Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Maintenance and diagnostics

Mean time between failures (MTBF)

Also known as: MTBF, Mean operating time between failures

German: Mittlere Betriebsdauer zwischen Ausfällen (MTBF)

In reliability engineering, the mean time between failures (MTBF) is the expected operating time between consecutive failures of a repairable item. IEC 60050-192 uses the term mean operating time between failures.

  • Maintenance

In one sentence

MTBF is the expected operating time between consecutive failures of a repairable item, a basic reliability figure in data sheets.

Example

A power supply data sheet states an MTBF of 500,000 hours at 40 °C, calculated according to a stated reliability prediction method.

How it applies

  • Engineering: MTBF values help compare components and estimate the availability of a system, together with the time needed to restore it.
  • Operation: Plants calculate MTBF from their own failure records to track reliability trends and to prioritize improvements.
  • Maintenance: A low MTBF points to items that need a different Maintenance strategy, a better component or a design change.
  • Documentation: When a data sheet or manual states an MTBF, it should also state the conditions (temperature, load) and the calculation method or standard used, otherwise values from different suppliers cannot be compared.

MTBF vs. MTTFd vs. lifespan

MTBF is a general reliability figure covering all failures of a repairable item. Mean time to dangerous failure (MTTFd) counts only dangerous failures and is used for the performance level according to ISO 13849-1; the two must not be substituted for each other. MTBF also says nothing about how long an individual item lasts; that is its Lifespan.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: IEC 60050-192, International Electrotechnical Vocabulary — Part 192: Dependability

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

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