LOPA starts with identifying a potential hazard within a plant process such as a pump failure or inadvertent closing of a valve. Next, additional quantitative evaluation is done by the likelihood of the cause and the severity of the hazard. The process is then further evaluated to identify existing layers of protection (i.e., alarms, relief valves, automatic shutdowns, etc.).

These layers of protection must be independent from the system (i.e., cannot share wiring, sensors, etc.) that caused the failure and are referred to as Independent Protection Layers (IPL). IPLs must detect and correct the problem and mitigate the hazard.

The more severe a potential hazard, the more layers of protection needed. Through the LOPA process, a hazard’s risk is determined and the number of protection layers needed to reduce the risk.

Using LOPA provides consistency in evaluations done in differing process units within a facility and even at different facilities while ensuring the proper level of protection for a risk.