What is a Bathtub Curve and How to Measure Asset Reliability

What is a Bathtub Curve and How to Measure Asset Reliability?

The Bathtub Curve: Understanding Asset Reliability

In the world of maintenance management, understanding and predicting asset reliability is crucial. Whether you want to enhance your preventive maintenance program or optimize your asset lifecycle management, anticipating and measuring asset reliability can save you substantial time and resources. One common tool for this purpose is the Bathtub Curve. In this article, we'll explore the concept of the Bathtub Curve and discuss how it's used to measure asset reliability.

What is the Bathtub Curve?

The Bathtub Curve is a graphical representation of the failure rates of a system over time. This curve, which takes the shape of a bathtub when plotted on a graph, is divided into three distinct phases: infant mortality, normal life, and wear-out.

Infant Mortality Phase
This phase occurs at the beginning of an asset's life cycle. During this phase, there are typically many failures due to manufacturing defects, installation errors, or other initial problems. As these problems are corrected, the failure rate drops steeply, leading to the next phase.
Normal Life Phase
Also known as the "random failures" phase, this phase is characterized by a low and relatively constant failure rate. During this phase, the asset is expected to perform with minimal failures.
Wear-out Phase
This phase occurs towards the end of the asset's life cycle. As the asset ages and components wear out, the failure rate increases again.

The Bathtub Curve is particularly useful for assets with a large initial failure rate and a significant increase in failure at the end of their life cycle. It helps maintenance teams identify when an asset might need attention or replacement.

Measuring Asset Reliability

Asset reliability measures an asset's ability to perform its intended function without failure over a specific period. Various factors can influence an asset's reliability, including its design, manufacturing quality, installation conditions, maintenance practices, and operating conditions.

Using the Bathtub Curve, you can estimate an asset's reliability during different phases of its life cycle. For example, during the normal life phase (the bottom of the curve), an asset is expected to have high reliability and a low failure rate. On the other hand, during the infant mortality and wear-out phases (the steep slopes of the curve), the asset's reliability decreases as the failure rate increases.

Understanding these phases can help you develop effective maintenance strategies. For instance, during the infant mortality phase, you might focus on thorough testing and swift repair or replacement of faulty components. You might implement a preventive maintenance checklist to maintain the asset's performance during the normal life phase. In the wear-out phase, you may plan for asset replacement to prevent unexpected breakdowns.

Leveraging Maintenance Management Software

Maintenance Management Software can help you implement and manage a preventive maintenance program based on the principles of the Bathtub Curve. Using this software, you can schedule routine inspections, tests, and maintenance activities to detect and rectify issues before they cause asset failure.

Moreover, with features like predictive maintenance, you can leverage historical data and advanced analytics to forecast when an asset might fail; This enables you to schedule maintenance activities just in time to prevent failure, enhancing the asset's reliability and extending its life cycle.

Understanding the Limitations

While the Bathtub Curve provides a useful conceptual model for understanding asset failure rates over time, it's important to note that not all assets follow this curve. The failure rate may remain constant or increase for some assets without a distinct wear-out phase. For others, the infant mortality phase may not be present, particularly for assets that have been rigorously tested and corrected for defects before use. As such, the Bathtub Curve should be used as a general guide, complemented by other tools and techniques for measuring asset reliability.


The Bathtub Curve is a powerful tool that helps maintenance professionals understand and predict asset reliability. By leveraging this concept and integrating it with Maintenance Management Software, you can enhance your preventive maintenance strategies, optimize your asset lifecycle management, and, ultimately, increase your operational efficiency. Whether you're dealing with Breakdown Maintenance or looking to enhance your preventive maintenance checklist, understanding and applying the principles of the Bathtub Curve can go a long way toward achieving maintenance success.

Certainly, let's illustrate the concept of the Bathtub Curve with a hypothetical example using a fleet of 100 identical machines that have been operational for a year.

Infant Mortality Phase

Let's say that during the first month, five machines fail due to factory defects or installation issues. The maintenance team replaces or repairs these machines. As a result, the number of failures drops drastically in the second month, with only two. By the third month, only one failure is reported. This high rate of failure at the beginning that decreases rapidly represents the infant mortality phase.

Normal Life Phase

For the next six months, the machines are operating under normal conditions. The failure rate during this period is low and constant. On average, one machine fails every two months. These random failures could be attributed to various factors, including environmental conditions or operational errors. This constant, low failure rate indicates the normal life phase.

Wear-out Phase

The failure rate increases as the machines approach the end of their first operational year. In the tenth month, two machines fail. In the eleventh month, three machines failed. Finally, in the twelfth month, five machines failed. These increasing failure rates are attributed to component wear-out, symbolizing the wear-out phase of the Bathtub Curve.

Using the Bathtub Curve for Maintenance Planning

Knowing the Bathtub Curve of these machines, the maintenance team can strategize their efforts more effectively. For instance, during the infant mortality phase, they can plan for rigorous initial testing and immediate response to faults. During the normal life phase, they can follow a preventive maintenance checklist to keep the machines in good condition. As the wear-out phase approaches, they can schedule replacements or major overhauls to prevent sudden breakdowns.

Remember, this is a hypothetical example. Real-world data could be more complex, and not all machines or equipment follow the Bathtub Curve. Nonetheless, this model provides a useful framework for understanding asset reliability and planning maintenance activities accordingly.

This example highlights the value of tracking and analyzing failure data over time. Maintenance Management Software lets you capture this data in real-time, generate insightful reports, and make data-driven decisions to enhance your maintenance strategies. It enables you to move from reactive to proactive maintenance, minimizing unplanned downtime and extending the lifespan of your assets.

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Amrapali Exports - Esteemed Clients of cryotos
Anuraj Sharma - Maintenance Manager

The best thing about Cryotos CMMS software is that it always tells me when something needs to be fixed - before it breaks and cost me a fortune!

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Jeevan Belliappa - Head, Information Technology

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Antony Jacob Ashish - Lead, R&D

Cryotos goes above and beyond when it comes to customer satisfaction. Planys Technologies use Cryotos for preventive/ corrective maintenance of our critical systems and not once did we face a problem that was not dealt with immediately. The team is extremely professional and helpful. We can rely on Cryotos when it comes to the operations and processes.

Thanks to the whole team for the amazing performance and thought leadership. It's rare to see teams that can put themselves in the customer's shoes and think from their perspectives - Cryotos team doesthat and more.

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Thanks to the team for an awesome job.

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Siva Shankar - AGM, (Operations & BD)

On behalf of Xpert FMS we would like to express our sincere appreciation for the excellent support Cryotos team have provided us for our building and facility management. Cryotos has always provided support that is timely and meets our expectations. Professionalism and quick response are the hallmarks of this team.

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Mukesh J - CIO

We are able to raised the workorder and tracking of these till the closure as helped us to provide better services our beneficiaries. Workflow-based work order management has helped us to define processes for each locations separatley. System provide notification once order is raised for assignment to engineer.

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This CMMS software is top-notch! I can't believe how much it has helped me with my facilities maintenance management. Customized reports and business intelligence have been invaluable in making better decisions.

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Mr. Vishnu S Nair

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B S Vijaya K. - Maintenance Engineer

At starting it felt some what difficult for scheduling but now it made to easy access.

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Nithin G. - Maintenance Incharge

Overall: Nice Software
Pros: Scheduling, work order creation, asset inventory, records.
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Aptiv8 IT Solutions
Hashim - Business Project Manager

This CMMS software is top-notch! I can't believe how much it has helped me with my facilities maintenance management. Customized reports and business intelligence have been invaluable in making better decisions.

The software offers a great deal of customization for each organization's specific needs. They are always updating the software with new features and improvements, which is great. The support team is fantastic - they are always quick to help with any questions or problems we have. This software has definitely made my life a lot easier! It's so easy to use and it's really helped me keep track of all my maintenance tasks in one place. I would definitely recommend it to anyone looking for a CMMS platform.

Gurit - Esteemed Clients of Cryotos
Mr. Mohanmurali R

I recently purchased Cryotos CMMS Software for asset management needs at my organization and after a few months of testing and monitoring, I'm incredibly pleased with the results. The software is user friendly, accessible and the design is very intuitive. It covers all the aspects of managing maintenance and repair, starting from preventive maintenance and standardizing operation cycles, to scheduling and streamlining workflows. I am highly satisfied with the performance and the range of features offered by Cryotos. Highly recommendable!

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Mr. Sanjay Beri

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Mr. Yuksel Aksin

As a customer of Cryotos CMMS software for asset management needs, I must say that I am thoroughly impressed with the features and functionality offered by the platform. Cryotos CMMS software has made managing my assets a breeze, and I no longer have to worry about missing maintenance or inspections.

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