The goal of performing a failure modes, effects, and diagnostics analysis (FMEDA) is to obtain important reliability and Safety metrics including:
- the failure rates per failure mode,
- automatic diagnostic effectiveness,
- useful life,
- and latent fault test (proof test) effectiveness of a device.
This information is used for many reasons including identification of weak areas in a design, warranty cost prediction, etc. But perhaps most importantly, FMEDA results are used to calculate the safety integrity of equipment designed for automatic protection purposes (often called safety instrumented systems - SIS). These safety integrity metrics are an essential part of functional safety certification.
As valuable as the FMEDA results are, many find that the engineering time needed to perform a quality FMEDA is excessive. How can we do better? There are several techniques that are used by top FMEDA professionals to not only reduce engineering hours but increase analysis quality. One of the most effective techniques is to organize the FMEDA input information into functional blocks, with functions and failure modes for each block documented. At first glance, the introduction of functional block information seems to add complexity without clarity. However, the advantages of doing this before starting the FMEDA analysis significantly outweigh the up-front effort. This paper describes the Functional Failure Mode FMEDA process.