Bathtub Curve
The bathtub curve is a reliability model showing early-life failures, a relatively stable useful-life period, and increasing wear-out failures.
What this term means in maintenance
The bathtub curve is a reliability model showing early-life failures, a relatively stable useful-life period, and increasing wear-out failures.
Three regions
The traditional curve includes:
- Infant mortality: decreasing failure rate
- Useful life: approximately constant failure rate
- Wear-out: increasing failure rate
Practical example
New electronic modules may fail early because of manufacturing defects. Surviving units operate reliably for years before age-related failure increases.
Maintenance implications
Different regions require different actions:
- Early life: quality, installation, commissioning
- Useful life: condition monitoring and random-failure controls
- Wear-out: replacement, overhaul, redesign
Limitations
Not every asset or failure mode follows a classic bathtub curve.
Common mistake
Applying age-based replacement to equipment with mainly random failures may add cost without improving reliability.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Infant Mortality Failure
Infant mortality failures are early-life failures occurring soon after installation, commissioning, repair, or manufacture.
Wear-Out Failure
A wear-out failure occurs when age, cycles, fatigue, erosion, corrosion, or material degradation progressively increases failure probability.
Weibull Analysis
Weibull analysis is a statistical method used to study failure-time data and understand whether failures are early-life, random, or wear-related.
Bathtub Curve FAQs
- What are the three bathtub-curve regions?
Infant mortality, useful life, and wear-out.
- Does every asset follow the curve?
No. Actual failure behavior varies by equipment and failure mode.
- How does maintenance use Bathtub Curve?
To choose installation controls, random-failure strategies, or age-related replacement.