MTBF and MTTR poster

Mean time between failures (MTBF) is how long a machine runs, on average, between failures: operating time divided by the number of failures. Mean time to repair (MTTR) is how long, on average, it is stopped each time: total time stopped divided by the number of failures. Together they give availability, MTBF ÷ (MTBF + MTTR). This poster follows one machine over four weeks, 320 planned hours with four failures, on a timeline, works out each number, and lists what raises MTBF and what cuts MTTR.

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The words on the poster

MTBF and MTTR

How often it fails, and how long it is down each time. One machine, four weeks.

One machine, four weeks, two shifts a day: 320 planned hours

Failure 1 at hour 46: Drive belt snapped 1.5 h from stop to restart.
Failure 2 at hour 131: Hydraulic pump failed, spare not in stock 4 h from stop to restart.
Failure 3 at hour 205: Sensor worked loose 0.5 h from stop to restart.
Failure 4 at hour 270: Gearbox bearing seized 2 h from stop to restart.

Worked out

Operating time 312 h Planned time − time stopped = 320 − 8.
MTBF 78 h Operating time ÷ number of failures = 312 ÷ 4.
MTTR 2 h Time stopped ÷ number of failures = 8 ÷ 4.
Availability 97.5% MTBF ÷ (MTBF + MTTR) = 78 ÷ 80, the same as operating time ÷ planned time.

Raise MTBF Basic conditions, breakdown analysis, weak points fixed.
Cut MTTR Spares on the shelf, standard repairs, fast call for help.

Terms after IEC 60050-192 and EN 13306. One example machine, illustrative figures.

On the floor

How to use it

Putting the MTBF and MTTR poster to work

1
Pin it by the maintenance KPI board, so MTBF and MTTR are read as hours of a real machine, not just numbers.
2
Use the worked month to teach how the numbers are calculated before anyone fills in a KPI tracker.
3
In the weekly review, ask which list a breakdown's fix belongs to: fail less often, or fix faster.
4
Pair it with the free maintenance KPI tracker and equipment downtime log.

Where the poster goes and how to teach with it, in the order to try them.

Which size to print

24 x 36 in or A2: a main wall or team board, read from a few metres away.
18 x 24 in or A3: a station or notice board. The A3 file also fits 11 x 17 in paper.
Letter or A4: a clipboard, binder or handout, on any office printer.

Every PDF is vector, so it stays sharp at full size. Nothing runs to the edge of the page, so no bleed is needed.

Sources and notes

The machine on the poster is a worked example with illustrative figures. MTTR here counts every hour from stop to restart, including waiting for people and parts, so availability = MTBF ÷ (MTBF + MTTR) equals operating time ÷ planned time. Some plants count only the hands-on repair time in MTTR, and some work MTBF out from total time rather than operating time; say which you use.