Mean-Time-Between-Failures (MTBF)
A measure of asset reliability.

The expected time interval between two consecutive asset failures either in the form of potential failure ("P") of functional failure (F").

Calculations of MTBF assume that a system is "renewed", i.e. fixed, after each failure, and then returned to service immediately after failure.  Equal to the total asset downtime in a given time period, divided by the total asset uptime in that period.  

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