Maintaining business premises
MTBF
MTBF (mean time between failures) is how long a repairable piece of equipment runs, on average, between one breakdown and the next. It is worked out by dividing the operating hours in a period by the number of failures recorded in that same period.
Also known asmean time between failures · mean time between breakdowns · average time between failures
What it is for and how to get it
If MTTR says how long a repair takes, MTBF says how long a machine keeps going without breaking down. The higher it is, the more reliable the machine. It is used to compare identical machines, to decide when one more repair is no longer worth it and to adjust the calendar for predictive maintenance or preventive work. Together with MTTR it gives availability, one of the most widely used maintenance KPIs.
An example with made-up numbers, in a gym with four identical exercise bikes. Over six months, bike 3 has been running for 1,200 hours and has stopped 4 times: its MTBF is 1,200 / 4 = 300 hours. The other three are at around 900. No more statistics are needed to see that bike 3 has a problem of its own (a part, a fixing, the spot where it stands) and is worth looking at before the next breakdown.
For the figure to mean anything, you have to decide what counts as a failure. The usual approach is to count only what takes the equipment out of service: scheduled stops for inspection are not failures, and nor is a noise that does not stop it being used.
Worth knowing
MTBF does not say when a particular machine will fail: it is an average, and an MTBF of 300 hours does not guarantee 300 hours of margin from today. The figure a manufacturer publishes is a prediction for normal use, not how long the machine will last in premises with dust, damp and rush hours. The one that helps you decide is the one the business measures itself.
Sources
Related terms
- Predictive maintenancePredictive maintenance decides when to step in from the actual condition of the equipment, measured with readings such as temperature, vibration or power draw. It does not wait for a breakdown, like corrective work, or for a fixed date, like preventive work: it acts when a reading says a fault is coming.
- MTTRMTTR (mean time to repair) is how long it takes, on average, to get a failed piece of equipment working again. It is worked out by adding up the time spent on all the repairs in a period and dividing that total by the number of repairs in the same period.
- Maintenance KPIsMaintenance KPIs (key performance indicators) are the few figures that show whether a business's maintenance is working: how long it takes to respond and to repair, how often each piece of equipment fails, how much of the time it is available, whether preventive work is done on time and how many faults come back.