Receivers

Defining receivers in EFFECTS

There are two types of receivers that can be defined in EFFECTS: congestion areas and vulnerable areas. Each type serves a distinct purpose in evaluating the impact of hazardous events like vapour cloud explosions, fires, and toxic releases.

Congestion areas

A congestion area acts as a confinement or congestion zone critical for assessing vapour cloud explosions. Congestion areas are instrumental in understanding the dynamics of such explosions and should always be integrated with flammable dispersion models to provide comprehensive assessments. A key point to remember is that a flammable cloud will only lead to an overpressure result if such a cloud experiences a certain level of congestion or confinement. If there is congestion, both a flash fire and a vapour cloud explosion occur. Without congestion, only a flash fire occurs.

That is why defining the 3D geometry of this congestion area is of utmost importance. Additionally, the orientation of a congestion area relative to the release point is crucial, as it determines the amount of explosive mass that can be contained within the area. Factors such as the "volume blockage ratio" and "average diameter of the obstacles" further influence the congestion area characteristics. These parameters collectively contribute to the congestion area's explosion strength, consequently defining the potential overpressure zone surrounding such areas. 

A congestion area, connected to a dispersion explosive mass model, will result in a report of congested mass, typical Multi Energy overpressure results, and a threshold overpressure contour. 

Note that if the area is out of reach of the LEL concentration of the release point, there will be no overpressure results.

Vulnerable areas

Vulnerable areas are defined by specific thresholds for vulnerability and typically include locations like hospitals, apartment buildings, or offices. These thresholds determine potential fatalities in the event of exposure to fire, explosion, or toxic dispersion. Vulnerable areas are characterised by their vulnerability thresholds for heat radiation, overpressure, or toxic concentration. The extent of damage depends on the distance from the accident site and the population within and around the area (inside and/or outside).

When connected to an accident model (i.e., fire, explosion or toxic dispersion models), they provide estimates for the number of victims due to exposure to such events. The results that will be reported from connecting a vulnerable area to typical end models, resulting in overpressure, heat radiation or toxic concentration, typically include damage contours and the number of victims inside and/or outside the area. Calculations can be based on a fixed wind direction or the worst-case scenario to determine the wind direction leading to maximum damage.

Summary

• Congestion areas: Critical for evaluating vapour cloud explosions, influenced by geometry, orientation, volume blockage ratio, and obstacle diameter. Must be integrated with flammable dispersion models.

• Vulnerable areas: Defined by thresholds for heat radiation, overpressure, or toxic concentration. Include population considerations and provide estimates for potential victims. Calculations can be based on fixed or worst-case wind directions.

Both types of receivers are essential for comprehensive safety assessments in EFFECTS, helping to predict and mitigate the impact of hazardous events.