Plants that have high safety and reliability requirements are mostly complex, redundant systems and have to be regarded in a comprehensive environmental context. The kind of redundancy, protective measures and diagnostics has to be coordinated and adapted to the functional and operational requirements. Other essential factors of the system reliability, availability and safety are external influences such as climate, interactions with other systems, maintenance, logistics and human actions. Conceptual lacks, if first recognized only in the operating stage, necessitate costly corrective actions. In addition, loss of reputation and liability claims, have to be considered.

Safety and reliability engineering recognizes the relevant influences already in the planning and implementation stage and converts them into reasonable measures. Therewith, legal requirements for safety and liability are fulfilled as well (safety plan, safety case).

Besides the costs of investment, financial considerations should also include operational and maintenance costs. The reliability analysis makes it possible to predict expected expenses for maintenance, interventions and outages due to disturbances during the useful life of the system. The means and measures implemented to obtain the reliability, availability and safety targets are important determinants of the life cycle costs (LCC). Therefore those are important evaluation criteria when considering alternative solutions.

System optimization demands an overall view of the system in its operational environment. It aims at the implementation of appropriate resources and measures, where they are most effective. Goal: minimal life cycle costs at acceptable risks.