MTBF - Mean Time Between Failure
A 'guesstimate' of the average, or mean
time between design or component failure or
disruption in the operation of the product, process,
procedure, or design occurs. Mean time between failures assumes that the
product can be repaired and the product can then resume it’s normal
operations. The repair of such a product is a non-value
adding activity.
MTBF is not related with items like expected
and/or operating life or other items that in general are not fixed or
replacement even though it sometimes may be.
When a failure rate is unvarying, the
likelihood that the product will perform without malfunctioning for a time
that is equal to or greater than it’s MTBF is only about 37%. This is
due to the exponential distribution. A contradiction to the view that
there is a 50-50, (or a 50% probability),
chance of going beyond the MTBF.
Increases in MTBF may not necessarily
result with a proportional rise in reliability.
Example ...
MTBF of 5 = 82%
MTBF of 10 = .90%
MTBF of 100 = 99%.
MTBF is not the correct tool for all
applications, but is a useful measurement of reliability.
Also see MTTF
- Mean Time To Failure, Design Life, Durability,
Expected Life, Failure
Rate, and R – Reliability.
