Validation of a mechanical component constant failure rate database

This paper reports on our successful efforts to validate statistically certain constant failure rate data in a mechanical component constant failure rate and failure mode database. To accomplish this, we use a Failure Modes, Effects, and Diagnostic Analysis (FMEDA) to predict the constant failure rate, lambda_D, for the fail-to-open condition of a particular series of pressure relief valves (PRV) using the failure rates from the mechanical component database. Next, we apply the quantal response method to four sets of PRV proof test data to calculate four estimates, lambda_D, for lambda, the true value of the failure rate. Finally, using each data estimate we test the hypothesis H₀: lambda = lambda_D vs H₁: lambda Gt lambda_D. Each proof test data set supports the FMEDA prediction at a 30% significance level, implying a 70% upper confidence limit. Further we show that the probability that this result could have been obtained by chance alone given reasonable alternative values of lambda is about 2.5% or less. While this does not validate the entire mechanical component database, it strongly supports its validity at least with respect to the component failure modes responsible for the PRV fail-to-open condition and, by extension, to the techniques used to create the database.