What is MTTR?
Mean time to repair (MTTR) is a maintenance metric that measures the average time required to troubleshoot and repair failed equipment. It reflects how quickly an organization can respond to unplanned breakdowns and repair them.
MTTR calculates the period between the start of the incident and the moment the system returns to production. This takes into account the time to:
- Notify technicians
- Diagnose the issue
- Fix the issue
- Allow the equipment to cool down
- Reassemble, align and calibrate the asset
- Set up, test, and start up the asset for production
This metric does not take into account lead-time for parts.
How to calculate MTTR
The MTTR formula is calculated by dividing the total unplanned maintenance time spent on an asset by the total number of failures that asset experienced over a specific period. Mean time to repair is most commonly represented in hours.
The MTTR calculation assumes that:
- Tasks are performed sequentially
- Tasks are performed by appropriately trained personnel
For example, if you have spent 50 hours on unplanned maintenance for an asset that has broken down eight times over the course of a year, the mean time to repair would be 6.25 hours.
What is considered world-class MTTR is dependent on several factors, like the type of asset, its criticality, and its age. However, a good rule of thumb is an MTTR of under five hours.
How is MTTR used?
Mean time to repair is used as a baseline for increasing efficiency, finding ways to limit unplanned downtime, and boosting the bottom line. Because long repair times for mission-critical equipment mean product scrap, missed orders, and soured business relationships, MTTR helps organizations identify why maintenance may be taking longer than is ideal and make more informed decisions to fix the underlying causes.
What does MTTR mean for maintenance?
Conducting an MTTR analysis can provide insight into the way your maintenance operation purchases equipment, schedules maintenance and completes tasks. Ultimately, MTTR helps your organization wipe out any inefficiencies that are causing lost production and the lost money that comes with that.
MTTR can be used for making repair or replace decisions on aging assets. If an asset takes longer to repair as it ages, it may be more economical to replace it. MTTR can also be used to inform the purchasing and design process by predicting lifecycle costs of new systems.
Tracking MTTR also helps to ensure your preventive maintenance program and PM tasks are as effective and efficient as possible. Although MTTR measures reactive maintenance, assets that take longer to repair may have PMs associated with them that aren’t working well. Mean time to repair is a gateway into the root cause of this problem and provides a path to a solution.
For example, if MTTR is increasing, it might be because PMs aren’t standardized, leading to more equipment failure. A work order may tell a technicians to lubricate a part, but it might not tell them which lubricant or how much. Adding this information to a work order will ensure work is done quickly and accurately, leading to less downtime.
Your business and MTTR
Mean time to repair is a tool for evaluating the quality of a facility’s maintenance practices and processes. It can also be used to investigate the value and performance of assets so an organization can make smarter decisions about asset management. MTTR is a starting point for assessing efficiency and eliminating redundancies, roadblocks, and confusion in maintenance so a business can avoid needless downtime and go back to what it does best — manufacturing and selling goods.
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