Bathtub Curve

The bathtub curve describes how an asset's failure rate changes over its life: high early failures from manufacturing or installation defects, a long flat period of low random failures, then a rising rate as wear-out sets in. Its shape guides maintenance strategy by life phase.

The name comes from the curve's profile. The early 'infant mortality' region argues for commissioning checks and burn-in to weed out defective units. The flat 'useful life' region has a roughly constant, random failure rate where condition monitoring and run-to-failure can be appropriate. The rising 'wear-out' region justifies time-based replacement before failures cluster. Recognising which phase an asset is in prevents both over-maintenance and surprise breakdowns.

Related terms

Weibull Analysis · Mean Time Between Failures (MTBF) · RCM (Reliability-Centred Maintenance)