RiskSpectrum I&AB

Calculate the reliability of repairable and reconfigurable systems

RiskSpectrum I&AB (Initiators and All Barriers) is a special algorithm developed for use in RiskSpectrum PSA. 

It offers a way to calculate safe, stable end-state without introducing mission times. Instead, the algorithm takes into account the possibility to return failed equipment to service after repair. This makes it possible to calculate system reliability for an unlimted time period. 

RiskSpectrum I&AB offers a great addition to the traditional modelling and calculation of reliability and unavailability for scenarios with a shorter duration or where we are only interested in knowing the unavailability during a limited time-frame.


Software In Action


Considering Repair

The image to the right illustrates a system where the difference between excluding or including the effect of repair has on the availability of the system. 

The lower graph illustrate that the difference in result is not significant when analysing only the first hours after a disturbance in the system. 

For systems where you have more time on your hands to repaire the system, the I&AB algorithm offers a more realistic assessment of unavailability (Q).   

The Methodology

A new methodology for calculating the reliability of repairable and reconfigurable systems.

The method makes it possible to return the component to service when it has been repaired

Consider a system of three repairable components where:

  • S1 is in operation; S2 and S3 in stand-by
  • Failure of S1 require S2 and S3 to start

The state graph corresponding to the I&AB assumptions:

  • Stand-by components start after IE and can be repaired and fail independently
  • Repair of IE means system cannot fail (absorbed)
  • No need for mission time
  • Repair MAY be taken into account