FMEA (Failure Mode and Effects Analysis)
The FMEA is applied especially in the design and development phase of new products and processes and is an analytic method of reliability engineering for the systematic identification of possible errors and for assessing the inherent risks. As to quality management and security management the FMEA is used preventatively to avoid failures and to rise the technical reliability.
The FMEA may be divided into several categories. The most common are:
- Product FMEA: Refers to products and their features, it is started at an early stage and is cultivated in all sample phases of the development.
- Process FMEA: Refers to procedures (e.g. welding process) and is executed with the aim to safeguard the process planning.
Typically the FMEA is performed in five steps:
- Structure analysis
- Function analysis
- Failure analysis
- Measure analysis
FMECA (Failure Mode and Effects and Criticality Analysis)
FMEA with an extension to include a criticality analysis. It is about to add a combined evaluation of the failure probability and the expected defect. This allows to rank the urgency of actions.
FMEDA (Failure Mode and Effects and Diagnostic Analysis)
FMEA with an extension to include a diagnostic analysis. A statement is made on whether a root cause is safety critical and if its detection is possible.
Parameters are to be determined which are required by standards:
- IEC 61508: SFF (safe failure fraction)
- ISO 26262: SPFM (single point fault metric) und LFM (latent fault metric)
SFF is the percentage of harmless or detected safety critical failures to the total number of failures.
FTA (Fault Tree Analysis)
Top down method that is used to analyze and structurally visualize events of failures. At first a TOP event is selected. This represents an event of failure that is at the top of a downward fanning fault tree and therefore defines the main event whose possibilities of occurrence are examined below. Afterwards all sub-events can be collected and placed as branches of the fault tree which may lead to the occurrence of this TOP event.
By categorizing the event types using predefined symbols (further divisible event (of failure), not further investigated event, sufficiently known basic event, etc.) the fault tree can be structured more detailed. Furthermore a distinction between several (logical) linking variants (“and”/”or” links) helps defining interactions more specifically.
By placing the occurrence possibilities of each sub-event, the possibility of the occurrence of an examined TOP event can be inferred.
FuSaCo (Functional safety concept)
To meet the safety objectives, functional solutions are discussed and defined.
- Conceptual design to meet the safety objectives
- Definition of safety requirements for each safety objective
- Definition of safety mechanisms
The FuSaCo is compiled during the concept phase of the safety life cycle.