This website provides information about failure rate analysis and how it relates to reliability and maintainability (RAM) software and analyses.

Failure rate can be defined as the anticipated number of times that an item fails in a specified period of time. It is a calculated value that provides a measure of reliability for a product. This value is normally expressed as failures per million hours, but can also be expressed as a FIT (Failures in time) Rate or failures per billion hours. For example, if a component has a failure rate of 2 failures per million hours, then it is anticipated that the component fails 2 times in a million hour time period.

A calculated failure rate is generally based on an established reliability prediction model (like MIL-HDBK-217 or Telcordia). Calculations are based on component data such as temperature, environment, and stress. Calculated failure rates for assemblies are a sum of the failure rates for components within the assembly.

A component manufacturer may sometimes provide a specified failure rate. This failure rate is usually based on field or laboratory test data. Similarly, a manufacturer can also provide a specified failure rate for an assembly.

Failure rate is also the inverse of the Mean Time Between Failures (MTBF) value for constant rate failure systems. For example: If a component has an MTBF value of 500,000 hours, and the failure rate is desired in failures per million hours, the failure rate would be:

Failure Rate = (1,000,000 hours) / (500,000 hours) = 2 failures per million hours

Relex Software Corporation produces software that enables users to use failure rate values in complex reliability analyses. Relex Software is a leader in reliability and maintainability software analysis tools. We specialize in software, training courses, and seminars covering all aspects of reliability engineering. Our products are used by thousands of engineers worldwide in a variety of businesses.

Please visit the Links page for more online information about the Relex Software visual reliability software modules, and about failure rate in general.

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