Validating the Risk Reduction Claimed for IPLs in LOPA

Layer of Protection Analysis (LOPA) is a widely used semi-quantitative tool that can be used to determine the safety integrity level in designing the protections of a safety instrumented system (SIS). It is often used to meet the objectives of:

1. Allocating safety functions to protection layers;
2. Determining the required safety instrumented functions;
3. Determine, for each safety instrumented function, the associated safety integrity level (SIL).

Inherent to this process is having the procedures that lead to a consistent consequence analysis and determination of failure frequencies. This allows one to determine if the frequency of occurrence of a hazardous event meets the numerical risk tolerance criteria established by the organization.

This talk will focus on the importance of having a specific set of rules that specify the default data for values assigned to independent protective layers (IPLs), as well as the process of assigning values to IPLs that do not exist in your library; in addition to the maintenance, testing and inspection programs required to achieve the values claimed in LOPA.