Glossary · Maintenance and diagnostics
Mean time to restoration (MTTR)
Also known as: Mean time to restore, Mean time to recovery
German: MTTR
In dependability engineering according to IEC 60050-192, the mean time to restoration (MTTR) is the expected time from the occurrence of a failure until the item is restored, including the time to detect the failure, administrative and logistic delays, and the repair itself.
- Maintenance
In one sentence
Mean time to restoration (MTTR) is the expected time from a failure until the item is restored, including detection, logistics and repair.
Example
The service contract commits to an MTTR of four hours, measured from the fault report until the line is running again.
How it applies
- Operation: Restoration time is what the plant actually experiences as downtime, so it is the more useful figure for availability targets and service contracts.
- Service: Remote maintenance, stocked spare parts and on-call staff reduce the non-repair parts of restoration time, which are often larger than the repair itself.
- Engineering: Diagnostic functions shorten detection and Fault isolation, two components of restoration time.
- Documentation: Service level documents and manuals should define which events start and stop the clock. Writers should avoid expanding the abbreviation MTTR without checking which definition the source uses.
Mean time to restoration vs. mean time to repair
Mean time to repair (MTTR) often refers only to the hands-on repair. Mean time to restoration includes everything from the failure to the restored function. Both share the abbreviation MTTR; the standard term is the restoration time.