Frequently asked questions
Aggregation of hazardous phenomena

When should the aggregations be carried out?

Aggregations are generally offered:

• or at the start of the analysis (this is the case, for example, for grouping similar equipment or defining equivalent piping);

• or at the end of the analysis, once the risk assessment grid has been completed using all the hazardous phenomena.

What are the criteria for considering equipment as similar?

To group equipment together, it must :

• are of similar design;

• are located in the same geographical area of the site;

• have MMRs with equivalent performance criteria (e.g. probability of failure, response time, efficiency);

• contain products whose release will lead to similar effects. For example, a tank containing a toxic product cannot be grouped with a tank containing...