A risk model of passenger ship fire safety and its application

A risk model for assessing a passenger ship's fire safety at the design stage is proposed. Current maritime legislation requires, in principle, compliance with prescriptive regulations of fire prevention, protection and extinction. In a forward step, the International Maritime Organization (IMO) permitted acceptance of fire-safety-equivalent designs on the basis of performance-based assessment procedures. However, the inherent randomness of onboard fire events has not yet been systematically accounted. In this respect, procedures currently applied for fire safety evaluation during ship design, lag behind those applied for the avoidance of ship capsize due to watertight compartments’ flooding, where a probabilistic approach has been in place since long ago. The current work is intended to enhance the probabilistic character of performance-based ship fire assessments; and to establish a consistent risk calculation framework which could also serve in the future as the backbone model of a more integrated approach to ship risk calculation. The core of the proposed model is a risk function combining the probability of ignition, the reliability of the installed suppression systems, and the prediction of the loss given a fire's growth. Design details, such as the space layout and the interior design materials, are fully taken into account. The estimation of the loss is realized by high fidelity simulations. The loss appears in the form of a distribution of fatalities. Several practical risk indices are extracted from the risk function, reflecting potential designer preferences. For demonstrating the practicality of the proposed risk model, a part of a cruise ship's fire zone, accommodating public spaces, is considered. The fire safety performance of the design is evaluated by using the extracted risk indices whose consistency in reflecting the safety level are discussed.