Elements for the calculation of PFH

The fault tree above can also be used to calculate the PFH of the modeled system. As the calculations are similar, we will only give some indications on the calculations of PFH by fault tree. 

We see that the equivalent average failure rate converges very slowly towards this asymptotic value. Using it as an estimate of the PFH is not conservative in this 

We note that here w(t) converges rapidly (two to three times the MTTR) to an asymptotic value, which is the PFH one. The equivalent average failure rate also 

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