Mean Time Between Failure (MTBF)

What is Mean Time Between Failures (MTBF)?

Mean Time Between Failures (MTBF) is the average time that passes between the resolution of one equipment failure to the start of the next. Knowing your MTBF gives you an idea of how long a piece of equipment will keep running after a fix, before it breaks down again, helping you plan for the future.

Table of Contents

Why MTBF is important
Examples of mean time between failures
How to calculate MTBF
The MTBF formula
7 Tips for improving MTBF & productivity
Take the guesswork out of MTBF

Why MTBF is important

Equipment failures can be expensive and damaging to an organization. MTBF helps you predict and prepare for breakdowns, helping you make quick and effective repairs that minimize the cost of downtime. 

It is also an important indicator of overall performance. If your MTBF value is low, you are experiencing a high frequency of breakdowns. This likely means there are systemic issues to explore.

What MTBF means for your organization

Manufacturers use mean time between failures as a way to predict the reliability and failure rate of equipment during the different stages of production. 

It is also commonly used today in:

• Mechanical and electronic systems design
• Safe plant operations
• Product procurement

MTBF calculations do not include planned maintenance, but they do help you plan inspections for preventive replacements. For instance, if you know how long an asset will run before the next failure, introducing preventive maintenance actions like lubrication or recalibration can help prevent that failure.

Knowing your MTBF helps save you money, increases total uptime, and makes you look good at your job – and who doesn’t want that?

Examples of mean time between failures 

MTBF is most commonly used to avoid downtime. But MTBF can also help predict, prevent, and prevail over the bulk of all your unplanned breakdowns. It can be used for: 

• Asset management, planning, and forecasting for inventory of spare parts and maintenance tools
• CAPEX budgeting 
• Planning a maintenance schedule 
• Evaluating the performance of your maintenance strategies 
• Evaluating the quality of your machine data and how it is used

How to calculate MTBF

Calculating MTBF doesn’t have to be hard. As long as you are tracking the total hours your asset has been operating and the total number of failures that have occurred, you have everything you need. You can even use easily accessible tools like Microsoft Excel to easily find your mean time between failure.  

The data needed to find your MTBF 

MTBF is a ratio of the total operating time on an asset to the unplanned failures in the same timeframe. 

Therefore, you will need to track total operational time for a piece of equipment by making note of: 

• The date and time any unplanned downtime begins
• The date and time equipment resumes operation after a repair

Note: MTBF doesn’t take predictive and preventative maintenance into account so do not include those periods in your calculation.  While they can sometimes cause brief outages, they do not qualify as breakdowns. 

The MTBF formula

The equation for MTBF is simple. It is the total number of hours of operating time divided by the number of failures.

For instance, let’s say you have a generator that was operational for 750.5 hours (or 750 hours and 30 minutes), but experienced 4 failures within that same timeframe. 

Entering those numbers into our formula gives us: 

MTBF = 750.5 / 4

MTBF = 187.625 hours

How to calculate MTBF using software and other reporting tools

While it is good to know how to measure MTBF by hand, it is impractical to plan to do it that way every time. A simple spreadsheet makes calculating MTBF easy as long as you are making note of the correct data. But a CMMS software basically does all the work for you.

Equipment failures are logged through the work request process in a CMMS, tracking downtime and operational time automatically. As a result, your mean time metrics begin calculating the second you begin using the system, building a dashboard of useful KPIs. 

However, if you aren’t quite ready to take the CMMS plunge, we have created a handy calculator. Download it, and see how nice it is to have the work done for you!

7 Tips to increase MTBF and productivity

The goal of any maintenance team should be a high MTBF. Here are a few small things you can do to increase your time between failures. 

1. Do more proactive maintenance work and follow checklists. Assets that are well-maintained are less likely to have critical failures. By using a CMMS, you can create monthly maintenance schedules in minutes. 
2. Use quality replacement parts. The cheapest part is not always the best. Make sure you are using quality, proven parts that will have the durability to keep working for a longer period of time. 
3. Use recommended input material. Whether it is the size of the chicken in the poultry processing system or the thickness of the foil used for product packaging, every machine is designed to work best within specific parameters. 
4. Ensure proper working conditions. Don’t push machines beyond their limits to make your productivity numbers look good. Misusing machines is a surefire way to decrease their useful life and increase the frequency of failures.
5. Have a solid onboarding program for machine operators. Assets should be used according to their design. Improper handling is bound to result in a low MTBF.
6. Implement a structured root cause analysis process. Taking the time to understand the true causes of failures will help your team apply effective repairs more quickly.
7. Understand the kinks of old equipment and aging assets. Sharing information and tips between maintenance technicians and machine operators helps keep assets in good shape.