Analysis of Independent Protection Layers Used In Three Typical Chemical Processes

Independent protection layers (IPLs) used to mitigate most severe consequences are analyzed for three chemical processes: Olefins, Low-density Polyethylene, and an intermediates chemical plant. The IPLs are categorized by type (i.e., interlocks, PSVs, independent alarms, etc.), by function (preventative versus response), by design (engineered versus administrative controls), and by systems used to ensure their integrity. Categorizations for all three plants revealed similar results and suggest that the analysis extends across the chemical industry. The data shows that the chemical plants depend much more heavily on IPLs which prevent an incident rather than respond to an incident once hazardous material is released. However, there is a large reliance on administrative controls to achieve an acceptable level of risk which are not viewed as reliable as engineered controls. Compounding this problem is the fact that systems designed to ensure the integrity of IPLs (i.e., testing and inspection, auditing, and management tracking through key metrics) are poorly used for administrative controls compared to engineered controls. Recommendations are made on how this can be addressed.