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Reliability Workbench

Reliability Workbench is Isograph’s flagship suite of reliability, safety and maintainability software. The software has been in continuous development since the 1980s. It is easy to use and is a great tool for all reliability and maintenance professionals.

ISO 26262 Certification

Our Reliability Workbench FaultTree+ and FMECA modules have been tested and certified by SGS-TÜV as suitable for safety analyses according to ISO26262.

Reliability Workbench Key Features

The Reliability Workbench suite includes all the tools you will need to manage your reliability and safety studies:

  • FMECA and FMEA
  • FaultTree+ Fault Tree Analysis
  • Reliability Block Diagram analysis
  • Reliability Allocation and Growth
  • Event Tree and Markov Analysis
  • Weibull Analysis of historical failure data
  • Integrated Parts Libraries
  • Extensive Reporting Tools
  • Import and Export Facilities
  • Enterprise class collaboration tools

What can you achieve with Reliability Workbench?

Reliability Workbench allows you to develop projects using one or more of the integrated analysis modules. Using the various modules you can answer questions such as:

  • What is the predicted reliability of a system?
  • Which are the critical components in my system?
  • What maintenance or design changes will improve the system reliability?
  • What are the consequences and risks of system failures?

How do the Modules Work Together?

Each of the modules is a powerful application in its own right and can be used independently, but more power is gained by the integration of the modules in to the Reliability Workbench environment.

The modules can dynamically share data for ease and consistency. Users only need to input data once but can use it several times.

Fault Tree Analysis

FaultTree+, the world’s most popular fault tree software package, has been incorporated into Reliability Workbench. There are many benefits of FaultTree+ being integrated into Reliability Workbench. You can read more about the other Reliability Workbench modules on their appropriate pages.

What’s in FaultTree+?

FaultTree+ in Reliability Workbench includes three modules:

  • Fault Tree Analysis. Allowing you to construct and analyze fault tree diagrams.
  • Event Tree Analysis. Event trees allow you to analyze the possible outcomes of an event occurring.
  • Markov Analysis. Enabling the construction of Markov models for components with large interdependencies.

What is Fault Tree Analysis?

Fault tree diagrams represent the logical relationship between sub-system and component failures and how they combine to cause system failures. The TOP event of a fault tree represents a system event of interest and is connected by logical gates to component failures known as basic events.

After creating the diagram, failure and repair data is assigned to the system components. The analysis is then performed, to calculate reliability and availability parameters for the system and identify critical components.

What is Event Tree Analysis?

Event tree diagrams provide a logical representation of the possible outcomes following a hazardous event. Event tree analysis provides an inductive approach to reliability and risk assessment and are constructed using forward logic.

FaultTree+ in Reliability Workbench includes integrated event tree analysis. The event tree model may be linked to the fault tree model by using fault tree gate results as the source of event tree probabilities.

What is Markov Analysis?

Markov analysis provides a method of analyzing the reliability and availability of sub-systems representing components with strong interdependencies. Markov analysis is often used to model dependencies such as:

  • Components in Warm/Cold Standby
  • Common maintenance personnel
  • Common spares with a limited on-site stock

FaultTree+ in Reliability Workbench allows the user to construct Markov models for use as the source of basic event data. The Markov models may also be analyzed independently of the fault tree analysis.

RBD Analysis

The RBD Module is a powerful systems reliability analysis tool that allows reliability block diagram analyses to be performed in an integrated environment.

What is a Reliability Block Diagram?

A Reliability Block Diagram is a method of modeling how components and sub-system failures combine to cause system failure. Reliability block diagrams may be analyzed to predict the availability of a system and determined the critical components from a reliability viewpoint.

RBDs and Minimal Cut Sets

The RBD Module of Reliability Workbench is capable of analyzing large and complex RBDs producing the full minimal cut set representation for systems and sub-systems.

Markov analysis capabilities are provided for analyzing components with strong dependencies.

RBDs and Importance Measures

The RBD Module calculates a range of importance measures as well as providing standard system and sub-system parameters such as unavailability, unreliability and expected failures.

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.

Common Cause Failures

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.

System Performance and Other Features

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 large RBDs.

A powerful Report Generator facility allows customized reports and graphs to be produced. Import and export facilities allow data to be transferred to and from databases, spreadsheets and files.


The FMECA Module of Reliability Workbench provides the full framework and reporting facilities to allow users to construct FMECAs to MIL-STD-1629A, BS 5760 Part 5, GJB 1391-92, AIAG FMEA 3, SAE J1739, ARP5580 and similar standards as well as customizing the FMECA to the user’s own requirements.

In addition Process and Design FMEAs and commercial aircraft FMEAs may also be constructed and analyzed within this module. EFA (European Fighter Aircraft) format FMECAs may also be constructed.

What is FMECA? What is FMEA?

A Failure Mode, Effects and Criticality Analysis is a procedure for identifying potential failure modes in a system and classifying them according to their severity values.

A FMECA is usually carried out progressively in two parts:

  • Identifying failure modes and their effects (Failure Mode and Effects Analysis).
  • Ranking failure modes according to the combination of severity and the probability of that failure mode occurring (Criticality Analysis).

How do I Construct a FMECA?

The FMECA procedure may be summarized as completing the following steps:

  • Define the system to be analyzed
  • Construct a hierarchical block diagram
  • Identify failure modes at all levels of indenture
  • Assign effects to the failure modes
  • Assign severity categories to effects
  • Enter other failure mode data such as failure detection methods, failure rates, etc.
  • Rank failure modes in terms of severity and criticality
  • Produce reports highlighting critical failures
  • Recommend redesign or maintenance actions to reduce critical failures

The FMECA Module provides interactive graphical facilities for constructing a block diagram representing the logical connection between the sub-systems and components constituting the overall plant or system. This diagram may be extended to represent failure modes at various hierarchical levels.

The FMECA Module permits the rapid entry of data using pop-up dialogs which may be accessed simply by clicking on the relevant part of the block diagram.

Automatic Calculation in FMECA

One of the most powerful features of the FMECA Module is its ability to automatically trace failure effects, severity values and failure causes through the system hierarchy. Failure rate and criticality values are automatically calculated by the program.

The FMECA Module will also filter detectable and non-detectable failures in reports and determine the ratio between the frequency of detectable failures and total failures.

A large proportion of data entered when performing a FMECA is descriptive text. The FMECA Module provides a master phrase library which contains commonly used descriptions of component parts, failure modes and effects. These phrases may be inserted into descriptive fields by selecting the required phrase from the library saving considerable typing and ensuring consistency.

Users may build up their own phrase libraries or add to the master library provided.

The FMECA Module provides an apportionment library facility which allows the user to create commonly used component and failure mode groupings. Each failure mode in a grouping is given an apportionment percentage. Users may add a component to the FMECA block diagram together with the appropriate failure modes by selecting the appropriate entry in the apportionment library. This saves considerable effort when constructing the block diagram.

Process and Design FMEA

Process and Design FMEAs provide an alternative approach to performing a Failure Mode and Effect Analysis. Occurrence, severity and detection rankings replace apportionments and failure rates. Risk Priority Numbers (RPN) are calculated by multiplying the severity, occurrence and detection ranking numbers together.

Commercial Aircraft FMEA

Commercial Aircraft FMEAs are a special format of FMEA allowing users to define failure modes and effects at unit, system, engine and aircraft level.

Reliability Prediction

The reliability prediction module enables you to predict failure rates for a set of components under given conditions. The data may be drawn from a selection of industry standard handbooks such as MIl-HDBK-217, 217 Plus, Telecordia, IEC TR 62380 and NSWC.

What’s in the Reliability Prediction Module?

The prediction module provides you with a powerful visual interface through which you can select components, define the conditions in which they operate such as the temperature or environmental conditions. The prediction software automatically carries out the failure rate calculation as defined by the standard and provides you with the results.

What Industry Standards are Included?

The Reliability Workbench Prediction module includes the following standards:

  • Telcordia SR-332 Issues 2 and 3
  • MIL-HDBK-217
  • Quanterion 217 Plus
  • IEC TR 62380 (RDF 2000)
  • NSWC handbook
  • GJB/z 299B and 299C
  • Siemens SN 29500

How do I use RWB Prediction?

The components that make up a system can be defined in a tree structure. The tree may be composed entirely of components or it could be subdivided into blocks each of which could hold other blocks or components.

The failure rate model for each component is made up of a base failure rate for that particular type of component and multiplying factors known as pi-factors. These factors depend on the operating conditions experienced by the component. You can input these conditions through simple dialogs and default parameter values are provided.

The failure rates of components are calculated immediately and displayed on the tree diagram. The contributions of components failure rates to blocks and systems failure rates are also displayed. You can examine the effects of stresses caused by the various environmental conditions by displaying the base failure rates and pi-factors for each component.