Why: Simple failure rates are a precursor of maintenance events and production interruptions that will occur into the future which drive up costs and cause chaos.
When: Failure rates derive from the history of operation or from well known data sources such as OREADA, IEEE 500, IEEE 493, EPRI, and other sources listed in reading lists for reliability including Weibull databases.
Where: The failure rates are used as an awareness criteria for the average person just as you used automobile fuel consumption rates for understanding the health of your automobile as well as anticipating your weekly/monthly/annual out-of-pocket expenditures for gasoline or diesel fuel. The failure rates drive the maintenance interventions, spare parts, and maintenance cost for the Maintenance Department. Similarly they predict the interruptions to the process and lead to misses on promised deliveries and result in negative variances for production costs. In sort, failure rates are precursors for the misery expected for the organization.
These definitions are written by H. Paul Barringer and are also posted on his web site at www.barringer1.com