8. Conclusion

It is important to bear in mind that failure probabilities are necessarily subject to uncertainty. Indeed, to carry out the calculations, the analyst needs to use failure rates, among other things, and to define the weight of common cause failures.

As far as failure rates are concerned, the use of databases is the most widespread way of feeding reliability calculations. However, depending on the database consulted, differences of over a factor of 10 can be observed. The choice of database and the correct interpretation of the data it contains are therefore crucial steps in the assessment of PFD _avg .

When it comes to estimating the weight of common-cause failures, the methods generally used are partly based on expert opinion.

The PFD _avg ...