RiskAchievementImportance

RiskAchievementImportance[rdist,t]

gives the risk achievement importances for all components in the ReliabilityDistribution rdist at time t.

RiskAchievementImportance[fdist,t]

gives the risk achievement importances for all components in the FailureDistribution fdist at time t.

Details

  • RiskAchievementImportance is also known as risk achievement worth.
  • The risk achievement importance at time t for component is given by , where is the probability that the system failed given that the ^(th) component has failed, and is the probability that the system has failed.
  • The results are returned in the component order given in the distribution list in rdist or fdist.

Examples

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Basic Examples  (3)

Two components connected in series, with different lifetime distributions:

The result is given in the same order as the distribution list in ReliabilityDistribution:

Two components connected in parallel, with different lifetime distributions:

Use fault tree-based modeling to define the system:

Scope  (19)

ReliabilityDistribution Models  (10)

Two components connected in parallel, with identical lifetime distributions:

The importance is identical:

Two components connected in series, with identical lifetime distributions:

The importance is identical:

A system where two out of three components need to work, with identical lifetime distributions:

The importance is identical:

A simple mixed system with identical lifetime distributions:

Compute the importance:

Component is most important, and and are equally important because of symmetry:

A system with a series connection in parallel with a component:

Show the importance:

Study the effect of a change in parameter in a simple mixed system:

Compute the importance:

Show the changes in importance when worsening one of the parallel components, :

One component in parallel with two others, with different distributions:

Find the importance measures at one specific point in time as exact results:

As machine-precision results:

As symbolic expressions:

Any valid ReliabilityDistribution can be used:

The more reliable component is more important:

ReliabilityDistribution can contain many different distributions:

Model the system in steps to get the importance measure for a subsystem:

Plot the importance over time:

FailureDistribution Models  (9)

Any of two basic events lead to the top event:

The importance is identical:

Only both basic events together lead to the top event:

The importance is identical:

A voting gate, with identical distributions on the basic events:

The importance is identical:

A simple system with both And and Or gates:

The basic event is most important:

A simple system with both And and Or gates:

Show the importance:

Study the effect of a change in parameter in a simple mixed system:

Compute the importance:

Show the changes in importance when worsening one of the basic events, :

Any valid FailureDistribution can be used:

The more reliable component is more important:

FailureDistribution can contain many different distributions:

Model the system in steps to get the importance measure for a subsystem:

Plot the importance over time:

Applications  (3)

Find out which component has the highest potential to make the system unreliable for a mission time of 1 day:

Show the importance over time:

With a mission time of 1 day, component could worsen the system reliability the most if it failed:

The importance measure is the factor with which the system unreliability can be increased by worsening . The worst case is a failed , which results in an unreliability of 1:

Analyze what component has the highest risk achievement importance for the launch of an aircraft. The hangar door can be opened electronically or manually:

Two fuel pumps require power to run:

Two more pumps run on reliable batteries, giving the following fuel transfer structure:

Also needed is deicing of the aircraft and a fuel storage tank:

Define the lifetime distributions:

Compute the importance:

The fuel storage should be monitored to avoid a high unreliability increase:

Consider a water pumping system, with one valve and two redundant pumps. The reliability of the components is given as probabilities:

The valve needs to be monitored and maintained most to avoid a high increase in unreliability:

Properties & Relations  (4)

RiskAchievementImportance can be defined in terms of Probability:

Compute the base reliability for the system:

The reliability for the system when the component is failed:

Divide the reliability with a failed component with the base reliability:

RiskAchievementImportance approaches 1 as :

The RiskAchievementImportance is the same for all components in a series system:

Irrelevant components have importance 1:

Introduced in 2012
 (9.0)