Fire Mitigating Features

Tools are available to assist in comparing the risk associated with two or more different processes. For example, the first sheet of the Dow Fire and Explosion Index (FEI) (Dow, 1994b) ranks the safety characteristics of the process from a fire/explosion standpoint, without taking credit for protective and mitigation features. The Dow Chemical Exposure Index (CEI) (Dow, 1994a) and Id s Mond Index (ICI, 1985 Tyler, 1985) are other ranking tools. 

The elimination of a fire hazard may be the ideal solution, but it is often not possible. In general, the optimum level of fire protection is achieved by selecting from the other appropriate prevention and mitigation options. The higher the performance availability (or lower the probability of failure-on-demand) of each selected fire protection feature, the more effective the overall fire protection system. The generally preferred approach to improve effectiveness is to select a combination oipassive and active fire protection features. 

In colder climates, enclosures may be necessary to mitigate freeze-related hazards. In enclosed process buildings, additional fire protection features should be added to compensate for reduced ventilation and dissipation of flammable vapors, limited access for firefighting, and handling of runoff from spills. 

Risk potential from outside of the warehouse, such as exposure to nearby high hazard operations should also be evaluated. Mitigating features, such as separation distance, fire walls, emergency response plans, and mutual aid programs should be considered in this evaluation. 

Adequate support bracing, use protective curbs and proper drainage, sprinklers, halon or other fire protection features to mitigate effects of an earthquake. 

Of the various scenarios evaluated, the most serious consequences resulted from the spill of volatile process materials or a fire in an SCB. Based on these evaluations, structures, systems and components with the potential to mitigate this hazard were identified. While many features in the HCF control or mitigate the hazards for both workers and the public, the most significant mitigative feature for the protection of the public is the filtered HCF exhaust ventilation system. 

In all of these scenario variations, the fire suppression system composed of a wet pipe sprinkler system could limit fire progression and possibly the extent of the release. As the sensor that starts the sprinkler water flow is passive and located near the high ceiling level, The sprinkler system may not start promptly to suppress the fire. In that case it will be more of a mitigation feature than a prevention feature so it was not included in the event tree analysis of radioactive material release. 

The scope of this book is to provide a practical knowledge and guidance in the understanding of prevention and mitigation principals and methodologies from the effects of hydrocarbon fires and explosions. The Chemical Process Industry (CPI), presents several different concerns that this book does not intend to address. However the basic protection features of the Hydrocarbon Process Industry (HPI) are also applicable to the chemical process industry and other related process industries. 

The classification system used in NFPA 231 and NFPA 231C is used to specify or determine the need for certain requirements that can prevent or mitigate the effects of fire. These includes automatic sprinkler protection, storage arrangement, and building construction features. 

A formal hazard analysis of the anticipated operations was conducted using Preliminary Hazard Assessment (PHA) and Failure Modes and Effects Analysis (FMEA) techniques to evaluate potential hazards associated with processing operations, waste handling and storage, quality control activities, and maintenance. This process included the identification of various features to control or mitigate the identified hazards. Based on the hazard analysis, a more limited set of accident scenarios was selected for quantitative evaiuation, which bound the risks to the public. These scenarios included radioactive material spills and fires and considered the effects of equipment failure, human error, and the potential effects of natural phenomena and other external events. The hazard analysis process led to the selection of eight design basis accidents (DBA s), which are summarized in Table E.4-1. 

Features for fire prevention were the mechanical properties of some metal material containers and radioactive material form to prevent or reduce the release, and sprinkler fire suppression systems to prevent or delay ignition of combustible materials. In addition, administrative operating procedures, hazardous materiai handling training and packaging requirements could also help prevent or mitigate a fire caused by an electrical wiring short or overheat. 

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