Failure modes, effects, and diagnostic analysis

For Functional Safety applications the IEC 61508 failure modes (safe, dangerous, annunciation, and no effect) are used.

A variation of DFMEA developed for functional safety applications is called Design Deviation and Mitigation Analysis (DDMA).

[5] The DDMA variation adds information not normally included in a DFMEA such as the automatic diagnostic mitigations, latent fault tests, and useful life.

The FMEDA technique was developed in the late 1980s by exida engineers based in part on a paper in the 1984 RAMS Symposium.

The second piece of information added to an FMEDA is the probability of the system or subsystem to detect internal failures via automatic on-line diagnostics.

[7] Functional safety failure modes were added and first documented in the book Evaluating Control System Reliability.

In the early 2000s functional failure mode analysis was added to the FMEDA process by John C. Grebe.

In early FMEDA work, component failure modes were mapped directly to "safe" or "dangerous" categories per IEC 61508, 1st Edition.

An additional column may be added to an FMEDA spreadsheet and probability of detection for each component failure mode is estimated.

Since constant failure rates are only valid during the useful life period, this metric is valuable for interpreting FMEDA result limitations.

The success of the FMEDA technique is supplying needed data in a relatively accurate way has allowed the probabilistic, performance approach to design to work.