The Impact of Human Factors On LOPA (and other risk assessment methods)

All initiating events (IEs) and independent protection layers (IPLs) are inherently tied to human error.  Human factors limit the risk reduction values and must be taken into account to ensure true independence of IPLs and to ensure the probability of failure on demand (PFD) of the IPL is achievable in actual implementation.  The paper explains the relationship between human factors and the resultant IE frequency and PFD and provides an overview of how to validate theses risk reduction values at a site.  The paper also covers the more involved topic of dependent human errors in IPLs, such as high integrity SIS and other high reliability IPLs such as relief systems.  Actual examples are provided to illustrate key learnings.