Properly assessing mechanical component failure rates

This paper overviews various methods by which a mechanical component´s dangerous failure rate, λ_D, is est imated or predicted for mechanical components used in safety applications. The methods are critically evaluated and the advantages and disadvantages of each are discussed. It is important to note that the same mechanical component may have different values for λ_D based on the safety application(s) in which the component will be used. Different methods for estimating or predicting λ_D are more appropriate for some safety applications than for others. An example is provided indicating the inaccuracies that can arise if a method that is well suited for one safety application produces a value for λ_D that is then used to compute a safety rating for the same component used in a very different way in another the safety application.