RBD in Reliability Workbench
This website gives a brief overview of the RBD module of the Reliability Workbench program for Microsoft Windows.
For more information on Reliability Workbench and associated training and support facilities visit www.isograph.com.
The structure of a reliability block diagram (RBD) defines the logical interaction of failures within a system. Individual blocks may represent single component failures, sub-system failures and other events that may contribute towards system failures. The reliability behaviour of an individual sub-system block may be represented by a RBD at a lower hierarchical level.
The logical flow of a RBD originates from an input node at the left hand side of the diagram to an output node at the right hand side of the diagram. Blocks are arranged in series and parallel arrangements between the system input and output nodes.
For the system to be successful in its operation at least one path must be maintained between the system input and output nodes. A simple series arrangement of 3 blocks A,B and C would only require one of the blocks to fail to eliminate the single success path from input to output node. A simple parallel arrangement of 3 blocks A,B and C would require all 3 blocks to fail to eliminate the 3 success paths from input to output node.
An RBD can represent the effect of common cause failures by repeating the same block in different parts of the diagram.
An RBD may also be used to represent voting arrangements. Nodes to the right of a parallel arrangement may be given a vote number to indicate how many success paths must be available through the parallel arrangement (if a vote number is not specified only one path need be available).
The RBD Module of Reliability Workbench is a powerful systems reliability analysis tool that allows reliability block diagram analyses to be performed in an integrated environment.
The RBD Module is capable of analysing a large and complex RBD producing the full minimal cut set representation for identified systems and sub-systems.
The RBD Module calculates a range of importance measures as well as providing standard system and sub-system parameters such as unavailability, unreliability, number of expected failures etc. The program allows users to construct a single project database containing failure model data and block diagrams representing one or more systems. Large block diagrams may be split into sub-systems (there is no limit to the number of hierarchical levels that may be specified for a project). Navigation between sub-systems is easily achieved using the Change Page or Find facilities provided by the program.
The RBD Module uses efficient minimal cut set generation algorithms to analyse a large and complex RBD. Markov analysis capabilities are also provided for analysing standby groups of blocks. Hot, cold and warm standby systems may be modelled taking into account the effect of maintenance queuing.
The RBD Module also includes a special Beta Factor Common Cause Failure (CCF) facility that allows users to associate groups of blocks with the same CCF model. During the analysis special CCF events are automatically generated by the program allowing the accurate evaluation of the effects of common cause failures.
The RBD Module automatically evaluates the system minimal cut sets and uses the cut sets to determine system performance parameters.
The program produces high quality reliability block diagram reports. Automatic pagination allows the user to quickly construct and print a large RBD.
A powerful Report Generator facility allows customised reports and graphs to be produced. Import and export facilities allow data to be transferred to and from databases, spreadsheets and files.
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