This website provides information about parts count reliability models, and how they relate to reliability and maintainability (RAM) software and analyses.

MIL-HDBK-217 was the original standard for reliability predictions. It was designed to provide reliability math models for nearly every conceivable type of electronic device. It is used by both commercial companies and the defense industry, and is accepted and known worldwide.

MIL-HDBK-217 includes the ability to perform a parts count analysis. A parts count analysis is a reliability prediction analysis that provides a rough estimate of a system's failure rate - how often the system will fail in a given time period. Parts count analyses are normally used early in a system design, when detailed information is not available.

Mean Time Between Failures (MTBF)

Parts count analyses also enable you to determine the Mean Time Between Failures (MTBF) of a system. MTBF is a basic measure of reliability for repairable items. It can be described as the number of hours that pass before a component, assembly, or system fails.

MTBF can be calculated as the inverse of the failure rate for constant failure rate systems. For example: If a component has a failure rate of 2 failures per million hours, the MTBF would be the inverse of that failure rate.

MTBF = (1,000,000 hours) / (2 failures) = 500,000 hours

Relex Software Corporation produces software that enables users to easily perform parts count analyses on complex products or systems. Relex Software is a leader in R&M (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 reliability analysis in general.

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