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Lifting is one of the most important processes in offshore platform fabricaction. This process involves structures with large loads and dimensions which can lead to structural failure. One of the failures that often occur in lifting operations is the failure of the crane hook structure. In this study, strength analysis of the rigging configuration and crane hook is carried out in the upper deck lifting process at the stacking phase using analytical and numerical methods. The hook crane model used is Ramshorn Forged Hooks with a design based on DIN15402. Furthermore, local stress analysis is carried out on the crane hook structure to determine the deformation, maximum Von Mises stress, and Von Mises stress in cross-section that occurs in the crane hook structure with a trapezoidal cross-section. Simulations are carried out using analytical and finite element method software. The results of the stress analysis on the trapezoidal cross-section will then be validated. Then the calculation of the safety factor (SF) based on the results of the analysis of the maximum Von Mises stress is carried out to determine the failure of the crane hook structure when given a predetermined load.

A Fixed Jacket Platform is usually designed using tubular structures in which every steel pipe has a thickness and diameter. Generally, for the structural analysis of this structure, the tubular members are represented using 1D beam elements. But stress distribution, plastic strain and also ovalization around the tubular member cannot be determined by a beam element. In this research, all tubular structures were modeled using 2D shell elements to identify how the stress distribution around a tubular member is. And the non-linear analysis was carried out to identify the initial plastic condition. This study was focusing on the splash zone where this area was assumed to be exposed to the extreme wave in 8 directions according to the API RP2A-WSD code, in addition to the structure weight and deck load. Due to each direction of the wave loads, the stress distribution and initial plastic condition are studied. The modeling and non-linear static analysis in this study were done using Altair Hyperworks software.

An FPU operated at a gas field in Madura Strait is designed to be the main process component of the gas processing facilities for a service life 20 years. This vessel using a catenary mooring system which made up of 12 points mooring divided into 4 groups of 3 mooring lines. This vessel is necessary to be analyzed its mooring tension to ensure safety while operation. The mooring line tension is analyzed by using 3D-Diffraction Calculation. This study presents the result of the dynamic mooring line tension conducted for full load condition of FPU in extreme wave condition. The mooring analysis compliance is based on DNV GL's technical standards, as well as an international accredited registrar and classification society. Verification of computed line tension against acceptance criteria has been carried out for the current condition of the mooring system. Results of the analysis indicate that mooring line tension meets the safety factor from DNVGL OS E301 with the Maximum tension of all mooring lines value is about 159.3 t, which happened in Line 4 by heading 67.5°.

It is important to consider geometric parameters on Stress Concentration Factor (SCF) at the tubular joint, especially multi-planar joint, when designing a jacket platform. Thus, a jacket platform capable to withstand the extreme environmental loads. Many researchers use the Finite Element (FE) method to analyze stress at joints and estimate the SCF with the variation of geometric parameters. That studies obtained the result that geometric parameters have significant effect on decreasing or increasing the SCF. Therefore, this study will delve the effect of geometric parameters (β, τ, and γ) on maximum SCF caused by axial loading, in-plane bending moment, and out-of-plane bending moment at DKT tubular joint. The increase of β results in the decrease in maximum SCF at brace-side and chord-side weld toe, respectively. The increase of τ and γ results in the increase in maximum SCF at brace-side and chord-side weld toe, respectively.

Fouling is an adverse problem for ship. Fouling itself is some kind of marine biota like shells, mussels, or barnacles, which grow and live on the surface of ship’s hull or inside the ship’s piping system. Many methods have been applied to prevent fouling. Impressed Current Anti Fouling (ICAF) was developed and applied as an alternative in mitigation of fouling. The aim of the research was to determine the effects of electrical current, duration time, salinity on Anadara granosa death in simple ICAF system. The simple ICAF reactor was operated in electric current of 1.5 A, and duration time (1,3,5,7 dan 9 h), variations of salinity (33 ‰, 35‰ and 37‰) and the size of shell (1-2 cm and 2-3 cm). Steel of AH36 has a role as a cathode, meanwhile pure copper (Cu) was an anode. The death of Anadara granosa was conducted using direct observation. The direct observation was carried out by opening the shells one by one. The death of mollusc can be confirmed by looking the response from the mollusc. If the mollusc showed no response when it was pierced, it indicated that the mollusc was dead. Besides that, there was white slime inside the mollusc. Based on the results, the death of Anadara granosa with shell size of 2-3 cm showed the highest percentage of 90% at electrical current of 1.5 A, duration time of 9 h, and salinity of 37 ‰. Meanwhile the smallest percentage of Anadara granosa death reached 10% at electrical current of 1.5 A, duration time of 7 h, and salinity of 33 ‰ for shell size of 1-2 cm. In conclusion, duration time and salinity were higher so that the death of Anadara granosa was higher too. Besides that, the small size of Anadara granosa was more resistant.

Recent years have shown the increasing number of SPAR offshore floating platforms built and delivered worldwide. This eventually is strongly related to the generic potential of such platforms, in term of economy and performance aspects, especially for the operation in deep water. For operation in harsh sea environment previous SPAR investigations suggested the addition of heave plate on its keel to enhance the heave motion quality. This paper reports an experimental study conducted on SPAR model, scaled 1: 125 from the full size, installed with a heave plate sized 1.3 of hull diameter. Results of the study demonstrate the additional of heave plate may reduce the heave reaction force due to wave excitation approximately 35% in comparison with that without heave plate. This in turn leads to the decreasing of heave response by as much as 54%. Evaluations suggest the reductions in heave reaction force and response are induced by the escalation of heave damping in the order of 49% generated by the heave plate. The experimental results are well verified by the outcomes of computations based on analytical method and strip theory.

Corrosion can cause damage to steel. One of the main causes of corrosion is biofouling. The Impressed Current Anti Fouling (ICAF) method is one way to prevent the microfouling. The purpose of the study was to calculate reduction of Chlorella Vulgaris population using a simple ICAF system. The simple ICAF reactor was operated with variation of electric current (0.3, 0.5 and 1 A) and duration time (5, 7 and 10 min). Steel of AH36 has a role as a cathode, meanwhile pure copper (Cu) was an anode. The cell number of Chlorella Vulgaris was determined using haemacytometer method. The concentration of Cu was determined using Atomic Absorption Spectrophotometers (AAS). Based on the results, the simple ICAF system showed the decreasing of Chlorella Vulgaris cell number with the highest percentage of 99.98% at electrical current of 1 A, duration time of 10 min and concentration of Cu (17.9 ± 0.07 mg/L). Meanwhile, the lowest of the cell number reduction was 97.57% at electrical current of 0.3 A, duration time of 5 min and concentration of Cu (15.52 ± 0.25 mg/L). In conclusion, ion Cu that was produced during operation simple ICAF system can reduce Chlorella Vulgaris population.

Structural reliability analysis is increasingly used in conjunction with the design of offshore structures which have high uncertainty. Two problems i.e. reliability and complexity of the structures resulted in Monte Carlo Finite Element Method (MCFEM) method of analysis. In the first part of this research, we will show results comparison between deterministic analysis software made in Proposed Software and analysis using commercial established software. In this case, object will assume as a simple Plane Truss structure with multi degrees of freedom applied dynamic load in the support of structure. The second part after obtaining a deterministic result compared by commercial software, further we will apply MCFEM algorithm to the deterministic analysis algorithm which has been made. The results of this research, contains a new procedure in the form of reliability simulation algorithm by combining Monte Carlo Simulation and Finite Element Method in Dynamic Model.

Offshore jacket platforms are designed to fulfil their intended purpose in oil and gas exploitation at designated service life periods. During the operational development, a number of field operators extend their platform service life if the reserves are still available. This technical paper proposes the method to assess the structural integrity of several aging platforms in a field with a simplified approach. Taking the case of “B” Field platforms installed in the mid-1990s, the detailed procedure and example are discussed thoroughly. Five indicators furnished with quantification procedures are also presented to propose the ranking methodology. This paper also proposes the method of jacket platforms grouping based on several similarity criteria. The results of this approach can be used as a baseline for more detailed structural integrity assessment for each group representation.

River pollution can cause coastal pollution due to many pollutants can not remove during water flow from upstream to downstream. River has a capability to do self purification to remediate many pollutans, but wastewater disposal occurred at along the river. One of pollution parameter that caused by organic pollutant was Chemical Oxygen Demand (COD). In this research, the design of reactor was adapted from reed bed system commonly used in constructed wetlands. The purpose of the study was to determine the COD removal by Rhizophora mucronata using reed bed system reactor. There were 8 reactors, with duplo replicates, namely RM15 and RM 25 for treatment with Rhizophora mucronata at 15 ‰ and 25 ‰, respectively, and RMVA15 and RMVA 25 for treatment with Rhizophora mucronata and addition of Vibrio alginolyticus, respectively. Parameter of COD was determined using digestion reactor and spectrophotometer. Based on the results, the highest removal of COD reached 82.06% after 14 days at reactor of RM15. The highest of removal COD with addition of Vibrio alginolyticus was 80.89% after Day 2 at reactor of RMVA15. In conclusion, the Rhizophora mucronata that was grown at reed bed system reactor demonstrated can be used in removing organic matter.