Glossary · IIoT, data and AI
Remaining useful life (RUL)
Also known as: RUL
German: Restnutzungsdauer (RUL)
In maintenance and prognostics, remaining useful life (RUL) is the estimated time or number of operating cycles until a component or machine is expected to reach a failure or end-of-life condition, given its current condition and expected future operation. ISO 13381-1 gives guidelines for prognostics in machine condition monitoring.
- IIoT
- Standards
In one sentence
Remaining useful life is the estimated time or number of cycles until a component reaches failure or end of life, based on its condition.
Example
Based on the current wear trend, the analytics system estimates the RUL of a spindle bearing at about 900 operating hours, with a stated uncertainty range.
How it applies
- Engineering: RUL estimates rely on degradation models, physical or data-driven, and on assumptions about future load. They should always come with an uncertainty range.
- Maintenance: RUL helps schedule replacements into planned stops and order spare parts in time. Decisions should consider the uncertainty, not only the point estimate.
- Documentation: State how RUL is calculated, which operating conditions it assumes and what users should do when it falls below a threshold.
RUL vs. MTBF
Mean time between failures (MTBF) is a statistical average for a population of items. RUL is a prediction for one specific item based on its own condition. A component can have a long MTBF and still a short RUL if it is already damaged. Neither value replaces required Proof tests of safety functions.