Availability indicators are often used to characterize the performance of machines, equipment, production lines, and plants. The spectrum of availability indicators is diverse because the quality of performance can be examined and quantified based on several aspects.
According to point 4.7 of the EN13306 standard, which describes the definition of maintenance terms, Availability* is defined as:
The ability of an item to be in a state to perform as and when required, under given conditions, assuming that the necessary external resources are provided. The standard adds the following 3 comments to the definition:
- Note: required external resources other than maintenance resources, do not affect the availability of the item although the item may not be available from the? user’s viewpoint.
- Note: this ability depends on the combined aspects of the reliability, maintainability of the item, the maintenance supportability and the maintenance actions carried out on the item.
- Note: availability may be quantified using appropriate measures or indicators and is then referred to as availability performance (see definition 4.9 of the standard).
The previously mentioned EN13306 standard, defines among others the instantaneous availability (4.8), time-based availability (4.9) and production-based availability (4.10).
It is important to note that the maintenance KPI’s-(Key Performance Indicators) standard EN15341 defines several availability performance indicators under the names M10, M11, M12 and PHA8. We will talk about these in further notes. Beyond the definitions, we also talk about the content of the data, highlighting some application risks.
It is also appropriate to briefly mention that the availability indicators, as in the case of other indicators characterizing the performance of maintenance, it is very important to observe two basic principles. The first is that the data collection and quantification should be based on a well and clearly defined concept system. If the definition of the various item (device) states and times is not clear, misinterpretation causes distortion of data. The second is to be consistent in the use of concepts and the application of possible boundary conditions when collecting data and in the process of analyses. In the absence of these, our comparative analysis (benchmarking) may lead to wrong conclusions.
In our next note, we will take a closer look at the concept of time-based availability.
*The English names of the technical terms used in the note are included in the article for the sake of clarity, consistently adhering to the requirements of the EN13306 and EN15341 standards.