Chapter 4 - Realistic Failure Rates and Prediction Confidence

Abstract

This chapter discusses realistic failure rates and the confidence limits of prediction. Failure data refers to the random failures or constant failure rates and a stated component, despite the same description, may exhibit a wide range of failure rates due to: failure rate data include items replaced during preventive maintenance, failure rates are affected by the tolerance of a design and causes variation in the values and component parts are often only described by reference to their broad types. Failure rate values can span one or two orders of magnitude as a result of different combinations of these factors and data are usually presented in one of two forms: tables and regression models. Sources of failure rate and failure mode data are classified as: site/company specific, industry specific and generic. The ratio of predicted failure rate to field failure rate are classified as: predictions using site-/company-specific data, predictions using industry-specific data and predictions using generic data.