Safeti QRA - Quantitative Risk Assessment

Phast and Phast Risk offer a simple and flexible process for analysing process industry hazards. Simulation of accidents from hazardous events can be conducted in several steps.

1. An example of the simple release case inputs
The vessel/pipe source can be used to efficiently describe releases scenarios such as ruptures, leaks, short pipe ruptures, long pipeline releases, relief valves & bursting discs, vent from atmospheric storage tanks, fixed duration releases and tank roof collapse. These releases can also be performed using an indoor model to investigate the effects of secondary containment and subsequent release to atmosphere.

Fig - the Material tab of the Vessel/Pipe source model, where stored material, inventory and process conditions are specified

2. An example of one of the many effect results
When performing consequence analysis you then would work with the array of consequence results to make decisions about your process plant design, operation, layout, and emergency response. Consequnce results include:

• Discharge details
• Dispersion results including full description of a dispersing cloud over time, provided through reports, and graphs of sideview, footprint and cross sections
• Pool formation and re-evaporation details
• Flammable: fireball, jet fire, pool fire radiation intensity, close and lethality
• Flash fire envelope graph
• Toxic dose, probit and lethality reports and graphs
• Explosion output, using TNT, TNO, Baker Strehlow Tang methods
• Phast and Phast Risk can simulate an array of release and effects under various weather conditions
  

Fig - An example of Jet Fire radiation versus distance results

Fig - An example of the Jet Fire radiation and effect zone over a satellite photo

3. Addition of further information used in Risk calculations
If you are interested in risk analysis you would continue to work with further information to describe your activities including onsite and 3rd party population, ignition sources and wind direction and condition probabilities.

Fig - An example of population and ignition sources located on a GIS map

Phast Risk then performs calculations to determine the impact of your flammable and/or toxic clouds and how they interact with the ignition sources and populations you have specified.

4. An example of Individual Risk Contours
The results are provided in a variety of useful forms such as Location Specific Individual Risk contours. Risk Contours visually describe the level of risk on your map, so you can determine whether the risk is tolerable in sensitive areas.

Fig - An example of Individual Risk Contours

5. An example of Societal Risk Curves
The risks can also be displayed as societal risk curves, commonly referred to as FN curves; which show the likelihood of fatality to various sizes of population who are exposed to the effects of your process plant activities.

Fig - An example of Societal Risk, FN Curve with Risk Criteria lines displayed

Phast Risk then contains an array of tools for ranking the risk by the contributing release case, effect type, even weather direction. When analysing societal impact Phast Risk can also tell you which populations have been impacted by the various releases, providing PLL (potential loss of life) and FAR (fatal accident rate) measures.