RBD – Reliability Block Diagram with Monte-Carlo simulation

RBD module allows performing the functional Reliability and Availability analysis of systems with variety of reliability distributions, and types of redundancy and repair factors. While the basic RAM Commander module provides the reliability calculations and predictions for non-redundant systems, RBD utilizes data defined in other modules (reliability, maintainability, FMECA), and performs either analytical calculation or Monte Carlo simulation depending on the type of a reliability configuration of the system.

RBD-supported configurations

• Series
• Parallel
• K-out-of-N with active (hot) redundancy
• K-out-of-N with stand-by (cold) redundancy
• Partially loaded K-out-of-N – warm redundancy
• K-out-of-N w/repair, w/o repair, w/restricted repair
• K-out-of-N with Switch
• Sub-RBD, K-out-of-N for Sub-RBDThe analytical technique is used mostly for exponential distributions. For each RBD, a graph of the reliability function R(t) can be drawn and MTBCF (Mean Time Between Critical Failures) can be calculated using numeric integration.Monte Carlo simulation with its’ high speed, accuracy, and large number of steps allows to evaluate Reliability and Availability for arbitrary configurations when there is no analytical solution, i.e. complex configurations, including standby, partially loaded and active redundancy; full or restricted repair with non-exponential distribution of time-to-repair; analysis under non-steady, transient state; dependent RBD elements; analysis of periodical inspection policy.


  • Exponential
  • Normal
  • Log-Normal
  • Weibull
  • Erlang
  • Uniform

Reliability Block Diagram and MTBCF graph

System Configuration feature of the RBD module is an ingenious answer to the requests of our customers who need to compare the reliability and availability of various system configurations created as the sub-sets of the project product tree. The creation of the unlimited number of system configurations, easy transformation of each configuration into an RBD, MTBCF calculation, synchronized with the product tree changes, and finally a clear and elegant graphical presentation – all this makes the System Configuration feature an invaluable addition to the RAM Commander performance.

RBD - System Configuration Table

System Configuration Table

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