Failure Rates

What are failure rates?

Failure rates, in the simplest form, are S(time in use)/S(number of failures) or the reciprocal of mean times to/between failure. For more sophisticated failure data bases such as Weibull data bases the failure rates can be disclosed without giving away proprietary data such as the shape factors, beta, which tell the failure mode for the equipment.

Why use failure rates?

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 to use failure rates?

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 to use failure rates?

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

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