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Mean time between failures (MTBF) describes the expected time between two failures for a repairable system. For example, three identical systems starting to function properly at time 0 are working until all of them fail. The first system fails after 100 hours, the second after 120 hours and the third after 130 hours.
A value of = indicates that the failure rate is constant over time. This might suggest random external events are causing mortality, or failure. The Weibull distribution reduces to an exponential distribution; A value of > indicates that the failure rate increases with time. This happens if there is an "aging" process, or parts that are more ...
The mean time between failures (MTBF, /) is often reported instead of the failure rate, as numbers such as "2,000 hours" are more intuitive than numbers such as "0.0005 per hour". However, this is only valid if the failure rate λ ( t ) {\displaystyle \lambda (t)} is actually constant over time, such as within the flat region of the bathtub curve.
The exponential distribution, which describes the time between consecutive rare random events in a process with no memory. The exponential-logarithmic distribution; The F-distribution, which is the distribution of the ratio of two (normalized) chi-squared-distributed random variables, used in the analysis of variance.
Annualized failure rate (AFR) gives the estimated probability that a device or component will fail during a full year of use. It is a relation between the mean time between failure ( MTBF ) and the hours that a number of devices are run per year.
If the time between observed AC failures is approximated using the exponential function, then the exponential curve gives the probability density function, f T, for AC failure times. Another useful way to display the survival data is a graph showing the cumulative failures up to each time point.
Reliability can be characterized in terms of mean time between failures (MTBF), with reliability = exp(−t/MTBF). [5] Availability means the probability that a system is operational at a given time, i.e. the amount of time a device is actually operating as the percentage of total time it should be operating. High-availability systems may ...
In a system the mean time between outages (MTBO) is the mean time between equipment failures that result in loss of system continuity or unacceptable degradation.. The MTBO is calculated by the equation,