Mean time between failures (MTBF)
MTBF is the average operating time between one failure and the next for repairable equipment, used as a reliability measure.
MTBF is the average operating time between one failure and the next for repairable equipment, used as a reliability measure.
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Also called: MTBF, mean time between failure.
MTBF — mean time between failures — measures reliability for equipment that gets repaired and put back into service. MTTR — mean time to repair — measures how quickly it comes back, which is maintainability rather than reliability. MTTF — mean time to failure — applies to things that are replaced rather than repaired, like bulbs and bearings.
The pair worth watching together is MTBF and MTTR: reliability and recovery. Equipment that fails rarely but takes a week to fix can be more disruptive than equipment that fails often and is back in an hour.
It is an average, and failures are not evenly distributed. Equipment characteristically fails early (manufacturing defects) and late (wear-out), with a reliable middle. An MTBF of 2,000 hours does not promise 2,000 good hours.
Small samples produce meaningless numbers. MTBF from three failures is arithmetic, not statistics. It is most useful across a fleet of similar items or a long history of one item.
The definition of "failure" decides the answer. If minor faults that get worked around are not logged, MTBF looks excellent while the equipment is visibly unreliable to everyone who uses it. Consistency in what gets recorded matters more than precision in the calculation.
MTBF = Total operating time ÷ Number of failures
A machine running 4,800 hours with 6 failures has an MTBF of 800 hours. Use operating time, not calendar time — idle hours are not a reliability test.
Without failure records tied to specific items, chronically unreliable equipment is defended anecdotally and replaced late, long after its repair spend passed the cost of a new one.
Itefy logs issues and repairs against the individual item, so failure frequency and repair cost per item accumulate as a record rather than as impressions. Read more.
It suggests so, but only if failures are recorded consistently and the sample is large enough to mean something. An MTBF that looks good because minor faults go unlogged is worse than no figure.
MTBF is how long it runs between failures; MTTR is how long it takes to fix. Read them together — rare failures that take a week can hurt more than frequent ones fixed in an hour.
Equipment downtime is time during which equipment is unavailable for its intended use, whether because it has failed or because it is being serviced.
DefinitionPreventive maintenance is servicing equipment on a planned schedule — by time or by usage — to reduce the chance of it failing unexpectedly in use.
DefinitionA service history is the complete record of maintenance, repairs and inspections carried out on a specific item, with dates, work done and cost.
DefinitionAn equipment condition report is a dated record of the physical and working state of a specific item, used to track deterioration and settle damage questions.
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