May 05, 2023

Reliability Predictions and FMEA Occurrence

26 minutes

Abstract

Carl and Fred discussing a reader question about FMEAs. Specifically, whether reliability predictions (for similar systems) are valid input to the Occurrence rating in an FMEA.

Key Points

Join Carl and Fred as they discuss the subject of Reliability Predictions, and whether they can be used in an FMEA.

Topics include:

Reliability Predictions methodology

Parts count can be misused as a way to predict reliability

Can Reliability Predictions be useful when assessing Occurrence rating in an FMEA?

Use of failure rates vs failure distributions in Supportability FMEA

Why Design FMEA Occurrence rating is subjective

Using a Reliability prediction from a handbook to inform FMEA occurrence rating gives a false sense of knowledge

Using less parts, as a strategy to improve reliability, can have validity

FMEA Occurrence rating is associated with the failure mode due to cause, not the aggregate component failure rate

Assumptions matter; if a reliability prediction assumes constant failure rate, this is often a wrong assumption

Field failure history can be important input to FMEA, as input to failure mode identification; this can help ensure field failures do not repeat

Beware of reliability software that takes the FMEA occurrence rating and transfers it to the System Reliability Analysis as component or system failure rates

Models are useful, however, the assumptions and methodologies must be correct

A “one-off” failure during product development should not be dismissed

Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches.

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