The Mean Time to Repair (MTTR), also referred to as Mean Corrective Maintenance Time, is a measure of the maintainability of equipment and repairable parts. It represents the average time needed to repair a failure until the equipment returns to a fully functional state.
A high Mean Time to Repair may indicate, for instance, that the substitution of a given piece of equipment should be preferred over its reparation. It may also lead to the decision of storing spare parts for the equipment in question. Knowing how to reduce the MTTR is essential to avoid or minimize downtime and the harm they may cause to your business.
So, how do you determine the MTTR?
It can be mathematically expressed by the division of the total corrective maintenance time during a given period, divided by the number of corrective maintenance actions performed, as shown by the following expression:
It is worth to note that the total corrective maintenance time (and thus, the Mean Time to Repair) can include the period since the failure is discovered until the actual reparation works start (that is, the time spent with identification, notification, acknowledgment and diagnostic of the failure). In this case, it is commonly referred to as the Mean Time to Recovery. For this reason, explicit distinction in the definition of the MTTR in maintenance contracts, for instance, is important.
The lead time for parts that are not readily available or other Administrative or Logistic Downtime (ALDT) is not included in the calculation.