Guidelines for Initiating Events and Independent Protection Layers in Layer of Protection Analysis (PDF)

The book is a guide for Layers of Protection Analysis (LOPA)
practitioners. It explains the onion skin model
and in particular, how it relates to the use of LOPA and the need
for non-safety instrumented independent protection layers. It
provides specific guidance on Independent Protection Layers (IPLs)
that are not Safety Instrumented Systems (SIS). Using the
LOPA methodology, companies typically take credit for risk
reductions accomplished through non-SIS alternatives; i.e.
administrative procedures, equipment design, etc. It
addresses issues such as how to ensure the effectiveness and
maintain reliability for administrative controls or
"inherently safer, passive" concepts.

This book will address how the fields of Human Reliability
Analysis, Fault Tree Analysis, Inherent Safety, Audits and
Assessments, Maintenance, and Emergency Response relate to LOPA and
SIS.

The book will separate IPL's into categories such as the
following:

* Inherent Safety

* eliminates a scenario or fundamentally reduces a hazard

* Preventive/Proactive

* prevents initiating event from occurring such as enhanced
maintenance

* Preventive/Active

* stops chain of events after initiating event occurs but before
an incident has occurred such as high level in a tank shutting off
the pump.

* Mitigation (active or passive)

* minimizes impact once an incident has occurred such as closing
block valves once LEL is detected in the dike (active) or the dike
preventing contamination of groundwater (passive).