Kriyo Sambodho

Risk Assessment on Subsea Gas Pipelines Located at Water Basin of Jetty Area due to Dredging and Operation After Dredging

This study addresses risk assessment of 14″ gas pipelines buried closed to jetty area due to the plan to dredge the water basin at jetty area. The dredging plan is aimed to enable a more spacious maneuvering basin at the jetty area to enable larger vessel to be served and easier control of tug boat operation during berthing process. Before dredging, the gas pipeline is located 133 m from the slope. This condition provides enough protection to the gas pipeline since large vessel will not reach the pipeline due to vessel’s draft restriction. After dredging, however, gas pipeline will be located only 49 m away from the slope. The water area after dredging allows larger vessel will be in the vicinity of the pipeline and hence impose risk to the existence of the gas pipeline. Risk to the pipelines due to dredging activities (drop/drag anchor, drop clamshell/object, ship sinking, and ground instability) and due to various vessels operation after dredging (drop/drag anchor, ship sinking, and ship grounding) are assessed by implementing quantitative risk assessment. Hence, this study is focused on the assessment of risk to the 14″ gas pipeline due to dredging activity including risk assessment during operation of the jetty after dredging. Based on pipeline and environmental data, all possible hazards are identified. Some hazards are screened out using ‘Failure Modes and Effects Analysis’ (FMEA) to obtain the list of potential hazards. In order to evaluate the acceptance criteria of all potential risks, the risk profiles are composed according to DNV-RP-F107 “Risk Assessment of Pipeline Protection”. As part of the assessment, geotechnical assessments of submarine landslide due to dredging are also considered. The effective stress approach is implemented to the assessment and submarine slope stability is analyzed using Bishop’s and Janbu’s methods of analysis. The risk profiles for all potential hazards are reported, and simulation results for different slope ratios are given to illustrate the stability of slope configuration during dredging.© 2013 ASME

Development of Eco-friendly Aquaculture Design for Lobster Cultivation in Indonesia

Lobster products are important for the economy in fishing community. Climate change will lead a threat to lobster productivity. Therefore, a solution offered is to cultivate certain lobsters, especially those with high economic value by using Aquaculture. This research aims to develop a small-scale aquaculture for the cultivation of lobsters with bamboo as primary material, which is environmentally friendly and inexpensive. The proposed design of lobster aquaculture in this research adapt lobster habitat in its nature. Therefore, it uses the artificial reef as a shelter for lobster. The main structure of the lobster cage uses bamboo and the floater use HDPE (High-density polyethylene) barrels. The result of aquaculture motion analysis using numerical model has been validated by experimental test in Flume Tank. The differences result of heave RAO (Response Amplitude Operator) motion between numerical model and experimental test is 0.05 m. The results of this validation analysis show that it is reasonable agreement.

Sea Level Rise on Tuban Coast in East Java and its Consistenty with MAGICC/SCENGEN Prediction

Sea level rise is one of the impacts of climate change and global warming caused by the increase of human activities leading to the increase of concentration of greenhouse gases in the atmosphere. The impacts of sea level rise itself will be greatly felt by coastal areas in island countries, one of them is Indonesia (specifically the district of Tuban). The purposes of this paper are (1) to indicate that tidal data in Semarang and Tuban (both of them are cities in the northern coast of Java) can be used to estimate the sea level rise in the region through the means of comparison, and (2) to compare sea level rise in MAGICC model and show that sea level trends for Tuban district are consistent with global values. The results shows that the tidal data in Tuban has a higher value than the tidal data in Semarang by a margin of 0.03 m, so the trend of sea level rise in Tuban is y = 0.002x + 0.751, consequently the sea level rise per year is 0.024 m. Comparison of sea level rises between the MSL data of Tuban district with MAGICC model indicates that the sea level trends for Tuban district (local) are consistent with global values, that is, in the year of 2100, the sea level rise will reach 2.64 m while emissions scenario that comes close is the WRE 550 scenario, that is, in the year of 2100, it will reach 2.9 m.

Anchor Strength Analysis for Mooring of a Floating Breakwater in Senoro Field, Central Sulawesi

This paper will describe complete investigations of the analysis anchor strength for mooring of a floating breakwater in Senoro Field. The terminal has berthing facilities located in a water depth about 30 meters, with the wave height of 2.7 meters that made difficult for tanker to berth properly. The requirement for berthing ships must have minimum wave heights of 0.7 meters to 1.5 meters as a requirement [1]. Considering the previously mentioned, a floating breakwater has suggested for reducing wave height. The purpose of this final project is to determine the tension mooring line and anchor pile strength to withstand all possible working loads. Response amplitude operator (RAO) of floating breakwater is used to find the structure characteristic as a response due to wave action. Based on the study, wire rope mooring was chosen due to its safety factor passed API RP 2SK standard, such as the biggest tension is 1389,68 kN on line 1 and the smallest is 1157,72 kN on line 8. Calculate anchor pile strength with three types: spun piles, spun square piles, and triangular piles. Anchor pile could be installed depending on three main factors, uplift capacity, bearing capacity and pile in compression. Based on the analysis, uplift capacity result for pile F is 1960.1 kN, while uplift load result is 1958.47 kN, and pile in compression result is 4155 kN while allowable compression result is 5532 kN. For pile G, uplift capacity result is 1960.7 kN, while uplift load result is 1958.47 kN, and pile in compression result is 4599 kN, while allowable compression result is 7189 kN.

Investigation of Risk Based Decision Making for Mobile Mooring System

This paper briefly presents the investigation of risk based decision making for mobile mooring system. This paper used bow tie analysis to analyze the risk of mobile mooring failure. Bow tie analysis consists of FTA (Fault Tree Analysis) on left part and ETA (Event Tree Analysis) on the right part. FTA is useful to determine the potential causes from critical top event until the undesired events are obtained. ETA (Event Tree Analysis) is helpful to define the possible consequence by relating an initiating event to various consequence models. The investigation consists of determining the critical hazards of mooring system failure through investigating the root causes, the consequences, and the frequency index.

DESIGN AND MODELING PILE BREAKWATER for LNG JETTY AT SENORO FIELD, CENTRAL SULAWESI

Senoro Gas Development Project is one part of a joint project between Pertamina and Medco E&P in the field of oil and gas exploration, located in Central Sulawesi, Indonesia. Senoro gas field built a jetty as berthing facility with length around 500 m from the shore. Based on the survey results showed that significant wave height is 2.7 m height at jetty area, while the requirement for vessel berthing larger than 50.000DWT is 0.7 to 1.5 m. Therefore, pile breakwater was planning to build in Senoro jetty area to protect and to reduce the wave height. From bathymetry data shows that the water depth in front of the jetty is between 20-30m. In this case, breakwater conventional or rubble mound type will not be effective for this depth. Thus, pile breakwater is one of the solutions as protection structures for protecting the jetty area from wave attack. The objective of this study is to modeling the performance of pile breakwater to reduce wave height with numerical model. For this study, analysis of the performance of the breakwater is done with numerical model of computational fluid dynamic analysis. The results indicated that pile breakwater was able to reduce the wave height for safety berthing requirement.

Identification of levee strenght for early warning system using fuzzy logic

There are still much potency of levee breaches in Indonesia. The levee strength is mostly influenced by the changing of its constituents. One of the key parameter of this phenomenon is the changing of soil water content in levee body. The increasing of soil water content will loosen the bonds among soil granules that may increase the potential of the levee breaches. The sequence of the changing parameter before levee breach is a crucial data. In this research, a monitoring system have been designed to collect the changing of soil water content using moisture sensor and to examine the changing of water level using ultrasonic sensor. These data will be further processed using fuzzy logic to identify the dangerous state describing the real of levee strength as an early warning system.