escalation is also described probabilistically. The consequences in this framework
Figure. 3
“fire protection”, a concept that includes detection, suppression and spread. The relevant weighting factors represent space criticality, e.g. fire effluents, occupancy, space topology and proximity to staircases, fire mains etc. In Risk Based Design, risk is defined
as the chance of a loss and, for practical purposes, is expressed as the frequency of occurrence of exactly N number of fatalities per ship-year (s-y). Developed from the broad approach used in SOLAS Ch.II-1 (probabilistic damaged stability), the FIREPROOF methodology can be summarised in the formulation shown in Figure 1. Tis formulation allows the risk to be expressed in one of two conventional ways; as a Potential Loss of Life (PLL) or an F-N Curve. Te use of these methods is being investigated as part of the FIREPROOF project. Tere are several key points regarding the
population of this equation with numerical data, which address the physical nature of fire and compliance with concepts and definitions laid down in SOLAS Ch.II-2. Fire ignition is treated as an event that
can take place at any time and in any space onboard without reference to its root causes. It is presented probabilistically, as a frequency of occurrence per ship-year, for each of the 14 types of spaces prescribed in SOLAS. Te escalation of fire outside the space
of origin is associated with failure to contain, control and suppress the fire by onboard means (mechanical or manual) and through human (passenger or crew) intervention. Fire escalation signifies the exposure of passengers and crew, located in the same fire zone, to the fire effluents (poisonous gases, oxygen depletion, heat, and visibility impediment), which could result in injuries and fatalities. Fire
The Naval Architect October 2012
correspond to loss of life, which occurs due to exposure to fire effects. Tis exposure is a result of the physical effects of the fire (heat, smoke, toxic gases) and the time taken to complete the evacuation process. Te latter element incorporates the effects of the arrangement of the ship and the potential blockage of the main escape routes due to fire. Te resulting fire risk is expressed as
the frequency of a number of (statistical) fatalities that could occur due to the fire occurring in a space per ship-year. Following the basic premise of the Risk Based Design methodology, a holistic risk assessment process is utilised, implying that the total fire risk should correspond to the summation of all risks due to all fire occurrences in all spaces onboard. It should be noted that summing this risk over the range of possible fatalities (i.e. from N=1 to N=total population) would give the expected number of fatalities per ship-year.
metrics represent knowledge about the relationships between ship features and the resulting fire and evacuation effects, where the knowledge has been gained from multiple simulations. Tese risk metrics, under development in the FIREPROOF project, are formulated in such a way that they can be applied to the new layout, being sensitive to those arrangement features found to determine the consequences of a fire. The use of simulations as a source of knowledge in combination with historical data is a key concept within the FIREPROOF methodology. It allows incidents that, fortunately, have not yet occurred to be examined, and the simulations can be developed in a structured and systematic manner. One of the motivations behind the
FIREPROOF project is the increasing interest in novel layout configurations and this means that the risk metrics may not always be applicable. Tus, in addition to the analytical metrics, the methodology makes use of bespoke simulations carried out on a proposed design configuration.
Generation of fire scenarios Returning to the overall
formulation Figure. 4
Application of the methodology The objective of the FIREPROOF methodology is to capture and describe the risk in new designs, to indicate which design options are safe and which are not, and to indicate where the risk lies in the design. Risk in a new design is to be assessed using a combination of analytical risk metrics and bespoke simulations performed on the proposed design configuration, as shown in Figure 2. Te analytical risk metrics are derived
from a combination of historical data and simulations on generic models representing realistic ship layout features. Tese risk
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of the FIREPROOF methodology in Figure 1, we define a fire scenario as encompassing the probabilities of ignition and escalation. Te probability of ignition is primarily based on historical data related to the 14 categories of spaces defined in SOLAS, as these are grouped broadly by fire risk based on contents and usage. Te subsequent fire development depends on various parameters, such as fire type and size, geometric and ventilation characteristics together with the effectiveness of suppression systems and actions. A range of approaches, such as
Figure. 5
Feature 2
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