not available

The non-availability is a reliability parameter and is used in the reliability model - for example the fault tree - for so-called stand-by components . The stand-by components include: B. the emergency diesel in the event of a power failure , the fire alarm and the fire pump in the event of a fire. When required, the component should come into operation, which is then either available or not available.

Examples of the unavailability sizes of technical components according to:

• Automatic fire detector: up to ${\displaystyle 3{,}5\cdot {10}^{-5}}$ ${\displaystyle 1{,}3\cdot {10}^{-3}}$
• Stationary fire pump: up to ${\displaystyle 8{,}5\cdot {10}^{-4}}$ ${\displaystyle 3{,}5\cdot {10}^{-2}}$

The unavailability is the complement to the availability . Both quantities are defined as qualitative as well as quantitative properties of a component:

Unavailability : "Ability or probability to find a unit in a non-functional state at a given point in time."

The combination of the probability quantities of availability (v) and unavailability (n) results from the following equation:

${\displaystyle v=1-n}$

literature

• VDI 4001, Part 2, Terminology of Reliability, July 2006
• VDI 4010, sheet 1, overview of reliability data systems (ZDS), March 1997
• IEV 191-02-05, German online edition of the IEV [2]

Individual evidence

1. ↑ cf. [1] (PDF file; 2.72 MB), BfS: Methods for Probabilistic Safety Analysis for Nuclear Power Plants, Dec. 1996, BfS-KT-16-97 , Chap. 3.2.5.2. and Appendix C1.1.
2. ↑ ^{a b c} data for the quantification of event flow charts and fault trees, March 1997, BfS-KT-18/97, chap. 2.1.4 and 6.3. (Unavailabilities for fire protection equipment).
3. ↑ VDI 4001, sheet 2 and VDI 4010, sheet 1.
4. ↑ VDI 4001, sheet 2 and VDI 4010, sheet 1 and IEV 191.