by
ayounul haq , Process Safety Engineer I , ENGRO CORP (formerly EXXON)
Process Hazard Analysis has several techniques and approaches which include what if , Hazop, FMEA, FTA, FRED modelling bow tie analysis LOPA etc
If the team is new to PHA and has less experience to plant what if approach which is more of qualitative approach is used.
Hazop is when team has a good experience of operational lnowledge of that plant and can correlate specefic key words with operation should adopt Hazop which is not a rae approach
For instrumenation failures where a cause and effect and logics are required Failure mode and effect analysis is the right apporach
Similarly FTA is used for major catastrophe and its branches top to down approach similarly bow tie analysis etc are used
For more quantitative risk assesment A proper FRED and QRA is done based on modelling software provided with the correct information which specify every loss of containment and its effect in numbers like100m3 of TOXIC material loss similarly realease impact is in no of fatalities etc
Lopa is somewhere in between qualitiative and quantitative risk assesment amd is a semi quantitative approach with each indepent layer provising its protection and is calculated.