What is Mean Time to Repair (MTTR)?

Mean Time to Repair (MTTR) is a critical measurement in maintenance that estimates the average time taken to diagnose and repair malfunctioning equipment. The following are the steps involved in MTTR:

1. Alerting the technicians of the problem.

2. Analyzing the nature of the issue.

3. Carrying out the corrective maintenance.

4. Cooling down the equipment, if necessary.

5. Rearranging and aligning the equipment and adjusting it.

6. Testing and restarting the equipment for regular use.

Note: The waiting period for spare parts is not included in MTTR.

📋Table of Contents 

👉 Calculating MTTR

👉 Application of MTTR

👉 Benefits of Measuring MTTR

👉 Challenges of Measuring MTTR

👉 What Does MTTR Mean for Maintenance?

👉 Modernizing MTTR for Your Maintenance Teams

👉 Your Business and MTTR

How to Calculate MTTR

MTTR is calculated by taking the total unplanned maintenance time and dividing it by the total number of failures for a specified period. It is usually measured in hours.

MTTR Formula:

MTTR = Total Maintenance Time / Number of Repairs

Example Calculation:

Suppose a factory machine breaks down 10 times in a month, and the total repair time across these incidents is 40 hours. The MTTR would be:

MTTR = 40 hours / 10 failures = 4 hours

It means that the machine is repaired in an average of 4 hours each time it fails.

Parameters Used:

• Total Maintenance Time: The sum of all time spent on unplanned maintenance.

• Number of Repairs: The total count of repair incidents over the specified period.

A world-class MTTR varies between different factors, such as the asset type, its criticality, and its age. In general, an efficient MTTR is usually below five hours.

How to Use MTTR

Since MTTR is the average time it takes to repair a failure, it's used as a baseline for increasing efficiency and reducing unplanned downtime, directly impacting the bottom line. Through the dissection of MTTR, organizations will be able to identify just why maintenance is longer than ideal, making informed choices to address these causal factors.

Application of MTTR Example:

Let's say there is a food and dairy packaging plant in which the conveyor belt malfunctions very often. Every time there is a breakdown, the clock starts ticking. Quickly, the maintenance team is notified for a diagnosis of the problem. So let's say it takes them an hour to identify that a motor needs to be replaced, two hours to replace the motor, and an hour to test and restart the system. So the MTTR for this event is 4 hours. Plotting the MTTR versus time enables the plant management to identify recurring issues and attend to root causes such as replacing low-quality motors with more reliable ones.

Benefits of Measuring MTTR

• Performance Benchmarking: It offers a benchmark of comparison by which maintenance performance over time and benchmarking against industry standards can be accomplished.

  
  

• Efficiency Evaluation: Measures how effectively maintenance teams and procedures work.

  
  

• Resource Allocation: Allows for proper resource allocation to meet the demands of maintenance.

  
  

• Uptime Maximization: Directly associated with the increment in uptime of equipment.

  
  

• Cost Savings: By saving repair time, labor and production costs are also saved significantly.

  
  

  
  

Challenges with Measuring MTTR

Measuring MTTR has a great ability to bring insights; however, it does come with some complications for organizations as they navigate through this:

• Varying Definitions: Different organizations may have a different starting point while measuring MTTR. For example, some start the clock when an incident is first reported, while others begin timing once a technician starts working on the repair. This variance can make benchmarking and comparisons across different organizations or industries difficult.

  
  

• Inconsistent Data Collection: If data collection techniques are not consistent and trustworthy, then MTTR cannot be accurately calculated. Similarly, if data collection is clumped up or incomplete, the answer for MTTR can be biased. For example, if there are some repair incidents that are not properly logged and the sum of these incidents is substantial, the total maintenance time can be significantly underestimated.

  
  

• Multiple Failures: Equipment may suffer multiple, simultaneous failures that make it difficult to clearly establish a beginning and end time for each failure. This complicates MTTR calculations. For example, should a piece of machinery fail simultaneously both mechanically and electrically, it may be difficult to separate the repair times between the two failures.

  
  

• Complex Repairs: Over a range of component times and work complexity, the average MTTR may not reflect the labor spent on certain complex repairs compared to the simpler types. For instance, the replacement of a simple part will consume an hour's work, yet one may end up spending several days on a major overhaul. These are outliers that affect the overall MTTR and which can make it be higher than usual most of the time.

  
  

• Human Factors: Technician skill levels, spare part availability, or the time of day can all contribute to repair duration. For instance, repairs during off-hours or on weekends may tend to have a longer duration because all staff members may not be on duty. Similarly, inexperienced technicians will take more time for the diagnosis and resolution of issues compared to their seasoned counterparts.

  
  

Mean Time to Repair - Maintenance Operations

MTTR provides insight into how effective and efficient the maintenance operation is overall. Direct impacts on maintenance strategies come from:

Decisions related to Repairs and/or Replacement:

Another common factor in the repair-versus-replace decision for equipment reaching the end of its useful life is MTTR. For instance, if an individual piece of equipment has a continual rising MTTR, this shows that the cost and time for repairs are outweighing the benefits of keeping the machine. This insight helps maintenance teams and management decide if investing in a new machine is more cost-effective in the long run.

Optimized Preventive Maintenance:

Even though the MTTR is reactive maintenance oriented, the measure can also help to guide for a preventive maintenance approach. For instance, a trend that suggests some of the assets are spending extended periods during repairs is an indication that the current PM tasks are not effective. This may result in the review and adjustment of the schedules of the PM tasks. For example, lubricating a certain item may take a significant amount of time if done regularly because the job is not well-documented. Better work orders with details about the procedure can significantly reduce the time consumed.

Improvement in MRO Inventory Management to Streamline the MTTR:

High levels of MTTR may be symptomatic of poor management of Maintenance, Repair, and Operations (MRO) inventories. For example, if repairs are delayed by often missing or wrongly identified spare parts, there is the need to manage inventory better. An effective inventory management system implemented guarantees that all necessary parts are always available and properly organized, thereby reducing time spent on repairs and MTTR.

Modernizing MTTR for Maintenance Teams

There are a few ways that modern technology allows one to optimize and reduce MTTR, thus making maintenance more efficient:

• Computerized Maintenance Management Systems (CMMS): These systems help track work orders, spare parts inventory, and schedule preventive maintenance. Real-time access to such data can greatly cut the time required to get a decision and start the repair. This could include notifying a maintenance technician that a scheduled occurrence was going to happen in short order and ensuring the readiness of both parts and tools.

  
  

• Predictive Maintenance (PdM): PdM involves sensors and analytics for predicting when equipment is likely to fail, thus enabling maintenance teams to preempt such failures. For example, the vibration sensor can capture early symptoms of bearing failure in a motor, which can signal a preplanned repair instead of full breakdown, and therefore can save downtime and MTTR.

  
  

• Augmented Reality (AR): In-course application of AR technology is expected to provide real-time guidance for the technician and overlay information in course of effecting the repair. For instance, the AR glass might overlay step-by-step repair instructions and even indicate specific equipment components in use at that time—this way, the AR will assist the repairman in mending the malfunctioning equipment in less time.

  
  

• Machine Learning and AI: Advanced algorithms can be applied to datasets analysis and trend picking; thus, predicting failures that a human would miss. For instance, analysis of past maintenance data can give insight into repeat failures and, therefore advise on the best repair strategy and time, hence reducing MTTR.

  
  

• Drones: Drones are able to conduct fast visual checks of vast equipment or installations and promptly identify any issues without people having to be used. For example, in the inspection of wind turbine blades or large industrial rooftops, which would be very time-consuming without a drone.

  
  

• Wearable Technology: Technicians can keep an eye on their tasks, receive alerts, and even check on biometrics to ensure they are not overstressed because of fatigue using gadgets such as smartwatches. They can, for example, warn a technician to take a break if their heart rate indicates undue stress to help ensure the technicians are as productive and safe as possible.

  
  

Your Business and MTTR

Understanding and optimizing MTTR is key to efficient maintenance operations and, on a larger scale, to your business. With the help of modern tools and the elimination of inefficiencies in operations, the MTTR can be considerably improved, consequently leading to smooth running and happy customers.

Learn More About Maintenance Metrics

• A Quick Introduction to Mean Time to Repair

• Tips on How to Troubleshoot Maintenance Better

• 10 Maintenance Metrics That Might be Overlooked Yet are Still Useful

• An Introduction to Preventive Maintenance Checklists