Page 15 - Root Cause Failure Analysis

GENERAL ANALYSIS TECHNIQUES

A number of general techniques are useful for problem solving. While many com-
mon, or overlapping, methodologies are associated with these techniques, there also
are differences. This chapter provides a brief overview of the more common methods
used to perform an RCFA.

FAILURE MODE AND EFFECTS ANALYSIS
A failure mode and effects analysis (FMEA) is a design-evaluation procedure used to
identify potential failure modes and determine the effect of each on system perfor-
mance. This procedure formally documents standard practice, generates a historical
record, and serves as a basis for future improvements. The FMEA procedure is a
sequence of logical steps, starting with the analysis of lower-level subsystems or com-
ponents. Figure 2-1 illustrates a typical logic tree that results with a FMEA.

The analysis assumes a failure point of view and identifies potential modes of fail-
ure along with their failure mechanism. The effect of each failure mode then is
traced up to the system level. Each failure mode and resulting effect is assigned a
criticality rating, based on the probability of occurrence, its severity, and its delecta-
bility. For failures scoring high on the criticality rating, design changes to reduce it
are recommended.

Following this procedure provides a more reliable design. Also such correct use of the
MEA process results in two major improvements: (1) improved reliability by antici-
pating problems and instituting corrections prior to producing product and (2)
improved validity of the analytical method, which results from strict documentation
of the rationale for every step in the decision-making process.

6