A bathtub curve visually represents the failure rate of one or more assets by plotting their failure occurrences over time. It has three stage: Infant mortality period, normal life period, and wear-out period.
Most manufacturing plants and industrial facilities see failure as a function of time.
Are assets likely to fail closer to the end of their lifecycles? Not always.
The truth is that they can also fail during their useful life or even before that. So, how do you make sense of asset failure probability?
With bathtub curve — a hazard and reliability function that predicts asset failure rate. Maintenance managers and technicians also rely on maintenance management software to detect failures, identify root causes, and prevent such failures from happening.
This article walks you through bathtub curve analysis basics and how to increase an asset’s useful life or availability with it.
What is a bathtub curve?
A bathtub curve visually represents the failure rate of one or more assets by plotting their failure occurrences over time. The name bathtub comes from the curve resembling a bathtub’s longitudinal section.
A bathtub curve has three stages:
Infant mortality period refers to the period when you start using a product for the first time.
Normal life period starts after the initial operation period and is also known as the useful life period.
Wear-out period refers to the time when assets start deteriorating after a certain usage period.
The bathtub graph helps you measure the reliability of assets and adopt the right run-to-failure maintenance management strategy.
Asset reliability specialists consider the bathtub curve as one of the most important graphical representations of chances of failure throughout an asset life cycle — let’s see why.
What is the purpose of a bathtub curve?
A bathtub curve is key to eliminating asset failure. Companies leverage bathtub curve analysis to set performance expectations of assets throughout their life cycle.
For example, you can use this curve to eliminate the initial failure and get rid of ‘dead on arrival’ products. Discovering defects during the initial period helps you get assets replaced under manufacturer warranty.
When assets experience failure in the normal period, that’s often because of random events. Bathtub curve analysis lets you predict those and asset breakdowns during the wear-out period as well.
These predictions help you adopt predictive maintenance techniques early on and keep assets with higher failure rates in tip-top shape.
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Stages of the bathtub curve
Efficient asset lifecycle management requires you to stay on top of asset failures—which you can do only if you know when assets are likely to fail.
That’s why it’s key to understand the three stages of the bathtub curve i.e. infant mortality, normal life, and wear-out period.
1. Infant Mortality Period
The early failure period or infant mortality period starts as you use a product or asset for the first time.
Common causes of asset failure at this stage include manufacturing defects, installation errors, insufficient components, design flaws, and incorrect start-up processes.
These causes often lead to a higher rate of failure during a short period—hence the name infant mortality. This period often starts with a high failure occurrence before the failure rate decreases and eventually plateaus.
So, what can you do to minimize asset failure during the infant mortality period?
Check out the common maintenance strategies to prevent infant mortality equipment failures.
Perform preliminary tests or purging using sensors or automatic technologies. These tests will aid you to discard defective equipment or send them for repair or replacement.
Run acceptance and reliability tests to reevaluate equipment and check replaced parts of an asset. You can also run these tests every time you change design, processes, or tools.
Test young assets under stress using accelerated and burn-in tests. Both of these tests help you understand how assets perform in more demanding or stressful conditions than usual.
Once you run these tests, you’ll have a clear idea of whether assets are likely to fail.
The best way to prevent asset failure during infant mortality is to use reactive or breakdown maintenance — a maintenance strategy that restores normal operating conditions when assets break down. Another way is to use warranties and request asset repairs from the manufacturer.
