As part of the business process dell'indusria Hazard and Risk assessment is carried out in accordance with the requirements of IEC 61511-1 applying the guidelines given in IEC 61511-2. Usually it is performed in 3 successive steps:
- Preliminary Hazard and Risk Assessment: has the purpose of determining, from the stage of design of the system, all the possible hazard of the process with a dual purpose:
- as far as feasible, eliminate and reduce the hazard by means the principles of intrinsic safety and good engineering practice;
- determine the architecture of the system before the definition of "process and Intrumentation (P & I) diagrams" is completed.
- Hazard and Risk analysis: has the following purposes::
- determine all hazardous situations and the events and the sequences of events that produce them. The identification of dangerous situations is done by making use of specific checklists, developed by the industry for standard processes (such as the checklists contained in the ISO 10418 and APIRP14C), or, for more complex projects and for non-standard processes, using a more structured approach, as defined in IEC 60300-3-9.
- determine the consequences and the probability of occurrence of the events and the event sequences that produce dangerous situations;
- determine the necessary risk reduction for each hazardous situation, for example, using the principle known as ALARP (as low as reasonably practicable);
- determinare i provvedimenti atti a ridurre o rimuovere i pericoli ed i rischi;
document the assumptions made during the analysis, including the estimated rate of requests of the system and the estimated rate of failure of the equipment / tools. To determine the previous estimates, when the complexity of the system is high, the "fault tree analysis (FTA)" is used, taking into account all the possible operating conditions of the system.
- Hazard and Risk final assessment: the purpose is to determine, among other things, if any failure of the safety systems introduces new hazards and consequently the need to define additional safety functions. The final analysis is usually done by means of fully documented formal procedures, for example the "hazard and operabilty Study (HAZOP)".