Mtbf
Mean Time Between Failures (MTBF) is the predicted average elapsed time between inherent failures of a repairable mechanical or electronic system during normal operation, expressed in operating hours. It is calculated as total operating time (uptime) divided by the total number of failures observed during that period.
In shop floor maintenance, MTBF is used within CMMS platforms like ServiceGrid to quantify equipment reliability, plan spare parts inventory, determine maintenance schedules, and estimate asset life-cycle costs. By identifying assets that fail frequently relative to their uptime, maintenance teams can prioritize interventions, optimize resource allocation, and reduce unplanned downtime. MTBF applies strictly to repairable systems; for non-repairable components, MTTF is used instead.
How does MTBF relate to the failure rate (λ)?
MTBF is the inverse of the failure rate for systems with a constant failure rate (λ), expressed as MTBF = 1/λ.
Why is MTBF invalid for non-repairable systems?
Non-repairable systems do not have intervals between failures because they cease operation permanently after the first failure; thus, MTTF is the correct metric.
What does an MTBF of 10,000 hours imply for a specific unit?
It is a statistical average for a population, not a guarantee that a specific unit will run for 10,000 hours without failure; individual units may fail much earlier or later.