MTTR
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MTTR (Mean Time To Repair) measures average maintenance responsiveness by calculating the average time to restore failed equipment to operation.
Definition
MTTR (Mean Time To Repair) is a maintainability metric that measures the average time required to restore failed equipment to normal operation. It includes the entire restoration process: failure detection, response, diagnosis, repair execution, and verification. Lower MTTR indicates faster recovery capability. MTTR complements MTBF—together they determine equipment availability. Improving MTTR requires attention to spare parts availability, technician skills, diagnostic aids, and equipment accessibility.
Examples
Analyzing breakdown data, a team found average repair time of 4 hours. Breaking down MTTR: 30 minutes to detect failure, 45 minutes for technician response, 90 minutes diagnosis, 60 minutes repair, 15 minutes verification. They reduced response time with dedicated maintenance and cut MTTR to 2.5 hours.
Key Points
- MTTR = Total Repair Time / Number of Repairs
- Lower MTTR indicates faster recovery capability
- Includes detection, response, diagnosis, repair, and verification time
- Availability = MTBF / (MTBF + MTTR)
Common Misconceptions
MTTR only measures repair skill. MTTR includes the entire restoration cycle—waiting time, travel time, and parts availability often dominate actual repair time. Reducing MTTR requires systemic improvements, not just faster hands-on work.
Reducing MTTR is always beneficial. Very low MTTR might indicate excessive maintenance resources or premature return to service. The goal is optimal MTTR that balances restoration speed with resource cost and repair quality.