Structural fire risk assessment

Identifying and analyzing fire hazards and scenarios is the next step in a fire risk assessment. The hazard identification should be structured, systematic, audit-able, and address all fire hazards, including nonprocess fires. The result of the hazard identification is a list of potential fire hazards that may occur at the facility, for example, jet, pool, flash, BLEVE, electrical, or Class A fires. This list should also include the location where each fire could occur. Hazard identification techniques used to identify potential hazards are shown in Table 6-1. 

A simplified fire safety evaluation of a building (see Table F.2). It consists of analyzing and scoring hazard and other related risk parameters to produce a rapid and simple estimate of relative fire risk. A detailed fire risk evaluation may not include attributes such as human behavior and attitudes. The structure of a risk index system facilitates quantification and inclusion of such factors. Where a quantitative fire safety evaluation is desirable, detailed fire risk assessment may not be cost-effective or appropriate. Fire risk indexing may provide a cost-effective means of fire safety... 

Passive measures relate to the ability of a building to withstand the effects of fire and also to prevent the spread of fire. These measures are usually part of the structure of the building and can result from a requirement of the Building Regulations or as a result of a fire risk assessment. 

For risk informed regulation and applications (RIR A), importance measures (IMs) (Borst et al. 2001, Kim et al. 2003, Vesely et al.l983, Wall et al. 1996), such as Fussell-Vesely (FV), Risk Reduction Worth (RRW) or Risk Achievement Worth (RAW), play a very important role. Especially, IMs in fire probabilistic risk assessment (PRA) as well as internal events PRA are important for the risk informed structures, systems and components (SSCs) categorizations (NRC 2002, NEI 2004). 

Accidental fires interact with their environment, should this be pipework, equipment and structures in process plants in petrochemical industry, or facilities on offshore oil and gas installations. For plant design and risk assessment, cautious best estimates and uncertainty ranges are required for a number of combustion parameters. These include release rates, flame size and shape, heat output, thermal radiation to its environment, and the heating-up of structures, pipework and items of equipment. The estimate can result in the assessment of time to loss of functionality of these structures and pressurized equipment. 

Moreover, the Advisory Committee on Reactor Safeguards (ACRS, 1999, pg. 2 see also ACRS, 2000) has noted that risk-informed regulation requires a strong research program. In particular, the ACRS (1999, pg. 3) was concerned about the adequacy of current risk assessment methods for dealing with fires software-based digital systems aging of structures, systems and components... human performance safety culture, and low-power and shutdown operations. ... 

The withstand required by plant systems, structures and components against internal hazards, such that appropriately safe operation can be maintained, has been addressed comprehensively in the European Design Control Document (DCD) (Reference 4.4), primarily in Chapter 3, and will be discussed for each hazard in turn, in the sub-section following. On the basis of the requirements for withstand being directly incorporated into the design basis for the plant systems, structures and components, only those postulated hazards with significant requirements on management are taken forward for further assessment in the Probabilistic Risk Assessment (PRA), to make sure that the requirements to ensure any potential vulnerabilities are identified and addressed. The internal hazards taken forward to the PRA for this purpose are internal fire and internal flood. 

A whole range of precautions may be based on the principles summarized earlier. However, general precautions, applicable to the majority of work situations, are listed in Table 5.13, many of which are included in legal requirements. For example, in the UK The Fire Precautions Act 1971 specifies requirements for fire resistance of surfaces and building structure, assessment of risk, means of escape, means for giving warning, firefighting equipment, and fire instruction and drills. 

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