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Reliability Block Diagram

Reliability block diagram (RBD) is a visual dependability analysis method that can be used to model the reliability technical structure of large and complex products, systems and process lines. Reliability block diagram describes the target with successive and parallel block placement or with the combination of these. Blocks can be used for modeling the function or equipment hierarchical structure of the examined object. In multi-levelled reliability block diagrams the reliability technical structure of the object can be described using different hierarchy types. In the most simple case reliability block diagram can be formed straight from the process diagrams or flow charts picturing the system. The examined object contains a group of different functions and subsystems that ensure the operation of the object while acting alongside each other. The requirement behind the operation of the object is an uninterrupted flow-type connection between the blocks that requires the thorough definition of the inputs and outputs of each block to the block diagram.

For supporting and enhancing the visual reliability block diagram it is possible to use different simulation qualities. The behaviour of the examined object can be for example analyzed by simulating the block diagram model based on the inputted failure and repair time data. The RBD tool of ELMAS software includes extensive simulation possibilities built around it. ELMAS also allows creating a more thorough inner structure for the RBD blocks by using fault trees to describe the reliability technical relations between the equipment located inside the block area.