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ITEM Software
Experts in reliability, safety and risk assessment software
  ProductsITEM ToolKitRBD

Reliability Block Diagram (RBD)

Do you need to analyse the reliability and availability of systems and sub-systems, and their failures with respect to parallel and series arrangements? Model your system's true redundancy or logical configuration, and evaluate the availability of the system during or after the design phase. Regardless of the system size and complexity, the Reliability Block Diagram (RBD) software module graphically represents the logical interaction of failures and other events within your systems.

As part of the ITEM ToolKit integrated program, the Reliability Block Diagram (RBD) software module offers easy construction of network diagrams using point and click or drag and drop techniques. Once complete, Boolean Algebra expressions are used to determine minimal cut sets or the minimum combination of failures required to cause a system failure. As well as 15 built-in failure models, Markov models can be used for standby systems with respect to maintenance arrangements. RBD calculates system failure frequency and unavailability.

Helian Model

The Reliability Block Diagram (RBD) module also features a capability to estimate performance degradation due to the unavailability of one or more blocks in the system. This Helian model feature allows the user to allocate processing capacities to each block in the model, and computes the reduced throughput of the system in case of partial system failure.

RBD Construction

ITEM ToolKit's RBD module offers powerful, yet flexible, options to construct the block diagram using different approaches. Using point and click or drag and drop techniques will allow you to construct your diagram efficiently. ITEM ToolKit's standard editing capabilities provides you with additional flexibility: from entering failure data to changing the colours of the blocks, or simply printing the diagram. As your systems are configured properly, and block data is provided, the failure rate, MTBF, reliability and availability of the system can be calculated. When the configuration of the diagram changes, the calculation results also change.


Performing a Reliability Block Diagram analysis is essential for determining unreliability, unavailability, expected number of failures, and down time.

  • Establishes reliability goals
  • Evaluates device failure impact on overall system safety
  • Provides a powerful "what if" analyses tool
  • Allocates device reliability by calculating system MTBF
  • Estimates system reliability
  • Uses efficient minimal cut sets to derive the causes of system failures
  • Determines system sensitivity to component failures through Importance Analysis
  • Multi Systems within the same Project
  • Transfer to and from other ToolKit modules
  • Easily transfer diagram into other applications such as Microsoft Word
  • Importance analysis with Fussell-Vesely, Birnbaum, and Barlow-Proschan
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  Specification Sheet

Reliability Block Diagram Software Screen Shot

 > Reliability Block Diagram (RBD) Software

 > Easy Construction of Network Diagrams

 > Estimates System Reliability

 > Calculate Availability of Systems

 > One of Thirteen ITEM ToolKit Modules

 > Extensive Reporting and Charting Facilities

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