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Fault Tree Analysis

FaultTree+ has enjoyed extraordinary success since its first release in 1987. Thanks to the advanced features introduced in direct response to the requirements of our customers FaultTree+ now provides the most comprehensive and easy to use fault tree analysis, event tree analysis and Markov analysis package on the market.

FaultTree+ is now combined with Reliability Workbench allowing direct links from reliability prediction and FMECA data to fault tree and event trees.

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

FaultTree+ is in use at over 1700 sites worldwide where it is used on many high profile projects. Our customers span a wide range of industries such as:

  • Aerospace
  • Automotive
  • Banking
  • Chemical
  • Defense
  • Electronics
  • Manufacturing
  • Mining
  • Oil and Gas
  • Power Generation
  • Process
  • Railways
  • Utilities

Isograph was founded in 1986 and is now one of the world’s leading companies in the development and provision of integrated Reliability, Availability, Maintainability and Safety software products. The company has offices near Manchester, UK and Salt Lake City, Utah.

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.

Event Tree Analysis

The FaultTree+ in Reliability Workbench event tree analysis module is unique in it’s ability to handle large scale problems and to fully handle success logic. The event tree model may be created independently of the fault tree model or may use fault tree analysis gate results as the source of event tree probabilities.

The event tree module handles both primary and secondary event trees, multiple branches and multiple consequence categories.

Markov Analysis

The FaultTree+ in Reliability Workbench Markov analysis module models systems which exhibit strong dependencies between component failures.

Constructing a Markov Model

The Markov module provides a visual interface to construct the state transition diagram and then uses numerical integration to solve the problem. The state transition diagram represents the discrete states of the system and the possible transitions between those states.

The Markov module models multiple phases representing continuous or discrete transitions. The module also analyses non-homogeneous processes by allowing time dependent transition rates to be defined. The phases allow the system lifetime to be split into periods representing (for example) preventative maintenance or standby.

The models created in the Markov analysis module may be linked to basic events in the fault tree and event tree analysis modules.

IEC 61508 – Safety Instrumented Systems

This standard involves a systematic approach to Life Cycle Safety of Safety Instrumented Systems (SIS). Systems such as these need to be maintained to be sure of a certain safety level during operation. It is concerned specifically with Electrical/Electronic/Programmable Electronic Safety-Related Systems (E/E/PESs).IEC 61508 provides guidelines to classify these systems by Safety Integrity Levels (SIL levels). Four SILs can be defined according to the risks associated with the system requirements with SIL4 being assigned to the highest risks. The standard adopts a risk based approach to calculate the required SIL, which represents the Probability of Failure on Demand of the target system.