Mean Time To Failure (MTTF) is a widely used concept in the field of reliability engineering. Show
Like its counterpart, Mean Time between Failure (MTBF), it represents an estimate of the amount of time a system is expected to run before failing. While MTBF refers to thetime between system failures, MTTF refers to the length of time a system can be expected to run without failure. In this article, we’ll take a closer look at MTTF along with some other commonly used maintenance metrics. And while you are reading, keep in mind what McKinsey says about digitally enabled reliability:
What Does Mean Time to Failure (MTTF) Mean?MTTF is an essential failure metric that helps managers to estimate how long non-repairable assets can work before they falter. Tracking MTTF can lead to minimized operational disruptions, maximized asset lifespans, and more effective O&M decision-making. Examples of assets for which maintenance departments calculate MTTF include tires, transistors, lightbulbs, forklift wheels, conveyor belt idler balls and rollers, and motor or engine fan belts. To calculate Mean Time to Failure: MTTF = Total Hours of Operation ÷ Total Number of Assets in Use While such assets are commonly placed on run-to-failure maintenance plans, proactive maintenance such as preventive maintenance or condition-based maintenance can help extend their lifespans even more. There are many situations when calculating MTTF can help improve an organization’s asset management strategy, such as:
MTTF helps develop effective maintenance strategies, reduce dependence on reactive maintenance, and reduce unplanned downtimes. How to Calculate Mean Time to FailureTo calculate MTTF, divide the total time of operation by the total number of items you are tracking: MTTF = Total Hours of Operation ÷ Total Number of Assets in Use Only calculate MTTF for identical assets and parts: their manufacturer, size, and even usage should match. For example, say you’re calculating the MTTF for a lightbulb. In this case, the wattage also should be the same. This will help calculate a more accurate value and help make more informed maintenance decisions. MTTF ExampleYou want to calculate the MTTF for conveyor belt rollers in your manufacturing facility. You have 125 rollers that have been used for a total of 60,000 operational hours in the past year. The MTTF is: MTTF = Total Hours of Operation ÷ Total Number of Assets in Use MTTF = 60,000 hours ÷ 125 assets MTTF = 480 hours The average lifespan of a conveyor belt roller at your production facility is 480 hours. You will need to make arrangements for a new roller every 480 hours before the current one fails. How to Improve MTTFSo, how can you improve MTTF to get more out of your assets before they fail? Here are a few tips to get started:
To a certain extent, proper inventory control also can help improve MTTF. When you overstock your inventory and materials stay for too long in the warehouse, they will likely get damaged, rusty, or expire. Faulty equipment and parts will serve you for a short period of time before breaking down. Other Types of Reliability MeasurementsIn addition to MTTF, facilities use two other failure metrics to determine asset reliability. They enable maintenance professionals to make data-driven maintenance decisions to improve asset uptime and availability: 1. Mean Time between Failures (MTBF)MTBF is the amount of time an asset can operate before experiencing failure. It measures the time between one failure and the next. MTBF is critical to estimating how long production can use an asset before the next unplanned downtime. It acknowledges the fact that failure is inevitable. The metric is only used for repairable assets. However, it doesn’t take into account planned shutdowns for preventive maintenance activities such as lubrication, servicing, recalibration, and parts replacement. As a result, MTBF measures both asset availability and reliability. The higher the MTBF, the more available and reliable the asset. MTBF = Total Uptime ÷ Number of Failures For example, if a water pump operated for nine hours and broke down unexpectedly on three different occasions, then its MTBF is: MTBF = 9 hours ÷ 3 MTBF = 3 hours The water pump works an average of three hours before experiencing unplanned downtime. Keep in mind that MTBF doesn’t factor in planned maintenance. So any planned shutdowns during that period aren’t included in the calculation. Failure in Time (FIT)Another way to report MTBF is Failure in Time (FIT). FIT helps estimate an asset’s operational lifetime. It reports the number of expected failures for every one billion hours of asset operation. A Confidence Limit is then assigned to the asset. A Confidence Limit of 95 percent usually means that failure won’t occur often. Component and semiconductor manufacturers are the primary organizations that use FIT. 2. Mean Time to Repair (MTTR)MTTR is a failure metric used to measure how long it takes to repair an asset and restore it to full functionality. It takes into account the period from when the initial problem is diagnosed to when normal operations are restored. MTTR = Total Maintenance Time ÷ Number of Repairs Let’s use the example of the water pump used in MTBF above. The pump broke down three times and the first repair lasted 30 minutes while the last two went on for 15 minutes each. The MTTR would be: MTTR = (30 + 15 +15) ÷ 3 MTTR = 60 ÷ 3 MTTR = 20 minutes It takes an average of 20 minutes to repair the water pump each time it breaks down. When calculating MTTR, it’s important to note the following:
MTTR measures the average time it will take to identify the cause of asset failure and fix it. It gives an idea of how quickly the maintenance team can respond to unplanned downtimes and restore asset functionality. When calculating MTTR, factor in the period from when the asset failed to when it resumed normal operations. This includes:
It’s worth emphasizing that MTTR doesn’t take into account the amount of time it takes to source replacement parts. It’s also not used for planned downtimes and maintenance tasks. Using modern computerized maintenance management system (CMMS) solutions can help to automate MTTR calculation for critical assets. A CMMS can automatically log the data when maintenance technicians open and close work orders. With that said, it’s not uncommon for folks to confuse MTTF and MTTR: What Is the Difference between MTTF and MTTR?It’s helpful to remember that whenever you come across the phrase “mean time to . . .” you’re measuring the average between two occurrences. Just like MTTF, Mean Time to Repair (MTTR) is another important failure metric that can help you improve your asset maintenance management. MTTR is a good baseline for identifying ways to improve maintenance efficiency and reduce unplanned downtimes. It also helps identify what makes maintenance take longer than normal. MTTR gives useful insights into how to purchase replacement parts and schedule maintenance activities. The major difference between MTTF and MTTR is that MTTF is only used for non-repairable assets while MTTR is used primarily for repairable assets. MTTF is the amount of time it takes before an asset fails and needs to be replaced. MTTR, on the other hand, is the average time it takes to repair an asset after a downtime. Track Maintenance Metrics with MaintainXAs an asset maintenance manager, it’s your responsibility to ensure maximum asset uptime and availability. Understanding MTTF and the other failure rate metrics can help identify ways to improve and optimize your maintenance programs. These metrics are key to shifting from reactive maintenance to a proactive strategy. The good news? Mobile software like MaintainX, as shown above, makes it easier than ever to track essential maintenance metrics, oversee maintenance scheduling, and manage parts/inventory! Click the banner below to download the world’s top-rated CMMS for free. What is mean time between failure for a software?Mean time between failures (MTBF) is the average time between system breakdowns. MTBF is a crucial maintenance metric to measure performance, safety, and equipment design, especially for critical or complex assets, like generators or airplanes. It is also used to determine the reliability of an asset.
What is MTBF and availability?MTBF means Mean Time Between Failures, and it is the average time elapsed between two failures in the same asset. Along with MTTR (Mean Time to Repair), it's one of the most important maintenance KPIs to determine availability and reliability. The higher the MTBF, the more reliable the asset.
What is the difference between Mean Time Between Failures and mean time to failure?MTBF can be calculated as the arithmetic mean (average) time between failures of a system. The term is used for repairable systems, while mean time to failure (MTTF) denotes the expected time to failure for a non-repairable system. The definition of MTBF depends on the definition of what is considered a failure.
What is the availability of a software with?Availability refers to a property of software that it is there and ready to carry out its task when you need it to be. This is a broad perspective and encompasses what is normally called reliability (although it may encompass additional considerations such as downtime due to periodic maintenance).
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