B&I has developed a model that allows us to simulate the effects of component failures in complex, redundant, systems. The model goes beyond standard fault-trees by allowing us to take account of common cause failures and complimentary states (e.g., if A fails then B is working). The model is totally general and has been applied to cases as varied as equipment safety instrumented systems, and oil and gas well integrity. The model starts by enumerating the interdependence of components in the system using intuitive network graphs that are simple to explain to engineers and, most importantly, your operators. The process of displaying the system as a network graph tool provides a remarkable way of showing how to improve system design and configuration. Monte Carlo simulation is then used to simulate how the system behaves in the event of a large number of ‘realizations’. Unlike fault-tree methods the results are very simple to check since we can examine the component and system states for a sample of realizations, this process has helped us work with engineers to improve their systems and can lead to system simplification and significant cost savings.