension on the mooring line increases in parallel with the increasing of tanker capacity. For the case of 35,000 DWT and 50,000 DWT shuttle tankers the operation can be performed in all environmental conditions. For the case of 75,000 DWT shuttle tanker with full load and 67% DWT capacity can fully operate in all environmental conditions, but with 47% DWT capacity could not be operated in the 100-year environmental condition with significant wave height 3.31 m for the direction of inline-L1, inline-L2, and between line-L1&L4. For the case of 111,000 DWT shuttle tanker at all capacity conditions can fully operate in the 1-year environmental condition with significant wave height up to 1.48 m.

Lazy Wave Flexible Riser Dynamic Tension Analysis with Variation of Diameter and Buoyancy Module Configuration in Extreme Condition Muhammad Farhan; Eko Budi Djatmiko; Murdjito
International Journal of Offshore and Coastal Engineering Vol. 9 No. 1 (2025)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j225800914.v9i1.4502

ABSTRACT Oil and Gas Production at floating offshore facilities is growing. It prompted the design of the Flexible Riser as a solution to channel exploration results to floating offshore facilities. In this final project, dynamic stress analysis of lazy wave flexible riser is carried out with variations in diameter and number of buoyancy modules under extreme conditions. This study discusses the maximum tension and minimum bending radius (MBR) on the flexible riser due to variations in diameter and number of buoyancy modules in extreme conditions with two system conditions, namely intact conditions and damage conditions. From the results of the analysis, the larger the diameter of the flexible riser, the greater the maximum tension at the SPM point. While it will be smaller at the PLEM point and the more buoyancy modules used, the smaller the maximum tension at the SPM point, the larger it will be at the PLEM point. The larger the diameter of the flexible riser, the smaller the MBR in the SagBend area. The larger the HogBend area and the more buoyancy modules used, the larger the MBR in the SagBend area, while the smaller the HogBend area.

Analysis of the Pretension Angle of Mooring Lines SPM and Its Effect on the Tension and Strength of Subsea Marine Hose Rabiatul Muthi’ah; Murdjito Murdjito; Eko Budi Djatmiko
International Journal of Offshore and Coastal Engineering Vol. 9 No. 1 (2025)
Publisher : Department of Ocean Engineering

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j225800914.v9i1.4506

The industry of oil and gas industry have developed along with advances in technology, so does the mooring system. Mooring system is a series that functions to keep the ship station or floating platform at all water depths. Currently, there are many types of moorings that can be used, one of which is Single Point Mooring (SPM). SPM itself consists of various types of mooring legs, as well as other supporting components such as subsea hose or riser. Subsea hose and mooring lines are closely related because in the application, the length of the mooring lines also determines the offset or limitation of motion of the SPM, while the subsea hose also has a maximum limit of pull caused by the movement of the SPM. In addition to the length of the mooring lines, another factor is the pretension angle. Therefore, in this study, an analysis was carried out by varying the pretension angle (45°, 50°, 55°, 60°) under extreme conditions and inline loading by reviewing the tensile forces on the mooring lines and risers. The larger the angle, the smaller the tensile force, so the offset would be larger, and vice versa. The results of this study indicate that the pretension angle applied must be appropriate so that the tensile force on the mooring lines that occurs can also be appropriate.

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