Mean Time to Repair (MTTR): What It Is & How to Calculate It
Failure of equipment can lead to business downtime, poor customer service and lost revenue.
Mean Time to Repair (MTTR) is an important failure metric that measures the time it takes to troubleshoot and fix failed equipment or systems.
By tracking MTTR, organizations can see how well they are responding to unplanned maintenance events and identify areas for improvement.
Let’s look at what Mean Time to Repair is, how to calculate it, and how to put it to good use in your business.
- What is Mean Time to Repair (MTTR)?
- Why is MTTR important?
- Failure metrics
- The four types of MTTR
- The difference between MTTR and MTBF
- A formula for calculating MTTR
- The limitations of MTTR
- How to use MTTR
- What is a good MMTR?
- How to improve MTTR
What is Mean Time to Repair?
Mean Time to Repair – or MTTR – is a metric used to measure how well equipment or services are being maintained, and how quickly issues are being responded to.
Mean Time to Repair is the average time it takes to detect an issue, diagnose the problem, repair the fault and return the system to being fully functional.
It is measured from the moment that a failure occurs until the point where the equipment is repaired, tested and available for use.
MTTR values generally include the following stages:
- An issue arises
- The issue is detected
- Technicians are notified
- The issue is diagnosed
- The issue is fixed
- The system is reassembled
- The system is restarted and tested
- The system is made available for use
Note: If the technician does not have the parts readily available to complete the repairs, this may extend the total time between the issue arising and the system becoming available for use again. If this occurs regularly, it may be helpful to include the acquisition of parts as a separate stage in the MTTR analysis.
MTTR is not intended to be used for preventive maintenance tasks or planned shutdowns.
Why is MTTR important?
Mean Time to Repair is one of the most important and commonly used metrics used in maintenance operations.
Downtime – the period during which a piece of equipment or system is unavailable for use – can be very expensive to a business, so minimizing MTTR is essential.
With the rapid pace of life and business these days, responding as quickly as possible to issues when they arise can sometimes mean the difference between keeping and losing a customer.
If your business provides maintenance or repair services, then monitoring MTTR can help you improve your efficiency and quality of service.
If MTTR increases over time, this may highlight issues with your processes or equipment, and if it goes down, then it may indicate that your service level to your customers is improving.
Measuring MTTR ensures that you know how you are performing and can take steps to improve the situation as required.
Mean Time to Repair is part of a larger group of metrics used by organizations to measure the reliability of equipment and systems.
Failure is not only used to describe non-functioning assets but can also describe systems that are not working at 100% and so have been deliberately taken offline.
Some other commonly used failure metrics include:
- Mean Time to Detect (MTTD): This measures the average time between the start of an issue with a system, and when it is detected by the organization. This metric is important because the longer it takes for a problem to even be picked, the longer it will be before it can be repaired.
- Mean Time Between Failures (MTBF): This measures the average time between failures of a repairable piece of equipment or a system. It reflects both availability and reliability of an asset, and the aim is for this value to be high as possible (ie a very long time).
- Mean Time to Failure (MTTF): This is the average time between non-repairable failures and is generally used for items that cannot be repaired, such a light bulb or a backup tape. It is a similar measure to MTBF.
There are additional metrics that may be used across industries, such as IT or software development, including mean time to innocence (MTTI), mean time to acknowledge (MTTA), and failure rate.
The four types of MTTR
There are actually four different definitions of MTTR in use, which can make it hard to be sure which one is being measured and reported on.
- Mean Time to Repair (MTTR) is the most commonly used variation of MTTR and measures the average time taken to repair a system, including diagnosis, repair and testing. This is more often used for technical or mechanical systems.
- Mean Time to Recovery (or Mean Time to Restore) is like Mean Time to Repair, as it represents the average time from system failure until it is fully operational again. This metric may be used for online services or software.
- Mean Time to Respond measures the time taken to repair a system, from the moment you are notified, until it is completely fixed. This does not include any time taken from the initial failure to when you are first alerted.
- Mean Time to Resolve extends Mean Time to Repair, by including any time taken to reduce the chances of the failure happening again. This additional time may occur after the system is back online but is definitely key to maximizing customer satisfaction.
Make sure you understand the difference between the four types of MTTR outlined above and be clear on which one your organization is tracking.
Creating a clear, documented definition of MTTR for your business will avoid any potential confusion.
The difference between MTTR and MTBF
Mean Time to Repair and Mean Time Between Failures (or Faults) are two of the most common failure metrics in use.
But what is the relationship between them?
Essentially, MTTR is the average time taken to repair a problem, and MTBF is the average time until the next failure.
In even simpler terms MTBF is how often things break down, and MTTR is how quickly they are fixed.
So together, the two values give us a sense of how much downtime an asset is having – or expected to have – in a given period (MTTR), and how much of that time it is operational (MTBF).
Keeping MTTR low relative to MTBF ensures maximum availability of a system to the users.
A formula for calculating MTTR
So how do you go about calculating MTTR?
Because MTTR represents the average time taken to address an issue, it is calculated by adding up all time spend on unscheduled or corrective maintenance in a period, and then dividing this total by the number of incidents in that period.
Here’s an example.
Let’s say you have a very expensive piece of medical equipment that is responsible for taking important pictures of healthcare patients.
Over the last year, it has broken down a total of five times. The time that each repair took was (in hours), 3 hours, 6 hours, 4 hours, 5 hours and 7 hours respectively, making a total maintenance time of 25 hours.
So the MTTR for this piece of equipment is:
MTTR = 25 / 5 = 5 hours
In calculating MTTR, the following is generally assumed.
- Repair tasks are completed in a consistent manner
- Repairs are carried out by suitably trained technicians
- Technicians have access to the resources they need to complete the repairs
Lead times for replacement parts are not generally included in the calculation of MTTR, although this has the potential to mask issues with parts management. When defining MTTR for your business, look at the specific nature of your business to decide whether or not parts acquisition should be included in your calculations.
Keep in mind that MTTR can be calculated for individual items, across a client’s assets or for an entire organisation, depending on what you’re trying to evaluate the performance of.
The limitations of MTTR
Mean Time to Repair is a high-level measure of the speed of your repair process, but it doesn’t tell the whole story.
Its purpose is to alert you to potential inefficiencies within your business or problems with your equipment.
But it can’t tell you where in your processes the problem lies, or with what specific part of your operations.
For that, you’ll need to measure the stages of the repair process in a more granular fashion, looking at things like:
- Alert systems
- Response times
- Inventory management
- Repair skills
Also remember that the MTTR you calculate is only as good as the data it is based on, so make it easy for technicians to log maintenance task time using specially designed service software, rather than manually entering data or filling out paperwork.
You also need a large enough sample to be sure that you’re getting an accurate measure of your failure metrics, so give yourself enough time to collect meaningful data.
And you need to be clear on exactly what units you’re measuring things in, which stages are included, and which exact metric you’re tracking.
And of course, MTTR can only ever been average figure, representing a “typical” repair time. Actual individual incidents may take more or less time than the MTTR.
How to use MTTR
Mean Time to Repair is generally used as an indication of the health of a system and the effectiveness of the organizations’ repair processes.
MTTR can be used to measure stability of operations, availability of resources, and to demonstrate the value of a department or repair team or service.
It is also a valuable piece of information when making data-driven decisions, and optimizing the use of resources.
A high Mean Time to Repair may mean that there are problems within the repair processes or with the system itself.
Possible issues within processes that may be indicated by a higher than average MTTR can include:
- Delays in the detection or notification of issues
- Difficulties with diagnosis
- Lack of availability of parts or resources
- A need for additional training for technicians
- Poor documentation of processes
But a high MTTR for a specific asset may reflect an underlying issue within the system itself, possibly due to age, meaning that the amount of time it takes to repair the equipment is increasing or unusually high.
Noting when the MTTR for a specific item becomes too high may then lead to a discussion about whether it’s more cost effective to repair the item, or simply replace it, saving money now and later.
You can also look at your MTTR and ask yourself questions like:
- Is it fast enough?
- How does it compare to our competitors? and
- How can we improve it?
What is a good MTTR?
When you start tracking MTTR in your business and being collecting data on your performance, how do you know what you should be aiming for?
Eventually, you’ll develop a comprehensive set of metrics for your specific business and customers that you’ll be able to benchmark your progress against, and this is best way to decide what a good MTTR looks like to you.
But to begin with, looking outside of your business to industry benchmarks or your competitors can give you a rough idea of what a good MTTR might look like.
Keep in mind that MTTR is highly dependent on the specific nature of the asset, the age of the item, the skill level of your technicians, how critical its function is to the business and more.
With that said, typical MTTRs can be in the range of 1 to 34 hours, with an average of 8. And supposedly the best repair teams have an MTTR of less than 5 hours.
How to improve Mean Time to Repair
Once you’ve established a baseline for your organization’s MTTR, then it’s time to look at ways to improve it.
And by “improve” we mean decrease. The aim with MTTR is always to reduce it, because that means that things are being repaired more quickly and downtime is being minimized.
If your MTTR is just a pretty number on a dashboard somewhere, then it’s not serving its purpose. It should be examined regularly with a view to identifying weaknesses and improving your operations.
And there’s a few things you can do to decrease your MTTR.
1. Detect issues faster
Wasting time simply because nobody is aware that there’s even a problem is completely unnecessary, easy to address and a fast way to improve MTTR.
Implementing better monitoring systems that alert your team as quickly as possible after a failure occurs will allow them to swing into action promptly and keep MTTR low.
2. Improve diagnostics
Diagnosing a problem accurately is key to rapid recovery after a failure, as no repair work can commence until the diagnosis is complete.
And with 90% of MTTR being attributed to this stage in some industries, it’s essential to make the process of identifying the problem as efficient as possible.
If diagnosis of issues is taking up too much time, consider:
- Upgrading diagnostic equipment
- Implementing clear and simple failure codes on equipment
- Providing additional training to technicians
This will reduce the amount of trial and error that is required to fix an issue, which can be extremely time-consuming.
Providing a full history of an asset to your technicians can also provide valuable clues that may help them narrow down the source of a problem.
3. Provide ready access to resources
Once a potential solution has been identified, then make sure that team members have the resources they need at their fingertips.
There’s no need to spend valuable time trawling through documents or rummaging around looking for the right part.
With the proper systems in place, including field mobility apps, good inventory management and digital document libraries, technicians can focus their time and attention on completing the repair as quickly as possible.
4. Improve processes
Ensuring that every problem is resolved correctly and fully in a consistent manner reduces the chance of a future failure of a system.
Each repair process should be documented in as much detail as possible, for everyone involved, to avoid steps being overlooked or completed incorrectly. The use of checklists and compliance forms is a great way ensure that critical tasks have been completed as part of a repair.
Using MTTR to improve your processes entails looking at every step in great detail and identifying areas of potential improvement, and helps you approach your repair processes in a systematic way.
Using MTTR in your business
At the end of the day, MTTR provides a solid starting point for tracking the performance of your repair processes.
It’s also a valuable way to assess the value of equipment and make better decisions about asset management.
And while it doesn’t give you the whole picture, it does provide a way to ensure that your team is working towards more efficient repairs and minimizing downtime.
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