One Company's Observations on the Implementation of LOPA

Layer of Protection Analysis (LOPA) is gaining popularity as a risk assessment tool, but often unexpected difficulties are encountered when rolling out LOPA. This presentation discusses the practical aspects of LOPA implementation at Marathon Petroleum Company LP. Specifically, it shows how scenarios are selected from a HAZOP and they are organized for conducting LOPA efficiently, and it discusses whether to conduct LOPA concurrently or after the HAZOP. The presentation also compares the cause->consequence or consequence-> cause methodology and addresses the implications of aggregating multiple causes in a single scenario.

Another key aspect of LOPA implementation is the set of numerical values used for frequencies, modifiers and risk-reduction factors. The presentation shows how a company’s numerical values should be tied to its risk matrix and how internal consistency is achieved through the use of standardized values and restrictions on the use of frequency modifiers. Finally, the presentation covers one possible approach to LOPA scenarios where the protections typical for the industry do not meet the LOPA risk-reduction criteria; Marathon Petroleum Company LP addresses such cases through the use of application standards.