Ship-to-ship LNG Bunkering: Risk Assessment and Safety Zones

In this paper risk assessment for the ship to ship LNG bunkering is carried out by exploiting the results of the projects “SUstainability PERformance of LNG-based maritime mobility – PLUS” (SUPER-LNG PLUS) financed by Interreg-Adrion and the project “Risk management system for design and operation of installations for LNG refuelling” (TRiTON) financed by the Greek government. Ship to ship bunkering constitutes a simple method when storage tanks cannot be installed in the port areas. In brief, risk assessment is conducted in the following basic steps: a) assessment of plant damage states and their frequency of occurrence, b) assessment of consequences and c) risk integration. First, the Master Logic Diagram (MLD) technique is used to identify the initial events that create a disturbance in the installation and have the potential to lead to an LNG release during a ship to ship bunkering operation. Moreover, safety functions and systems for preventing LNG release, are identified and Event trees are developed to model the accident sequences which lead to damage states. By exploiting available failure rate data, the frequency of each damage state is estimated. In parallel, the consequences of LNG release are estimated based on the heat radiation or overpressure dose an individual receives. Finally, iso-risk contours are calculated by combining the frequencies of the various accidents with the corresponding consequences. A case study for a ship to ship bunkering in a Greek port is presented.