Making sense of maintenance metrics: Mean time to repair

Welcome to our series of blog posts about maintenance metrics. This post outlines everything you need to know about mean time to repair (MTTR), from how to calculate MTTR to its benefits and how to improve it. Click here to see the rest of the series.

What is mean time to repair?

Mean time to repair is the average time required to complete an assigned maintenance task. MTTR is one way for a maintenance operation to measure how well they are using their time by tracking how quickly they can respond to and repair a problem. It is measured from the point of failure to the moment the system returns to production. Analyzing MTTR is a gateway to improving maintenance processes and achieving greater organizational efficiency.

There may be a weak link somewhere between the time a failure is noticed and when production begins again. MTTR acts as an alarm bell, so you can catch these inefficiencies.

Everything is quicker these days. Online purchases are delivered in less than 24 hours. Computers take your order at restaurants so you can get your food faster. Checking in for a flight only takes a minute or two with your phone.

Time matters. Maintenance teams and manufacturing facilities have known this for a long time. That’s why mean time to repair is one of the most valuable and commonly used maintenance metrics.

How to calculate MTTR

Calculate MTTR by dividing the total time spent on unplanned maintenance by the number of times an asset has failed over a specific period. The most common time increment for mean time to repair is hours.

For example, one of your assets may have broken down six times during production last year. The total time it took to repair the asset across all six failures was 44 hours (about 2 days). In this case, the MTTR calculation would look like this:

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When you calculate MTTR, it’s essential to take into account the time spent on all elements of the work order and repair process, which includes:

1. Notifying technicians
2. Diagnosing the issue
3. Fixing the issue
4. Allowing the equipment to cool down
5. Reassembling, aligning and calibrating the asset
6. Setting up, testing, and starting up the asset for production

The mean time to repair formula does not factor in lead time for parts and isn’t meant to be used for planned maintenance tasks or planned shutdowns.

There are also a couple of assumptions that must be made when you calculate MTTR. The first is that repair tasks are performed in a consistent order. The second is that appropriately trained technicians perform the repairs.

Time obviously matters. Maintenance teams and manufacturing facilities have known this for a long time. That’s why mean time to repair is one of the most valuable and commonly used maintenance metrics.

Benchmarking your facility’s MTTR against best-in-class facilities is difficult. What is considered world-class MTTR depends on several factors, like the kind of asset you’re analyzing, how old it is, and how critical it is to production. However, as a general rule, the best maintenance teams in the world have a mean time to repair of under five hours.

How is MTTR used?

Mean time to repair can tell you a lot about the health of a facility’s assets and maintenance processes. Conducting an MTTR analysis gives organizations another piece of the puzzle for making more informed, data-driven decisions and maximizing resources.

Making repair or replace decisions

As equipment ages, MTTR can trend upwards, meaning an asset takes longer to repair when it fails. When you see this happening, it’s time to make a repair or replace decision. When calculating MTTR, you can measure future spending on the existing asset and the money you’ll lose on lost production. It’s easy to compare these costs to those of a new machine, which will be expensive but run with fewer breakdowns and use parts that are easier to repair. With all this information, you can make decisions that’ll save money now and in the long term.

Refining the work order process

Tracking mean time to repair allows you to uncover problems in your work order process and put measures in place to correct them. If MTTR ticks higher, it can mean there’s a weak link between when a failure is noticed and when production begins again. MTTR acts as an alarm bell so that you can catch these inefficiencies. There can be any number of areas that are lacking, like how technicians are notified of breakdowns, the availability of repair resources (like manuals), or the level of training the team has on a certain asset. MTTR flags these deficiencies, one by one, to bolster the work order process.

Organizing spare parts

MTTR doesn’t account for the time spent waiting for parts to be delivered, but it does consider the minutes and hours spent finding the parts you already have. Most maintenance teams will tell you that while it might sound easy to locate a part, the task can be anything but straightforward. Storerooms can be disorganized with mislabeled parts and obsolete inventory hanging around. A high MTTR might signal that improper inventory or asset management is wreaking havoc on repair times and give you the insight to implement a better system for your spare parts.

How to improve MTTR

MTTR is just a number languishing on a spreadsheet if it doesn’t lead to decisions, change, and improvement. Analyzing mean time to repair can give you insight into the weaknesses at your facility, so you can turn them into strengths, and reap the rewards of less downtime and increased efficiency.

1. Standardize and fine-tune processes

There’s no such thing as too much detail regarding maintenance processes. Because MTTR can be affected by the smallest action (or inaction), every step of a repair must be outlined clearly for everyone involved, including operators, technicians, inventory managers, and others.

For example, operators may know how to fill out a work order, but do they have a template so information is complete and consistent? Technicians might have a task list for a repair, but are the instructions thorough enough? Are exact specs or measurements included? Improving MTTR means looking at all these elements and seeing what can be fine-tuned. The outcome of this will be standard instructions that create a normal quality of work and expected results.

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2. Make resources more available

Speaking of unnecessary snags in the repair process, when technicians look for asset histories, manuals, SOPs, diagrams, and other vital documents, it pushes MTTR higher. Trudging back and forth to an office, finding misplaced files, and struggling to make sense of old documents could be more productive. Instead, eliminate the headaches caused by physical files by making all these resources digital and available through a mobile device. Maintenance can be done quicker, and MTTR can be whittled down.

3. Create and use failure codes

Technicians can’t fix an asset if they don’t know what’s wrong with it. The longer it takes to determine the breakdown’s source, the higher the MTTR. The solution is to make diagnosing a problem easier. The best way to do that is through failure codes. Failure codes are a way of organizing the most common causes of failure into a list that a technician can quickly reference. Determining why an asset broke down without failure codes can be labor-intensive and include time-consuming trial and error. Failure codes eliminate wild goose chases and dead ends, allowing you to complete a task faster.

Building a foundation for success with MTTR

If maintenance is a race from point A to point B, measuring mean time to repair gives you a roadmap for avoiding traffic and reaching the finish line faster, better, and safer. A healthy MTTR means your technicians are well-trained, your inventory is well-managed, and your scheduled maintenance is on target. MTTR gives you the insight you need to uncover hidden issues in your maintenance processes so your operation can achieve its full potential, spend less time fixing problems, and focus on producing high-quality products.