AS NZS IEC 60812:2020 pdf free download – Failure modes and efects analysis (FMEA and FMECA)
For large or complex systems (e.g. a railway), it might be necessary to sub-divide the system into subsystems (e.g. rolling stock, signalling, control room) for each of which an FMEA is performed. The sub-division may be along physical or functional boundaries, and might be influenced by contractual requirements or organizational factors. The sub-division should be selected so that the size of each FMEA is manageable and each FMEA is logically connected to any others so that the influences of the subsystems on each other, and on the system as a whole are considered. Special attention should be paid to the interfaces between the subsystems and the boundaries within which they fall should be clearly defined.
5.2.3.2 Determine level and approach
An FMEA can be applied at any level of sub-division of an item or process hierarchy (Table 1 ). The FMEA may be approached in different ways depending on the analysis purpose and stage. Annex A provides guidance and examples.
EXAMPLE During early development stages an FMEA can be applied to the top- or mid-levels in the hierarchy and the causes for the failure modes limited to the failure of the elements in the next lower level(s). In later stages of development, elements at the lowest level of the hierarchy relevant to the objectives are considered. All failure modes associated with that element and their effects on the next higher level are identified. The FMEA will, however, always identify the effects of failure modes on the top level of the hierarchy within the analysis scope.
5.2.3.3 Define the boundaries of the subject of the analysis
The boundaries, relationships, dependencies and interfaces between the subject of the FMEA and other parts of the system, including human interfaces, should be delineated. The definition of boundaries should include inputs to, and outputs from, the item or process and explicitly specify which interfaces are within the scope of analysis and which are excluded.
The boundaries depend on the context and might be influenced by factors such as design or intended use. It may be necessary to explicitly place items or process steps outside the boundaries in order to constrain the size of the FMEA or because detailed knowledge of them cannot be obtained.
Where possible, boundaries should be defined to facilitate each FMEA and its integration with other related studies. In some cases, it might be useful to define boundaries from a functional viewpoint to limit the number of links to other items or processes outside the analysis. This is often the case if the item or process is functionally complex with multiple interconnections within or across the boundaries.