Glossary · Maintenance and diagnostics
Mean time to repair (MTTR)
Also known as: MTTR, Mean repair time
German: Mittlere Reparaturzeit (MTTR)
In maintenance and reliability engineering, the mean time to repair (MTTR) is the average time needed to repair a failed item and return it to operation. Depending on the organization, it covers only the active repair or also diagnosis, waiting for parts and functional testing, so its definition must be stated.
- Maintenance
In one sentence
MTTR, mean time to repair, is the average time needed to repair a failed item and return it to operation; its scope must be defined.
Example
Over the last year, the plant recorded an MTTR of 45 minutes for servo drive faults, mainly because spare drives were stocked next to the line.
How it applies
- Engineering: Modular design, quick-release connectors, good diagnostics and clear labeling reduce repair time.
- Maintenance: Plants track MTTR to find where time is lost, for example in diagnosis, spare part logistics or restart procedures.
- Operation: Together with Mean time between failures (MTBF), MTTR determines availability; a common approximation is MTBF divided by the sum of MTBF and MTTR.
- Documentation: Clear Troubleshooting instructions, correct spare part numbers and exchange procedures shorten repair time directly. When a contract or data sheet states an MTTR, the documentation should say which activities it includes.
Mean time to repair vs. mean time to restoration
The abbreviation MTTR is used for both. IEC 60050-192 defines MTTR as Mean time to restoration (MTTR), which covers the whole time until the item is restored, while the pure repair time is called mean repair time. Check which one a figure refers to before comparing values.