Glossary · Maintenance and diagnostics
Lifespan
Also known as: Service life, Useful life
German: Lebensdauer
In engineering, the lifespan of an item is the period from its first use until it can no longer perform its required function economically or safely, expressed in time, operating hours or cycles. For wear parts it is often stated as a statistical value, such as a B10 life or a number of switching cycles.
- Maintenance
In one sentence
Lifespan is the period, in time, hours or cycles, during which an item can perform its required function before it wears out or must be replaced.
Example
The data sheet states a mechanical lifespan of 10 million switching cycles for the contactor, which the maintenance plan converts into a replacement interval.
How it applies
- Engineering: Designers select components whose lifespan fits the intended use of the machine, taking duty cycle, load and environment into account.
- Functional safety: For safety-related components, the mission time and parameters such as B10D values determine when components must be replaced, regardless of their visible condition.
- Maintenance: Lifespan data turns into replacement intervals in the Maintenance plan and into stock levels for Spare parts.
- Documentation: The documentation must state lifespans and replacement intervals that the user has to observe, with the unit (years, hours or cycles). Values should come from the design data, not be estimated by the writer.
Lifespan vs. MTBF
Lifespan describes how long an item lasts before wear-out. Mean time between failures (MTBF) describes the average operating time between failures, usually during the useful-life period. An MTBF of 100,000 hours does not mean an individual item will last 100,000 hours.