TS EN 61078

TS EN 61078 is the standard for modelling and analysing system dependability with reliability block diagrams (RBDs). In practical terms, an RBD represents a system through connected functional blocks so that the success of the whole system can be studied by looking at the success paths and the dependency structure between blocks.

How reliability block diagrams are used

In general technical use, RBDs are a core dependability modelling tool alongside fault tree analysis and Markov methods. They are especially useful when the system can be expressed as a set of success relations rather than a detailed failure propagation model. Each block typically stands for a component, subsystem, or function, and the arrangement of blocks describes how system success is achieved. This makes RBDs well suited to availability and reliability studies for systems with clearly defined functional architecture.

What this edition covers

This standard describes the requirements for using RBDs in dependability analysis, the procedures for modelling dependability with RBDs, and the use of RBDs for qualitative and quantitative analysis. It also sets out procedures for calculating availability, failure frequency, and reliability measures for different kinds of systems with constant or time-dependent block success/failure probabilities, including non-repaired and repaired blocks. In addition, it discusses theoretical aspects and limitations of such calculations and explains the relationship of RBDs with fault tree analysis and Markov techniques.

• Supports both constant and time-dependent block probabilities.
• Covers repaired and non-repaired blocks.
• Addresses availability, failure frequency, and reliability measures.
• Includes expanded treatment of Boolean algebra methods, non-coherent and dynamic RBDs, and electrical analogy.
• Introduces annexes on time-dependent probabilities, importance factors, Petri net models, and numerical examples.