Risk Based Decision Making of Mobile Mooring System

Floating structure uses mooring system for station keeping in any water depth. The mooring accident can cause serious injury or damage to the vessel, and hence it is necessary to establish systematic decision making for minimizing the risk failure. This paper investigates the risk based decision making that involve potential causes and possible outcomes of mooring accidents. The potential causes of mooring failure are analyzed using Fault Tree Analysis (FTA) and the possible sequence outcomes of the accident events are defined using Event Tree Analysis (ETA). FTA is a deductive method that is useful to generate the potential causes of mooring system failure into undesired events. ETA is an inductive method which is helpful to define all possible outcomes of accidental event. The objectives of this paper are to determine the potential causes of mooring system failure, to find the possible sequence outcomes of an accidental (initiating) event and to evaluate the frequency of hazards. The initiating events for mobile mooring system that are investigated are mooring line break (MLB), anchor failure (AF), anchor handling failure (AHF) and appurtenances connection failure (ACF). These events are then broken-down in order to determine the root cause, to define the sequence of the outcomes and to evaluate the frequency of occurrence based on the engineering judgments. The result of the study will be helpful to predict the risk level and to define the mitigation strategy of mobile mooring system.