Quest’s risk mapping software, CANARY+, is a tool for combining the results of CANARY hazard calculations (consequences) with event probabilities (likelihoods) in Quantitative Risk Analysis (QRA) studies. The software is designed to evaluate a wide range of site-specific weather conditions (wind speed, stability class, and wind direction), as well as multiple release hole sizes, orientations, and hazard types.
Using specific accident locations, a spatial and numerical description of risk surrounding the hazardous material facility is created. CANARY+ presents risk results in:
- Risk contours (public, worker, equipment, or environmental risk)
- f/N curves (societal risk)
Other measures of risk, such as Individual Risk Per Annum (IRPA), Potential Loss of Life (PLL), or overpressure exceedance curves, can be developed from the CANARY+ outputs.
Scenarios are chosen based upon the flammable or toxic components in the process as well as parameters such as pressure, temperature and phase of the material. Once a release is chosen, detailed equipment counts are performed in order to define the probability of the accident occurring.
Quest uses the equipment counts as well as the probability of failure of the individual types of equipment to determine the probability of occurrence of a single accident. The timing and probability of ignition is used to determine the outcomes of a release. Following the mapping of the hazard maps and the associated probability of occurrence yields us risk contours.
The last step in the analysis is to determine the probability that some portion of the population (or worker population) is exposed at any given time. This additional step yields societal risk measures (e.g. f/N curves).
Weather data is obtained or collected for the area where the facility is located in order to more accurately determine how a consequence for a given accident will affect the surroundings. Average temperatures, wind speeds, and the stability of the atmosphere can have a significant effect on vapor cloud dispersion. Some areas may have a lower average wind speed which may allow for larger vapor clouds to form. The stability class of the atmosphere effects how quickly the hazardous materials disperse. The weather data may play a large role in determining the site specific risk in an analysis. For additional information, read our paper on the importance of weather data.
Risk Contours combine the consequences of a unique release with the probability that it will occur. A release can be modeled in , but it has a certain probability of occurring in many directions. Contour maps demonstrate the probability of a specific impact in all directions.
Contour Maps take into account all possible releases from all analyzed processes from every section of a facility or plant and presents the risk in a two- dimensional format. Risk Contours can be developed for the public or worker population, or the equipment or environment. Risk Contours are a vital output from a QRA and are critical when assessing risk.
These maps are helpful in fulfilling governmental regulation in many parts of the world, as well as showing quantitative evidence of the risk a facility poses to it’s own workers, neighboring facilities, and the general public.
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