The purpose of the EERA(Emergency Evacuation Rescue Analysis) study is to ensure that evacuation means (e.g. escape routes, muster areas, primary, secondary and tertiary means of evacuation) can be safely used and that all personnel within the platform can be evacuated in the event of a major accident hazards (MAHs). The hazards will be determined by reviewing the existing MAH assessments i.e. the Fire Risk Analyses, the Explosion Risk Analysis and the toxic and flammable gas dispersion results provided within the Quantitative Risk Analyses. Specific calculations shall be performed in this study to determine the smoke impairment frequencies.
The escape, evacuation and rescue analysis (EERA) makes a distinction between two different types of calculations performed independently which are:
- The calculation of escape and evacuation time considering worst case workers’ locations
- The assessment of impairment frequencies of the various EER facilities (muster areas, life rafts…)
Escape and Evacuation time prediction
The possible development of events prior to emergency evacuation of an installation is difficult to predict. In order to simplify the range of possibilities, events are normally assumed to follow a generic EER sequence. In order to assess evacuation and escape times, assumptions considered for each step of the sequence shall be presented in the assumption register. This represents a sequence applying to a typical (i.e. generic) installation. The required time to evacuate the installation should be regarded as a theoretical time estimate, as the estimated time is based on generic values and expert judgment.
In reality, these sequences only apply as long as the evacuation remains orderly. If the initiating incident is severe, the evacuation may be disrupted as the evacuation means are impaired or the personnel are not able to reach the mustering station. The following are the sequence considered for estimating the time.
- Alarm and delay time to start mustering
- Escape to muster area
- Roll-call and don lifejackets / survival suits
- Evacuation / escape to the sea
- Rescue / Recovery to a place of safety
- Total escape and evacuation time
- Critical aspects in escape and evacuation time calculations
Impairment of EER facilities
The impairment of EER facilities i.e. muster areas, primary, secondary and tertiary means of evacuation and the escape routes are studied to ensure that they can be safely used and that all personnel within the platform can be evacuated in the event of a major accident hazards (MAHs). Their impairment is assessed with regards to the hazards determined by the existing MAH assessments and the toxic and flammable gas dispersion results provided within the Quantitative Risk Analyses.
Consequences of all types of hazardous outcomes are thus re-used from other reports except the smoke dispersion which is specifically calculated for the EERA study.
The main assumptions related to the impairment of the EER facilities are the thresholds selected to represent impairment for radiations, smoke, overpressures, flammable and toxic gas concentration. In some cases, these thresholds represent a structural impairment of the EER means, and in some other cases, they represent a temporary unavailability of EER means. They also differ between the different EER facilities depending on their vulnerability to the various hazardous outcomes.