LNG Bunkering Operations: Establish probabilistic safety distances for LNG bunkering operations.
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The environmental and economical advantages of using LNG as marine fuel have been recognized by the industry. In response to increasing demand, construction of LNG bunkering infrastructure is under rapid development. Several ports are preparing to supply LNG, but uncertainties concerning the bunkering process and operational safety still exist. Recently, much work has been done to standardize LNG bunkering solutions, including a launch of an ISO guideline and a Recommended Practice (RP) by DNV. One of the main topics of these documents and of international discussion is operational safety and the establishment of safety zones around the operations. High risk is particularly associated with vulnerable objects (i.e. third parties, like ferry passengers) in the vicinity of the bunkering operation. Ferries are currently the main LNG fuel consumer and some ferries have passengers on at all times. Current regulations do not allow passenger presence during bunkering. This limitation reduces the functionality and competitiveness of LNG, and has proved to be problematic for ferry companies. The goal of this thesis is to establish probabilistic safety zones for a generic ship-to-ship (STS) bunkering case. Threats to vulnerable objects and the associated likelihood, in the event of an LNG leak, is identified. The specific purpose is to determine whether acceptable safety levels for passengers are present onboard a ferry performing LNG bunkering operations. This study will assess the risks involved and calculate safety zones through an established probabilistic approach, known as Quantitative Risk Assessment (QRA) methodology. This method includes frequency and consequence calculations of possible Loss of Containment (LOC) scenarios. The acceptable risk level for third parties per bunkering operation is assessed against the widely used criteria of 10E-06.Based on the contour results provided by PHASTRisk (the DNV risk analysis software tool), it is clearly demonstrated that passenger safety can be maintained during bunkering operations. This study concludes that there is no unreasoning risk in allowing passenger presence during bunkering. Passenger safety issues should consequently not limit the application of LNG as fuel for ferries.