A risk assessment approach to improve the resilience of a seaport system using Bayesian networks

Over the years, many efforts have been focused on developing methods to design seaport systems, yet disruption still occur because of various human, technical and random natural events. Much of the available data to design these systems are highly uncertain and difficult to obtain due to the number of events with vague and imprecise parameters that need to be modelled. A systematic approach that handles both quantitative and qualitative data, as well as means of updating existing information when new knowledge becomes available is required. Resilience, which is the ability of complex systems to recover quickly after severe disruptions, has been recognised as an important characteristic of maritime operations. This paper presents a modelling approach that employs Bayesian belief networks to model various influencing variables in a seaport system. The use of Bayesian belief networks allows the influencing variables to be represented in a hierarchical structure for collaborative design and modelling of the system. Fuzzy Analytical Hierarchy Process (FAHP) is utilised to evaluate the relative influence of each influencing variable. It is envisaged that the proposed methodology could provide safety analysts with a flexible tool to implement strategies that would contribute to the resilience of maritime systems

Facilitating Improvement of Design for Safety and Operations of a Seaweed Harvester: A Hybrid Traditional Safety Method

Sea harvester is a vital marine vessel needed in sea safety and cleanliness. Reliability and safety of the operations of the vessel need to be ensured via identification of hazards/failures that tends to affect the system and prevent them from occurring and also mitigate their consequences. In this research, a traditional hybrid methodology is employed in ensuring the reliability and safety of a sea harvester. The methodology is a logical combination of preliminary hazard analysis (PHA), risk matrix approach (RMA) and event tree analysis (ETA). Fire, flood, machinery failure and capsize that pose to affect optimal operations of a sea harvester are identified using a PHA method. RMA is incorporated in application of the PHA method to estimate the risks associated with them. Due the fact that risks associated with fire, flood, machinery failure and capsize are classified as very high, identifying preventing measures becomes necessary. Furthermore, systems which by means of their operability and non-operability can mitigate fire, flood, machinery failure, capsize and grounding consequences are captured using an ETA method. Therefore, the traditional hybrid methodology developed is successfully applied in design for safety, construction and operation of a sea harveste

Decision-supporting models for human-reliability based safety promotion in offshore Liquid Natural Gas terminal

We would like to give great thanks to the experienced engineers in the Beihai Offshore LNG Terminal for their helpful support during the preparation of this paper. We would also like to express thanks to the editor and the anonymous reviewer for the valuable comments.Peer reviewedPostprin

An Integrated Human Reliability Based Decision Pool Generating and Decision Making Method for Power Supply System in LNG Terminal

Acknowledgement We would like to give sincerely thank to Zhonghe Zhang, the principle expert in Sinopec and other relevant staff in Beihai LNG terminal for their valuable and constructive support during the development of this work. We would also like to express our very great appreciation to the respected reviewers. Their valuable suggestions and comments have enhanced the strength of this paper.Peer reviewedPostprin

ENVIRONMENTAL AND COST-EFFECTIVENESS COMPARISON OF DUAL FUEL PROPULSION OPTIONS FOR EMISSIONS REDUCTION ONBOARD LNG CARRIERS

The selection of the suitable propulsion system for LNG carrier highly affects the ship capital and life cycle costs. The current paper compares between the available propulsion systems for LNG carriers from environmental and economic points of view operated with heavy fuel oil (HFO) and marine gas oil (MGO). In addition, the cost-effectiveness for emission reduction due to using dual fuel propulsion options using natural gas fuel (NG) is calculated. As a case study, large conventional LNG carrier class has been investigated. The results show that steam turbine (ST), Ultra-ST, dual fuel diesel engine (DFDE), and combined gas and steam (COGAS) propulsion options can comply with NOx and SOx emissions regulations set by IMO using dual fuel mode with NG percentages of 87.5%, 82%, 98.5% and 94%, respectively. DFDE operated with pilot HFO and NG is the most economic propulsion option. It reduces the dual fuel costs by 1.37 MUS$/trip compared with HFO cost. The annual cost-effectiveness for the most economic and emission compliance propulsion option is 6.07$/kg, 6.39 $/kg, and 0.55$/kg for reducing NOx, SOx, and CO2 emissions, respectively

EXERGY ANALYSIS OF THE MAIN PROPULSION STEAM TURBINE FROM MARINE PROPULSION PLANT

The paper presents exergy analysis of main propulsion steam turbine from LNG carrier steam propulsion plant. Measurement data required for turbine exergy analysis were obtained during the LNG carrier exploitation at three different turbine loads. Turbine cumulative exergy destruction and exergy efficiency are directly proportional - they increase during the increase in propulsion propeller speed (steam turbine load). Cumulative exergy destruction and exergy efficiency amounts 2041 kW and 66.01 % at the lowest (41.78 rpm), up to the 5923 kW and 80.72 % at the highest (83.00 rpm) propulsion propeller speed. Increase in propulsion propeller speed resulted with an increase in analyzed turbine developed power from 3964 kW at 41.78 rpm to 24805 kW at 83.00 rpm. Analyzed turbine lost power at the highest propulsion propeller speed is the highest and amounts 3339 kW. Steam content at the main propulsion turbine outlet decreases during the increase in propulsion propeller speed. Exergy flow streams can vary considerably, even for a small difference in propulsion propeller speed. Steam turbine in land-based power plant (high power steam turbine) or in marine steam plant (low power steam turbine) is not the component which exergy destruction or exergy efficiency is significantly influenced by the ambient temperature change

Management and Usage of Nitrogen Systems on Liquefied Natural Gas (LNG) Carriers

The importance of liquefied natural gas (LNG) vessels and the technology that enables their operations is steadily growing. Hence, in addition to professional interest, the general public also displays a considerably large interest in this issue. Today LNG carriers belong to the category of the most technologically developed vessels and therefore managing these vessels requires not only the general knowledge but also the specific knowledge relating to their cargo handling systems. To ensure the safe and economical transport of LNG by sea and to minimize the risk of fire or explosion it is necessary to understand the properties of LNG and nitrogen, an inert gas used in all phases of the carriage and transfer of liquefied gas. The subject of this research is the overall process of nitrogen management in daily operations on board LNG carriers. The aim of the research is to explain, evaluate and define the various applications of nitrogen systems on LNG carriers

LNG Bunkering Network Design in Inland Waterways

Growing awareness of the environment and new regulations of the International Maritime Organization and the European Union are forcing ship-owners to reduce pollution. The use of liquefied natural gas (LNG) is one of the most promising options for achieving a reduction in pollution for inland shipping and short sea shipping. However, the infrastructure to facilitate the broad use of LNG is yet to be developed. We advance and analyze models that suggest LNG infrastructure development plans for refueling stations that support pipeline-to-ship and truck-to-ship bunkering, specifying locations, types, and capacities, and that take into account the characteristics of LNG, such as boil-off during storage and loading. We develop an effective primal heuristic, based on Lagrangian relaxation, for the solution of the models. We validate our approach by performing a computational study for the waterway network in the Arnhem-Nijmegen region in the West-European river network, including, among others, multi-year scenarios in which capacity expansion and reduction are possible

Comparison of Exergy and Various Energy Analysis Methods for a Main Marine Steam Turbine at Different Loads

This paper present energy and exergy analysis of the main marine steam turbine, which is used for the commercial LNG (Liquefied Natural Gas) carrier propulsion, at four different loads. Energy analysis is performed by using four different methods. The presented analysis allows distinguishing advantages and disadvantages of all observed energy analysis methods and its comparison to exergy analysis of the same steam turbine. Each analysis is based on the measurement results obtained in main turbine exploitation conditions. Main turbine is composed of two cylinders – High Pressure Cylinder (HPC) and Low Pressure Cylinder (LPC). At low turbine loads, the dominant power producer is HPC, while at middle and high loads the dominant power producer is LPC. Energy analysis Method 1 which is based on the same principles as exergy analysis, should be avoided if the majority of turbine losses are not known. Other observed energy analysis methods can be applied in the analysis of any steam turbine, with a note that increase in ideal (isentropic) steam expansion process divisions will result with an increase in energy losses and with a decrease in energy efficiency. Energy analysis Method 2 which consist of only one ideal (isentropic) steam expansion process, for the whole turbine and at all observed loads, results with the lowest energy losses (in the range between 639.98 kW and 6434.17 kW) as well as with the highest energy efficiency (in a range between 53.70% and 79.40%) in comparison to other applicable energy analysis methods. For the observed loads, whole main turbine exergy destruction is in range from 608.64 kW to 5922.86 kW, while the exergy efficiency range of the whole turbine is between 54.94% and 80.73%. Exergy analysis and all three applicable energy analysis methods show that increase in the main turbine load results with simultaneous increase in turbine losses and efficiencies (both energy and exergy)