What is Mean Time to Failure?

There are several maintenance metrics worth analyzing for your organization, and mean time to failure is one that should be on your radar. First, what is mean time to failure or MTTF exactly?

MTTF measures the expected lifespan of a non-repairable asset or component, such as fan belts or light bulbs.

Mean time to failure is often confused with mean time between failures (MTBF), which is used for repairable assets and components. Even though MTTF is for assets you can’t repair, it is still a highly useful metric to know.

Why is this Failure Metric Important?

Knowing the estimated lifespan of non-repairable components actually contributes to understanding the reliability of a larger piece of equipment. If your business relies heavily on the equipment, the need to replace even the smallest component leads to expensive downtime. A shorter MTTF means a part must be replaced more often than one with a longer MTTF, which means more downtime. A mean time to failure report can help you ensure you have replacement parts on hand when you need them. This reduces the time needed for replacement and assists you in decisions on the quality of those parts. For example, you may find it is more cost-effective to spend a bit more on a higher quality component with a longer MTTF, which would reduce your overall downtime.

How to Calculate Mean Time to Failure

The key to calculating MTTF is collecting data on the item over an extended period of time to track how long it lasts. The calculation is the total time in operation divided by the total number of items. For example, you have three assets of the same type with a belt. The three belts lasted 3,000 hours, 3,500 hours, and 4,000 hours.

MTTF = (3,000 + 3,500 + 4,000) / 3

MTTF = 10,500 / 3

MTTF = 3,500 hours

As you can see in this example, MTTF doesn’t provide a precise expiration date for that part. It provides an average expected lifespan. Some components may last longer and some may fail sooner, but mean time to failure will still give you a better number to plan from than if you didn’t measure this at all.

What is a Good MTTF?

One thing to keep in mind is that with most maintenance metrics, lower is better. However, a higher MTTF is better! What is good or bad will vary based on what asset you are measuring. Checking the manufacturer-provided lifespan and comparing across products will provide you an idea of the possible range. For example, light bulbs often come with a statement of expected hours of operation. An incandescent bulb will have a lower MTTF, while a LED bulb will have a higher MTTF. While it is a simple one, this is the perfect example of spending a bit more on a component upfront to achieve a higher MTTF and reduce the downtime needed for replacements.

How to Improve Mean Time to Failure

The LED bulb versus an incandescent bulb example illustrates the main way to increase mean time to failure. You can start by determining your most essential assets and analyzing the MTTF of their non-repairable components. If there are better quality components with a higher MTTF, then you can make that change to reduce downtime frequency. Additionally, you can compare your actual MTTF to the manufacturer-recommended MTTF. If your components are failing sooner than should be expected, this could be a red flag for issues of proper installation, humidity, heat, pressure, voltage, etc.

You can streamline your MTTF data collection and reporting process with Redlist. The biggest hurdle for businesses is the time it typically takes to collect this data and create a report. However, Redlist digitizes the work order and maintenance processes, allowing your data to automatically generate an MTTF report in real-time.

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