Mean Time To Failure

Mean Time to Failure (MTTF) is a metric that estimates the average time a system or equipment will run before failure. The primary purpose of MTTF is to estimate how long an asset will operate before breaking down. 

MTTF is crucial in maintaining equipment, parts, and various non-replaceable assets like tires and tubes. It also helps in the decision-making process for inventory management. However, applying mean time to failure analysis can be difficult or ineffective in uncertain situations.

• Mean time to failure is a management standard metric that helps understand the average hours an asset or part will survive before it fails.  
• It is also known as "MTTF." It applies to non-repairable parts, which cannot be repaired. Thus, they are replaced by a new part upon failure. 
• During World War I, German Mathematician Eric Pieruschka assisted aerospace engineer Wernher Von Braun in finding failures in the V-1 rockets.
• The formula for mean time to failure (MTTF) is the ratio of total hours of operation divided by the total number of assets in use. 

Mean time to failure refers to a metric that applies to non-repairable assets that need urgent replacement and allows firms to calculate the average time a system will operate in its lifetime. So, with the MTTF, firms can calculate the number of hours an asset, such as a tire, can live. Therefore, it plays an important role, particularly in incident management.

The concept of mean time to failure is commonly employed in reliability engineering. While it's not specific to a particular industry, it is widely used in industries like electronics, automotive, aerospace, medical devices, etc., where the reliability and uptime of equipment or systems are important elements.

The application of mean time to failure is more focused on non-repairable assets as they need to be more durable. So, if this part plays a vital role in the final product, the latter's lifetime of the asset can be disrupted. Therefore, assets with higher MTTF are favorable. Thus, firms tend to purchase parts with longer lifespans. For example, if a company uses low-value MTTF tubes in cars, the efficiency of the vehicle will be reduced. However, if they continue to do so, the market value of the product will drop drastically. 

MTTF is equally crucial in inventory management. Thus, businesses installing high MTTF equipment can maintain proper inventory control. In addition, there is no wastage since firms go for high-quality parts that result in higher lifetime value. Therefore, non-repairable assets with high expiry plus quality will benefit them.

A part's quality determines the mean time to failure reliability. Yet, some factors are to consider, like a part's quality, way of installation, environmental condition, and others. Thus, a low-value part will disrupt the mean time to failure reliability. However, some business units refuse quality parts in exchange for a low cost. As a result, they degrade at a much faster rate compared to alternative options. For example, if a company uses low-graded blades in a mixer, it will lose its sharpness easily. As a result, the customer will find it irritating and might break their loyalty to the brand. 

MTTF has limitations, including its assumption of a constant failure rate, neglect of wear and aging effects, and lack of consideration for repairability and non-failure scenarios. It may not accurately reflect real-world conditions, especially in the presence of common cause failures or for complex systems.

Let us look at the formula for the mean time to failure calculation for a better understanding:

Mean Time to Failure = Total Hours of Operation / Total Number of Assets in Use

Where:

Total hours of operation refer to the number of hours the equipment or asset has worked in one year.

The total assets in use are the exact number of identical parts used in operation.

Let us look at the examples of mean time to failure analysis for a better understanding of the concept:

Example #1

Suppose Sheldon is a senior quality control manager in a factory that manufactures laptops and computer units. Sheldon uses MTTF because, in laptop manufacturing, the MTTF application is important to derive the average lifespan of various products before they are expected to fail. For instance, if a laptop's hard drive, battery, and screen collectively last for a certain duration, the MTTF provides Sheldon insights into when these components might need replacement or maintenance. This helps in designing good-quality laptops and planning for product warranties and support.

Example #2

MTTF analysis is relevant for household budgeting, safety, and energy efficiency. It helps plan replacements, address safety concerns, and influence insurance decisions. Overall, it contributes to the decision-making for a well-managed and sustainable household.

Assume Phoebe has four bulbs installed in the drawing room, bedroom, kitchen, and bathroom. These fluorescent bulbs, which are in use, lasted for approximately 7000 hours in the past year. So, what is the average number of hours or MTTF for the bulbs to stop working?

Mean Time to Failure = Total Hours of Operation / Total Number of Assets in Use

                                       =  7000 / 4

                                      = 1,750 hours/ failure

Thus, the average lifespan of a bulb in Phoebe's house is 1750 hours or two months for its failure. 

This article has been a guide to what is Mean Time To Failure (MTTF). Here, we explain the topic in detail, including its formula and examples. You may also find some useful articles here –

• Idle Time Meaning
• Internal Failure Cost
• External Failure Cost