MTBF by Another Name…
MTxx or MTxxx. I’ve lost count of how many variations of MTBF there exist.
MTBUR is mean time between unscheduled replacements, for example.
I’m sure you have a short list in mind already of your organizations or industries set of metrics.
What each difference does is define what is included or not included in the total time or counted as a failure. The same issue occurs with warranty or field reliability metrics. We consider was it a real failure or not. From the customer’s point of view, it didn’t work as expected so it failed. As a business we want to know the root cause of the failure and more importantly is the rate of failures increasing or not.
The many variations of MTBF, a misunderstood metric, doesn’t help with the overall understanding of what reliability performance we want or have achieved. Adding layers of new and often vague definitions to a non-intuitive metric doesn’t help. What we want is to understand not create a new four letter acronym.
…. Is Reliability
Generally when asking someone what they really want when asking for MTBF (or one of the many flavors) is how long will this last, or what is the chance of survival till the end of the year. They define reliability when they describe what they want when asking for reliability.
Let’s use the name of what we want directly: Reliability.
Let’s call a rose by its name, as calling it MTBF, generally doesn’t work.