UNDERSTAND THE CONCEPT
A common MTBF estimate for repairable equipment is total operating exposure divided by the number of relevant failures. Define the population, failure event and observation period before calculating. Calendar time is not automatically operating time.
Pooling similar machines can improve exposure, but combining unrelated duties can conceal important differences. Report the event count alongside the estimate, and consider uncertainty. Zero observed failures does not establish infinite reliability; it indicates limited evidence within a defined exposure.
Questions to take back to your team
- What counts as a qualifying failure?
- Is exposure actual operating time?
- Are the equipment duties comparable enough to pool?
Further reading
Explore the primary references below. Requirements and applicability depend on your organization and jurisdiction.
