Hazard and Operability Study (HAZOP) is one of the most popular methodologies for Process Hazard Analysis (PHA). Layer of protection analysis (LOPA) is a methodology to further quantify the risk following up on the PHA.
These two exercises pave the foundation for the design of the Safety Instrumented System (SIS). We will first look at the basic ideas about PHA and LOPA and look at the causes for the problems. Finally we will move on to a few consequences and the impacts of a bad HAZOP and LOPA on the SIS.