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Failure is a great teacher, and there's a lot to learn from maintenance failure metrics. 

 With mean time to repair (MTTR), maintenance managers can track and evaluate the overall efficiency of their teams, adjust parts and materials inventory control, and make data-driven decisions on repair or replace. 

It all starts with a simple formula. 

First, let's clear up any possible confusion. 

Definition of mean time to repair 

Mean time to repair (MTTR) measures how efficiently the maintenance department gets an asset back up and running after an unplanned breakdown. It is the amount of time it takes for the department to organize technicians, find and diagnose the problem, fix it, test the repairs, and set the asset back up, ready for production. You don't include time spent waiting for parts in the calculation, but you do include something like time spent waiting for the asset to cool down or warm up. 

MTTR is specific to one asset. So, the maintenance department does not have an MTTR. Instead, it has a MTTR for each of the assets and pieces of equipment it maintains and repairs. 

MTTR: mean time to repair, mean time to recovery, or mean time to respond 

Confusingly, it's all three. The difference is when you start the clock. For mean time to recovery, it starts at the time of the failure. But for mean time to repair, you don't start counting until the technicians start working. 

That difference becomes crucial when negotiating maintenance service agreements as a part of vendor management. Companies charge different rates for an MTTR of, for example, 24 hours versus 7 days. 

There is also mean time to respond, which is the amount of time it takes for the people responsible for fixing the asset to acknowledge there's a problem and takes steps to correct it. 

How to calculate mean time to repair 

To calculate MTTR, start by adding up the amount of time you spent repairing an asset after it suffered unscheduled downtime. Do not include in the calculation any time the maintenance team spent on preventive maintenance inspections or tasks. Look at only downtime you didn't see coming.   

For example, you might have a press you spent a total of four hours repairing: first for an hour and a half, and then for two and a half. Or you could have something like 30 minutes the first time and three and a half the second. 

It doesn't matter if the individual lengths of time are similar or not. But what needs to be similar is the relative experience and proficiency of the technicians doing the work. The MTTR calculation assumes that properly trained technicians with the right combination of tools and training are doing the work. 

Also: make sure to pull out time for breaks and interruptions. It's a simple example, but if the techs took an hour for lunch one of the times they were repairing the asset, don't include that hour. 

So, there might be times when you need to work the numbers a bit to get an accurate MTTR. If your junior tech did some of the work, assume that they took longer than a senior tech would have, and massage the numbers accordingly. If the team did the work in separate blocks, make sure to pull out any time spent not working on the asset. 

How to use the mean time to repair formula 

Use this MTTR formula to calculate your MTTR: 

Take the total amount of time (which we already said was four hours) and divide it by the number of times you worked on the asset (which we said was two). Here, times you worked on the asset just means the number of times it broke down. 

Your MTTR is 2 hours. 

Why use MTTR software 

Once you have the MTTR for an asset, you can start to look for ways to make it as small as possible. MTTR software helps you track all the numbers that go into the calculation, and because you can track them, you can improve them. 

Resource management 

One way to decrease your MTTR is to increase your training and sharing. Offer more opportunities for techs to learn and easier ways for them to share information with one another. 

On the most basic level, if it's taking the team a long time to repair a certain asset, it's time to invest in some additional training. Remember, the MTTR is specific to each asset; you can prepare tailored, focused training.    

Or you might find that there's a lot of variation in the average repair times: sometimes an asset is up and running within 30 minutes while other times it takes hours. Although it could be related to the types of failures you're experiencing, there's also a chance it's because of uneven levels of training and experience among the techs. 

If that's the case, a good solution is using MTTR software to build out the related on-demand and preventive maintenance work orders with checklists and step-by-step instructions. That way, every technician has equal access to the department's collective knowledge. 

Another related benefit to a modern mobile software platform is the ability for techs to access the asset's maintenance and repair histories quickly. It's easier to troubleshoot an issue when you can see the past work. 


Inventory control 

You can also use MTTR to better control inventory, including which parts and materials to keep onsite and how much to keep of each. If you have an asset with a long MTTR, you can bump your associated part levels to ensure you have what you need as soon as you need it. 

MTTR software makes this much easier with an integrated inventory control module. When you generate a new work order, all associated parts and materials are automatically connected. When the technicians close the work order, the software automatically adjusts your parts and materials levels, keeping your counts up to date in real time. As soon as you hit your customizable par levels     

Asset replacement and selection 

MTTR helps you decide which assets to retire and how best to replace them. 

Over the course of an asset's life cycle, MTTR tends to increase due to more frequent breakdowns that take the team longer to troubleshoot and repair. Eventually, the cost of keeping the asset up and running is higher than the value it delivers. It would be like making a $100 a week delivering pizzas in a car that averages $150 a week in repairs. 

By keeping an eye on the MTTR, your organization can make better decisions about when to repair an asset or decommission and replace it. 

MTTR can also help you when selecting replacement assets. Because the maintenance department knows it's tracking MTTR, and an important component of MTTR is how quickly the techs can troubleshoot and repair an asset, the organization has an incentive to find assets that are easier to look after. 

What makes an asset easier to repair? Sometimes it's as simple as having the access panels in the right spots. Imagine trying to change the oil on your car if you couldn't open the hood. But it can also be a more fundamental shift to a modular design where technicians can remove and replace modules of parts instead of having to fix an asset part by part. 

Next steps 

Failure metrics are a powerful tool for improving processes and procedures, and the easiest way to get them working for you is with the right software solution. 

If you've been thinking about making the jump to data-driven maintenance management, now's the time to reach out to providers. They can give you a sense of your options and what's going to work best for you. 

Wayne Metro success story

About The Author

Jonathan Davis

Jonathan has been covering asset management, maintenance software, and SaaS solutions since joining Hippo CMMS. Prior to that, he wrote for textbooks and video games.
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