TABLE OF CONTENTS The way quantitative risk analysis in the petroleum industry has been conducted for many years makes the comprehensive analysis of dependencies between barriers impossible. Reliability analysis of barrier systems and elements is conducted to a limited extent as input to the node probabilities in event trees. These reliability studies are usually conducted separately for each node, often in a superficial manner, and without consideration of the influence from utility systems.
An exception, where comprehensive analysis of barriers is usually conducted, is when a HIPPS (High Integrity Pressure Protection System) is used, and reliability is extremely crucial. The analysis is however often limited to the pressure protection function.
In the QRA studies for nuclear power plants, it is common to perform extensive event tree and fault tree analysis, to an extent where dependencies may be analysed in detail. The most commonly used tool is RiskSpectrum (Relcon, 2006). This analysis tool has event trees and fault trees in a common manner, but has the ability to transform event trees to fault trees, such that all fault trees for barriers then may be integrated into a huge common fault tree. From this overall fault tree, dependencies may be analysed in detail, using common techniques for analysis of cut sets, common mode failures and importance calculations. The RiskSpectrum analysis tool gives the following advantages:
Dependencies may be identified, together with common mode failures.
Importance measures may be calculated for components, systems and failures.
The...
